Metals

11 pages, 3370 KiB

Open AccessArticle

Effect of Cooling Rate after Solution Treatment on Subsequent Phase Separation Evolution in Super Duplex Stainless Steel 25Cr-7Ni (wt.%)

by Jianling Liu, Yadunandan Das, Stephen M. King, Jan Y. Jonsson, Sten Wessman and Peter Hedström

Metals 2022, 12(5), 890; https://doi.org/10.3390/met12050890 - 23 May 2022

Cited by 4 | Viewed by 2142

Abstract

The effect of cooling rate after solution treatment on the initial structure of super duplex stainless steel 25Cr-7Ni (wt.%), and the effect of the initial structure on phase separation (PS) evolution during subsequent aging were investigated. The nanostructure in the bulk of the [...] Read more.

The effect of cooling rate after solution treatment on the initial structure of super duplex stainless steel 25Cr-7Ni (wt.%), and the effect of the initial structure on phase separation (PS) evolution during subsequent aging were investigated. The nanostructure in the bulk of the steel was studied using small-angle neutron scattering (SANS). Ex situ SANS experiments showed that the rate of PS differs during aging, due to the different initial structures imposed by the difference in cooling rate after solution treatment. In situ SANS experiments revealed that the PS is already pronounced after aging at 475 °C for 180 min and that a slower cooling rate after solution treatment will lead to more significant PS. Hence, PS depends on the plate thickness, imposing different cooling rates in the production of duplex stainless steels. Full article

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14 pages, 3097 KiB

Open AccessArticle

Atomistic Investigation on the Strengthening Mechanism of Single Crystal Ni-Based Superalloy under Complex Stress States

by Bin Xie, Xinyu Wang, Yongsheng Fan and Ruizhi Li

Metals 2022, 12(5), 889; https://doi.org/10.3390/met12050889 - 23 May 2022

Cited by 4 | Viewed by 2435

Abstract

Single crystal Ni-based superalloy, with excellent mechanical properties in high temperature, always works under complex stress states, including multiaxial tension and compression, which results in various strengthening mechanisms. In this paper, the atomistic simulation is applied to investigate the microstructure evolution under complex [...] Read more.

Single crystal Ni-based superalloy, with excellent mechanical properties in high temperature, always works under complex stress states, including multiaxial tension and compression, which results in various strengthening mechanisms. In this paper, the atomistic simulation is applied to investigate the microstructure evolution under complex mechanical loading conditions, including uniaxial, equibiaxial, and non-equibiaxial tensile–compressive loadings. By comparison of the strain–stress curves and analysis of dislocation motion, it is believed that the tension promotes the bowing out of dislocations into the channel at loading direction, while compression limits it. Moreover, the dislocation analysis shows that the initial dislocation network, comprised of Lomer dislocations, will dissociate to form Lomer–Cottrell lock upon loading, which acts as a barrier to the further glide of dislocations. The mechanism of dislocation evolution is analyzed in detail by combining Schmid factor analysis and the comparison of energy density difference between γ and γ′ phases. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Properties of Nanoscale Metallic Materials)

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18 pages, 10699 KiB

Open AccessArticle

The Microstructure Evolution of Mg-RE Alloy Produced by Reciprocating Upsetting Extrusion during Hot Compression

by Ziwei Zhang, Jianmin Yu, Zeru Wu, Hongbing Hu, Zhimin Zhang, Mo Meng, Yong Xue and Xubin Li

Metals 2022, 12(5), 888; https://doi.org/10.3390/met12050888 - 23 May 2022

Viewed by 1833

Abstract

Mg-13Gd-4Y-2Zn-0.4Zr (wt. %) alloy bar produced by three passes reciprocating upsetting extrusion (named as RUE-ed bar) exhibited fine grain with the average grain size of 3.02 μm. Hot compression tests of the RUE-ed bar were carried out on Gleeble-3800 compression unit at different [...] Read more.

Mg-13Gd-4Y-2Zn-0.4Zr (wt. %) alloy bar produced by three passes reciprocating upsetting extrusion (named as RUE-ed bar) exhibited fine grain with the average grain size of 3.02 μm. Hot compression tests of the RUE-ed bar were carried out on Gleeble-3800 compression unit at different deformation temperatures (653, 683, 713, and 743 K) and strain rates (0.001–1 s, 0.01–1 s, 0.1–1 s, and 0.5–1 s). This alloy showed work hardening and softening stages in hot compression, the thermal activation energy of the RUE-ed bar was 150 ± 1 kJ/mol and the constitutive equation was:

\dot{ε} = 1.80 \times 10^{9} {[\sinh (0.0174 σ)]}^{2.47} e x p [- \frac{150 \times 10^{3}}{8.314 \times T}]

. Numerous Mg₅ (Gd, Y, Zn) phase re-dissolved in α-Mg matrix appeared in the RUE-ed samples during hot compression deformation. The movement of the dislocation stimulated the re-dissolution of the Mg₅ (Gd, Y, Zn) phase. The re-dissolution of Mg₅ (Gd, Y, Zn) phase promoted texture strengthening and DRX grains growth in this experiment. In addition, the transformation and kinking of LPSO phase played an important coordinating role in the process of hot compression; 18R-LPSO was changed to 14H-LPSO phase at low strain rate while the LPSO phase kinked dominant to coordinated deformation at high strain rate. Full article

(This article belongs to the Topic Advanced Forming Technology of Metallic Materials)

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10 pages, 2383 KiB

Open AccessEditor’s ChoiceArticle

A New Strategy for Dissimilar Material Joining between SiC and Al Alloys through Use of High-Si Al Alloys

by Yongjing Yang, Ayan Bhowmik, Jin Lee Tan, Zehui Du and Wei Zhou

Metals 2022, 12(5), 887; https://doi.org/10.3390/met12050887 - 23 May 2022

Cited by 1 | Viewed by 2565

Abstract

Joining metals and ceramics plays a crucial role in many engineering applications. The current research aims to develop a simple and convenient approach for dissimilar material joining between SiC and Al alloys. In this work, Al alloys with Si contents varying from 7 [...] Read more.

Joining metals and ceramics plays a crucial role in many engineering applications. The current research aims to develop a simple and convenient approach for dissimilar material joining between SiC and Al alloys. In this work, Al alloys with Si contents varying from 7 wt.% to 50 wt.% were bonded with SiC at a high temperature of 1100 °C by a pressure-less bonding process in a vacuum furnace, and shear tests were carried out to study the bonding strength. When using low-Si Al alloys to bond with SiC, the bonding strength was very low. The bonding strength of Al/SiC joints increased significantly through the use of high-Si Al alloys with 30 wt.% and 50 wt.% Si. The shear strength achieved (28.8 MPa) is far higher than those reported previously. The remarkable improvement in bonding strength is attributed to the suppression of brittle interfacial products and reduced thermal stresses. This research provides a new strategy for joining between SiC and a wide range of Al alloys through the use of high-Si Al alloys as the interlayers. Full article

(This article belongs to the Special Issue Advances in Welding, Joining and Surface Coating Technology)

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16 pages, 5129 KiB

Open AccessArticle

Macro-Micro-Coupling Simulation and Space Experiment Study on Zone Melting Process of Bismuth Telluride-Based Crystal Materials

by Huxiang Xia, Xiaoya Li and Qingyan Xu

Metals 2022, 12(5), 886; https://doi.org/10.3390/met12050886 - 23 May 2022

Cited by 1 | Viewed by 1934

Abstract

Zone melting is one of the main techniques for preparing bismuth telluride-based crystal thermoelectric materials. In this research, a macro-micro-coupled simulation model was established to analyze the distribution of temperature and heat flow during the zone melting process. The simulation results show the [...] Read more.

Zone melting is one of the main techniques for preparing bismuth telluride-based crystal thermoelectric materials. In this research, a macro-micro-coupled simulation model was established to analyze the distribution of temperature and heat flow during the zone melting process. The simulation results show the melting temperature tends to affect the length of the melting zone, while the moving velocity of the melting furnace tends to affect the curvature of the melting and solidification interface. There are two small plateaus observed in the temperature curve of the central axis of bismuth telluride ingot when the moving velocity of the heat source is higher than 20 mm/h. As the moving velocity of the heat source increases, the platform effect is becoming more obvious. Based on the simulation results, the zone melt experiments were carried out both under microgravity condition on the Tiangong II space laboratory and conventional gravity condition on the ground. The experimental results indicate that the bismuth telluride-based crystal prepared in microgravity tends to possess more uniform composition. This uniform composition will lead to more uniform thermoelectric performance for telluride-based crystals. In the space condition, the influence of surface tension is much higher than that of gravity. The bismuth telluride ingot is very vulnerable to the influence of surface tension on the surface morphology during the solidification process. If the solidification process is not well controlled, it will be easier to produce uneven surface morphology. Full article

(This article belongs to the Special Issue Solidification and Casting of Engineering Metals: Modeling and Simulation)

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11 pages, 3143 KiB

Open AccessArticle

Liquid Formation in Sinters and Its Correlation with Softening Behaviour

by Vaishak Kamireddy, Dongqing Wang, Wen Pan, Shaoguo Chen, Tim Evans, Fengqiu Tang, Baojun Zhao and Xiaodong Ma

Metals 2022, 12(5), 885; https://doi.org/10.3390/met12050885 - 23 May 2022

Cited by 3 | Viewed by 2102

Abstract

Modern blast furnaces with extensive operational volume demand better-quality iron agglomerates as feed for stable operation. Sinter is the principal feed used in blast furnaces across Asia. Liquid generated during the sintering process plays an essential role in the coalescence of the sinter [...] Read more.

Modern blast furnaces with extensive operational volume demand better-quality iron agglomerates as feed for stable operation. Sinter is the principal feed used in blast furnaces across Asia. Liquid generated during the sintering process plays an essential role in the coalescence of the sinter blend and in sinter quality. Therefore, an estimation of liquid properties at peak bed conditions during sintering helps manage sintering liquid behaviour, leading to better control of final sinter properties. In this study, three different iron sinters were reheated to sinter bed conditions, followed by quenching. Electron probe X-ray microanalysis (EPMA) was used to identify the resultant phases and quantify their chemical compositions. The impact of sinter bulk compositions was analysed, especially on sintering liquid properties. Furthermore, experiments were conducted to study the softening and melting behaviour of the sinters, and the cohesive range of the sinters was identified. Finally, the effect of the sinter bulk compositions on sintering liquid properties and softening behaviour is detailed. Full article

(This article belongs to the Special Issue Fundamentals of Advanced Pyrometallurgy)

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9 pages, 2923 KiB

Open AccessArticle

Enhanced Mechanical Performance of a Biodegradable Fe–Mn Alloy Manufactured by Metal Injection Molding and Minor Carbon Addition

by Ye Zhang, Song Li, Dongyang Li, Yimin Li, Hao He and Chang Shu

Metals 2022, 12(5), 884; https://doi.org/10.3390/met12050884 - 23 May 2022

Cited by 2 | Viewed by 2053

Abstract

At present, FeMn-based degradable alloys prepared by direct sintering generally face the problems of Mn volatilization, difficult densification, and poor mechanical properties. In this work, a Fe-35Mn-0.5C alloy with low Mn volatility, high density, and favorable mechanical properties is fabricated by the metal [...] Read more.

At present, FeMn-based degradable alloys prepared by direct sintering generally face the problems of Mn volatilization, difficult densification, and poor mechanical properties. In this work, a Fe-35Mn-0.5C alloy with low Mn volatility, high density, and favorable mechanical properties is fabricated by the metal injection molding (MIM) process. The effects of sintering pressure and minor carbon addition on microstructure and mechanical properties were studied. The corresponding mechanical deformation mechanism was discussed. The results show that a significant reduction in the proportion of Mn volatilization to less than 0.5% and higher relative density of 97 ± 0.30% are achieved in the MIM-treated Fe-35Mn-0.5C alloy by pressurized sintering at 5 atm and 0.5 wt.% carbon addition. The optimized tensile properties are attained, with an ultimate tensile strength of 772 MPa, yield strength of 290 MPa, and elongation of 35% at room temperature, which meets the mechanical needs of metallic materials for biologically implantable medical devices. Full article

(This article belongs to the Topic Advanced Forming Technology of Metallic Materials)

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17 pages, 7411 KiB

Open AccessArticle

Effect of 1wt%Zn Addition on Microstructure and Mechanical Properties of Mg-6Er Alloys under High Strain Rates

by Hui Yu, Junchao Ren, Shaoming Kang, Wei Yu, Zhifeng Wang, Jianhang Feng, Qingzhou Wang, Puguang Ji, Xin Zhang and Fuxing Yin

Metals 2022, 12(5), 883; https://doi.org/10.3390/met12050883 - 23 May 2022

Cited by 2 | Viewed by 1890

Abstract

In this study, we investigated the high strain rate response of Mg-6wt%Er alloys with 1wt%Zn addition by split Hopkinson pressure bar (SHPB) tests in a range of 900–2500 s⁻¹. Their related microstructures were also characterized by optical microscopy (OM), scanning electron [...] Read more.

In this study, we investigated the high strain rate response of Mg-6wt%Er alloys with 1wt%Zn addition by split Hopkinson pressure bar (SHPB) tests in a range of 900–2500 s⁻¹. Their related microstructures were also characterized by optical microscopy (OM), scanning electron microscopy (SEM), electron back-scattering diffraction (EBSD), and transmission electron microscopy (TEM). In particular, the twinning and stacking faults (SFs) in Mg-6Er and Mg-6Er-1Zn alloys are characterized, and the interactions between twin/SFs and dislocations are analyzed in detail. Compared with twins, the dispersed and dense SFs seem to more readily interact with dislocations, resulting in the enhancement of the strength of alloys. Especially at a high strain rate of 1450 s⁻¹, dislocations are prone to tangle around the twins and SFs, forming low-angle grain boundaries (LAGBs). The addition of Zn in Mg-6Er can make LAGBs more easily transform into high-angle grain boundaries (HAGBs) due to the existence of SFs. Full article

(This article belongs to the Special Issue Forming Mechanism for Extrusion of Metals and Alloys)

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18 pages, 4625 KiB

Open AccessArticle

Fractionation of Transition Metals by Solvent Extraction and Precipitation from Tannic Acid-Acetic Acid Leachate as a Product of Lithium-Ion Battery Leaching

by Erik Prasetyo, Corby Anderson, Arya Fitra Jaya, Widya Aryani Muryanta, Anton Sapto Handoko, Muhammad Amin, Muhammad Al Muttaqii and Fathan Bahfie

Metals 2022, 12(5), 882; https://doi.org/10.3390/met12050882 - 23 May 2022

Cited by 1 | Viewed by 2327

Abstract

Solvent extraction and precipitation schemes are applied to isolate copper, cobalt, manganese and nickel from leachate, produced from spent lithium-ion battery leaching using tannic acid-acetic acid as lixiviant. The metal separation and purification were developed based on a ketoxime (LIX^® 84-I) and [...] Read more.

Solvent extraction and precipitation schemes are applied to isolate copper, cobalt, manganese and nickel from leachate, produced from spent lithium-ion battery leaching using tannic acid-acetic acid as lixiviant. The metal separation and purification were developed based on a ketoxime (LIX^® 84-I) and a phosphinic acid (Cyanex^® 272) extraction system. Aside from the leachate’s initial pH, which dictates the metal isolation flowsheet, other parameters affecting metal extraction rate, such as phase ratio, extractant concentration, and acid stripping will be evaluated. Copper was selectively removed from leachate at pH 3, using LIX^® 84-I 10% v/v followed by cobalt and manganese co-extraction from the raffinate using Cyanex^® 272 10% v/v at pH 5. After both metals were stripped using sulfuric acid 0.2 M, manganese was quantitatively precipitated out from the strip solution using potassium permanganate or sodium hypochlorite. Nickel was isolated using LIX^® 84-I from raffinate at pH 5, producing a lithium- rich solution for further treatment. No third phase was formed during the extraction, and sulfuric acid was proved suitable for organic phase regeneration. Full article

(This article belongs to the Special Issue New Science Based Concepts for Increased Efficiency in Battery Recycling 2023)

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18 pages, 6285 KiB

Open AccessArticle

Influence of Supersaturation on Growth Behavior and Mechanical Properties of Polycrystalline 3C-SiC on W Wire Substrate

by Shuai Liu, Xian Luo, Bin Huang and Yanqing Yang

Metals 2022, 12(5), 881; https://doi.org/10.3390/met12050881 - 23 May 2022

Cited by 2 | Viewed by 1968

Abstract

As an important reinforcement for metal matrix composites, the microstructure and mechanical properties of W-core SiC filament have drawn increasing attentions among researchers. In this work, the growth behavior of polycrystalline 3C-SiC on W-wire substrate in the chemical vapor deposition (CVD) process and [...] Read more.

As an important reinforcement for metal matrix composites, the microstructure and mechanical properties of W-core SiC filament have drawn increasing attentions among researchers. In this work, the growth behavior of polycrystalline 3C-SiC on W-wire substrate in the chemical vapor deposition (CVD) process and the evolution of mechanical properties in preparation of W-core SiC filament, were investigated as a function of gas-phase supersaturation. Kinetic studies revealed that the growth of 3C-SiC grains was limited by surface reactions at both 850 °C and 1050 °C, and the deposit experienced similar morphological changes from a porous structure to large clusters, with the increase in supersaturation. Structural analyses and mechanical tests show that the production of pores and the amorphous phase with a low supersaturation, of 9.6 × 10⁷ at 850 °C, resulted in a reduction in the modulus and hardness of the polycrystalline deposits, to 270.3 GPa and 33.9 GPa, while the reduced structural defects (e.g., stacking faults and twins) in highly (111) orientated 3C-SiC grains, as well as the improved surface quality obtained with the medium supersaturation of 1.6 × 10⁷ at 1050 °C, enhanced the tensile strength and the Weibull modulus of W-core SiC filament to 2.88 GPa and 11.2, respectively. During the growth of 3C-SiC grains, the variation in structural defects density is controlled by the critical nucleation energy of the two-dimensional (2D) nucleus. Full article

(This article belongs to the Special Issue Research on Microstructure and Mechanical Properties of Metallic Materials and Metal-Matrix Composites)

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16 pages, 7679 KiB

Open AccessArticle

Surface Residual Stress Analysis in GMAW and LBW of the Dissimilar TRIP-DP Steels Joint: An Experimental Approach

by Víctor H. Baltazar-Hernández, Enrique A. López-Baltazar, Francisco Alvarado-Hernández, Salvador Gómez-Jiménez, José Jorge Ruiz-Mondragón, Elliot Biro and Norman Zhou

Metals 2022, 12(5), 880; https://doi.org/10.3390/met12050880 - 23 May 2022

Cited by 3 | Viewed by 2227

Abstract

A transformation-induced plasticity (TRIP) steel and a dual-phase (DP) steel were paired together by employing gas metal arc welding (GMAW) and laser beam welding (LBW) processes. The post-weld microstructure, the hardness profile, and the uniaxial tensile behavior of the welded steels have been [...] Read more.

A transformation-induced plasticity (TRIP) steel and a dual-phase (DP) steel were paired together by employing gas metal arc welding (GMAW) and laser beam welding (LBW) processes. The post-weld microstructure, the hardness profile, and the uniaxial tensile behavior of the welded steels have been analyzed in detail. The experimental surface residual stress distribution across the weldment was measured through the X-ray diffraction sin²Ψ technique. The results indicate that although a harder microstructure composed of predominant martensite was observed along the weldment, the uniaxial tensile behavior resulted in better elongation properties and a higher UTS in the LBW specimen as compared to the GMAW specimen. The resultant residual stress distribution in the heat-affected zone (HAZ) had an increase to a maximum value, followed by a steady decrease up to the base metal following the trend: upper-critical UC-HAZ (maximum) → inter-critical IC-HAZ (moderated) → subcritical SC-HAZ (lowered), which was particularly more evident on the GMAW specimen. Overall, the resultant residual stresses along the weldment were lower on the LBW specimen (172 MPa maximum) which clearly contrasts to the GMAW specimen (421 MPa maximum). Finally, the tensile residual stresses in both the GMAW or LBW did not influence the overall tensile properties of the weldments. Full article

(This article belongs to the Special Issue Welding and Joining of Advanced High-Strength Steels)

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13 pages, 1591 KiB

Open AccessArticle

Influence of Th, Zr, and Ti Dopants on Solution Property of Xe in Uranium Dioxide with Defects: A DFT + U Study

by Liu Pan, Zhen Wang, Qingqing Wang, Zhixiao Liu, Min Pan, Zheng Huang and Lu Wu

Metals 2022, 12(5), 879; https://doi.org/10.3390/met12050879 - 23 May 2022

Cited by 3 | Viewed by 2256

Abstract

To ensure the safety and efficient operation of nuclear reactors, it is imperative to understand the effects of various dopants (Ti, Th, and Zr) on the solubility of the fission product Xe in UO₂. In this study, Hubbard corrected density functional [...] Read more.

To ensure the safety and efficient operation of nuclear reactors, it is imperative to understand the effects of various dopants (Ti, Th, and Zr) on the solubility of the fission product Xe in UO₂. In this study, Hubbard corrected density functional theory (DFT + U) and occupation matrix control were used to investigate the bulk and defect properties of UO₂. The results show that the UO₂-Ti system is more favorable for Xe dissolution in vacancies, whereas the UO₂-Th system has little effect on the dissolution of Xe atoms. Th, Zr, and Ti inhibit the aggregation of Xe clusters, and Ti is the least favorable for the nucleation and growth of Xe clusters. Full article

(This article belongs to the Section Computation and Simulation on Metals)

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20 pages, 2768 KiB

Open AccessArticle

Experimental Modeling of the Bifurcation Set Equation of the Chip-Splitting Catastrophe in Symmetrical Straight Double-Edged Cutting

by Qingfa You, Mingxian Xu, Baoyi Zhu, Liangshan Xiong and Kai Yin

Metals 2022, 12(5), 878; https://doi.org/10.3390/met12050878 - 22 May 2022

Cited by 3 | Viewed by 1704

Abstract

The chip-splitting catastrophe (CSC) generated by symmetrical cutting with a straight double-edged tool will lead to a significant reduction in cutting force. This has enormous potential for energy-saving machining and for the design of energy efficient cutting tools. The premise of the utilization [...] Read more.

The chip-splitting catastrophe (CSC) generated by symmetrical cutting with a straight double-edged tool will lead to a significant reduction in cutting force. This has enormous potential for energy-saving machining and for the design of energy efficient cutting tools. The premise of the utilization is to establish a mathematical model that can predict the critical conditions of CSC. However, no related literature has studied the prediction model of CSC. Therefore, this paper proposes an experimental method based on catastrophe theory to establish a model of CSC bifurcation set equations that can predict critical conditions. A total of 355 groups of experiments are conducted to observe the critical conditions of CSC in symmetrical straight double-edged cutting, and 22 groups of experimental data of the critical conditions were acquired. The modeling process is converted into the optimal solution of the function coefficient value when the mapping function from a set of actual control parameters to theoretical control parameters (u, v, w) is a linear function. The bifurcation set equation of CSC is established, which can predict CSC in the symmetrical cutting of a straight double-edged turning tool with any combination of edge angle and rake angle. With verification, it is found that the occurrence of CSC has obvious regularity, and the occurrence of CSC will lead to a maximum reduction of 64.68% in the specific cutting force. The predicted values of the critical cutting thickness for the CSC of the established equation are in good agreement with the experimental results (the average absolute error is 5.34%). This study lays the foundation for the energy-saving optimization of tool geometry and process parameters through the reasonable utilization of CSC. Full article

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18 pages, 6082 KiB

Open AccessFeature PaperArticle

Bending Behaviour Analysis of Aluminium Profiles in Differential Velocity Sideways Extrusion Using a General Flow Field Model

by Wenbin Zhou and Ziqi Xi

Metals 2022, 12(5), 877; https://doi.org/10.3390/met12050877 - 21 May 2022

Cited by 5 | Viewed by 1923

Abstract

The work in this paper concerns an analytical model for quantitatively describing the bending behaviour of aluminium profiles produced in a novel extrusion process: the differential velocity sideways extrusion (DVSE), in which two opposing rams with a velocity of

v_{1}

and [...] Read more.

The work in this paper concerns an analytical model for quantitatively describing the bending behaviour of aluminium profiles produced in a novel extrusion process: the differential velocity sideways extrusion (DVSE), in which two opposing rams with a velocity of

v_{1}

and

v_{2}

were employed, respectively. The analytical model was built on the basis of the upper bound theorem utilising a general streamline equation controlled by a shape factor n, and the curvature was calculated using the material flow velocity gradient across the die exit orifice. The predicted material flow velocity across the die exit orifice, and extrudate curvature agreed well with the finite element (FE) modelling results, which were found to be irrespective of the shape factor n of the streamline equation. For a given extrusion ratio, the minimum value of n = 2 leads to the minimum and closest theoretical extrusion pressure, the n value for obtaining the best approximated mean effective strain of the extruded profile increases with the increase of the velocity ratio

v_{2} / v_{1}

, and the value of n = 3.5 gives the closest mean effective strain as a whole. Full article

(This article belongs to the Special Issue Sustainable Manufacturing of Metallic Materials and Structures: Design, Processing and Characterization)

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11 pages, 4524 KiB

Open AccessArticle

The Role of Grain Boundaries in the Corrosion Process of Fe Surface: Insights from ReaxFF Molecular Dynamic Simulations

by Zigen Xiao, Yun Huang, Zhixiao Liu, Wangyu Hu, Qingtian Wang and Chaowei Hu

Metals 2022, 12(5), 876; https://doi.org/10.3390/met12050876 - 21 May 2022

Cited by 7 | Viewed by 3283

Abstract

Intergranular corrosion is the most common corrosion phenomenon in Fe-based alloys. To better understand the mechanism of intergranular corrosion, the influence of grain boundaries on Fe-H₂O interfacial corrosion was studied using molecular dynamics simulation based on a new Fe-H₂O [...] Read more.

Intergranular corrosion is the most common corrosion phenomenon in Fe-based alloys. To better understand the mechanism of intergranular corrosion, the influence of grain boundaries on Fe-H₂O interfacial corrosion was studied using molecular dynamics simulation based on a new Fe-H₂O reaction force field potential. It is found that the corrosion rate at the polycrystalline grain boundary is significantly faster than that of twin crystals and single crystals. By the analysis of stress, it can be found that the stress at the polycrystalline grain boundary and the sigma5 twin grain boundary decreases sharply during the corrosion process. We believe that the extreme stress released at the grain boundary will promote the dissolution of Fe atoms. The formation of vacancies on the Fe matrix surface will accelerate the diffusion of oxygen atoms. This leads to the occurrence of intergranular corrosion. Full article

(This article belongs to the Special Issue Numerical Modeling of Materials under Extreme Conditions)

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13 pages, 4547 KiB

Open AccessArticle

Effect of Vertical High Magnetic Field on the Morphology of Solid-Liquid Interface during the Directional Solidification of Zn-2wt.%Bi Immiscible Alloy

by Bangfei Zhou, Xianghui Guo, Wenhao Lin, Ying Liu, Yifeng Guo, Tianxiang Zheng, Yunbo Zhong, Hui Wang and Qiuliang Wang

Metals 2022, 12(5), 875; https://doi.org/10.3390/met12050875 - 21 May 2022

Cited by 4 | Viewed by 1923

Abstract

The morphology of the solid-liquid (S-L) interface is crucial for the directionally solidified microstructures of various alloys. This paper investigates the effect of vertical high magnetic field (VHMF) on the morphology evolution of the S-L interface and the solidified microstructure during the directional [...] Read more.

The morphology of the solid-liquid (S-L) interface is crucial for the directionally solidified microstructures of various alloys. This paper investigates the effect of vertical high magnetic field (VHMF) on the morphology evolution of the S-L interface and the solidified microstructure during the directional solidification of Zn-2wt.%Bi immiscible alloy. The results indicate that the morphology of the S-L interface is highly dependent on the VHMF, resulting in various solidified microstructures. When the growth rate was 1 μm/s, the aligned droplets were formed directly at the disturbed S-L interface under a 1 T VHMF. However, the stability of the S-L interface was improved to form a stable Bi-rich fiber under a 5 T VHMF. When the growth rate was 5 μm/s, the S-L interface was changed from cellular to dendritic to cellular again with increasing magnetic flux density. A theory regarding constitutional supercooling and efficient solute diffusion has been proposed to explain the S-L interface transition under the VHMF. The difference in the effective diffusion capacity of the solute originates from the thermoelectric magnetic effect and the magneto-hydrodynamic damping effect. The present work may initiate a new method to transform the solidified microstructures of immiscible alloys via an applied magnetic field during directional solidification. Full article

(This article belongs to the Special Issue Electromagnetic Preparation of Metallic Materials)

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10 pages, 3529 KiB

Open AccessArticle

Actual Marine Atmospheric Pre-Corrosion Fatigue Performance of 7075-T73 Aluminum Alloy

by Laixin Shi, Lin Xiang, Jianquan Tao, Qiang Chen, Jun Liu and Yong Zhong

Metals 2022, 12(5), 874; https://doi.org/10.3390/met12050874 - 21 May 2022

Cited by 7 | Viewed by 2051

Abstract

Actual marine atmospheric pre-corrosion behavior and its effect on the fatigue performance of 7075-T73 aluminum alloy were studied by means of marine atmospheric outdoor exposure testing and fatigue testing. The surface and cross-sectional microstructures of aluminum alloy specimens after different numbers of days [...] Read more.

Actual marine atmospheric pre-corrosion behavior and its effect on the fatigue performance of 7075-T73 aluminum alloy were studied by means of marine atmospheric outdoor exposure testing and fatigue testing. The surface and cross-sectional microstructures of aluminum alloy specimens after different numbers of days of exposure were analyzed. Localized pitting, and intergranular and exfoliation corrosion occurred during the outdoor exposure of aluminum alloy specimens in a marine atmosphere. The degree of severity of atmospheric corrosion increased with increasing duration of exposure. The effects of Fe-rich constituent particles (Al₂₃CuFe₄) and grain boundary precipitates (MgZn₂) on the marine atmospheric corrosion behavior were discussed. In addition, when the exposure time was increased from 0 days to 15 days, the average fatigue life of aluminum alloy specimens decreased dramatically from about 125.16 × 10⁴ cycles to 16.58 × 10⁴ cycles. As the exposure time was further increased to 180 days, the average fatigue life slowly decreased to about 6.21 × 10⁴ cycles. The fatigue fracture characteristics and the effect mechanism of marine atmospheric pre-corrosion on the fatigue life of 7075-T73 aluminum alloy were also analyzed. Full article

(This article belongs to the Special Issue Fatigue Damage Mechanism and Fatigue Life Prediction of Metallic Materials)

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12 pages, 5904 KiB

Open AccessArticle

Face Bend Property of 7N01-T4 Aluminum Alloy MIG Welded Joint by Using Different Welding Wires

by Ping Wei, Mingfang Wu, Dashuang Liu, Yun Liang and Ziqiang Zhao

Metals 2022, 12(5), 873; https://doi.org/10.3390/met12050873 - 20 May 2022

Cited by 1 | Viewed by 1921

Abstract

7N01-T4 aluminum alloy were welded into three layers by metal inert gas (MIG) welding, with ER5087 welding wire containing Zr and ER5356 welding wire without Zr, respectively. The microstructures and face bend properties of the ER5356 and ER5087 welded joints were investigated. The [...] Read more.

7N01-T4 aluminum alloy were welded into three layers by metal inert gas (MIG) welding, with ER5087 welding wire containing Zr and ER5356 welding wire without Zr, respectively. The microstructures and face bend properties of the ER5356 and ER5087 welded joints were investigated. The weld zone (WZ) of the ER5087 welded joint had a smaller grain size than that of the ER5356 welded joint. Two kinds of welded joints were not broken via the face-bend test. However, there were some small holes and microcracks on the surface of the ER5356 welded joint, and there were no obvious defects on the surface of the ER5087 welded joint. The face bending specimen metallography shows that the grains of the cover layer were elongated, and the grains of the bottom layer were extruded. The ER5087 welded joint had a better bending performance than the ER5356 welded joint due to the microstructure refinement of the WZ through adding Zr element in ER5087 welding wire. Full article

(This article belongs to the Special Issue Advances in Welding, Joining and Surface Coating Technology)

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17 pages, 13929 KiB

Open AccessArticle

Prediction of Fracture Toughness Scatter Based on Weibull Stress Using Crystal Plasticity Finite Element Method

by Zhibo He, Chen Li, Yuebing Li, Weiya Jin and Zengliang Gao

Metals 2022, 12(5), 872; https://doi.org/10.3390/met12050872 - 20 May 2022

Cited by 1 | Viewed by 1764

Abstract

A multi-scale prediction method was proposed to investigate the scatter of fracture toughness by combining the local approach (LA) to cleavage fracture and the crystal plasticity finite element method (CPFEM). The parameters in the crystal plasticity constitutive model were firstly determined by comparing [...] Read more.

A multi-scale prediction method was proposed to investigate the scatter of fracture toughness by combining the local approach (LA) to cleavage fracture and the crystal plasticity finite element method (CPFEM). The parameters in the crystal plasticity constitutive model were firstly determined by comparing the simulated stress-strain curves with tested curves for SA508-III steel. Then CT samples were modeled using the CPFEM to calculate Weibull stress. Using the calibration process of local approach, the relevant parameters of the Beremin model were obtained with m = 30 and σ_u = 2590 MPa. The fracture toughness was analyzed including the scatter for a given temperature, the master curve in a temperature range. The distribution of predicted fracture toughness shows good agreement with the test results. All of the tested fracture toughness value are fall in the range of 5% to 95% that precited using the proposed combined approach. Full article

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18 pages, 8281 KiB

Open AccessArticle

Comparative Analysis on the Corrosion Resistance to Molten Iron of Four Kinds of Carbon Bricks Used in Blast Furnace Hearth

by Cui Wang, Jianliang Zhang, Wen Chen, Xiaolei Li, Kexin Jiao, Zhenping Pang, Zhongyi Wang, Tongsheng Wang and Zhengjian Liu

Metals 2022, 12(5), 871; https://doi.org/10.3390/met12050871 - 20 May 2022

Cited by 5 | Viewed by 2120

Abstract

The corrosion resistance to molten iron of four kinds of carbon bricks used in blast furnace hearth were investigated to elaborate the corrosion mechanism through the macroscopic and microscopic analysis of carbon bricks before and after reaction and thermodynamic analysis. The macroscopic analysis [...] Read more.

The corrosion resistance to molten iron of four kinds of carbon bricks used in blast furnace hearth were investigated to elaborate the corrosion mechanism through the macroscopic and microscopic analysis of carbon bricks before and after reaction and thermodynamic analysis. The macroscopic analysis showed that brick A had the lowest degree of corrosion and highest uniformity at different heights, attributing to its moderate carbon content of 76.15%, main phases of C, Al₂O₃, SiC, and Al₆Si₂O₁₃ (mullite), and lower resistance to molten iron infiltration, etc. The microscopic analysis showed that all the carbon bricks had more and larger pores than the original carbon bricks. The phenomena of the iron beads adhering to carbon brick and iron infiltration were observed between the interface of carbon brick and molten iron. In addition, the obvious corrosion process was presented that the carbon matrix was broken and peeled off during the iron infiltration process. For the carbon brick being corroded, the dissolution of carbon was the predominant reaction. The higher the carbon solubility of the molten iron, the easier the corrosion on the carbon brick. Al₂O₃ and SiC enhanced the corrosion resistance to molten iron of carbon bricks, and SiO₂ could react with carbon to form pores as channels for the penetration of molten iron and increase the corrosion on carbon bricks. A higher graphitization degree of carbon bricks was beneficial to lessen their corrosion degree. The corrosion on carbon bricks by molten iron could be attributed to three aspects: carburization, infiltration, and scouring of molten iron. The carburization process of molten iron was the main reaction process. The molten iron infiltration into the carbon bricks facilitated the dissolution of carbon and destroyed the structure and accelerated the corrosion of the carbon bricks. The scouring of molten iron subjected the iron–carbon interface to interaction forces, promoting the separation of the exfoliated fragmented carbon brick from the iron–carbon interface to facilitate a new round of corrosion process. Full article

(This article belongs to the Special Issue Fundamentals of Advanced Pyrometallurgy)

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15 pages, 45656 KiB

Open AccessFeature PaperArticle

In-Situ Thermography Investigation of Crack Growth in Armco Iron under Gigacycle Fatigue Loading

by Victor Postel, Johann Petit, Chong Wang, Kai Tan, Isabelle Ranc-Darbord, Qingyuan Wang and Daniele Wagner

Metals 2022, 12(5), 870; https://doi.org/10.3390/met12050870 - 20 May 2022

Cited by 2 | Viewed by 2103

Abstract

A non-destructive thermographic methodology based on the temperature field is utilized to determine the crack tip position during the very high cycle fatigue (VHCF) test of pure iron and deduce the corresponding fatigue crack growth rate (FCGR). To this end, a piezoelectric fatigue [...] Read more.

A non-destructive thermographic methodology based on the temperature field is utilized to determine the crack tip position during the very high cycle fatigue (VHCF) test of pure iron and deduce the corresponding fatigue crack growth rate (FCGR). To this end, a piezoelectric fatigue machine is employed to test 1 mm thick pure iron samples at 20 kHz in push–pull fatigue loading. Two cameras are placed on each side of the plate sample, an infrared one for measuring the temperature fields on the specimen surface and an optical one for visualizing the crack tip verification. The centre section of the specimen is notched to initiate the crack. The temperature field is converted into intrinsic dissipation to quantify the inelastic strain energy according to energy conservation. The maximum value of intrinsic dissipation in each thermal image is related to the position of the crack tip and thus allows monitoring of the crack evolution during the fatigue test. The obtained results show that one specific specimen broke at 7.25 × 10⁷ cycles in the presence of a very low-stress amplitude (122 MPa). It is observed that the intrinsic dissipation has a low-constant level during the initiation and the short cracking, then sharply grows during the long cracking. This transition is visible on the polished surface of the sample, where the plasticity appears during the long cracking and slightly before. The material parameters in the Paris equation obtained from the intrinsic dissipation in the short crack growth are close to the results available in the literature as well as those obtained by the optical camera. Full article

(This article belongs to the Special Issue Fatigue Design of Steel and Composite Structures)

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15 pages, 1851 KiB

Open AccessFeature PaperArticle

Identification of Requirements for FE Modeling of an Adaptive Joining Technology Employing Friction-Spun Joint Connectors (FSJC)

by Annika Oesterwinter, Christian Wischer and Werner Homberg

Metals 2022, 12(5), 869; https://doi.org/10.3390/met12050869 - 20 May 2022

Cited by 1 | Viewed by 1960

Abstract

The adaptive joining process employing friction-spun joint connectors (FSJC) is a promising method for the realization of adaptable joints and thus for lightweight construction. In addition to experimental investigations, numerical studies are indispensable tools for its development. Therefore, this paper includes an analysis [...] Read more.

The adaptive joining process employing friction-spun joint connectors (FSJC) is a promising method for the realization of adaptable joints and thus for lightweight construction. In addition to experimental investigations, numerical studies are indispensable tools for its development. Therefore, this paper includes an analysis of boundary conditions for the spatial discretization and mesh modeling techniques, the material modeling, the contact and friction modeling, and the thermal boundary conditions for the finite element (FE) modeling of this joining process. For these investigations, two FE models corresponding to the two process steps were set up and compared with the two related processes of friction stir welding and friction drilling. Regarding the spatial discretization, the Lagrangian approach is not sufficient to represent the deformation that occurs. The Johnson-Cook model is well suited as a material model. The modeling of the contact detection and friction are important research subjects. Coulomb’s law of friction is not adequate to account for the complex friction phenomena of the adaptive joining process. The thermal boundary conditions play a decisive role in heat generation and thus in the material flow of the process. It is advisable to use temperature-dependent parameters and to investigate in detail the influence of radiation in the entire process. Full article

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8 pages, 1780 KiB

Open AccessArticle

Hydrogen Degassing of Zirconium under High-Vacuum Conditions

by Francesco Fagnoni and Piotr Konarski

Metals 2022, 12(5), 868; https://doi.org/10.3390/met12050868 - 19 May 2022

Cited by 2 | Viewed by 2223

Abstract

Micromechanics techniques, such as nano-indentation and micro-pillar compression, can be applied to study hydrogen-charged zirconium alloys at elevated temperatures, which is highly relevant for the nuclear industry. Such experiments are often conducted inside a scanning electron microscope (SEM) under high-vacuum conditions (10⁻⁵ [...] Read more.

Micromechanics techniques, such as nano-indentation and micro-pillar compression, can be applied to study hydrogen-charged zirconium alloys at elevated temperatures, which is highly relevant for the nuclear industry. Such experiments are often conducted inside a scanning electron microscope (SEM) under high-vacuum conditions (10⁻⁵ mbar). The combination of a high-temperature and high-vacuum environment causes some hydrogen to escape from the sample into the chamber. Although this effect is evident at temperatures above 600 °C, the extent of hydrogen desorption at lower temperatures is still unclear. In the presented study, the desorption of hydrogen was assessed in zirconium cladding tube material under temperature and hydrogen content conditions comparable to those faced by used nuclear fuel during dry storage. The measured hydrogen loss due to the high vacuum was compared to the simulations obtained using an extended version of a hydrogen behavior tool developed at PSI. Full article

(This article belongs to the Special Issue Advanced Characterization and Testing of Nuclear Materials)

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16 pages, 664 KiB

Open AccessFeature PaperArticle

Modeling of Diffusion-Controlled Crystallization Kinetics in Al-Cu-Zr Metallic Glass

by Anders Ericsson and Martin Fisk

Metals 2022, 12(5), 867; https://doi.org/10.3390/met12050867 - 19 May 2022

Cited by 3 | Viewed by 2066

Abstract

Crystallization is a major challenge in metallic glass production, and predictive models may aid the development of controlled microstructures. This work describes a modeling strategy of nucleation, growth and the dissolution of crystals in a multicomponent glass-forming system. The numerical model is based [...] Read more.

Crystallization is a major challenge in metallic glass production, and predictive models may aid the development of controlled microstructures. This work describes a modeling strategy of nucleation, growth and the dissolution of crystals in a multicomponent glass-forming system. The numerical model is based on classical nucleation theory in combination with a multicomponent diffusion-controlled growth model that is valid for high supersaturation. The required thermodynamic properties are obtained by coupling the model to a CALPHAD database using the Al-Cu-Zr system as a demonstrator. The crystallization of intermetallic

{(Al, Cu)}_{m} {Zr}_{n}

phases from the undercooled liquid phase were simulated under isothermal as well as rapid heating and cooling conditions (

10^{- 1} - 10^{6} {Ks}^{- 1}

). The obtained time–temperature transformation and continuous-heating/cooling transformation diagrams agree satisfactorily with the experimental data over a wide temperature range, thereby, demonstrating the predictability of the modeling approach. A comparison of the simulation results and experimental data is discussed. Full article

(This article belongs to the Special Issue Formation, Mechanical Properties and Thermal Stability of Bulk Metallic Glasses)

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22 pages, 8526 KiB

Open AccessArticle

Evolution of Microstructure and Hardness of the Nitrided Zone during Plasma Nitriding of High-Alloy Tool Steel

by Pierre Landgraf, Tim Bergelt, Lisa-Marie Rymer, Christian Kipp, Thomas Grund, Günter Bräuer and Thomas Lampke

Metals 2022, 12(5), 866; https://doi.org/10.3390/met12050866 - 19 May 2022

Cited by 11 | Viewed by 3101

Abstract

Plasma nitriding is widely used in various industrial applications to improve surface hardness and wear properties. Especially for tool steels, it is also used to improve the support and adhesion of diamond-like carbon (DLC) coatings. The properties of the nitrided zone produced by [...] Read more.

Plasma nitriding is widely used in various industrial applications to improve surface hardness and wear properties. Especially for tool steels, it is also used to improve the support and adhesion of diamond-like carbon (DLC) coatings. The properties of the nitrided zone produced by plasma nitriding are influenced by the applied process parameter, in particular temperature and time. However, for high-alloy tool steels, a deeper understanding of the underlying diffusion processes of the nitrogen and the interaction with the existing microstructure, as well as the effects on the case depth is still lacking. Therefore, in this study, specimens of high-alloy tool steel X153CrMoV12 were plasma nitrided at varying temperatures (480 °C, 520 °C, 560 °C) and treatment times (2 h, 4 h, 16 h). The resulting nitrided zones were investigated by optical and scanning electron microscopy (OM and SEM), depth-dependent glow discharge optical emission spectroscopy (GDOES), X-ray diffraction (XRD), and hardness measurements to characterize their microstructure, chemical composition, and hardness depending on the process parameters. The distribution of carbides (M₇C₃), e.g., chromium carbides, affects the diffusion of the nitrogen and the layer growth. An increase of temperature and duration leads to an increased layer thickness. The composition of the compound layer is, e.g., influenced by the process parameters:

ε

nitrides (Fe_2–3N) occurred preferentially at lower temperatures, while

γ^{'}

nitrides (Fe₄N) appeared mostly at higher temperatures. In order to investigate the influence of the carbides of the high-alloy tool steel on the nitriding process, a new methodology was developed by means of finite element analysis (FE), which makes it possible to analyze this influence on the development of the nitrogen concentration profile. This methodology makes it possible for the first time to map the heterogeneous nitrogen evolution and distribution. Full article

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15 pages, 7931 KiB

Open AccessArticle

Effect of Water Vapor on the Microstructure of Al₂O₃ on the Free-Standing MCrAlY Alloy at 1100 °C

by Minxuan Wu, Biju Zheng, Defeng Zhang, Taihong Huang, Chao Li, Qing Li, Wenlang Huang, Luyang Zhang and Peng Song

Metals 2022, 12(5), 865; https://doi.org/10.3390/met12050865 - 19 May 2022

Cited by 1 | Viewed by 1605

Abstract

The oxidation resistance of the MCrAlY binding coat is due to the formation of protective Al₂O₃ oxide scale at high temperature. The oxidation behavior of NiCrAlYHf alloy in 1100 °C air and air-water vapor atmosphere was studied. The effect of [...] Read more.

The oxidation resistance of the MCrAlY binding coat is due to the formation of protective Al₂O₃ oxide scale at high temperature. The oxidation behavior of NiCrAlYHf alloy in 1100 °C air and air-water vapor atmosphere was studied. The effect of water vapor on the microstructure and distribution of reactive elements was discussed. The results showed that the oxide scale in air has a double layer structure composed of columnar and equiaxed crystals, while the oxide scale in water vapor contains fine alumina grains, which provides more channels for the diffusion of reactive elements. In addition, The Cr element in the oxide scale is mainly concentrated in the outer equiaxed crystal zone, and the Hf oxide is mainly concentrated in the columnar crystal boundary. In air-water vapor atmosphere, the Cr element is uniformly distributed in the oxide scale. Full article

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13 pages, 2941 KiB

Open AccessArticle

Use of Ion-Exchange Resins to Adsorb Scandium from Titanium Industry’s Chloride Acidic Solution at Ambient Temperature

by Eleni Mikeli, Danai Marinos, Aikaterini Toli, Anastasia Pilichou, Efthymios Balomenos and Dimitrios Panias

Metals 2022, 12(5), 864; https://doi.org/10.3390/met12050864 - 18 May 2022

Cited by 5 | Viewed by 2917

Abstract

Scandium metal has generated a lot of interest during the past years. This is due to the various crucial applications it has found ground in and the lack of production in countries outside China and Russia. Apart from rare earth ores, scandium is [...] Read more.

Scandium metal has generated a lot of interest during the past years. This is due to the various crucial applications it has found ground in and the lack of production in countries outside China and Russia. Apart from rare earth ores, scandium is present in a variety of wastes and by-products originating from metallurgical processes and is not currently being sufficiently valorised. One of these processes is the production of titanium dioxide, which leaves an acidic iron chloride solution with a considerably high concentration of scandium (10–140 ppm) and is currently sold as a by-product. This research aims to recover scandium without affecting the solution greatly so that it can still be resold as a by-product after the treatment. To achieve this, two commercial ion-exchange resins, VP OC 1026 and TP 260, are used in the column setup. Their breakthrough curves are plotted with mathematical modelling and compared. Results indicate that VP OC 1026 resin is the most promising for Sc extraction with a column capacity of 1.46 mg/mL, but Zr, Ti, and V coextract have high capacities, while Fe does not interfere with the adsorption. Full article

(This article belongs to the Special Issue Advanced Sorbents for Separation of Metal Ions)

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31 pages, 6813 KiB

Open AccessEditor’s ChoiceArticle

The Holes of Zn Phosphate and Hot Dip Galvanizing on Electrochemical Behaviors of Multi-Coatings on Steel Substrates

by Thiago Duarte, Yuri A. Meyer and Wislei R. Osório

Metals 2022, 12(5), 863; https://doi.org/10.3390/met12050863 - 18 May 2022

Cited by 36 | Viewed by 2905

Abstract

The aim of this investigation is focused on the evaluation of distinctive coatings commonly applied in the automotive industry. The resulting corrosion behavior is analyzed by using electrochemical impedance spectroscopy (EIS), equivalent circuit (EC) and potentiodynamic polarization curves. The novelty concerns a comparison [...] Read more.

The aim of this investigation is focused on the evaluation of distinctive coatings commonly applied in the automotive industry. The resulting corrosion behavior is analyzed by using electrochemical impedance spectroscopy (EIS), equivalent circuit (EC) and potentiodynamic polarization curves. The novelty concerns a comparison between tricationic phosphate (TCP), cataphoretic electrodeposition (CED) of an epoxy layer, TCP + CED and HDG (hot-dip galvanized) + TCP + CED multi-coatings. Both the naturally deposited and defect-induced damage (incision) coatings are examined. The experimental impedance parameters and corrosion current densities indicate that multi-coating system (HDG + TCP + CED layers) provides better protection. Both planar and porous electrode behaviors are responsible to predict the corrosion mechanism of the majority of samples examined. Although induced-damage samples reveal that corrosion resistances decreased up to 10×, when compared with no damaged samples, the same trend of the corrosion protection is maintained, i.e., TCP < CED < TCP + CED < HDG + TCP + CED. It is also found that the same trend verified by using electrochemical parameters is also observed when samples are subjected under salt spray condition (500 h). It is also found that porous electrode behavior is not a deleterious aspect to corrosion resistance. It is more intimately associated with initial thickness coating, while corrosion resistance is associated with adhesion of the CED layer on TCP coating. The results of relative cost-to-efficiency to relative coating density ratios are associated with fact that a CED coating is necessary to top and clear coating applications and the TCP + CED and the HDG/TCP + CED coating systems exhibit the best results. Full article

(This article belongs to the Special Issue Investigations on Mechanical Properties and Corrosion Resistance of Alloys and Compounds)

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12 pages, 3027 KiB

Open AccessReview

Continuous Casting Practices for Steel: Past, Present and Future

by Roderick I. L. Guthrie and Mihaiela M. Isac

Metals 2022, 12(5), 862; https://doi.org/10.3390/met12050862 - 18 May 2022

Cited by 14 | Viewed by 14008

Abstract

This historical review of casting methods used to produce sheets of steel for automobiles, household products, rocket bodies, etc., all point toward the development of one-step commercial processes, which are capable of casting liquid steel directly into a final sheet product. Progress towards [...] Read more.

This historical review of casting methods used to produce sheets of steel for automobiles, household products, rocket bodies, etc., all point toward the development of one-step commercial processes, which are capable of casting liquid steel directly into a final sheet product. Progress towards this goal is confirmed by successful advances being made, but there remain major difficulties in reaching it. We concur that the conventional continuous casting method remains the current process of choice for highest-quality steel sheet products, but the ESP TSC (Endless Strip Production—Thin Slab Caster) approach is now highly competitive. Similarly, the original goal of Sir Henry Bessemer to produce a direct strip-making twin-drum caster, in 1856, finally came to lasting commercial fruition at CASTRIP/NUCOR. Nonetheless, a newer approach, promoted by Salzgitter, termed DSP (Direct Strip Production), or promoted by MMPC/MetSim as HSBC (Horizontal Single Belt Casting), has several advantages over CASTRIP in terms of microstructures and productivity. As such, the pros and cons of current methods are reviewed within this brief history of casting. Full article

(This article belongs to the Special Issue Modeling and Simulation of Metallurgical Processes in Ironmaking and Steelmaking)

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11 pages, 7560 KiB

Open AccessArticle

Grindability of Ti−Nb−Cu Alloys for Dental Machining Applications

by Masatoshi Takahashi, Masafumi Kikuchi and Yukyo Takada

Metals 2022, 12(5), 861; https://doi.org/10.3390/met12050861 - 18 May 2022

Cited by 1 | Viewed by 1829

Abstract

We developed high-strength Ti−Nb−Cu alloys and investigated their grindability. The grindability of each alloy was evaluated based on the volume of metal removed per minute (grinding rate) and on the ratio of the metal volume removed to the volume of the wheel material [...] Read more.

We developed high-strength Ti−Nb−Cu alloys and investigated their grindability. The grindability of each alloy was evaluated based on the volume of metal removed per minute (grinding rate) and on the ratio of the metal volume removed to the volume of the wheel material lost (grinding ratio). The grinding rate of the Ti-6%Nb-4%Cu, Ti-18%Nb-2%Cu, and Ti-24%Nb-1%Cu alloys significantly exceeded that of unalloyed titanium at high, medium, and low grinding speeds, respectively. Additionally, the Ti-6%Nb-4%Cu alloy exhibited an excellent grinding ratio. Generally, materials with high strength and hardness frequently exhibit poor machinability; however, the Ti−Nb−Cu alloys developed in our study presented favorable grindability characteristics and, therefore, demonstrated good potential for application as dental titanium alloys that can be subjected to computer-aided design/manufacturing processes. Full article

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