Microstructural and Mechanical Characterization of Alloys

A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Inorganic Crystalline Materials".

Deadline for manuscript submissions: closed (30 April 2020) | Viewed by 28459

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Department of Engineering Materials and Biomaterials, Mechanical Engineering Faculty, Silesian University of Technology, ul. Konarskiego, 18a, 44-100 Gliwice, Poland
Interests: steel; alloys; mechanical properties; precipitates; microstructure; welded joints, creep; heat treatment
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Guest Editor
Politechnika Czestochowska, Czestochowa, Poland
Interests: steel; heat treatment; mechanical properties; precipitates; welded joints
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The crucial stage when designing constructions and appliances is the choice of a proper grade of engineering material with the required functional properties. Currently, engineers can choose from four basic groups of engineering materials, including: Metals and their alloys, ceramics, polymers, and composites. A set of specific mechanical and physical properties decides on the common use of metals and alloys as materials for construction, tools, or specific purposes. The deciding factor is also the easiness of forming with the use of casting methods, cold and hot working, as well as the possibility of joining metal elements by welding, pressure welding, soldering, gluing, etc. and the affordable price. Mechanical properties of alloys are determined by the type of the metal microstructure, characterized by the chemical composition and the crystalline structure of phases, the size and shape of grains of the particular phases and their mutual distribution, the extent of crystal lattice defects, and the way of spacial distribution of the defects. The microstructure of alloys is shaped through building a proper chemical composition and selecting the right conditions of the applied heat, thermochemical or plastic treatment.

We invite researchers to submit papers related to alloys (engineering materials) to discuss potential materials, the method of improvement of strength and cyclic properties of alloys, the stability of microstructures, the possible application of new (or improved) alloys, and the use of treatment for alloys improvement.

Dr. Marek Sroka
Prof. Dr. Grzegorz Golański
Guest Editors

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Keywords

  • Alloys
  • Chemical composition
  • Microstructure
  • Mechanical properties
  • Treatment

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Editorial

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3 pages, 158 KiB  
Editorial
Microstructural and Mechanical Characterization of Alloys
by Marek Sroka and Grzegorz Golański
Crystals 2020, 10(10), 945; https://doi.org/10.3390/cryst10100945 - 17 Oct 2020
Viewed by 1671
Abstract
This Special Issue on “Microstructural and Mechanical Characterization of Alloys” features eight papers that cover the recent developments in alloys (engineering materials), methods of improvement of strength and cyclic properties of alloys, the stability of microstructure, the possible application of new (or improved) [...] Read more.
This Special Issue on “Microstructural and Mechanical Characterization of Alloys” features eight papers that cover the recent developments in alloys (engineering materials), methods of improvement of strength and cyclic properties of alloys, the stability of microstructure, the possible application of new (or improved) alloys, and the use of treatment for alloy improvement. Full article
(This article belongs to the Special Issue Microstructural and Mechanical Characterization of Alloys)

Research

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13 pages, 7308 KiB  
Article
Effect of Equal Channel Angular Pressing on Microstructure and Mechanical Properties of a Cu-Mg Alloy
by Muzhi Ma, Xi Zhang, Zhou Li, Zhu Xiao, Hongyun Jiang, Ziqi Xia and Hanyan Huang
Crystals 2020, 10(6), 426; https://doi.org/10.3390/cryst10060426 - 27 May 2020
Cited by 11 | Viewed by 2586
Abstract
A Cu-0.43Mg (wt.%) alloy was processed by equal channel angular pressing (ECAP) up to eight passes via a processing route (Bc). The hardness distribution on the longitudinal and transverse sections was collected and the microstructure in the central and bottom regions on the [...] Read more.
A Cu-0.43Mg (wt.%) alloy was processed by equal channel angular pressing (ECAP) up to eight passes via a processing route (Bc). The hardness distribution on the longitudinal and transverse sections was collected and the microstructure in the central and bottom regions on the longitudinal section was examined. The result showed that the hardness was improved significantly at the initial stage of the ECAP process, and the lower hardness region appeared at the area nearby the bottom surface. With the number of ECAP passes, the hardness gently increased and finally became saturated. The inhomogeneity of the hardness distribution along the normal direction gradually weakened and finally disappeared. The shear microstructure in the central region was different from that in the bottom region after one ECAP pass, and they became similar to each other after two ECAP passes, except the rotation angle of the elongated grains. With the further increasing ECAP passes, there was no obvious microstructure difference between the central and bottom regions. The inhomogeneities of the hardness and the microstructure along the normal direction in the alloy after one ECAP passes should be attributed to the non-zero outer arc of curvature of the ECAP die and the friction between the bottom surface of the billets and the ECAP die walls. The yield strength of the alloy increased from 124 MPa before the ECAP process to 555 MPa after eight ECAP passes. The improvement of yield strengths of the ECAPed Cu-Mg alloy should be mainly attributed to the dislocation strengthening and the grain boundary strengthening. Full article
(This article belongs to the Special Issue Microstructural and Mechanical Characterization of Alloys)
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15 pages, 7473 KiB  
Article
Hot Deformation Behavior and Microstructure Characterization of an Al-Cu-Li-Mg-Ag Alloy
by Lingfei Cao, Bin Liao, Xiaodong Wu, Chaoyang Li, Guangjie Huang and Nanpu Cheng
Crystals 2020, 10(5), 416; https://doi.org/10.3390/cryst10050416 - 22 May 2020
Cited by 18 | Viewed by 2887
Abstract
The flow behavior of an Al-Cu-Li-Mg-Ag alloy was studied by thermal simulation tests at deformation temperatures between 350 °C and 470 °C and strain rates between 0.01–10 s−1. The microstructures of the deformed materials were characterized by electron backscattered diffraction. Constitutive [...] Read more.
The flow behavior of an Al-Cu-Li-Mg-Ag alloy was studied by thermal simulation tests at deformation temperatures between 350 °C and 470 °C and strain rates between 0.01–10 s−1. The microstructures of the deformed materials were characterized by electron backscattered diffraction. Constitutive equations were developed after considering compensation for strains. The processing maps were established and the optimum processing window was identified. The experimental data and predicted values of flow stresses were in a good agreement with each other. The influence of deformation temperature and strain rates on the microstructure were discussed. The relationship between the recrystallization mechanism and the Zener–Hollomon parameter was investigated as well. Full article
(This article belongs to the Special Issue Microstructural and Mechanical Characterization of Alloys)
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17 pages, 4371 KiB  
Article
Mathematical Modeling and Analysis of Tribological Properties of AA6063 Aluminum Alloy Reinforced with Fly Ash by Using Response Surface Methodology
by Alaa Mohammed Razzaq, Dayang Laila Majid, Mohamad Ridzwan Ishak and Uday Muwafaq Basheer
Crystals 2020, 10(5), 403; https://doi.org/10.3390/cryst10050403 - 16 May 2020
Cited by 9 | Viewed by 3599
Abstract
Lightweight, high-strength metal matrix composites have attracted considerable interest because of their attractive physical, mechanical and tribological properties. Moreover, they may offer distinct advantages due to good strength and wear resistance. In this research, AA6063 was reinforced with FA particles using compocasting methods. [...] Read more.
Lightweight, high-strength metal matrix composites have attracted considerable interest because of their attractive physical, mechanical and tribological properties. Moreover, they may offer distinct advantages due to good strength and wear resistance. In this research, AA6063 was reinforced with FA particles using compocasting methods. The effects of fly ash content, load, sliding speed and performance tribology of AA6063 –FA composite were evaluated. Dry sliding wear tests were carried out according to experimental design using the pin-on-disc method with three different loads (24.5, 49 and 73.5 N) and three speeds (150, 200 and 250 rpm) at room temperature. Response surface methodology (RSM) was used to analyze the influence of the process parameters on the tribological behavior of the composites. The surface plot showed that the wear rate increased with increasing load, time and sliding velocity. In contrast, the friction coefficient decreased with increasing these parameters. Optimal models for wear rate and friction coefficient showed appropriate results that can be estimated, hence reducing wear testing time and cost. Full article
(This article belongs to the Special Issue Microstructural and Mechanical Characterization of Alloys)
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14 pages, 5730 KiB  
Article
Simulation and Prediction of the Vickers Hardness of AZ91 Magnesium Alloy Using Artificial Neural Network Model
by Alaa F. Abd El-Rehim, Heba Y. Zahran, Doaa M. Habashy and Hana M. Al-Masoud
Crystals 2020, 10(4), 290; https://doi.org/10.3390/cryst10040290 - 10 Apr 2020
Cited by 13 | Viewed by 3230
Abstract
In this study, an artificial neural network (ANN) model was used to simulate and predict the Vickers hardness of AZ91 magnesium alloy. The samples of AZ91 alloy were aged at different temperatures (Ta = 100 to 300 °C) for different durations [...] Read more.
In this study, an artificial neural network (ANN) model was used to simulate and predict the Vickers hardness of AZ91 magnesium alloy. The samples of AZ91 alloy were aged at different temperatures (Ta = 100 to 300 °C) for different durations (ta = 4 to 192 h) followed by water quenching at 25 °C. The age-hardening response of the samples was investigated by hardness measurements. The microstructure investigations showed that only discontinuous precipitates formed at low aging temperatures (100 and 150 °C), while continuous precipitates invaded all the samples at a high aging temperature (300 °C). Both discontinuous and continuous precipitates formed at the intermediate aging temperatures (200 and 250 °C). X-ray diffraction (XRD) analysis revealed that the microstructure comprised two phases: The α-Mg matrix and intermetallic β-Mg17Al12 phase. The alteration of the crystalline lattice parameters a, c, and c/a ratio with the aging time at various aging temperatures was also investigated. Both c and c/a ratio had the same behavior with aging time while a had an inverse trend. The observed variations of the lattice parameters were attributed to the mode of precipitation in AZ91 alloy. The ANN findings for the simulation and prediction perfectly conformed to the experimental data. Full article
(This article belongs to the Special Issue Microstructural and Mechanical Characterization of Alloys)
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16 pages, 5845 KiB  
Article
Microstructural Stability and Softening Resistance of a Novel Hot-Work Die Steel
by Ningyu Du, Hongwei Liu, Paixian Fu, Hanghang Liu, Chen Sun, Yanfei Cao and Dianzhong Li
Crystals 2020, 10(4), 238; https://doi.org/10.3390/cryst10040238 - 25 Mar 2020
Cited by 17 | Viewed by 3374
Abstract
A novel hot-work die steel, named 5Cr5Mo2, was designed to obtain superior thermal stability. The proposed alloy is evaluated in terms of its hardness, microstructure, and tempering kinetics. Compared with the commonly used H13 steel, the softening resistance of the designed steel is [...] Read more.
A novel hot-work die steel, named 5Cr5Mo2, was designed to obtain superior thermal stability. The proposed alloy is evaluated in terms of its hardness, microstructure, and tempering kinetics. Compared with the commonly used H13 steel, the softening resistance of the designed steel is superior. Based on SEM and transmission electron microscopy (TEM) observations, a higher abundance of fine molybdenum carbides precipitate in 5Cr5Mo2 steel. Strikingly, the coarseness rate of the carbides is also relatively low during the tempering treatment. Moreover, owing to their pinning effect on dislocation slip, the dislocation density of the 5Cr5Mo2 steel decreases more slowly than that of the H13 steel. Furthermore, a mathematical softening model was successfully deduced and verified by analyzing the tempering kinetics. This model can be used to predict the hardness evolution of the die steels during the service period at high temperature. Full article
(This article belongs to the Special Issue Microstructural and Mechanical Characterization of Alloys)
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12 pages, 12639 KiB  
Article
The Effect of Lath Martensite Microstructures on the Strength of Medium-Carbon Low-Alloy Steel
by Chen Sun, Paixian Fu, Hongwei Liu, Hanghang Liu, Ningyu Du and Yanfei Cao
Crystals 2020, 10(3), 232; https://doi.org/10.3390/cryst10030232 - 23 Mar 2020
Cited by 40 | Viewed by 4366
Abstract
Different austenitizing temperatures were used to obtain medium-carbon low-alloy (MCLA) martensitic steels with different lath martensite microstructures. The hierarchical microstructures of lath martensite were investigated by optical microscopy (OM), electron backscattering diffraction (EBSD), and transmission electron microscopy (TEM). The results show that with [...] Read more.
Different austenitizing temperatures were used to obtain medium-carbon low-alloy (MCLA) martensitic steels with different lath martensite microstructures. The hierarchical microstructures of lath martensite were investigated by optical microscopy (OM), electron backscattering diffraction (EBSD), and transmission electron microscopy (TEM). The results show that with increasing the austenitizing temperature, the prior austenite grain size and block size increased, while the lath width decreased. Further, the yield strength and tensile strength increased due to the enhancement of the grain boundary strengthening. The fitting results reveal that only the relationship between lath width and strength followed the Hall–Petch formula of. Hence, we propose that lath width acts as the effective grain size (EGS) of strength in MCLA steel. In addition, the carbon content had a significant effect on the EGS of martensitic strength. In steels with lower carbon content, block size acted as the EGS, while, in steels with higher carbon content, the EGS changed to lath width. The effect of the Cottrell atmosphere around boundaries may be responsible for this change. Full article
(This article belongs to the Special Issue Microstructural and Mechanical Characterization of Alloys)
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13 pages, 6267 KiB  
Article
Comparison of the Crystal Structure and Wear Resistance of Co-Based Alloys with Low Carbon Content Manufactured by Selective Laser Sintering and Powder Injection Molding
by Anna Ziębowicz, Krzysztof Matus, Wojciech Pakieła, Grzegorz Matula and Miroslawa Pawlyta
Crystals 2020, 10(3), 197; https://doi.org/10.3390/cryst10030197 - 13 Mar 2020
Cited by 11 | Viewed by 3549
Abstract
Cobalt alloys are widely used in biomedicine, implantology, and dentistry due to their high corrosion resistance and good mechanical properties. The high carbon improves the wear properties, but causes fragility and dangerous cracking of elements during use. The aim of the present work [...] Read more.
Cobalt alloys are widely used in biomedicine, implantology, and dentistry due to their high corrosion resistance and good mechanical properties. The high carbon improves the wear properties, but causes fragility and dangerous cracking of elements during use. The aim of the present work was to analyze and compare the structure and wear resistance of Co-based alloy samples with low carbon content, produced by Selective Laser Sintering (SLS) and Powder Injection Molding (PIM). Structure characterization, mainly with the use of transmission electron microscopy, was applied to investigate the differences in tribological properties. The better resistance to abrasive wear for SLS was explained by the presence of a hard, intermetallic phase, present as precipitates limited in size and evenly distributed in the cobalt matrix. The second factor was the structure of the cobalt matrix, with dominant content of the hexagonal phase. By combining the characteristic features of the matrix and the reinforcing phase, the analyzed material gains an additional advantage, namely a higher resistance to abrasive wear. Full article
(This article belongs to the Special Issue Microstructural and Mechanical Characterization of Alloys)
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12 pages, 5601 KiB  
Article
Effect of ECAP on the Microstructure and Mechanical Properties of a Rolled Mg-2Y-0.6Nd-0.6Zr Magnesium Alloy
by Xiaofang Shi, Wei Li, Weiwei Hu, Yun Tan, Zhenglai Zhang and Liang Tian
Crystals 2019, 9(11), 586; https://doi.org/10.3390/cryst9110586 - 8 Nov 2019
Cited by 5 | Viewed by 2453
Abstract
A fine-grained Mg-2Y-0.6Nd-0.6Zr alloy was processed by bar-rolling and equal-channel angular pressing (ECAP). The effect of ECAP on the microstructure and mechanical properties of rolled Mg-2Y-0.6Nd-0.6Zr alloy was investigated by optical microscopy, scanning electron microscopy, electron backscattered diffraction and a room temperature tensile [...] Read more.
A fine-grained Mg-2Y-0.6Nd-0.6Zr alloy was processed by bar-rolling and equal-channel angular pressing (ECAP). The effect of ECAP on the microstructure and mechanical properties of rolled Mg-2Y-0.6Nd-0.6Zr alloy was investigated by optical microscopy, scanning electron microscopy, electron backscattered diffraction and a room temperature tensile test. The results show that the Mg-2Y-0.6Nd-0.6Zr alloy obtained high strength and poor plasticity after rolling. As the number of ECAP passes increased, the grain size of the alloy gradually reduced and the texture of the basal plane gradually weakened. The ultimate tensile strength of the alloy first increased and then decreased, the yield strength gradually decreased, and the plasticity continuously increased. After four passes of ECAP, the average grain size decreased from 11.2 µm to 1.87 µm, and the alloy obtained excellent comprehensive mechanical properties. Its strength was slightly reduced compared to the as-rolled alloy, but the plasticity was greatly increased. Full article
(This article belongs to the Special Issue Microstructural and Mechanical Characterization of Alloys)
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