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Metals, Volume 10, Issue 7 (July 2020) – 139 articles

Cover Story (view full-size image): A new methodology has been developed to manufacture high-quality Al/AlN composite powders from inexpensive aluminum powders using laser technology. Al/AlN composite powders have been synthesized by spraying aluminum powder through a HPD Laser beam in a nitrogen-rich environment. The high temperature induced by the laser beam activates the in-situ nitridation of the outer zone of the particles through different nitridation mechanisms. This treatment has been evaluated in different aluminum alloy powders and the obtained product consists of an aluminum matrix reinforced with nano-sized AlN particles. By analyzing the AlN atomic structure obtained, a correlation between the temperature distribution of the particles, their composition, and the nitridation reaction mechanisms was established. Finally, composite coatings have been fabricated by reactive direct laser deposition using these powders and its [...] Read more.
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11 pages, 5767 KiB  
Article
Effect of Decreasing Temperature Reciprocating Upsetting-Extrusion on Microstructure and Mechanical Properties of Mg-Gd-Y-Zr Alloy
by Wenlong Xu, Jianmin Yu, Guoqin Wu, Leichen Jia, Zhi Gao, Zhan Miao, Zhimin Zhang and Feng Yan
Metals 2020, 10(7), 985; https://doi.org/10.3390/met10070985 - 21 Jul 2020
Cited by 7 | Viewed by 2959
Abstract
The decreasing temperature reciprocating upsetting-extrusion (RUE) deformation experiment was carried out on Mg-Gd-Y-Zr alloy to study RUE deformation on the influence of microstructure of the alloy. This work showed that with the gradual increase of RUE deformation passes, the continuous dynamic recrystallization (CDRX) [...] Read more.
The decreasing temperature reciprocating upsetting-extrusion (RUE) deformation experiment was carried out on Mg-Gd-Y-Zr alloy to study RUE deformation on the influence of microstructure of the alloy. This work showed that with the gradual increase of RUE deformation passes, the continuous dynamic recrystallization (CDRX) process and the discontinuous dynamic recrystallization (DDRX) process occurred at the same time, and the grain refinement effect was obvious. Particulate precipitation induced the generation of DRX through particle-stimulated nucleation (PSN). In addition, after one pass of RUE deformation, the alloy produced a strong basal texture. As the RUE experiment proceeded, the basal texture intensity decreased. The weakening of the texture was due to the combined effect of DRX and alternating loading forces in the axial and radial directions. After four RUE passes, the mechanical properties of the alloy had been significantly improved, which was the result of the combined effect of dislocation strengthening, fine grain strengthening, and second phase strengthening. Full article
(This article belongs to the Special Issue Lightweight Metals: Process, Microstructure, and Properties)
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14 pages, 7294 KiB  
Article
Minimal Invasive Diagnostic Capabilities and Effectiveness of CFRP-Patches Repairs in Long-Term Operated Metals
by Grzegorz Lesiuk, Bruno A. S. Pedrosa, Anna Zięty, Wojciech Błażejewski, Jose A. F. O. Correia, Abilio M. P. De Jesus and Cristiano Fragassa
Metals 2020, 10(7), 984; https://doi.org/10.3390/met10070984 - 21 Jul 2020
Cited by 11 | Viewed by 2619
Abstract
The paper deals with the subject of diagnostics and the quick repairs of long-term operated metallic materials. Special attention was paid to historical materials, where the structure (e.g., puddle iron) is different from modern structural steels. In such materials, the processes of microstructural [...] Read more.
The paper deals with the subject of diagnostics and the quick repairs of long-term operated metallic materials. Special attention was paid to historical materials, where the structure (e.g., puddle iron) is different from modern structural steels. In such materials, the processes of microstructural degradation occur as a result of several decades of exposure, which could overpass 100 years. In some cases, their intensity can be potentially catastrophic. For this reason, the search for minimally invasive diagnostic methods is ongoing. In this paper, corrosion and fracture toughness tests were conducted, and the results of these studies were presented for two material states: post-operated and normalized (as a state “restoring” virgin state). Moreover, through the use of modern numerical methods, composite crack-resistant patches have been designed to reduce the stress intensity factors under cyclic loads. As a result, fatigue lifetime was extended (propagation phase) by more than 300%. Full article
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21 pages, 12013 KiB  
Article
On the Surface Quality of CFRTP/Steel Hybrid Structures Machined by AWJM
by Fermin Bañon, Bartolome Simonet, Alejandro Sambruno, Moises Batista and Jorge Salguero
Metals 2020, 10(7), 983; https://doi.org/10.3390/met10070983 - 21 Jul 2020
Cited by 14 | Viewed by 3321
Abstract
The joining of dissimilar materials in a hybrid structure is a line of research of great interest at present. Nevertheless, the machining of materials with different machinability requires specific processes capable of minimizing defectology in both materials and achieving a correct surface finish [...] Read more.
The joining of dissimilar materials in a hybrid structure is a line of research of great interest at present. Nevertheless, the machining of materials with different machinability requires specific processes capable of minimizing defectology in both materials and achieving a correct surface finish in terms of functional performance. In this article, abrasive water jet machining of a hybrid carbon fiber-reinforced thermoplastics (CFRTP)/Steel structure and the generated surface finish are studied. A parametric study in two stacking configurations (CFRTP/Steel and Steel/CFRTP) has been established in order to determine the range of cutting parameters that generates the lowest values in terms of arithmetic mean roughness (Ra) and maximum profile height (Rz). The percentage contribution of each cutting parameter has been identified through an ANOVA analysis for each material and stacking configuration. A combination of 420 MPa hydraulic pressure with an abrasive mass flow of 385 g/min and a travel speed of 50 mm/min offers the lowest Ra and Rz values in the CFRTP/Steel configuration. The stacking order is a determining factor, obtaining a better surface quality in a CFRTP/Steel stack. Finally, a series of contour diagrams relating surface quality to machining conditions have been obtained. Full article
(This article belongs to the Special Issue Metal Machining—Recent Advances, Applications and Challenges)
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14 pages, 1589 KiB  
Article
Viscosity of BOF Slag
by Oleksandr Kovtun, Iurii Korobeinikov, Srishilan C, Ajay Kumar Shukla and Olena Volkova
Metals 2020, 10(7), 982; https://doi.org/10.3390/met10070982 - 21 Jul 2020
Cited by 20 | Viewed by 4490
Abstract
The viscosities of the industrial basic oxygen furnace (BOF) slag with varying compositions of MgO, Al2O3, TiO2, and MnO were continuously measured at a temperature range between 1400 and 1700 °C using the rotating bob method. Three [...] Read more.
The viscosities of the industrial basic oxygen furnace (BOF) slag with varying compositions of MgO, Al2O3, TiO2, and MnO were continuously measured at a temperature range between 1400 and 1700 °C using the rotating bob method. Three characteristic temperatures for the melting behavior of the BOF slag were investigated using a high-temperature microscope. The solid fraction of the slag was calculated by FactSage 7.2 using the FTOxid database. General observations from the experimental data show that the increase in MgO tends to increase viscosity. However, Al2O3, TiO2, and MnO decrease viscosity up to a certain level, and beyond that, they also increase the viscosity. The measured values of the viscosity of BOF slags were compared and discussed with known data from the literature. Finally, the activation energy of BOF slags with different compositions of MgO, Al2O3, TiO2, and MnO was calculated in the temperature range of industrial operations. Full article
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11 pages, 4472 KiB  
Article
A Sustainable Approach for Cadmium Recovery from Oxide Using Molten Salt Slag
by Ervins Blumbergs, Vera Serga, Ernests Platacis, Michail Maiorov, Arturs Brekis and Andrei Shishkin
Metals 2020, 10(7), 981; https://doi.org/10.3390/met10070981 - 21 Jul 2020
Viewed by 3542
Abstract
Alkaline nickel-cadmium batteries are among the most used industrial high-power sources. Despite stricter environmental requirements, nickel-cadmium batteries still remain as the main choice for highly reliable power sources for heavy-loaded equipment. Therefore, recovery of cadmium (Cd) from spent batteries is a challenge for [...] Read more.
Alkaline nickel-cadmium batteries are among the most used industrial high-power sources. Despite stricter environmental requirements, nickel-cadmium batteries still remain as the main choice for highly reliable power sources for heavy-loaded equipment. Therefore, recovery of cadmium (Cd) from spent batteries is a challenge for the modern recycling industry, particularly as it displays high bio-toxicity. The present study describes a new green approach for Cd recovery from cadmium oxide (CdO). The paper discusses using a ternary chloride composition consisting of calcium, potassium and sodium chloride, thereby avoiding the release of Cd vapour from the reaction volume during the reduction reaction from CdO. For the protective slag layer during the reduction process (which occurs at 650 °C), a 0.515:0.0796:0.405 molar ratio of CaCl2:KCl:NaCl was chosen, with the aim of achieving a melting point at 483 °C. To describe phase and elemental composition of obtained products X-ray diffraction analysis and energy dispersive X-ray spectroscopy, respectively, were applied. Electron and optical microscopy were used for morphological observations. The presence of the metallic Cd was noted. During the reduction reaction, it was noted that slag separated into two parts: a protective upper layer and bottom layer. It was also noted that metallic Cd accumulated with increasing reaction time in the bottom part of the slag. Full article
(This article belongs to the Special Issue Metal Removal and Recycling)
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19 pages, 10064 KiB  
Article
Experimental Research and Numerical Simulation of Weld Repair with High Energy Spark Deposition Method
by Yingjie Zhang, Kai Yang and Jianping Zhao
Metals 2020, 10(7), 980; https://doi.org/10.3390/met10070980 - 21 Jul 2020
Cited by 4 | Viewed by 2573
Abstract
For long-serviced pressure equipment that is under severe working conditions such as a high temperature, high pressure, and corrosion, the material properties and structure will be unavoidably damaged or degraded, especially cracks and other damages at key positions such as welded joints, which [...] Read more.
For long-serviced pressure equipment that is under severe working conditions such as a high temperature, high pressure, and corrosion, the material properties and structure will be unavoidably damaged or degraded, especially cracks and other damages at key positions such as welded joints, which seriously threaten the safe operation of the equipment. In order to promote the sustainable development of industries such as the chemical and petrochemical industries, remanufacturing technology has emerged worldwide, and various surface repair processes have also rapidly developed. As an important branch of surface repair technology, the high energy spark deposition (HESD) process is a new pulse cold welding repair technology developed from electro-spark deposition, which combines the advantages of multiple surface repair processes. The HESD process has the characteristics of a smaller heat affected zone and lower welding residual stress. It is a new type of repair method that is worthy of popularization and application. The process has been initially applied in the fields of surface modification and die steel repair. In this paper, the application of the HESD process to the repair of welded joints was introduced, the mechanical properties of the joints and the residual stress distribution after welding were analyzed, and the feasibility of HESD as a repair welding method for pressure structures was discussed. First, a numerical simulation of the temperature and stress field of HESD was proposed by using ABAQUS and the related subprograms, and the validity of the simulation results was verified by the residual stress test with the indentation strain method. Due to the precise control of the heat and pulse discharge working mode, the heat-affected zone and deformation caused by the HESD were extremely small, and the residual stress that was generated was low and only concentrated on the repair welding seam. Second, according to the numerical simulation and the test results of the mechanical properties of the welded joint, the optimal repair welding process parameters were obtained through the orthogonal experiment: peak current 45 A, pulse width 90 ms, and output voltage 10 V. Full article
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13 pages, 6844 KiB  
Article
Residual Stress Analysis of a 2219 Aluminum Alloy Ring Using the Indentation Strain-Gauge Method
by Yunlong Ma, Nianpu Xue, Qiong Wu, Hanjun Gao and Jian Wu
Metals 2020, 10(7), 979; https://doi.org/10.3390/met10070979 - 20 Jul 2020
Cited by 11 | Viewed by 3481
Abstract
Aerospace thin-walled rings are vulnerable to machining distortion during the manufacturing process. Various research results show that the main factor causing machining deformation is initial residual stress inside the blank. In this study, the residual stress of a 2219 aluminum alloy ultra-large rolling [...] Read more.
Aerospace thin-walled rings are vulnerable to machining distortion during the manufacturing process. Various research results show that the main factor causing machining deformation is initial residual stress inside the blank. In this study, the residual stress of a 2219 aluminum alloy ultra-large rolling ring was measured by using the indentation strain-gauge method. Results showed the maximum residual maximum principal stress was +265 MPa and stress distribution was uneven. To homogenize the initial residual stress of the ring, an expansion method is proposed based on the principle of pre-stretching plate, and the feasibility of the expansion method was analyzed by establishing a simplified theoretical model of ring. A FE (Finite Element) model was established to investigate residual-stress evolution during the rolling ring and the expanding ring process. The expansion simulation results show that the reduction rates of residual stress were greater than 40% and the maximum residual stress was only 65 MPa. Full article
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13 pages, 3907 KiB  
Article
Bioleaching of Phosphate Minerals Using Aspergillus niger: Recovery of Copper and Rare Earth Elements
by Laura Castro, Maria Luisa Blázquez, Felisa González and Jesús Angel Muñoz
Metals 2020, 10(7), 978; https://doi.org/10.3390/met10070978 - 20 Jul 2020
Cited by 42 | Viewed by 5440
Abstract
Rare earth elements (REE) are essential in high-technology and environmental applications, where their importance and demand have grown enormously over the past decades. Many lanthanide and actinide minerals in nature are phosphates. Minerals like monazite occur in small concentrations in common rocks that [...] Read more.
Rare earth elements (REE) are essential in high-technology and environmental applications, where their importance and demand have grown enormously over the past decades. Many lanthanide and actinide minerals in nature are phosphates. Minerals like monazite occur in small concentrations in common rocks that resist weathering. Turquoise is a hydrous phosphate of copper and aluminum scarcely studied as copper ore. Phosphate-solubilizing microorganisms are able to transform insoluble phosphate into a more soluble form which directly and/or indirectly contributes to their metabolism. In this study, bioleaching of heavy metals from phosphate minerals by using the fungus Aspergillus niger was investigated. Bioleaching experiments were examined in batch cultures with different mineral phosphates: aluminum phosphate (commercial), turquoise, and monazite (natural minerals). The experiments were performed at 1% pulp density and the phosphorous leaching yield was aluminum phosphate > turquoise > monazite. Bioleaching experiments with turquoise showed that A. niger was able to reach 8.81 mg/l of copper in the aqueous phase. Furthermore, the fungus dissolved the aluminum cerium phosphate hydroxide in monazite, reaching up to 1.37 mg/L of REE when the fungus was grown with the mineral as the sole phosphorous source. Furthermore, A. niger is involved in the formation of secondary minerals, such as copper and REE oxalates. Full article
(This article belongs to the Special Issue Leaching/Bioleaching and Recovery of Metals)
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14 pages, 4260 KiB  
Article
Prediction of Fatigue Crack Growth in Metallic Specimens under Constant Amplitude Loading Using Virtual Crack Closure and Forman Model
by Sanjin Krscanski and Josip Brnic
Metals 2020, 10(7), 977; https://doi.org/10.3390/met10070977 - 20 Jul 2020
Cited by 9 | Viewed by 3985
Abstract
This paper considers the applicability of virtual crack closure technique (VCCT) for calculation of stress intensity factor range for crack propagation in standard metal specimen geometries with sharp through thickness cracks. To determine crack propagation rate and fatigue lifetime of a dynamically loaded [...] Read more.
This paper considers the applicability of virtual crack closure technique (VCCT) for calculation of stress intensity factor range for crack propagation in standard metal specimen geometries with sharp through thickness cracks. To determine crack propagation rate and fatigue lifetime of a dynamically loaded metallic specimen, in addition to VCCT, standard Forman model was used. Values of stress intensity factor (SIF) ranges ΔK for various crack lengths were calculated by VCCT and used in conjunction with material parameters available from several research papers. VCCT was chosen as a method of choice for the calculation of stress intensity factor of a crack as it is simple and relatively straightforward to implement. It is relatively easy for implementation on top of any finite element (FE) code and it does not require the use of any special finite elements. It is usually utilized for fracture analysis of brittle materials when plastic dissipation is negligible, i.e., plastic dissipation belongs to small-scale yielding due to low load on a structural element. Obtained results showed that the application of VCCT yields good results. Results for crack propagation rate and total lifetime for three test cases were compared to available experimental data and showed satisfactory correlation. Full article
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12 pages, 6118 KiB  
Article
Microstructural Characterization of Friction-Stir Processed Ti-6Al-4V
by Sergey Mironov, Yutaka S. Sato, Hiroyuki Kokawa, Satoshi Hirano, Adam L. Pilchak and Sheldon Lee Semiatin
Metals 2020, 10(7), 976; https://doi.org/10.3390/met10070976 - 20 Jul 2020
Cited by 15 | Viewed by 3556
Abstract
The present work was undertaken to shed additional light on the globular-α microstructure produced during FSP of Ti-6Al-4V. To this end, the electron backscatter diffraction (EBSD) technique was employed to characterize the crystallographic aspects of such microstructure. In contrast to the previous reports [...] Read more.
The present work was undertaken to shed additional light on the globular-α microstructure produced during FSP of Ti-6Al-4V. To this end, the electron backscatter diffraction (EBSD) technique was employed to characterize the crystallographic aspects of such microstructure. In contrast to the previous reports in the literature, neither the texture nor the misorientation distribution in the α phase were random. Although the texture was weak, it showed a clear prevalence of the P1 and C-fiber simple-shear orientations, thus providing evidence for an increased activity of the prism-<a> and pyramidal <c+a> slip systems. In addition, the misorientation distribution exhibited a crystallographic preference of 60° and 90° boundaries. This observation was attributed to a partial α→β→α phase transformation during/following high-temperature deformation and the possible activation of mechanical twinning. Full article
(This article belongs to the Special Issue Titanium Alloys and Titanium-Based Matrix Composites)
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13 pages, 13397 KiB  
Article
DC Arc Plasma Treatment for Defect Reduction in WC-Co Granulated Powder
by Hirotomo Itagaki, Taisei Yachi, Hisato Ogiso, Harumichi Sato, Yorihiro Yamashita, Junichi Yasuoka and Yoshinori Funada
Metals 2020, 10(7), 975; https://doi.org/10.3390/met10070975 - 20 Jul 2020
Cited by 6 | Viewed by 3522
Abstract
Tungsten carbide–cobalt (WC–Co) agglomerated powder is widely used for additive manufacturing and spray coating, and a reduction in internal gaps in the powder is required to obtain a product of high quality. In this paper, we investigate plasma effects on agglomerated powder when [...] Read more.
Tungsten carbide–cobalt (WC–Co) agglomerated powder is widely used for additive manufacturing and spray coating, and a reduction in internal gaps in the powder is required to obtain a product of high quality. In this paper, we investigate plasma effects on agglomerated powder when WC–12%Co powder is directly subjected to direct current (DC) arc plasma treatment to reduce gaps in the WC–Co powder. We obtain a plasma-treated powder with reduced gaps among WC particles. Furthermore, plasma-treatment improves the sphericity of the powder particles, due to the spheroidization effect, so that the percentage of plasma-treated particles exceeding 95% sphericity is 50%, which is 1.7 times that of raw powder. Concern regarding the possible generation of W2C by plasma treatment is unfounded, with W2C levels kept very low according to X-ray diffraction (XRD) analysis, showing a value of 0.0075 for the area ratio W2C(002)/WC(100). XRD analysis also reveals that plasma treatment relaxes residual strains in the powder. From these results, the DC plasma treatment of WC agglomerated powder produces a spherical powder with fewer gaps and strains in the powder, making it more suitable for additive manufacturing while suppressing decarburization. Full article
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23 pages, 24515 KiB  
Article
Numerical Verification of Tests on the Influence of the Imposed Thermal Cycles on the Structure and Properties of the S700MC Heat-Affected Zone
by Tomasz Kik, Jacek Górka, Aleksandra Kotarska and Tomasz Poloczek
Metals 2020, 10(7), 974; https://doi.org/10.3390/met10070974 - 20 Jul 2020
Cited by 15 | Viewed by 3180
Abstract
The article presents the results of studies on the influence of simulated thermal cycles parameters on the structure and properties of the heat-affected zone (HAZ) of thermo-mechanically rolled S700MC steel. For this purpose, resistance heating tests of the tested samples were carried out [...] Read more.
The article presents the results of studies on the influence of simulated thermal cycles parameters on the structure and properties of the heat-affected zone (HAZ) of thermo-mechanically rolled S700MC steel. For this purpose, resistance heating tests of the tested samples were carried out to determine the effect of maximum temperatures of the imposed thermal cycles with different maximum temperatures at a constant cooling time in the temperature range between 800 and 500 °C (t8/5) and to study the influence of changes of this time on the structure and hardness as well as the tensile strength, elongation and toughness of the simulated HAZ in S700MC steel. The results of the tests, were supported by the results of finite element method (FEM) analyses in the VisualWeld (SYSWELD Code) software of the ESI Group. Selected heat distributions during heating, distributions of individual metallurgical phases and hardness were compared with results from real tests. On the basis of the results presented, an attempt was made to explain the decrease in mechanical and plastic properties in the HAZ area caused by the influence of the welding heat cycle. Full article
(This article belongs to the Special Issue Fusion Welding)
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15 pages, 18014 KiB  
Article
Numerical and Experimental Investigation of Germanium Refining via Fractional Crystallization Based Innovative Rotary Cooling Device
by Danilo C. Curtolo, Semiramis Friedrich, Michael Noack and Bernd Friedrich
Metals 2020, 10(7), 973; https://doi.org/10.3390/met10070973 - 18 Jul 2020
Cited by 2 | Viewed by 3543
Abstract
This paper focuses on the principle study and application of a fractional crystallization methodology using a rotating and internally gas cooled crystallizer (so called cooled finger, developed at IME/RWTH Aachen) first applied to the refining of germanium. For this purpose, a series of [...] Read more.
This paper focuses on the principle study and application of a fractional crystallization methodology using a rotating and internally gas cooled crystallizer (so called cooled finger, developed at IME/RWTH Aachen) first applied to the refining of germanium. For this purpose, a series of experimental trials were performed using a model metal—Aluminum—to gather the temperature profile needed for the numerical simulation that provides an initial process window used for the purification of germanium in a vacuum resistance furnace. The results of the simulation showed good agreement with the experimental results and the conducted trials based on that process window enabled the single step purification of germanium from an initial purity of 98.8% up to 99.9%. Full article
(This article belongs to the Special Issue 10th Anniversary of Metals: Metallurgy and Metal Technology)
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11 pages, 4091 KiB  
Communication
Toward a Fossil Free Future with HYBRIT: Development of Iron and Steelmaking Technology in Sweden and Finland
by Martin Pei, Markus Petäjäniemi, Andreas Regnell and Olle Wijk
Metals 2020, 10(7), 972; https://doi.org/10.3390/met10070972 - 18 Jul 2020
Cited by 127 | Viewed by 23458
Abstract
The Swedish and Finnish steel industry has a world-leading position in terms of efficient blast furnace operations with low CO2 emissions. This is a result of a successful development work carried out in the 1980s at LKAB (Luossavaara-Kiirunavaara Aktiebolag, mining company) and [...] Read more.
The Swedish and Finnish steel industry has a world-leading position in terms of efficient blast furnace operations with low CO2 emissions. This is a result of a successful development work carried out in the 1980s at LKAB (Luossavaara-Kiirunavaara Aktiebolag, mining company) and SSAB (steel company) followed by the closing of sinter plants and transition to 100% pellet operation at all of SSAB’s five blast furnaces. However, to further reduce CO2 emission in iron production, a new breakthrough technology is necessary. In 2016, SSAB teamed up with LKAB and Vattenfall AB (energy company) and launched a project aimed at investigating the feasibility of a hydrogen-based sponge iron production process with fossil-free electricity as the primary energy source: HYBRIT (Hydrogen Breakthrough Ironmaking Technology). A prefeasibility study was carried out in 2017, which concluded that the proposed process route is technically feasible and economically attractive for conditions in northern Sweden/Finland. A decision was made in February 2018 to build a pilot plant, and construction started in June 2018, with completion of the plant planned in summer 2020 followed by experimental campaigns the following years. Parallel with the pilot plant activities, a four-year research program was launched from the autumn of 2016 involving several research institutes and universities in Sweden to build knowledge and competence in several subject areas. Full article
(This article belongs to the Special Issue Challenges and Prospects of Steelmaking Towards the Year 2050)
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11 pages, 3897 KiB  
Article
Ultrasonic Assisted Sintering Using Heat Converted from Mechanical Energy
by Zhiyuan Liu, Yang Ge, Dandan Zhao, Yan Lou, Yong Liu, Yuan Wu, Peng Yu and Chunyan Yu
Metals 2020, 10(7), 971; https://doi.org/10.3390/met10070971 - 18 Jul 2020
Cited by 9 | Viewed by 3896
Abstract
A new sintering method, namely ultrasonic assisted sintering (UAS), has been proposed using mechanical heat converted from high frequency motion between particles. Pure aluminum specimens with diameter of 5 mm and thickness of ~2 mm have been successfully sintered in two seconds. Based [...] Read more.
A new sintering method, namely ultrasonic assisted sintering (UAS), has been proposed using mechanical heat converted from high frequency motion between particles. Pure aluminum specimens with diameter of 5 mm and thickness of ~2 mm have been successfully sintered in two seconds. Based on the thermodynamic analysis, the underlying heating mechanism is quantitatively interpreted, which involves high-frequency interparticle friction and plastic deformation driven by ultrasonic squeezing. Consequently, temperature rises rapidly at a speed of about 300 K/s, and the maximum temperature reaches up to 0.9 times of melting point of the aluminum during UAS. The sintered specimens have a high density of dislocations, under the combined effects of dislocations and undulating stress field, volume diffusion coefficient for sintering increases by several orders of magnitude, therefore, rapid densification can be accomplished in seconds. In addition, the sintered aluminum has ultrahigh nanohardness (~1.13 GPa), which can be attributed to the hierarchical structure formed during UAS process. Full article
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4 pages, 166 KiB  
Editorial
Forming Processes of Modern Metallic Materials
by Tomasz Trzepieciński
Metals 2020, 10(7), 970; https://doi.org/10.3390/met10070970 - 18 Jul 2020
Cited by 3 | Viewed by 2844
Abstract
The plastic working of metallic materials is one of the most efficient and important manufacturing technologies used in industry today [...] Full article
(This article belongs to the Special Issue Forming Processes of Modern Metallic Materials)
17 pages, 8161 KiB  
Article
Structural Properties of Interfacial Layers in Tantalum to Stainless Steel Clad with Copper Interlayer Produced by Explosive Welding
by Henryk Paul, Robert Chulist and Izabela Mania
Metals 2020, 10(7), 969; https://doi.org/10.3390/met10070969 - 17 Jul 2020
Cited by 16 | Viewed by 4311
Abstract
A systematic study of explosively welded tantalum and 304 L stainless steel clad with M1E copper interlayer was carried out to characterize the microstructure and mechanical properties of interfacial layers. Microstructures were examined using transmission and scanning (SEM) electron microscopy, whereas mechanical properties [...] Read more.
A systematic study of explosively welded tantalum and 304 L stainless steel clad with M1E copper interlayer was carried out to characterize the microstructure and mechanical properties of interfacial layers. Microstructures were examined using transmission and scanning (SEM) electron microscopy, whereas mechanical properties were evaluated using microhardness measurements and a bending test. The macroscale analyses showed that both interfaces between joined sheets were deformed to a wave-shape with solidified melt zones located preferentially at the crest of the wave and in the wave vortexes. The microscopic analyses showed that the solidified melt zones are composed of nano-/micro-crystalline phases of different chemical composition, incorporating elements from the joined sheets. SEM/electron backscattered diffraction (EBSD) measurements revealed the microstructure of layers of parent sheets that undergo severe plastic deformation causing refinement of the initial grains. It has been established that severely deformed areas can undergo recovery and recrystallization already during clad processing. This leads to the formation of new stress-free grains. The microhardness of welded sheets increases significantly as the joining interface is approaching excluding the volumes directly adhering to large melted zones, where a noticeable drop of microhardness, due to recrystallization, is observed. On lateral bending the integrity of the all clad components is conserved. Full article
(This article belongs to the Special Issue Impact Welding of Materials)
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12 pages, 4794 KiB  
Article
Influence of Particle Reinforcement and Heat Treatment on the Wear Resistance of Inductively Melted Hardpaint Coatings
by Patrick Schwarz, Sebastian Weber and Friederike Deuerler
Metals 2020, 10(7), 968; https://doi.org/10.3390/met10070968 - 17 Jul 2020
Cited by 2 | Viewed by 2551
Abstract
Wear-resistant coatings can reduce the high economic damage caused by wear processes. In this study, various protective layers based on the alloy X400CrVMo17-15-2 were investigated. Commonly, the prealloyed metal powder is used for plasma transferred arc powder surfacing. However, in this work, the [...] Read more.
Wear-resistant coatings can reduce the high economic damage caused by wear processes. In this study, various protective layers based on the alloy X400CrVMo17-15-2 were investigated. Commonly, the prealloyed metal powder is used for plasma transferred arc powder surfacing. However, in this work, the cost-efficient hardpaint technology was used to produce particle-reinforced (fused tungsten carbides) and non-reinforced coatings. To analyze the wear behavior, the coatings were subjected to abrasion wear and scratch tests. For the abrasion wear test, a grinding pin (Al2O3) is pressed with a defined force against the surface of the rotating sample for 6 h. For the scratch test, a loaded diamond pyramid indenter was employed to create a circular groove on the coatings at a predefined speed. The wear grooves were analyzed with the aid of laser scanning microscopy. In comparison to the coatings in the as-processed condition, the non-reinforced protective layers were investigated after quenching, with and without deep cryogenic treatment, and tempering. The determination of proper heat treatment parameters was supported by computational thermodynamics. It has been confirmed that it is possible to improve the wear resistance of the unreinforced coatings by heat treatment. However, the reinforced layers showed the highest resistance against abrasion. Full article
(This article belongs to the Special Issue Tribological Study of Metals)
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12 pages, 7348 KiB  
Article
Investigation on Solid-State Phase Transformations in a 2510 Duplex Stainless Steel Grade
by Irene Calliari, Marco Breda, Claudio Gennari, Luca Pezzato, Massimo Pellizzari and Andrea Zambon
Metals 2020, 10(7), 967; https://doi.org/10.3390/met10070967 - 17 Jul 2020
Cited by 19 | Viewed by 2996
Abstract
Duplex and Super Duplex Stainless Steels are very prone to secondary phases formation related to ferrite decomposition at high temperatures. In the present paper the results on secondary phase precipitation in a 2510 Duplex Stainless Steel, heat-treated in the temperature range 850–1050 °C [...] Read more.
Duplex and Super Duplex Stainless Steels are very prone to secondary phases formation related to ferrite decomposition at high temperatures. In the present paper the results on secondary phase precipitation in a 2510 Duplex Stainless Steel, heat-treated in the temperature range 850–1050 °C for 3–30 min are presented. The precipitation starts at grain boundaries with a consistent ferrite transformation for very short times. The noses of the Time–Temperature–Precipitation (TTP) curves are at 1000 °C for σ-phase and at 900 °C for χ-phase, respectively. The precipitation sequence involves a partial transformation of χ into σ, as previously evidenced in 2205 and 2507 grades. Furthermore, the experimental data were compared to the results of Thermo-Calc calculations. Understanding and ability to predict phase stability in 2510 duplex stainless steel is a key factor to design optimal welding processes that avoid any secondary phase precipitation in the weld bead as well as in the heat-affected zone. Full article
(This article belongs to the Special Issue Heat Treatment of Iron- and Aluminum-Based Alloys)
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17 pages, 2368 KiB  
Article
Influence of Heat Treatment on the Corrosion Resistance of Aluminum-Copper Coating
by Mieczyslaw Scendo, Slawomir Spadlo, Katarzyna Staszewska-Samson and Piotr Mlynarczyk
Metals 2020, 10(7), 966; https://doi.org/10.3390/met10070966 - 17 Jul 2020
Cited by 6 | Viewed by 2980
Abstract
Influence of heat treatment on the corrosion resistance of the aluminum-copper (Al-Cu) coating on the aluminum substrate was investigated. The coating was produced by the electrical discharge alloying (EDA) method. The surface and microstructure of the specimens were observed by a scanning electron [...] Read more.
Influence of heat treatment on the corrosion resistance of the aluminum-copper (Al-Cu) coating on the aluminum substrate was investigated. The coating was produced by the electrical discharge alloying (EDA) method. The surface and microstructure of the specimens were observed by a scanning electron microscope (SEM). The phase analysis of the composite materials by X-ray diffraction (XRD) and energy-dispersive spectroscopy (EDS) indicated that intermetallic compounds (i.e., CuAl2 and Cu9Al4) were formed through reactions between Al and Cu. during the EDA process. A significant increase in the hardness of the Al-Cu coating was affected by the improvement of the alloy structure. The heat treatment of materials was carried out at 400 °C or 600 °C in the air atmosphere. A corrosion test of materials was carried out by using electrochemical methods. The corrosive environment was acidic chloride solution. After heat treatment at 400 °C the mechanical properties of the Al/Cu alloy increased significantly and the oxide layer protect of the alloy surface against corrosion. However, after heat treatment at elevated temperature, i.e., 600 °C it was found that the (Al2O3)ads and (CuO)ads coatings were destroyed. The mechanical properties of the Al/Cu alloy decreased, and its surface has undergone deep electrochemical corrosion. Full article
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14 pages, 3677 KiB  
Article
Concurrent Multiscale Simulations of Rough Lubricated Contact of Aluminum Single Crystal
by Jie Zhang, Lihong Su and Zhongnan Wang
Metals 2020, 10(7), 965; https://doi.org/10.3390/met10070965 - 17 Jul 2020
Cited by 3 | Viewed by 2657
Abstract
In this paper, a concurrent multiscale simulation strategy coupling atomistic and continuum models was proposed to investigate the three-dimensional contact responses of aluminum single crystal under both dry and lubricated conditions. The Hertz contact is performed by using both the multiscale and full [...] Read more.
In this paper, a concurrent multiscale simulation strategy coupling atomistic and continuum models was proposed to investigate the three-dimensional contact responses of aluminum single crystal under both dry and lubricated conditions. The Hertz contact is performed by using both the multiscale and full molecular dynamics (MD) simulations for validation. From the contact area, kinetic energy and stress continuity aspects, the multiscale model shows good accuracy. It can also save at least five times the computational time compared with the full MD simulations for the same domain size. Furthermore, the results of lubricated contact show that the lubricant molecules could effectively cover the contact surfaces; thereby separating the aluminum surfaces and bearing the support loads. Moreover, the surface topography could be protected by the thin film formed by the lubricant molecules. It has been found that the contact area decreases obviously with increasing the magnitude of load under both dry and lubricated contacts. Besides, a decrease in contact area is also seen when the number of lubricant molecules increases. The present study has confirmed that the dimension of lubricated contacts could be greatly expanded during the simulation using the proposed multiscale method without sacrificing too much computational time and accuracy. Full article
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18 pages, 7716 KiB  
Article
Bidirectional Response of Weak-Axis End-plate Moment Connections: Numerical Approach
by Eduardo Nuñez, Guillermo Parraguez and Ricardo Herrera
Metals 2020, 10(7), 964; https://doi.org/10.3390/met10070964 - 17 Jul 2020
Cited by 6 | Viewed by 6136
Abstract
Brittle failure mechanisms can affect the seismic performance of structures composed of intersecting moment resisting frames, if the biaxial effects are not considered. In this research, the bidirectional cyclic response of H-columns with weak-axis moment connections was studied using numerical models. Several configurations [...] Read more.
Brittle failure mechanisms can affect the seismic performance of structures composed of intersecting moment resisting frames, if the biaxial effects are not considered. In this research, the bidirectional cyclic response of H-columns with weak-axis moment connections was studied using numerical models. Several configurations of joints with bidirectional effects and variable axial loads were studied using the finite element method (FEM) in ANSYS v17.2 software. The results obtained showed a ductile behavior when cyclic loads are applied. No evidence of brittle failure mechanisms in the studied joint configurations was observed, in line with the design philosophy established in current seismic provisions. However, beams connected to the column minor axis reached a partially restrained behavior. Joints with four beams connected to the column exhibited a partially restrained behavior for all axial load levels. An equivalent force displacement method was used to compare the hysteretic response of 2D and 3D joints, obtaining higher deformations in 3D joints with respect to 2D joints with a similar number of connected beams. Consequently, design procedures are not capable of capturing the 3D deformation phenomenon. Full article
(This article belongs to the Special Issue Advances in Structural Steel Research)
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13 pages, 20784 KiB  
Article
Effect of Vacuum Annealing on the Nickel-Based Coatings Deposited on a CGI Cast Iron through Atmospheric Plasma Spraying
by Peihu Gao, Baiyang Chen, Shencong Zeng, Zhong Yang, Yongchun Guo, Minxian Liang, Tao Xu and Jianping Li
Metals 2020, 10(7), 963; https://doi.org/10.3390/met10070963 - 16 Jul 2020
Cited by 7 | Viewed by 2477
Abstract
Plasma-sprayed nickel-based self-fusion alloy coatings were annealed in a vacuum at 990, 1020 and 1050 °C for 20 min to increase the bonding between the compacted graphite cast iron substrate and coating, as well as the inner cohesion of the coatings. It was [...] Read more.
Plasma-sprayed nickel-based self-fusion alloy coatings were annealed in a vacuum at 990, 1020 and 1050 °C for 20 min to increase the bonding between the compacted graphite cast iron substrate and coating, as well as the inner cohesion of the coatings. It was found that nickel and chromium diffused between nickel-based alloy coatings and compacted graphite cast iron substrate. A metallurgical translation zone with a thickness up to 1145 μm formed during the vacuum annealing, which resulted in an enhancement of the adhesion between the coating and substrate. The adhesion strength at room temperature was increased from the as-sprayed coating of 33.4 MPa to the annealed one of 163 MPa. Meanwhile, the adhesion strength at 500 °C reached 146 MPa. Conversely, the inner cohesion of the coating was improved with the particles’ interfaces healed after vacuum annealing. The micro-hardness of the annealed coatings was increased to 902 HV from the as-sprayed one of 578 HV. Full article
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25 pages, 9316 KiB  
Article
The Effect of the Processing Parameters on the Properties of the Liquid Phase Spark Plasma Sintered 80Fe-20(Al + MWCNT) Magnetic Metal Matrix Nanocomposites
by Alexandre Tugirumubano, Sun Ho Go, Lee Ku Kwac, Hee Jae Shin and Hong Gun Kim
Metals 2020, 10(7), 962; https://doi.org/10.3390/met10070962 - 16 Jul 2020
Cited by 2 | Viewed by 2785
Abstract
In this paper, the liquid phase sintering was performed using spark plasma sintering to produce iron (Fe: 80 vol%)–aluminum (Al)–multi-walled carbon nanotubes (MWCNTs) magnetic hybrid metal matrix nanocomposites. The properties of the nanocomposites were investigated by considering different parameters of materials processing. The [...] Read more.
In this paper, the liquid phase sintering was performed using spark plasma sintering to produce iron (Fe: 80 vol%)–aluminum (Al)–multi-walled carbon nanotubes (MWCNTs) magnetic hybrid metal matrix nanocomposites. The properties of the nanocomposites were investigated by considering different parameters of materials processing. The reinforcement of MWCNT with a content of 0–2 vol% did not affect the saturation magnetization of the nanocomposites but increased the coercivity and reduced both the electrical resistivity and the mechanical transverse rupture strength. It was found that milling the powders for 24 h resulted in composite with high saturation magnetization (148.820 A·m2/kg) and high coercivity (2175.6 A/m) but further milling time had reduced the values of magnetic properties. The mixture of Fe nanoparticles and Fe microparticles in composites with a nanoparticles-to-microparticles volume ratio of 1:1 has led to the enhanced saturation magnetization up to 157.820 A·m2/kg and reduced the coercivity of 50.20% in comparison with the Fe nanoparticles based nanocomposites. That mixture exhibited good electrical resistivity but caused the reduction of mechanical strength. The post-sintering annealing has significantly improved the magnetic softness of the composites by reducing the coercivity up to 854.30 A/m and increased the saturation magnetization. Full article
(This article belongs to the Special Issue Spark Plasma Sintering of Metals and Metal Matrix Nanocomposites)
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14 pages, 7124 KiB  
Article
Microstructural Investigations of Novel High Temperature Alloys Based on NiAl-(Cr,Mo)
by Camelia Gombola, Alexander Kauffmann, Golnar Geramifard, Malte Blankenburg and Martin Heilmaier
Metals 2020, 10(7), 961; https://doi.org/10.3390/met10070961 - 16 Jul 2020
Cited by 13 | Viewed by 3170
Abstract
Apart from the reported transition from the fibrous morphology in NiAl-34Cr to lamellae by adding 0.6 at.% Mo, further morphology transformations along the eutectic trough in the NiAl-(Cr,Mo) alloys were observed. Compositions with at least 10.3 at.% Cr have lamellar morphology while the [...] Read more.
Apart from the reported transition from the fibrous morphology in NiAl-34Cr to lamellae by adding 0.6 at.% Mo, further morphology transformations along the eutectic trough in the NiAl-(Cr,Mo) alloys were observed. Compositions with at least 10.3 at.% Cr have lamellar morphology while the first tendency to fiber formation was found at 9.6 at.% Cr. There is a compositional range, where both lamellae and fibers are present in the microstructure and a further decrease in Cr to 1.8at.% Cr results in fully fibrous morphology. Alongside these morphology changes of the (Cr,Mo)ss reinforcing phase, its volume fraction was found to be from 41 to 11 vol.% confirming the trend predicted by the CALPHAD approach. For mixed morphologies in-situ X-ray diffraction experiments performed between room and liquidus temperature accompanied by EDX measurements reveal the formation of a gradient in composition for the solid solution. A new Mo-rich NiAl-9.6Cr-10.3Mo alloy clearly shows this effect in the as-cast state. Moreover, crystallographic orientation examination yields two different types of colonies in this composition. In the first colony type, the orientation relationship between NiAl matrix and (Cr,Mo)ss reinforcing phase was ( 100 ) NiAl|| ( 100 ) Cr,Mo and 100 NiAl|| 100 Cr,Mo. An orientation relationship described by a rotation of almost 60° about 111 was found in the second colony type. In both cases, no distinct crystallographic plane as phase boundary was observed. Full article
(This article belongs to the Special Issue Advances in Superalloys and High Temperature Intermetallics)
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14 pages, 1481 KiB  
Article
Preparing Sc-Bearing Master Alloy Using Aluminum–Magnesium Thermoreduction Method
by Junhui Xiao, Wei Ding, Yang Peng, Tao Chen and Kai Zou
Metals 2020, 10(7), 960; https://doi.org/10.3390/met10070960 - 16 Jul 2020
Cited by 8 | Viewed by 3495
Abstract
In this study, preparation of Al–Mg–Sc master alloy tests were carried out by Al–Mg thermoreduction method. Stirring by blowing argon and pressing with molten salt jar were adopted to reduce scandium segregation and upgrading scandium recovery of scandium-bearing master alloy. The results show [...] Read more.
In this study, preparation of Al–Mg–Sc master alloy tests were carried out by Al–Mg thermoreduction method. Stirring by blowing argon and pressing with molten salt jar were adopted to reduce scandium segregation and upgrading scandium recovery of scandium-bearing master alloy. The results show that the Al–Mg–Sc master alloy ingot contained 2.90% Sc, 5.73% Mg, 0.0058% Cu, 0.29%, 0.029% Ti, 0.13% Fe, 0.075% Zn, 0.025% Na, and 96.72% recovered scandium obtained under the comprehensive conditions used: m(Al): m(Mg): m(ScCl3) = 10:1:1.5, stirring speed of eight rpm, reduction temperature of 1223 K, reduction time of 40 min. The experimental results are in agreement with the thermodynamic predictions, and Al–Mg–Sc master alloy indicator was ideal. Full article
(This article belongs to the Special Issue Aluminum Alloys and Aluminum Matrix Composites)
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12 pages, 4522 KiB  
Article
Precipitate Characterization in Model Al-Zn-Mg-(Cu) Alloys Using Small-Angle X-ray Scattering
by Daniel Freiberg, Wenhui Zhu, Jun-Sang Park, Jonathan D. Almer and Paul Sanders
Metals 2020, 10(7), 959; https://doi.org/10.3390/met10070959 - 16 Jul 2020
Cited by 7 | Viewed by 3490
Abstract
Model 7000 series alloys with and without copper were fabricated into sheets to study precipitation hardening behavior under isothermal aging conditions. Samples of each alloy were subjected to 3 h annealing treatments at various temperatures to produce a range of precipitate size distributions. [...] Read more.
Model 7000 series alloys with and without copper were fabricated into sheets to study precipitation hardening behavior under isothermal aging conditions. Samples of each alloy were subjected to 3 h annealing treatments at various temperatures to produce a range of precipitate size distributions. Hardness, electrical conductivity, and small-angle X-ray scattering (SAXS) were used to characterize the aging behavior of the two alloys. Precipitate size distributions were modeled from the scattering curves for each annealing condition using a maximum entropy method (MEM) and compared to select transmission electron microscopy (TEM) results. The measured average precipitate diameters from TEM were in good agreement with the average precipitate diameters determined from the scattering curves. Full article
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16 pages, 8535 KiB  
Article
Microstructural and Wear Properties of Annealed Medium Carbon Steel Plate (EN8) Cladded with Martensitic Stainless Steel (AISI410)
by Shubrajit Bhaumik, Manidipto Mukherjee, Parijat Sarkar, Anish Nayek and Viorel Paleu
Metals 2020, 10(7), 958; https://doi.org/10.3390/met10070958 - 16 Jul 2020
Cited by 7 | Viewed by 4307
Abstract
Limited work on the wear properties of martensitic stainless-steel weld clads initiated this work which included investigations on microstructural and wear properties of cladded AISI 410 (filler wire)/EN 8 plates (substrate). Three layers of martensitic stainless steel (AISI 410) were deposited using metal [...] Read more.
Limited work on the wear properties of martensitic stainless-steel weld clads initiated this work which included investigations on microstructural and wear properties of cladded AISI 410 (filler wire)/EN 8 plates (substrate). Three layers of martensitic stainless steel (AISI 410) were deposited using metal inert gas (MIG) welding on medium carbon steel (EN 8) achieving a 51.5 ± 2.35 HRC of top layer. The elemental and phase fractions of the cladded layers indicated 98% martensite phase and retained austenite (2%). About 40% dilution was observed between EN 8 and the first weld layer. The results of tests carried out on pin on disc tribometer revealed an enhancement of anti-wear life of the martensitic weld cladded EN 8 by three times that of uncladded EN 8. The uncladded EN 8 plate suffered severe damage and high wear, leading to its failure at 478 s. The failure of the uncladded EN 8 sample was identified by the occurrence of high vibration of the pin on disc tribometer which ultimately stopped the tribometer. On the other hand, the cladded EN 8 sample continued running for 3600 s, exhibiting normal wear. After the tribo test, the surfaces of the pins of both cladded and uncladded EN 8 were analyzed using scanning electron microscope (SEM) and 3D profilometer. The surface characterization of tribo pairs indicated ploughing and galling to be the primary wear mechanisms. The average grain size of top and middle layer was in the range of 2–3.5 µm, while the base metal showed 5.02 µm mean grain size, resulting in higher hardness of clad layers than base metal, also favoring better wear resistance of the cladded EN 8 samples as compared to uncladded EN 8 samples. Full article
(This article belongs to the Special Issue Friction and Wear of Metals)
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19 pages, 10236 KiB  
Article
Effect of Annealing Prior to Cold Rolling on the Microstructure Evolution and Energy Losses of Low-Si, Ultra-Low-C Hot-Rolled Electrical Steel
by Héctor Ortiz Rangel, Armando Salinas Rodríguez and Omar García Rincón
Metals 2020, 10(7), 957; https://doi.org/10.3390/met10070957 - 16 Jul 2020
Cited by 3 | Viewed by 3415
Abstract
The microstructure of a low Si, ultra-low-C, hot-rolled electrical steel strip is modified by annealing at T < To, the α→γ transformation temperature. This heat treatment causes the abnormal anisotropic growth of surface grains which consumes the original hot-rolled microstructure. The growth of [...] Read more.
The microstructure of a low Si, ultra-low-C, hot-rolled electrical steel strip is modified by annealing at T < To, the α→γ transformation temperature. This heat treatment causes the abnormal anisotropic growth of surface grains which consumes the original hot-rolled microstructure. The growth of the surface grains first takes place parallel to the rolling direction and then in a columnar form parallel to the normal direction until grains growing in opposite directions from the surfaces impinge at the center of the strip. It is shown that cold rolling and a short annealing treatment at temperatures between 700 and 800 °C leads to microstructures which result in iron energy losses that can be as much as 30% lower than those observed in the same material not subjected to the annealing prior to cold rolling. The magnitude of the reduction in energy losses depends on strip thickness and processing parameters. The major effect is observed in material annealed at 710 °C and the relative effect (with respect to material that is not annealed prior to cold rolling) decreases as the strip thickness decreases. It is shown that these effects can be attributed to the effect of the processing conditions on texture and grain size. The maximum reduction in energy losses is observed when the final microstructure consists of ferrite grains ~1.5 times larger than those obtained if the material is not annealed prior to cold rolling. Full article
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21 pages, 8123 KiB  
Article
Hot Deformation Behaviors and Intrinsic Hot Workability Map of Ti-12Mo-4Zr-5Sn Alloy Based on Physical Model and Polar Reciprocity Model
by Peng Wan, Hang Zou, Kelu Wang, Zhengzhi Zhao, Shiqiang Lu and Huifen Nie
Metals 2020, 10(7), 956; https://doi.org/10.3390/met10070956 - 15 Jul 2020
Cited by 7 | Viewed by 2475
Abstract
The hot compression tests of Ti-12Mo-4Zr-5Sn alloy were tested on the thermo-mechanical simulator of Gleeble-3500 under isothermal and constant strain rate. We studied this alloy’s behavior during thermal deformation at the conditions of T = 670~820 °C, ε ˙ = 0.001~10 s−1 [...] Read more.
The hot compression tests of Ti-12Mo-4Zr-5Sn alloy were tested on the thermo-mechanical simulator of Gleeble-3500 under isothermal and constant strain rate. We studied this alloy’s behavior during thermal deformation at the conditions of T = 670~820 °C, ε ˙ = 0.001~10 s−1, and deformation degree 70%. The rheological stress curves of the alloy were modified, the characteristics of the rheological stress curves were analyzed, and the activation energy map of hot deformation was established. A physical constitutive model of the alloy based on strain compensation was established, which has taken the relationship between Young’s modulus and self-diffusion coefficient and temperature into account. Moreover, the intrinsic hot workability ξ map of the alloy was established based on the polar reciprocity model. The results show that this alloy’s rheological stress will descend when the temperature of deformation rises and grow when the strain rate increases, and has negative sensitivity of temperature and positive sensitivity of strain rate. According to the error calculation, the physical constitutive model’s correlation coefficient is 0.9910 and the average relative error is 3.97%, which has good accuracy. Through the analysis of the microstructures of the instability zone and the stability zone, it was found that the instability mode of the instability zone was dominated by the local flow, and the deformation mechanism of the stability zone was dominated by the dynamic recrystallization. The optimum processing parameters of the alloy known from ξ map and metallographic structure are the following: T = 790~820 °C and ε ˙ = 0.001~0.01 s−1. Full article
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