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12 pages, 6920 KiB

Open AccessArticle

Failure Analysis of Cracking of Cast Aluminum Alloy Manhole Cover

by Facai Ren and Hezong Li

Materials 2023, 16(4), 1561; https://doi.org/10.3390/ma16041561 - 13 Feb 2023

Viewed by 3032

Abstract

In this paper, the abnormal fracture failure of a ZL104 aluminum alloy quick-opening manhole cover of a cement tank truck is systematically studied to discover the root cause of an accident. The unloading operation procedures of cement tank trucks, the effectiveness of safety [...] Read more.

In this paper, the abnormal fracture failure of a ZL104 aluminum alloy quick-opening manhole cover of a cement tank truck is systematically studied to discover the root cause of an accident. The unloading operation procedures of cement tank trucks, the effectiveness of safety valves, the chemical composition, mechanical properties and material quality of aluminum alloy manhole covers, and the macroscopic and microscopic morphology of fractures were comprehensively analyzed. The results show that although the Mg content in the chemical composition of an aluminum alloy manhole cover exceeds the standard, it is not the root cause of the accident. The root cause of the failure is that, during the unloading operation, the operator did not strictly follow the unloading procedures. One of the buckles was in the released state, which led to uplift cracking, resulting in the successive cracking and slipping of adjacent buckles, and the manhole cover finally cracked and flew out. Based on the failure causes, suggestions are put forward to prevent the manhole cover from failing during the unloading operation of cement tank trucks in the future. Full article

(This article belongs to the Special Issue Commemorating the Launch of the Section 'Metals and Alloys')

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12 pages, 3214 KiB

Open AccessArticle

Ultrafine Grain Ferrite Transformed from Fine Austenite Grains Produced by Dynamic Reversal Transformation

by Hongbin Li, Xiaoping Zheng, Lifeng Fan, Haiwei Xu, Yaqiang Tian, Xin Dai and Liansheng Chen

Materials 2022, 15(24), 8727; https://doi.org/10.3390/ma15248727 - 7 Dec 2022

Cited by 1 | Viewed by 1592

Abstract

The medium carbon steel warm deformation was carried out in a Gleeble-3500 simulator, and the microstructure was observed on a scan electron microscopy (SEM) and optical microscope (OM). The results show that the dynamic reversal transformation (DRT) of austenite occurred during the multipass [...] Read more.

The medium carbon steel warm deformation was carried out in a Gleeble-3500 simulator, and the microstructure was observed on a scan electron microscopy (SEM) and optical microscope (OM). The results show that the dynamic reversal transformation (DRT) of austenite occurred during the multipass deformation at a temperature of 675 °C. The austenite grain size is about 3.4 μm at the stain of 2.67. The thermodynamics was discussed based on the stress activation model. The critical stress of DRT is in the range of 265.94–294.28 MPa, which is related to the Schmit factor, without considering the distortion energy. Meanwhile, the submicron ferrite was obtained after the air cooling stage. The texture of the ultrafine ferrite possessed the characteristics of good, deep drawing properties. Full article

(This article belongs to the Special Issue Commemorating the Launch of the Section 'Metals and Alloys')

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13 pages, 6513 KiB

Open AccessArticle

Effect of Reinforcement Size on Mechanical Behavior of SiC-Nanowires-Reinforced 6061Al Composites

by Qiqi Zhao, Boyu Ju, Keguang Zhao, Junhai Zhan, Mingda Liu, Ningbo Zhang, Jinrui Qian, Ziyang Xiu, Pengchao Kang and Wenshu Yang

Materials 2022, 15(23), 8484; https://doi.org/10.3390/ma15238484 - 28 Nov 2022

Cited by 3 | Viewed by 1675

Abstract

In the present study, the effects of SiC nanowires (SiCnws) with diameters of 100 nm, 250 nm and 450 nm on the microstructure and mechanical behavior of 20 vol.% SiCnws/6061Al composites prepared by pressure infiltration were studied. It was found that the interface [...] Read more.

In the present study, the effects of SiC nanowires (SiCnws) with diameters of 100 nm, 250 nm and 450 nm on the microstructure and mechanical behavior of 20 vol.% SiCnws/6061Al composites prepared by pressure infiltration were studied. It was found that the interface between SiCnws and Al matrix was well bonded, and no interface product was found. The thicker SiCnws are beneficial to improve the density. In addition, the bamboo-like and bone-like morphologies of SiCnws produce a strong interlocking effect between SiCnws and Al, which helps to improve the strength and plasticity of the material. The tensile strength of the composite prepared by SiCnws with a diameter of 450 nm reached 544 MPa. With a decrease in the diameter of SiCnws, the strengthening effect of SiCnws increases. The yield strength of SiCnws/6061Al composites prepared by 100 nm is 13.4% and 28.5% higher than that of 250 nm and 450 nm, respectively. This shows that, in nano-reinforced composites, the small-size reinforcement has an excellent improvement effect on the properties of the composites. This result has a guiding effect on the subsequent composite structure design. Full article

(This article belongs to the Special Issue Commemorating the Launch of the Section 'Metals and Alloys')

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22 pages, 7932 KiB

Open AccessArticle

Study on the Mechanical Properties of Perforated Steel Plate Reinforced Concrete

by Chunbao Li, Gaojie Li, Liang Zheng, Xiaohui Liu, Shen Li, Xukai Wang, Valentina Y. Soloveva, Hojiboev Dalerjon, Zhiguang Fan and Pengju Qin

Materials 2022, 15(19), 6944; https://doi.org/10.3390/ma15196944 - 6 Oct 2022

Cited by 2 | Viewed by 1907

Abstract

In this paper, the mechanical properties of perforated steel plate reinforced concrete were studied. Through the compression test of the specimen, the failure mode, the compressive ultimate bearing capacity, and the stress–strain curve of the specimen were obtained. The results show that the [...] Read more.

In this paper, the mechanical properties of perforated steel plate reinforced concrete were studied. Through the compression test of the specimen, the failure mode, the compressive ultimate bearing capacity, and the stress–strain curve of the specimen were obtained. The results show that the compressive strength of perforated steel plate reinforced concrete is twice that of the same grade of plain concrete; through the pull-out test of the specimen, the failure mode and the ultimate uplift bearing capacity were obtained. The finite element software ANSYS was used to simulate the perforated steel plate reinforced concrete specimen, and the results show that the model is reliable. Through the range analysis method, the influence degree of the three factors of the thickness of the perforated steel plate, the hole diameter, and the hole spacing on the compressive strength and the ultimate bearing capacity of the pull-out was studied, and the optimal solution was obtained. The analysis results show that the order of the three factors on the compression and pull-out tests is: the plate thickness of the perforated steel plate > the hole diameter > the hole spacing; the optimal combination of the compressive strength of the perforated steel plate reinforced concrete specimen is that the thickness of the perforated steel plate is 0.75 mm, the diameter of the perforated steel plate is 15 mm, and the spacing of the perforated steel plate is 5 mm; the optimal combination of the ultimate bearing capacity of the pull-out is that the thickness of the steel plate with holes is 1.0 mm, the diameter of the steel plate with holes is 15 mm, and the spacing of the steel plate with holes is 15 mm. Full article

(This article belongs to the Special Issue Commemorating the Launch of the Section 'Metals and Alloys')

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21 pages, 8100 KiB

Open AccessArticle

Clarification of Temperature Field Evolution in Large-Scale Electric Upsetting Process of Ni80A Superalloy through Finite Element Method

by Jiang Zhao, Guo-Zheng Quan, Yu-Qing Zhang and Jian-Sheng Zhang

Materials 2022, 15(18), 6358; https://doi.org/10.3390/ma15186358 - 13 Sep 2022

Cited by 1 | Viewed by 1927

Abstract

Electric upsetting has been widely employed to manufacture the preformed workpiece of large-scale exhaust valves. The temperature field in the electric upsetting process plays an important role in microstructure evolution and defect formation. In order to uncover the temperature evolution in a larger-scale [...] Read more.

Electric upsetting has been widely employed to manufacture the preformed workpiece of large-scale exhaust valves. The temperature field in the electric upsetting process plays an important role in microstructure evolution and defect formation. In order to uncover the temperature evolution in a larger-scale electric upsetting process, the electric-thermal-mechanical multi-field coupling finite element model was developed to simulate the electric upsetting forming process of Ni80A superalloy. The temperature distribution characteristics and their formation mechanisms under different stages were analyzed systematically. Results indicate that at the preheating stage, the billet temperature increases from 20 °C to 516.7 °C, and the higher temperature region firstly appears at the contact surface between billet and anvil due to the combined effects of contact resistance and volume resistance. With increasing preheating time, the higher temperature region is transferred to the interior of the billet because the contact resistance is reduced with increasing temperature. As for the forming process, the billet is gradually deformed into an onion shape. The highest billet temperature increases to 1150 °C and keeps relatively constant. The high temperature region always appears at the neck of the onion due to the relatively higher current density at this place. It enlarges continuously in the primary stage and intermediate stage, and then decreases at the stable deformation stage. The low temperature regions lie in the contact surface and the outer surface of the onion because a lot of heat is lost to the anvil and surroundings through thermal conduction and radiation. Finally, the established finite element model was verified by an actual electric upsetting experiment. The average relative error between simulated temperatures and experimental ones was estimated as 7.54%. The longitudinal and radial errors between simulated onion shape and the experimental one were calculated as 1.38% and 2.70%, respectively. Full article

(This article belongs to the Special Issue Commemorating the Launch of the Section 'Metals and Alloys')

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20 pages, 21582 KiB

Open AccessArticle

Effect of Deformation Parameters of an Initial Aged GH4169 Superalloy on Its Microstructural Evolution during a New Two-Stage Annealing

by Mingsong Chen, Quan Chen, Yumin Lou, Yongcheng Lin, Hongbin Li, Guanqiang Wang and Hongwei Cai

Materials 2022, 15(16), 5508; https://doi.org/10.3390/ma15165508 - 11 Aug 2022

Cited by 6 | Viewed by 2541

Abstract

This study aims to explore the effect of deformation parameters on microstructure evolution during the new two-stage annealing method composed of an aging treatment (AT) and a cooling recrystallization annealing treatment (CRT). Firstly, the hot compressive tests with diverse deformation parameters were finished [...] Read more.

This study aims to explore the effect of deformation parameters on microstructure evolution during the new two-stage annealing method composed of an aging treatment (AT) and a cooling recrystallization annealing treatment (CRT). Firstly, the hot compressive tests with diverse deformation parameters were finished for an initial aged deformed GH4169 superalloy. Then, the same two-stage annealing method was designed and carried out for the deformed samples. The results show that the deformation parameters mainly affect the grain microstructure during CRT by influencing the content, distribution and morphology of the δ phase after deformation. The reason for this is that there is an equilibrium of the content of the δ phase and Nb atom. When the deformation temperature is high, the complete dissolution behavior of the δ phase nuclei promotes the dispersion distribution of the δ phase with rodlike and needle-like shapes during AT. Thus, the fine and heterogeneous microstructure is obtained after annealing because the recrystallization nucleation is enhanced in those dispersed δ phases during CRT. However, when the retained content of δ phase nuclei is high after deformation, the clusters of intragranular δ phases will form during AT, resulting in the pinning of the motion for dislocation. The elimination of the mixed grain microstructure is slowed down due to the low static recrystallization (SRX) nucleation rate within the deformed grain. Full article

(This article belongs to the Special Issue Commemorating the Launch of the Section 'Metals and Alloys')

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14 pages, 5111 KiB

Open AccessArticle

The Relationship between Microstructure and Fracture Behavior of TiAl/Ti₂AlNb SPDB Joint with High Temperature Titanium Alloy Interlayers

by Minxing Liao, Hao Tian, Lei Zhao, Boxian Zhang and Jianchao He

Materials 2022, 15(14), 4849; https://doi.org/10.3390/ma15144849 - 12 Jul 2022

Cited by 2 | Viewed by 2370

Abstract

In this paper, spark plasma diffusion bonding technology was employed to join TiAl and Ti₂AlNb with high temperature titanium alloy interlayer at 950 °C/10kN/60 min, then following furnace cooling at cooling rate up to 100 °C/min. After welding, the joint was [...] Read more.

In this paper, spark plasma diffusion bonding technology was employed to join TiAl and Ti₂AlNb with high temperature titanium alloy interlayer at 950 °C/10kN/60 min, then following furnace cooling at cooling rate up to 100 °C/min. After welding, the joint was aging heat-treated at 800 °C for 24 h. The microstructure and the elements diffusion of the TiAl/Ti₂AlNb joint was analyzed by field emission scanning electron microscopy (FESEM) with EDS. Moreover, the tensile properties of the joint were tested at room temperature, 650 °C, and 750 °C. The results show that the spark plasma diffusion bonding formed a high quality TiAl/Ti₂AlNb joint without microcracks or microvoids, while also effectively protecting the base metal. Significant differences in the microstructure of the joint appeared from TiAl side to Ti₂AlNb side: TiAl BM (Base Metal) → DP(Duplex) and NG (Near-Gamma) → α₂-phase matrix with needle-like α-phase → bulk α₂-phase → needle-like α-phase → metastable β-phase → Ti₂AlNb BM. After heat treatment at 800 °C for 24 h, the microstructure of the TiAl side and the interlayer region did not change, but the density and size of the needle-like α-phase in region 3 increased slightly. The microstructure of Ti₂AlNb near the weld changed obviously, and a large number of fine O phases are precipitated from the metastable β phase matrix after heat treatment. Except for the Ti₂AlN near-interface region, the effect of heat treatment on the microstructure of the joint is not significant. The microhardness of the joint is in the shape of a mountain peak. The maximum microhardness at the interface is above 500 HV, and it is significantly reduced to 400 HV after heat treatment. The fracture of the joint occurred at the interface at room temperature, 650 °C, and 750 °C. with the tensile strength 450 MPa, 540 MPa, and 471 Mpa, respectively, and mainly showing brittle fracture. Full article

(This article belongs to the Special Issue Commemorating the Launch of the Section 'Metals and Alloys')

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16 pages, 6728 KiB

Open AccessArticle

Microstructural Evolution and an Improved Dynamic Recrystallization Kinetic Model of a Ni-Cr-Mo Alloy in Hot Deformation

by Xintao Yan, Yuchi Xia, Daoguang He and Y. C. Lin

Materials 2022, 15(9), 3161; https://doi.org/10.3390/ma15093161 - 27 Apr 2022

Cited by 6 | Viewed by 2286

Abstract

Microstructural evolution and dynamic recrystallization (DRX) behaviors of a Ni-Cr-Mo alloy were researched utilizing hot compressive experiments. The changed features of dislocation, subgrain and grain structure correlating to forming parameters were examined by transmission electron microscope (TEM) and electron backscatter diffraction (EBSD). Results [...] Read more.

Microstructural evolution and dynamic recrystallization (DRX) behaviors of a Ni-Cr-Mo alloy were researched utilizing hot compressive experiments. The changed features of dislocation, subgrain and grain structure correlating to forming parameters were examined by transmission electron microscope (TEM) and electron backscatter diffraction (EBSD). Results illustrate that the consumption of dislocation and the coarsening of substructure/DRX grain are prominently enhanced with an increased forming temperature. However, the annihilation/interaction of dislocation and the expansion of subgrain/DRX grain boundary can be limited at a larger strain rate. Meanwhile, considering the discrepancy in DRX variation rates concerning the strain rate’s ranges, an improved DRX kinetic model was developed. Compared to the classical DRX kinetic model, the good consistency between the forecasted and tested results demonstrates that the established improved DRX kinetic model can precisely characterize the DRX features of the Ni-Cr-Mo alloy over a wide strain rate range. Additionally, the EBSD’s quantitative statistical results proved that the variation of DRX grain size can be supremely defined as the power formulation of the forming temperature and strain rate. Full article

(This article belongs to the Special Issue Commemorating the Launch of the Section 'Metals and Alloys')

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16 pages, 9082 KiB

Open AccessArticle

Effect of Silicon on Dynamic/Static Corrosion Resistance of T91 in Lead–Bismuth Eutectic at 550 °C

by Ji Li, Xikou He, Bin Xu, Zhengxin Tang, Caishun Fang and Gang Yang

Materials 2022, 15(8), 2862; https://doi.org/10.3390/ma15082862 - 14 Apr 2022

Cited by 15 | Viewed by 2564

Abstract

The 9–12% Cr ferritic–martensitic heat-resistant steel is the main candidate structural material for the Lead-cooled Faster Reactor. The lower Gibbs free energy change of Si oxide can promote the formation of a stable oxide layer, which can improve the corrosion resistance of the [...] Read more.

The 9–12% Cr ferritic–martensitic heat-resistant steel is the main candidate structural material for the Lead-cooled Faster Reactor. The lower Gibbs free energy change of Si oxide can promote the formation of a stable oxide layer, which can improve the corrosion resistance of the material. Therefore, it is of great significance to study the effect of silicon (Si) on the corrosion resistance of T91 steel in lead–bismuth eutectic (LBE). The corrosion resistance of T91 steel with Si contents of 0.5 wt.%, 1.3 wt.%, and 2.0 wt.%, both in dynamic and static LBE at 550 °C, was investigated. The microstructure was analyzed by X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM), while the oxide films were characterized by electron probe microanalysis (EPMA). Results show that the addition of Si is conducive to improving the corrosion resistance of T91 steel in LBE. T91 steel with high Si content has a thinner and more stable oxide film. The change of Si content can change the contact angle between the steel and LBE, and the contact angle is the largest when the Si content is 1.3 wt.%. The Si-rich oxide layer is usually located in the inner oxide layer, which promotes the formation of a Cr oxide layer located in the internal oxidation zone (IOZ). Si will not enter the precipitated phase, but only change the ferrite content. The oxidation model of T91 steel containing Si in LBE was also proposed. Full article

(This article belongs to the Special Issue Commemorating the Launch of the Section 'Metals and Alloys')

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12 pages, 4412 KiB

Open AccessArticle

Microstructure Evolution of Graphene and the Corresponding Effect on the Mechanical/Electrical Properties of Graphene/Cu Composite during Rolling Treatment

by Ziyang Xiu, Boyu Ju, Junhai Zhan, Ningbo Zhang, Zhijun Wang, Yong Mei, Jinming Liu, Yuhan Feng, Yixin Guo, Pengchao Kang, Qiang Zhang and Wenshu Yang

Materials 2022, 15(3), 1218; https://doi.org/10.3390/ma15031218 - 6 Feb 2022

Cited by 8 | Viewed by 2390

Abstract

Rolling enables the directional alignment of the reinforcements in graphene/Cu composites while achieving uniform graphene dispersion and matrix grain refinement. This is expected to achieve a breakthrough in composite performance. In this paper, the process parameters of rolling are investigated, and the defects, [...] Read more.

Rolling enables the directional alignment of the reinforcements in graphene/Cu composites while achieving uniform graphene dispersion and matrix grain refinement. This is expected to achieve a breakthrough in composite performance. In this paper, the process parameters of rolling are investigated, and the defects, thickness variations of graphene and property changes of the composite under different parameters are analyzed. High-temperature rolling is beneficial to avoid the damage of graphene during rolling, and the prepared composites have higher electrical conductivity. The properties of graphene were investigated. Low-temperature rolling is more favorable to the thinning and dispersion of graphene; meanwhile, the relative density of the composites is higher in the low-temperature rolling process. With the increase of rolling deformation, the graphene defects slightly increased and the number of layers decreased. In this paper, the defect states of graphene and the electrical conductivity with different rolling parameters is comprehensively investigated to provide a reference for the rolling process of graphene/copper composites with different demands. Full article

(This article belongs to the Special Issue Commemorating the Launch of the Section 'Metals and Alloys')

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13 pages, 4507 KiB

Open AccessArticle

Multi-Dimensional Revealing the Influence Mechanism of the δ Phase on the Tensile Fracture Behavior of a Nickel-Based Superalloy on the Mesoscopic Scale

by Qiang Zhu, Linfu Zhang, Chuanjie Wang, Gang Chen, Heyong Qin and Peng Zhang

Materials 2022, 15(2), 610; https://doi.org/10.3390/ma15020610 - 14 Jan 2022

Cited by 2 | Viewed by 1945

Abstract

As the key materials of aircraft engines, nickel-based superalloys have excellent comprehensive properties. Mircotensile experiments were carried out based on in situ digital image correlation (DIC) and in situ synchrotron radiation (SR) technique. The effects of the δ phase on the grain orientation, [...] Read more.

As the key materials of aircraft engines, nickel-based superalloys have excellent comprehensive properties. Mircotensile experiments were carried out based on in situ digital image correlation (DIC) and in situ synchrotron radiation (SR) technique. The effects of the δ phase on the grain orientation, surface roughening, and strain localization were investigated. The results showed that the average kernel average misorientation (KAM) value of the fractured specimens increased significantly compared with that of the heat-treated specimens. The surface roughness decreased with an increasing volume fraction of the δ phase. The strain localization of specimens increased with the increasing ageing time. The size and volume fraction of voids gradually increased with the increase in plastic strain. Some small voids expanded into large voids with a complex morphology during micro-tensile deformation. The needle-like δ phase near the fracture broke into short rods, while the minor spherical δ phase did not break. The rod-like and needle-like δ phases provided channels for the propagation of the microcrack, and the accumulation of the microcrack eventually led to the fracture of specimens. Full article

(This article belongs to the Special Issue Commemorating the Launch of the Section 'Metals and Alloys')

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12 pages, 64858 KiB

Open AccessArticle

Effect of Annealing Temperature on the Microstructure and Mechanical Properties of High-Pressure Torsion-Produced 316LN Stainless Steel

by Yuanyuan Dong, Zhe Zhang, Zhihai Yang, Ruixiao Zheng and Xu Chen

Materials 2022, 15(1), 181; https://doi.org/10.3390/ma15010181 - 27 Dec 2021

Cited by 7 | Viewed by 3152

Abstract

316LN stainless steel is a prospective structural material for the nuclear and medical instruments industries. Severe plastic deformation (SPD) combined with annealing possesses have been used to create materials with excellent mechanical properties. In the present work, a series of ultrafine-grained (UFG) 316LN [...] Read more.

316LN stainless steel is a prospective structural material for the nuclear and medical instruments industries. Severe plastic deformation (SPD) combined with annealing possesses have been used to create materials with excellent mechanical properties. In the present work, a series of ultrafine-grained (UFG) 316LN steels were produced by high-pressure torsion (HPT) and a subsequent annealing process. The effects of annealing temperature on grain recrystallization and precipitation were investigated. Recrystallized UFG 316LN steels can be achieved after annealing at high temperature. The σ phase generates, at grain boundaries, at an annealing temperature range of 750–850 °C. The dislocations induced by recrystallized grain boundaries and strain-induced nanotwins are beneficial for enhancing ductility. Moreover, microcracks are easy to nucleate at the σ phase and the γ-austenite interface, causing unexpected rapid fractures. Full article

(This article belongs to the Special Issue Commemorating the Launch of the Section 'Metals and Alloys')

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10 pages, 5201 KiB

Open AccessArticle

Experimental Study on Bead on Plate (BOP) Welding of 6 mm Thick 9% Nickel Steel by Fiber Laser Welding

by Jaewoong Kim, Changmin Pyo, Yonghyun Kim, Sungwook Kang, Taegon Yeo, Kwangsan Chun and Du-Song Kim

Materials 2021, 14(24), 7699; https://doi.org/10.3390/ma14247699 - 13 Dec 2021

Viewed by 2497

Abstract

Nine percent nickel steel has excellent properties in a cryogenic environment, so it has recently been used as a tank material for most LNG fuel-powered ships. However, 9% nickel steel causes arc deflection due to its tendency of magnetization during manual FCAW welding [...] Read more.

Nine percent nickel steel has excellent properties in a cryogenic environment, so it has recently been used as a tank material for most LNG fuel-powered ships. However, 9% nickel steel causes arc deflection due to its tendency of magnetization during manual FCAW welding and the currently used filler metal is 10–25 times more expensive as a base metal compared to other materials, depending on manufacturers. Furthermore, the properties of its filler metal cause limitation in the welding position. To overcome these disadvantages, in this study, the tendency of penetration shape was analyzed through a fiber laser Bead on Plate (BOP) welding for 9% nickel steel with a thickness of 6 mm and a range of welding conditions for 1-pass laser butt welding of 6 mm thick 9% nickel steel with I-Groove were derived. Through this study, basic data capable of deriving optimal conditions for laser butt welding of 9% nickel steel with a thickness of 6 mm were obtained. Full article

(This article belongs to the Special Issue Commemorating the Launch of the Section 'Metals and Alloys')

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13 pages, 10798 KiB

Open AccessArticle

A Study on Minimizing Welding Deformation of Joints for the Sealing of Emission After-Treatment Structure

by Sungwook Kang, Wangho Yun, Hwanjin Kim, Jaewoong Kim, Changwook Ji, Kwangjin Lee, Jaehwang Kim, Hong-Lae Jang and Kwangsan Chun

Materials 2021, 14(22), 6982; https://doi.org/10.3390/ma14226982 - 18 Nov 2021

Cited by 4 | Viewed by 2022

Abstract

As the environmental pollution issue has recently become significant, environmental regulations in Europe and the United States are being strengthened. Thus, there is a demand for the quality improvement of emission after-treatment systems to satisfy the strengthened environmental regulations. Reducing the amount of [...] Read more.

As the environmental pollution issue has recently become significant, environmental regulations in Europe and the United States are being strengthened. Thus, there is a demand for the quality improvement of emission after-treatment systems to satisfy the strengthened environmental regulations. Reducing the amount of welding heat distortion by optimization of the welding order of each part could be a solution for quality improvement since the emission after-treatment system consists of many parts and each assembly is produced by welding individual ones. In this research, a method to derive a welding sequence that effectively minimizes welding deformation was proposed. A two-stage simulation was performed to obtain the optimal welding sequence. In the first stage, the welding sequence was derived by analyzing the number of welding groups in each assembly of a structure. The derived welding sequence was verified by performing a thermal elasto-plastic analysis and comparing it with the experimental results. Full article

(This article belongs to the Special Issue Commemorating the Launch of the Section 'Metals and Alloys')

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18 pages, 9139 KiB

Open AccessArticle

An Innovative Approach of Parameter Loading Path Design for Grain Refinement and Its Application in Ni80A Superalloy

by Guo-Zheng Quan, Yan-Ze Yu, Xue Sheng, Kun Yang and Wei Xiong

Materials 2021, 14(21), 6703; https://doi.org/10.3390/ma14216703 - 7 Nov 2021

Cited by 4 | Viewed by 2192

Abstract

In order to obtain the desired mechanical properties of products, an innovative method of loading parameter designs for acquiring the desired grain refinement is proposed, and it has been applied in the compression process of Ni80A superalloy. The deformation mechanism maps derived from [...] Read more.

In order to obtain the desired mechanical properties of products, an innovative method of loading parameter designs for acquiring the desired grain refinement is proposed, and it has been applied in the compression process of Ni80A superalloy. The deformation mechanism maps derived from processing maps based on the Dynamic Materials Model (DMM) theory were constructed, since the critical indicator values corresponding to dynamic recrystallization (DRX) and dynamic recovery (DRV) mechanisms were determined. The processing-parameter domains with DRX mechanisms were separated from the deformation mechanism map, while such domains were chaotic and difficult to apply in innovative parameter loading path design. The speed-loading path derived from strain rate-loading path in a compression process was pursued. The grain refinement domains are discretized into a finite series of sub-domains with clear processing parameters, and the optimal strain rate of each sub-domain is determined by step-by-step finite element simulation. A 3D response surface of the innovative optimal loading path of strain rate was fitted by interpolating methods. Finally, the isothermal compression experiments for Ni80A superalloy were conducted, and the microstructure observations indicated that the desired grain refinement was achieved. This innovative method of parameter loading path design contributes to the microstructure adjustment of the alloys with DRX mechanism. Full article

(This article belongs to the Special Issue Commemorating the Launch of the Section 'Metals and Alloys')

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18 pages, 5033 KiB

Open AccessArticle

Modification of Surface and Subsurface Properties of AA1050 Alloy by Shot Peening

by Yasemin Yıldıran Avcu, Berkay Gönül, Okan Yetik, Fikret Sönmez, Abdulkadir Cengiz, Mert Guney and Egemen Avcu

Materials 2021, 14(21), 6575; https://doi.org/10.3390/ma14216575 - 1 Nov 2021

Cited by 15 | Viewed by 3407

Abstract

AA1050 Al alloy samples were shot-peened using stainless-steel shots at shot peening (SP) pressures of 0.1 and 0.5 MPa and surface cover rates of 100% and 1000% using a custom-designed SP system. The hardness of shot-peened samples was around twice that of unpeened [...] Read more.

AA1050 Al alloy samples were shot-peened using stainless-steel shots at shot peening (SP) pressures of 0.1 and 0.5 MPa and surface cover rates of 100% and 1000% using a custom-designed SP system. The hardness of shot-peened samples was around twice that of unpeened samples. Hardness increased with peening pressure, whereas the higher cover rate did not lead to hardness improvement. Micro-crack formation and embedment of shots occurred by SP, while average surface roughness increased up to 9 µm at the higher peening pressure and cover rate, indicating surface deterioration. The areal coverage of the embedded shots ranged from 1% to 5% depending on the peening parameters, and the number and the mean size of the embedded shots increased at the higher SP pressure and cover rate. As evidenced and discussed through the surface and cross-sectional SEM images, the main deformation mechanisms during SP were schematically described as crater formation, folding, micro-crack formation, and material removal. Overall, shot-peened samples demonstrated improved mechanical properties, whereas sample surface integrity only deteriorated notably during SP at the higher pressure, suggesting that selecting optimal peening parameters is key to the safe use of SP. The implemented methodology can be used to modify similar soft alloys within confined compromises in surface features. Full article

(This article belongs to the Special Issue Commemorating the Launch of the Section 'Metals and Alloys')

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21 pages, 10292 KiB

Open AccessArticle

Creep-Fatigue Crack Initiation Simulation of a Modified 12% Cr Steel Based on Grain Boundary Cavitation and Plastic Slip Accumulation

by Xin Jin, Run-Zi Wang, Yang Shu, Jia-Wen Fei, Jian-Feng Wen and Shan-Tung Tu

Materials 2021, 14(21), 6565; https://doi.org/10.3390/ma14216565 - 1 Nov 2021

Cited by 4 | Viewed by 2647

Abstract

High-temperature components in power plants may fail due to creep and fatigue. Creep damage is usually accompanied by the nucleation, growth, and coalescence of grain boundary cavities, while fatigue damage is caused by excessive accumulated plastic deformation due to the local stress concentration. [...] Read more.

High-temperature components in power plants may fail due to creep and fatigue. Creep damage is usually accompanied by the nucleation, growth, and coalescence of grain boundary cavities, while fatigue damage is caused by excessive accumulated plastic deformation due to the local stress concentration. This paper proposes a multiscale numerical framework combining the crystal plastic frame with the meso-damage mechanisms. Not only can it better describe the deformation mechanism dominated by creep from a microscopic viewpoint, but also reflects the local damage of materials caused by irreversible microstructure changes in the process of creep-fatigue deformation to some extent. In this paper, the creep-fatigue crack initiation analysis of a modified 12%Cr steel (X12CrMoWvNBN10-1-1) is carried out for a given notch specimen. It is found that creep cracks usually initiate at the triple grain boundary junctions or at the grain boundaries approximately perpendicular to the loading direction, while fatigue cracks always initiate from the notch surface where stress is concentrated. In addition to this, the crack initiation life can be quantitatively described, which is affected by the average grain size, initial notch size, stress range and holding time. Full article

(This article belongs to the Special Issue Commemorating the Launch of the Section 'Metals and Alloys')

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16 pages, 6672 KiB

Open AccessArticle

Microstructural Variation and a Physical Mechanism Model for a Ti-55511 Alloy during Double-Stage Hot Deformation with Stepped Strain Rates in the β Region

by Dao-Guang He, Gang Su, Yong-Cheng Lin, Yu-Qiang Jiang, Zhou Li, Zi-Jian Chen, Xin-Tao Yan, Yu-Chi Xia and Yang-Chen Xie

Materials 2021, 14(21), 6371; https://doi.org/10.3390/ma14216371 - 25 Oct 2021

Cited by 10 | Viewed by 2184

Abstract

The microstructural variation and high-temperature flow features of a Ti-55511 alloy in the β region are studied by utilizing double-stage compression with a stepped strain rate. The results demonstrate that the stresses in the latter stage of hot compression markedly reduce as the [...] Read more.

The microstructural variation and high-temperature flow features of a Ti-55511 alloy in the β region are studied by utilizing double-stage compression with a stepped strain rate. The results demonstrate that the stresses in the latter stage of hot compression markedly reduce as the strain at the previous stage or the strain rate at the previous/latter stage drops. Moreover, the annihilation/interaction of substructures is promoted, and the distinct refinement of the dynamic recrystallization (DRX) in the β grain can be found. However, the coarsening of the β grain and the consumption of dislocation substructures are accelerated at high temperatures. Furthermore, the principal DRX nucleation mechanism of the Ti-55511 alloy during double-stage compression with a stepped strain rate in the β region is discontinuous DRX. Additionally, by using the microstructural variation characteristics related to the forming parameters, a physical mechanism equation is modeled to forecast the forming features, the DRX fraction, and the size of the β grain in the investigated alloy. The forecasted results are in accordance with the tested results, indicating that the established model can accurately forecast the microstructure variation and flow features of the studied alloy. Full article

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14 pages, 4394 KiB

Open AccessArticle

External Surface Quality of the Graphite Crystallizer as a Factor Influencing the Temperature of the Continuous Casting Process of ETP Grade Copper

by Paweł Kwaśniewski, Paweł Strzępek, Grzegorz Kiesiewicz, Szymon Kordaszewski, Krystian Franczak, Michał Sadzikowski, Wojciech Ściężor, Anna Brudny, Joanna Kulasa, Barbara Juszczyk, Romuald Wycisk and Michał Śliwka

Materials 2021, 14(21), 6309; https://doi.org/10.3390/ma14216309 - 22 Oct 2021

Cited by 10 | Viewed by 3333

Abstract

Today’s world is a place where lack of electrical energy would be unimaginable for most of society. All the conductors in the world, both aluminum and copper, have their origin in various types of casting lines where the liquid metal after crystallization is [...] Read more.

Today’s world is a place where lack of electrical energy would be unimaginable for most of society. All the conductors in the world, both aluminum and copper, have their origin in various types of casting lines where the liquid metal after crystallization is being processed into the form of wires and microwires. However, the efficiency of the continuous casting processes of metals and the final quality of the manufactured product strictly depend on the design of the used crystallizers, the materials used during its production and its quality. Research conducted in this paper focuses on the latter, i.e., external surface quality of the graphite crystallizer at the place of contact with the primary cooling system. In order to quantify its influence on the continuous casting process numerical analyses using the finite element method has been conducted, which results have been further confirmed during empirical tests in laboratory conditions. It has been proven with all of the proposed methods that the temperature of the obtained cast rod is closely linked to the aforementioned surface quality, as when its roughness coefficient surpasses a certain value the temperature of the obtained product increases almost twofold from approx. 150–170 °C to 300–320 °C. These values might influence the quality and final properties of the cast rod, the susceptibility to wire drawing process and possible formation of wire drawing defects and therefore be of much importance to the casting and processing industry. Full article

(This article belongs to the Special Issue Commemorating the Launch of the Section 'Metals and Alloys')

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11 pages, 4228 KiB

Open AccessArticle

Optimization of Abrasive Water Jet Machining of SiC Reinforced Aluminum Alloy Based Metal Matrix Composites Using Taguchi–DEAR Technique

by Muthuramalingam Thangaraj, Mahmoud Ahmadein, Naser A. Alsaleh and Ammar H. Elsheikh

Materials 2021, 14(21), 6250; https://doi.org/10.3390/ma14216250 - 20 Oct 2021

Cited by 48 | Viewed by 2851

Abstract

Since the importance of introducing new engineering materials is increasing, the need for machining such higher strength materials has also considerably increased. In the present research, an endeavor was made to introduce a Taguchi–DEAR methodology for the abrasive water-jet machining process, while machining [...] Read more.

Since the importance of introducing new engineering materials is increasing, the need for machining such higher strength materials has also considerably increased. In the present research, an endeavor was made to introduce a Taguchi–DEAR methodology for the abrasive water-jet machining process, while machining a SiC-reinforced aluminum composite. Material removal rate, taper angle, and surface roughness were considered as the quality measures. The optimal arrangement of input process factors in the AWJM process was found to be 2800 bar (WP), 400 mg/min (AF), 1000 mm/min (FR), and 4 mm (SOD), among the chosen factors, with an error accuracy of 0.8%. The gas pressure had the most significance for formulating the performance measures, owing to its ability to modify the impact energy and crater size of the machined specimen. Full article

(This article belongs to the Special Issue Commemorating the Launch of the Section 'Metals and Alloys')

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18 pages, 8815 KiB

Open AccessArticle

Effect of the Position of the Boundary Rivets on the Quality of Riveted Single Strap Butt Joints

by Anan Zhao, Yongliang Zhang, Chunrun Zhu, Zhengwei Zhong and Yunbo Bi

Materials 2021, 14(18), 5127; https://doi.org/10.3390/ma14185127 - 7 Sep 2021

Cited by 3 | Viewed by 3084

Abstract

Riveting is widely used in aircraft manufacturing. The strap butt joint is often used in the aircraft’s main bearing area such as the aircraft docking area. The connection quality affects the reliability and safety of the aircraft directly. To study the effect of [...] Read more.

Riveting is widely used in aircraft manufacturing. The strap butt joint is often used in the aircraft’s main bearing area such as the aircraft docking area. The connection quality affects the reliability and safety of the aircraft directly. To study the effect of the rivet position on the connection quality of the strap butt joints, this paper analyzed the distribution of stress around the rivet hole at different positions by the finite element method, and then further analyzed the influence of the different rivet layouts on the connection quality of the strap butt joints by experiments. The static load tensile failure test of the joints was carried out, and the obtained tensile strength and failure mode of the strap butt joints showed that the main static tensile failure form of the single strap butt joint is that the whole rivets is sheared and the connecting sheets are separated. By changing the layout of different rivets, the connection strength can be maximized by reducing the outer row spacing (ORSD) of rivets. The results can be used for reference in the design of the riveting structure of aircraft panels. Full article

(This article belongs to the Special Issue Commemorating the Launch of the Section 'Metals and Alloys')

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13 pages, 7485 KiB

Open AccessArticle

Effects of Aging Treatment on Corrosion Behavior of a Tensile Deformed Al-Cu-Mn-Fe-Zr Alloy in 3.5% NaCl Solution

by Qing Tian, Qiu-Mei Yang, Yong-Cheng Lin, Jun-Quan Wang and Xu-Hao Zhu

Materials 2021, 14(17), 5062; https://doi.org/10.3390/ma14175062 - 3 Sep 2021

Cited by 8 | Viewed by 2861

Abstract

In this paper, the effects of an aging treatment on the corrosion resistance/mechanism of a tensile deformed Al-Cu-Mn-Fe-Zr alloy are investigated. The impedance magnitude and polarization resistance increase, while the corrosion current decreases with the increased aging time and temperature. The discontinuously-distributed precipitates [...] Read more.

In this paper, the effects of an aging treatment on the corrosion resistance/mechanism of a tensile deformed Al-Cu-Mn-Fe-Zr alloy are investigated. The impedance magnitude and polarization resistance increase, while the corrosion current decreases with the increased aging time and temperature. The discontinuously-distributed precipitates and precipitation-free zone, which can cut the corrosion channels, appear at grain boundaries when the temperature is relatively high and the aging time is relatively long. They can improve the corrosion resistance. Additionally, the intergranular and pitting corrosion are the main mechanisms. The intergranular corrosion is likely to occur in an under-aged alloy. This is because the potential difference between the grain boundaries and grains is high, due to the segregation of Cu atoms. When the aging degree is increased, the grain boundary precipitates reduce the potential difference, and the intragranular precipitates make the surrounding matrix prone to dissolution. As such, the pitting corrosion is likely to occur in the over-aged alloys. Full article

(This article belongs to the Special Issue Commemorating the Launch of the Section 'Metals and Alloys')

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11 pages, 4551 KiB

Open AccessArticle

Mitigating Inhomogeneity and Tailoring the Microstructure of Selective Laser Melted Titanium Orthorhombic Alloy by Heat Treatment, Hot Isostatic Pressing, and Multiple Laser Exposures

by Igor Polozov, Kirill Starikov, Anatoly Popovich and Vadim Sufiiarov

Materials 2021, 14(17), 4946; https://doi.org/10.3390/ma14174946 - 30 Aug 2021

Cited by 11 | Viewed by 2687

Abstract

Titanium orthorhombic alloys based on intermetallic Ti₂AlNb-phase are attractive materials for lightweight high-temperature applications. However, conventional manufacturing of Ti₂AlNb-based alloys is costly and labor-consuming. Additive Manufacturing is an attractive way of producing parts from Ti₂AlNb-based alloys. High-temperature [...] Read more.

Titanium orthorhombic alloys based on intermetallic Ti₂AlNb-phase are attractive materials for lightweight high-temperature applications. However, conventional manufacturing of Ti₂AlNb-based alloys is costly and labor-consuming. Additive Manufacturing is an attractive way of producing parts from Ti₂AlNb-based alloys. High-temperature substrate preheating during Selective Laser Melting is required to obtain crack-free intermetallic alloys. Due to the nature of substrate preheating, the temperature profile along the build height might be uneven leading to inhomogeneous microstructure and defects. The microstructural homogeneity of the alloy along the build direction was evaluated. The feasibility of mitigating the microstructural inhomogeneity was investigated by fabricating Ti₂AlNb-alloy samples with graded microstructure and subjecting them to annealing. Hot isostatic pressing allowed us to achieve a homogeneous microstructure, eliminate residual micro defects, and improve mechanical properties with tensile strength reaching 1027 MPa and 860 MPa at room temperature and 650 °C, correspondingly. Annealing of the microstructurally graded alloy at 1050 °C allowed us to obtain a homogeneous B2 + O microstructure with a uniform microhardness distribution. The results of the study showed that the microstructural inhomogeneity of the titanium orthorhombic alloy obtained by SLM can be mitigated by annealing or hot isostatic pressing. Additionally, it was shown that by applying multiple-laser exposure for processing each layer it is possible to locally tailor the phase volume and morphology and achieve microstructure and properties similar to the Ti2AlNb-alloy obtained at higher preheating temperatures. Full article

(This article belongs to the Special Issue Commemorating the Launch of the Section 'Metals and Alloys')

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19 pages, 5135 KiB

Open AccessArticle

Shape Analysis of the Elastic Deformation Region throughout the Axi-Symmetric Wire Drawing Process of ETP Grade Copper

by Paweł Strzępek, Andrzej Mamala, Małgorzata Zasadzińska, Grzegorz Kiesiewicz and Tadeusz Antoni Knych

Materials 2021, 14(16), 4713; https://doi.org/10.3390/ma14164713 - 20 Aug 2021

Cited by 7 | Viewed by 3026

Abstract

The wire drawing process is commonly perceived as one of the best studied metal forming processes in almost every aspect; however, when considering elastic deformation, researchers usually focus on the uniaxial tensile forces after the material exits the drawing die and not the [...] Read more.

The wire drawing process is commonly perceived as one of the best studied metal forming processes in almost every aspect; however, when considering elastic deformation, researchers usually focus on the uniaxial tensile forces after the material exits the drawing die and not the elastic deformation region before entering the drawing die, even though it may have a significant impact on the strength parameters and the nature of metal flow inside the drawing die. The aim of this research is to theoretically and experimentally identify the deformation in the elastic region and to further link the shape of this region and the values of stress occurring in it with the geometrical parameters of the drawing process and assess its impact on its strength parameters. In order to achieve the assumed goals, numerical analyses using the finite element method and experimental research on the drawing process in laboratory conditions were carried out using Vickers hardness tests and resistance strain gauges measuring deformation in stationary and non-stationary conditions. The obtained results indicate that the shape and the extent of the region of elastic deformations generated in the material before the plastic deformation region during the drawing process depends on the applied deformation coefficient and stationarity of the process. Full article

(This article belongs to the Special Issue Commemorating the Launch of the Section 'Metals and Alloys')

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12 pages, 12062 KiB

Open AccessArticle

Effects of Isothermal Temperature and Soaking Time on Water Quenched Microstructure of Nickel-Based Superalloy GH3536 Semi-Solid Billets

by Guanfei Xiao, Jufu Jiang, Ying Wang, Yingze Liu, Ying Zhang and Yinfeng Tian

Materials 2021, 14(16), 4668; https://doi.org/10.3390/ma14164668 - 19 Aug 2021

Cited by 3 | Viewed by 2663

Abstract

Semi-solid billets of GH3536 alloy were prepared by semi-solid isothermal treatment of wrought superalloy method. GH3536 samples were soaked at several semi-solid temperatures (1350 °C, 1360 °C, 1364 °C, and 1367 °C) for 5–120 min. The effects of temperature and soaking time on [...] Read more.

Semi-solid billets of GH3536 alloy were prepared by semi-solid isothermal treatment of wrought superalloy method. GH3536 samples were soaked at several semi-solid temperatures (1350 °C, 1360 °C, 1364 °C, and 1367 °C) for 5–120 min. The effects of temperature and soaking time on the microstructure of GH3536 billets were studied. The results indicated that the microstructure was affected by coalescence mechanism, Ostwald ripening mechanism, and breaking up mechanism. Semi-solid microstructure of GH3536 alloy was composed of spherical solid particles and liquid phases, and the liquid phases affected the microstructure greatly. At 1350 °C, the coalescence mechanism was dominant at the early stage of isothermal treatment, then the Ostwald ripening mechanism played a major role for the longer soaking times. At higher temperatures, the breaking up mechanism occurred to form large irregular grains and small spherical grains. As the heating continued, the Ostwald ripening mechanism was dominant. However, at 1364 °C and 1367 °C, the solid grains had irregular shapes and large sizes when the isothermal time was 120 min. The optimum parameters for the preparation of GH3536 semi-solid billets were: temperature of 1364–1367 °C and soaking time of 60–90 min. Full article

(This article belongs to the Special Issue Commemorating the Launch of the Section 'Metals and Alloys')

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14 pages, 12296 KiB

Open AccessArticle

Effects of Double-Stage Annealing Parameters on Tensile Mechanical Properties of Initial Aging Deformed GH4169 Superalloy

by Guanqiang Wang, Mingsong Chen, Yongcheng Lin, Yumin Lou, Hongbin Li, Yanyong Ma, Zonghuai Zou, Quan Chen and Yuchi Xia

Materials 2021, 14(15), 4339; https://doi.org/10.3390/ma14154339 - 3 Aug 2021

Cited by 11 | Viewed by 3089

Abstract

This study takes large size samples after hot-upsetting as research objects and aims to investigate the optimization double-stage annealing parameters for improving the mechanical properties of hot-upsetting samples. The double-stage annealing treatments and uniaxial tensile tests for hot-upsetting GH4169 superalloy were finished firstly. [...] Read more.

This study takes large size samples after hot-upsetting as research objects and aims to investigate the optimization double-stage annealing parameters for improving the mechanical properties of hot-upsetting samples. The double-stage annealing treatments and uniaxial tensile tests for hot-upsetting GH4169 superalloy were finished firstly. Then, the fracture mode was also studied. The results show that the strength of hot-upsetting GH4169 superalloy can be improved by the double-stage annealing treatment, but the effect of annealing parameters on the elongation of GH4169 alloy at high temperature and room temperature is not significant. The fracture mode of annealed samples at high-temperature and room-temperature tensile tests is a mixture of shear fracture and quasi-cleavage fracture while that of hot-upsetting sample is a shear fracture. The macroscopic expressions for the two fracture modes belong to ductile fracture. Moreover, it is also found that the improvement of strength by the double-stage annealing treatment is greater than the single-stage annealing treatment. This is because the homogeneity of grains plays an important role in the improvement of strength for GH4169 superalloy when the average grain size is similar. Based on a comprehensive consideration, the optimal annealing route is determined as 900 °C × 9–12 h(water cooling) + 980 °C × 60 min(water cooling). Full article

(This article belongs to the Special Issue Commemorating the Launch of the Section 'Metals and Alloys')

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13 pages, 7020 KiB

Open AccessArticle

Exploitation Characteristics of Teeth Flanks of Gears Regenerated by Three Hard-Facing Procedures

by Svetislav Marković, Dušan Arsić, Ružica R. Nikolić, Vukić Lazić, Branislav Hadzima, Vladimir P. Milovanović, Renata Dwornicka and Robert Ulewicz

Materials 2021, 14(15), 4203; https://doi.org/10.3390/ma14154203 - 28 Jul 2021

Cited by 38 | Viewed by 2392

Abstract

Numerous phenomena that occur during the process of machine parts’ regeneration have a significant impact on the loss of their working ability. Therefore, the properties of the working surfaces of the teeth flanks of repaired gears were analyzed in this research. The hereditary [...] Read more.

Numerous phenomena that occur during the process of machine parts’ regeneration have a significant impact on the loss of their working ability. Therefore, the properties of the working surfaces of the teeth flanks of repaired gears were analyzed in this research. The hereditary properties of the gear teeth are expressed by the interdependence of their geometric and physical-mechanical-metallurgical parameters created during the technological operations of regeneration of worn teeth by welding/hard-facing. The hard-facing was executed with three filler metal types, namely: combination Inox 18/8/6 + EDur 600, Castolin 2 and UTP 670. The tested properties included geometrical accuracy, microstructure and microhardness. Evaluation of the executed regeneration procedures was done by comparing the mentioned parameters of the regenerated gears and the new ones. The tested gears were not withdrawn from production due to damage, but they were newly manufactured and intentionally damaged gears, made of the same materials, subjected to the same manufacturing process. In this way, all influences except for the considered filler metal type were eliminated. Based on results of the conducted experiments, it was possible to establish the influence of the filler metal type on the surface characteristics of the regenerated gears’ teeth flanks. Full article

(This article belongs to the Special Issue Commemorating the Launch of the Section 'Metals and Alloys')

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28 pages, 22164 KiB

Open AccessArticle

Investigation into the Effect of RFSSW Parameters on Tensile Shear Fracture Load of 7075-T6 Alclad Aluminium Alloy Joints

by Andrzej Kubit, Tomasz Trzepieciński, Elżbieta Gadalińska, Ján Slota and Wojciech Bochnowski

Materials 2021, 14(12), 3397; https://doi.org/10.3390/ma14123397 - 19 Jun 2021

Cited by 18 | Viewed by 3042

Abstract

The aim of the investigations was to determine the effect of parameters of refill friction stir spot welding (RFSSW) on the fracture load and failure mechanisms of the resulting joint. RFSSW joints were made in 7075-T6 Alclad aluminium alloy sheets using different welding [...] Read more.

The aim of the investigations was to determine the effect of parameters of refill friction stir spot welding (RFSSW) on the fracture load and failure mechanisms of the resulting joint. RFSSW joints were made in 7075-T6 Alclad aluminium alloy sheets using different welding parameters. The load capacity of joints was determined under tensile/shear loadings. Finite element-based numerical simulations of the joint-loading process were carried out, taking into account the variability of elasto-plastic properties of weld material through the joint cross-section. The influence of welding parameters on selected phenomena occurring during the destruction of the joint is presented. The considerations were supported by a fractographic analysis based on SEM images of fractures. It was found that there is a certain optimal amount of heat generated, which is necessary to produce the correct joint in terms of its load capacity. This value should not be exceeded, because it leads to weakening of the base material and thus to a reduction in the strength of the joint. Samples subjected to uniaxial tensile shear load showed three types of failure mode (tensile fracture, shear fracture, plug type fracture) depending on the tool rotational speed and duration of welding. Prediction of the fracture mode using FE-based numerical modelling was consistent with the experimental results. The samples that were damaged due to the tensile fracture of the lower sheet revealed a load capacity (LC) of 5.76 KN. The average value of LC for the shear fracture failure mechanism was 5.24 kN. The average value of the LC for plug-type fracture mode was 5.02 kN. It was found that there is an optimal amount of heat generated, which is necessary to produce the correct joint in terms of its LC. Excessive overheating of the joint leads to a weakening of the base metal and thus a reduction in the strength of the joint. Measurements of residual stresses along the axis specimens showed the presence of stresses with a certain constant value for the welded area on the side of the 1.6 mm thick plate. Full article

(This article belongs to the Special Issue Commemorating the Launch of the Section 'Metals and Alloys')

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19 pages, 8267 KiB

Open AccessArticle

Experimental and Numerical Study of Combined High and Low Cycle Fatigue Performance of Low Alloy Steel and Engineering Application

by Zhanzhan Tang, Zheng Chen, Zhixiang He, Xiaomei Hu, Hanyang Xue and Hanqing Zhuge

Materials 2021, 14(12), 3395; https://doi.org/10.3390/ma14123395 - 18 Jun 2021

Cited by 17 | Viewed by 3295

Abstract

The fatigue behaviors of metals are different under different in-service environment and loading conditions. This study was devoted to investigating the combined effects of high and low cycle fatigue loads on the performance of the low alloy steel Q345. Three kinds of experiments [...] Read more.

The fatigue behaviors of metals are different under different in-service environment and loading conditions. This study was devoted to investigating the combined effects of high and low cycle fatigue loads on the performance of the low alloy steel Q345. Three kinds of experiments were carried out, including the pure high cycle fatigue (HCF) tests, the pure low cycle fatigue (LCF) tests, and the combined high and low cycle fatigue (HLCF) tests. The prediction formulae were proposed for the combined high and low cycle fatigue failure. Scanning electron microscopy (SEM) and stereo microscope were used to analyze the microstructure and fracture morphology due to different fatigue loads. Case study on the combined high and low cycle fatigue damage of a steel arch bridge was carried out based on the FE method and the proposed formula. The results show that the LCF life decreases evidently due to the prior HCF damages. The HLCF fracture surface is relatively flat near the crack initiation side, and rugged at the other half part. The fatigue damages at the bridge joints increase significantly with consideration of the pre-fatigue damages caused by traffic load. In the 100th anniversary of service, the fatigue damage index without considering the HCF pre-damage is only about 50% of the coupled damage value. Full article

(This article belongs to the Special Issue Commemorating the Launch of the Section 'Metals and Alloys')

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24 pages, 6212 KiB

Open AccessEditor’s ChoiceReview

A Review of Trends in Corrosion-Resistant Structural Steels Research—From Theoretical Simulation to Data-Driven Directions

by Di Xu, Zibo Pei, Xiaojia Yang, Qing Li, Fan Zhang, Renzheng Zhu, Xuequn Cheng and Lingwei Ma

Materials 2023, 16(9), 3396; https://doi.org/10.3390/ma16093396 - 26 Apr 2023

Cited by 9 | Viewed by 4027

Abstract

This paper provides a review of models commonly used over the years in the study of microscopic models of material corrosion mechanisms, data mining methods and the corrosion-resistant performance control of structural steels. The virtual process of material corrosion is combined with experimental [...] Read more.

This paper provides a review of models commonly used over the years in the study of microscopic models of material corrosion mechanisms, data mining methods and the corrosion-resistant performance control of structural steels. The virtual process of material corrosion is combined with experimental data to reflect the microscopic mechanism of material corrosion from a nano-scale to macro-scale, respectively. Data mining methods focus on predicting and modeling the corrosion rate and corrosion life of materials. Data-driven control of the corrosion resistance of structural steels is achieved through micro-alloying and organization structure control technology. Corrosion modeling has been used to assess the effects of alloying elements, grain size and organization purity on corrosion resistance, and to determine the contents of alloying elements. Full article

(This article belongs to the Special Issue Commemorating the Launch of the Section 'Metals and Alloys')

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36 pages, 6973 KiB

Open AccessReview

Silane Coatings for Corrosion and Microbiologically Influenced Corrosion Resistance of Mild Steel: A Review

by Saad Al-Saadi and R. K. Singh Raman

Materials 2022, 15(21), 7809; https://doi.org/10.3390/ma15217809 - 5 Nov 2022

Cited by 15 | Viewed by 6476

Abstract

Mild steel continues to be the most extensively used construction material in several industries and constructions. However, corrosion of mild steel in aggressive environments is a major concern. Under the tremendously increasing demand for improving the coatings strategies because of the environmental concerns [...] Read more.

Mild steel continues to be the most extensively used construction material in several industries and constructions. However, corrosion of mild steel in aggressive environments is a major concern. Under the tremendously increasing demand for improving the coatings strategies because of the environmental concerns due to some of the traditional coatings, silane pre-treatments have been emerging as one of the effective solutions, among other strategies. Different approaches, such as adding particles of metal oxide (such as SiO₂, ZrO₂, Al₂O₃, TiO₂ and CeO₂), incorporating plant extracts and impregnating 2D materials into the coatings, have been employed for durable corrosion resistance, including for mitigating enhanced corrosion due to the presence of bacteria. This review discusses the critical mechanistic features of silane coatings such as the role of hydrolysis and condensation in the bonding of silanes with metal surfaces. The factors that influence the performance of the silane coatings for corrosion resistance of mild steel are discussed. In particular, this review provides insight into silane coatings for mitigating microbiologically influenced corrosion (MIC) of mild steel. Full article

(This article belongs to the Special Issue Commemorating the Launch of the Section 'Metals and Alloys')

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