Magnesium (Mg) alloys, as the lightest structural metallic materials, hold significant potential for various applications in modern society. However, their limited strength and ductility have restricted their widespread use. Herein, a precisely controlled secondary hot extrusion (SHE) process with extremely low extrusion speed (a cross-head rate of 0.1 mm·min) was employed to achieve ultra-fine microstructure with an average grain size of 0.45 µm and uniform precipitation of nano-sized Mn-rich secondary phase in a rare-earth (RE)-free Mg-1.5Ag-0.2Mn-0.1Ca (wt.%) (MACM) alloy. Nano-sized Mn-rich secondary phase with an average particle size of 2.7 nm could inhibit the basal slip and result in the simultaneous activation of multiple slip systems, contributing to excellent ductility. Additionally, substantial elemental segregation occurred at the grain boundaries of the α-Mg phase in the SHEed Mg-Ag-Mn-Ca alloy after tensile deformation, providing significant solute drag pressure and Zener pressure. This phenomenon induces grain boundary segregation strengthening and activates non-basal slip. Consequently, the secondary hot extruded (SHEed) alloy exhibited an ultra-high ultimate tensile strength (UTS) of ∼422 MPa, a yield strength (YS) of ∼362 MPa, and an excellent elongation of 30.0%. Quantitative analysis of strengthening behavior in the SHEed MACM alloys revealed that the primary strengthening mechanism is grain refinement, with consideration given to the influences of Orowan strengthening and work hardening. This study provides a novel approach to synchronously ameliorate the strength and ductility in Mg-based materials for load-bearing applications.
{"title":"Achieving ultra-high strength and ductility in a rare-earth-free magnesium alloy via precisely controlled secondary hot extrusion process with an extremely low extrusion speed","authors":"Wei Gao, Xin Wang, Yingjian Lin, Xiao Wang, Debao Liu, Xiaohao Sun","doi":"10.1016/j.jma.2024.07.015","DOIUrl":"https://doi.org/10.1016/j.jma.2024.07.015","url":null,"abstract":"Magnesium (Mg) alloys, as the lightest structural metallic materials, hold significant potential for various applications in modern society. However, their limited strength and ductility have restricted their widespread use. Herein, a precisely controlled secondary hot extrusion (SHE) process with extremely low extrusion speed (a cross-head rate of 0.1 mm·min) was employed to achieve ultra-fine microstructure with an average grain size of 0.45 µm and uniform precipitation of nano-sized Mn-rich secondary phase in a rare-earth (RE)-free Mg-1.5Ag-0.2Mn-0.1Ca (wt.%) (MACM) alloy. Nano-sized Mn-rich secondary phase with an average particle size of 2.7 nm could inhibit the basal slip and result in the simultaneous activation of multiple slip systems, contributing to excellent ductility. Additionally, substantial elemental segregation occurred at the grain boundaries of the α-Mg phase in the SHEed Mg-Ag-Mn-Ca alloy after tensile deformation, providing significant solute drag pressure and Zener pressure. This phenomenon induces grain boundary segregation strengthening and activates non-basal slip. Consequently, the secondary hot extruded (SHEed) alloy exhibited an ultra-high ultimate tensile strength (UTS) of ∼422 MPa, a yield strength (YS) of ∼362 MPa, and an excellent elongation of 30.0%. Quantitative analysis of strengthening behavior in the SHEed MACM alloys revealed that the primary strengthening mechanism is grain refinement, with consideration given to the influences of Orowan strengthening and work hardening. This study provides a novel approach to synchronously ameliorate the strength and ductility in Mg-based materials for load-bearing applications.","PeriodicalId":16214,"journal":{"name":"Journal of Magnesium and Alloys","volume":null,"pages":null},"PeriodicalIF":17.6,"publicationDate":"2024-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142227778","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-01DOI: 10.1016/j.jma.2023.01.009
A series of Zn-xAl (x = 0‒35 wt.%) alloy filler metals were designed to join AZ31 Mg alloy to 6061 Al alloy by laser-TIG hybrid welding. The effect of Al content on the wettability of filler metals, microstructure evolution and strength of joint was investigated. The results indicated that the strength of joints was improved with the increase of Al content in filler metals. When Zn-15Al filler was used, the ultimate fracture load reached the maximum of 1475.3 N/cm, which was increased by 28% than that with pure Zn filler. The reason is that the Al element acts as a "reaction depressant" in filler metal, which contributes to inhibiting the dissolution of Mg base metal and the Mg-Zn reaction. The addition of appropriate quantity of Al element promoted the precipitation of Al-rich solid solution instead of Zn solid solution. The MgZn2 IMCs have lower lattice mismatch with Al solid solution than Zn solid solution, thus the strength of joints is improved. However, the excessive addition of Al caused the formation of brittle Mg32(Al,Zn)49 ternary compounds, leading to the deterioration of joint performance.
{"title":"Microstructure and mechanical performance of AZ31/6061 lap joints welded by laser-TIG hybrid welding with Zn-Al alloy filler metal","authors":"","doi":"10.1016/j.jma.2023.01.009","DOIUrl":"10.1016/j.jma.2023.01.009","url":null,"abstract":"<div><div>A series of Zn-<em>x</em>Al (<em>x</em> = 0‒35 wt.%) alloy filler metals were designed to join AZ31 Mg alloy to 6061 Al alloy by laser-TIG hybrid welding. The effect of Al content on the wettability of filler metals, microstructure evolution and strength of joint was investigated. The results indicated that the strength of joints was improved with the increase of Al content in filler metals. When Zn-15Al filler was used, the ultimate fracture load reached the maximum of 1475.3 N/cm, which was increased by 28% than that with pure Zn filler. The reason is that the Al element acts as a \"reaction depressant\" in filler metal, which contributes to inhibiting the dissolution of Mg base metal and the Mg-Zn reaction. The addition of appropriate quantity of Al element promoted the precipitation of Al-rich solid solution instead of Zn solid solution. The MgZn<sub>2</sub> IMCs have lower lattice mismatch with Al solid solution than Zn solid solution, thus the strength of joints is improved. However, the excessive addition of Al caused the formation of brittle Mg<sub>32</sub>(Al,Zn)<sub>49</sub> ternary compounds, leading to the deterioration of joint performance.</div></div>","PeriodicalId":16214,"journal":{"name":"Journal of Magnesium and Alloys","volume":null,"pages":null},"PeriodicalIF":15.8,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2213956723000270/pdfft?md5=2a29a53b335b1d40c4d6fc82c54608a3&pid=1-s2.0-S2213956723000270-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49207880","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-01DOI: 10.1016/j.jma.2022.11.009
Hot flow forming (HFF) is a promising forming technology to manufacture thin-walled cylindrical part with longitudinal inner ribs (CPLIRs) made of magnesium (Mg) alloys, which has wide applications in the aerospace field. However, due to the thermo-mechanical coupling effect and the existence of stiffened structure, complex microstructure evolution and uneven microstructure occur easily at the cylindrical wall (CW) and inner rib (IR) of Mg alloy thin-walled CPLIRs during the HFF. In this paper, a modified cellular automaton (CA) model of Mg alloy considering the effects of deformation conditions on material parameters was developed using the artificial neural network (ANN) method. It is found that the ANN-modified CA model exhibits better predictability for the microstructure of hot deformation than the conventional CA model. Furthermore, the microstructure evolution of ZK61 alloy CPLIRs during the HFF was analyzed by coupling the modified CA model and finite element analysis (FEA). The results show that compared with the microstructure at the same layer of the IR, more refined grains and less sufficient DRX resulted from larger strain and strain rate occur at that of the CW; various differences of strain and strain rate in the wall-thickness exist between the CW and IR, which leads to the inhomogeneity of microstructure rising firstly and declining from the inside layer to outside layer; the obtained Hall-Petch relationship between the measured microhardness and predicted grain sizes at the CW and the IR indicates the reliability of the coupled FEA-CA simulation results.
热流成形（HFF）是制造镁合金纵向内肋薄壁圆柱形零件（CPLIR）的一种很有前途的成形技术，在航空航天领域有着广泛的应用。然而，由于热机械耦合效应和刚性结构的存在，镁合金薄壁带纵向内肋的圆柱壁（CW）和内肋（IR）在加氢脱硫过程中容易出现复杂的微观结构演变和微观结构不均匀。本文采用人工神经网络（ANN）方法，建立了考虑变形条件对材料参数影响的镁合金改进单元自动机（CA）模型。研究发现，与传统 CA 模型相比，ANN 修正 CA 模型对热变形微观结构的预测能力更强。此外，通过将修正的 CA 模型与有限元分析（FEA）相结合，分析了 ZK61 合金 CPLIR 在热变形过程中的微观结构演变。结果表明，与 IR 层的微观组织相比，CW 层的微观组织由于应变和应变速率较大而导致晶粒更细化、DRX 更不充分；CW 层和 IR 层之间壁厚上的应变和应变速率存在各种差异，导致微观组织的不均匀性由内层向外层先上升后下降；CW 层和 IR 层的实测显微硬度与预测晶粒大小之间的 Hall-Petch 关系表明 FEA-CA 耦合模拟结果是可靠的。
{"title":"Study of microstructure evolution of magnesium alloy cylindrical part with longitudinal inner ribs during hot flow forming by coupling ANN-modified CA and FEA","authors":"","doi":"10.1016/j.jma.2022.11.009","DOIUrl":"10.1016/j.jma.2022.11.009","url":null,"abstract":"<div><div>Hot flow forming (HFF) is a promising forming technology to manufacture thin-walled cylindrical part with longitudinal inner ribs (CPLIRs) made of magnesium (Mg) alloys, which has wide applications in the aerospace field. However, due to the thermo-mechanical coupling effect and the existence of stiffened structure, complex microstructure evolution and uneven microstructure occur easily at the cylindrical wall (CW) and inner rib (IR) of Mg alloy thin-walled CPLIRs during the HFF. In this paper, a modified cellular automaton (CA) model of Mg alloy considering the effects of deformation conditions on material parameters was developed using the artificial neural network (ANN) method. It is found that the ANN-modified CA model exhibits better predictability for the microstructure of hot deformation than the conventional CA model. Furthermore, the microstructure evolution of ZK61 alloy CPLIRs during the HFF was analyzed by coupling the modified CA model and finite element analysis (FEA). The results show that compared with the microstructure at the same layer of the IR, more refined grains and less sufficient DRX resulted from larger strain and strain rate occur at that of the CW; various differences of strain and strain rate in the wall-thickness exist between the CW and IR, which leads to the inhomogeneity of microstructure rising firstly and declining from the inside layer to outside layer; the obtained Hall-Petch relationship between the measured microhardness and predicted grain sizes at the CW and the IR indicates the reliability of the coupled FEA-CA simulation results.</div></div>","PeriodicalId":16214,"journal":{"name":"Journal of Magnesium and Alloys","volume":null,"pages":null},"PeriodicalIF":15.8,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2213956722002821/pdfft?md5=8ad0dbec87392bd14c40b9ddd3178d7b&pid=1-s2.0-S2213956722002821-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48554147","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-01DOI: 10.1016/j.jma.2024.08.006
MgH2 and TiH2 have been extensively studied as potential anode materials due to their high theoretical specific capacities of 2036 and 1024 mAh/g, respectively. However, the large volume changes that these compounds undergo during cycling affects their performance and limits practical applications. The present work demonstrates a novel approach to limiting the volume changes of active materials. This effect is based on mechanical support from an intimate interface generated in situ via the reaction between MgH2 and Ti within the electrode prior to lithiation to form Mg and TiH2. The resulting Mg can be transformed back to MgH2 by reaction with LiH during delithiation. In addition, the TiH2 improves the reaction kinetics of MgH2 and enhances electrochemical performance. The intimate interface produced in this manner is found to improve the electrochemical properties of a MgH2-Ti-LiH electrode. An exceptional reversible capacity of 800 mAh/g is observed even after 200 cycles with a high current density of 1 mA/cm2 and a high proportion of active material (90 wt.%) at an operation temperature of 120 °C. This study therefore showcases a new means of improving the performance of electrodes by limiting the volume changes of active materials.
{"title":"In situ formation of an intimate solid-solid interface by reaction between MgH2 and Ti to stabilize metal hydride anode with high active material content","authors":"","doi":"10.1016/j.jma.2024.08.006","DOIUrl":"10.1016/j.jma.2024.08.006","url":null,"abstract":"<div><div>MgH<sub>2</sub> and TiH<sub>2</sub> have been extensively studied as potential anode materials due to their high theoretical specific capacities of 2036 and 1024 mAh/g, respectively. However, the large volume changes that these compounds undergo during cycling affects their performance and limits practical applications. The present work demonstrates a novel approach to limiting the volume changes of active materials. This effect is based on mechanical support from an intimate interface generated <em>in situ</em> via the reaction between MgH<sub>2</sub> and Ti within the electrode prior to lithiation to form Mg and TiH<sub>2</sub>. The resulting Mg can be transformed back to MgH<sub>2</sub> by reaction with LiH during delithiation. In addition, the TiH<sub>2</sub> improves the reaction kinetics of MgH<sub>2</sub> and enhances electrochemical performance. The intimate interface produced in this manner is found to improve the electrochemical properties of a MgH<sub>2</sub>-Ti-LiH electrode. An exceptional reversible capacity of 800 mAh/g is observed even after 200 cycles with a high current density of 1 mA/cm<sup>2</sup> and a high proportion of active material (90 wt.%) at an operation temperature of 120 °C. This study therefore showcases a new means of improving the performance of electrodes by limiting the volume changes of active materials.</div></div>","PeriodicalId":16214,"journal":{"name":"Journal of Magnesium and Alloys","volume":null,"pages":null},"PeriodicalIF":15.8,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S221395672400286X/pdfft?md5=575caaa196d01288bdc67d87c7894f74&pid=1-s2.0-S221395672400286X-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142312092","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-01DOI: 10.1016/j.jma.2024.07.029
In this study, the mechanical behavior of crystal group of hexagonal close-packed (hcp; α phase) and body-centered cubic (bcc; β phase) during tensile loading was investigated to elucidate the mechanism from elastic to plastic deformation transition of the rolled LZ91 Mg alloy using transmission-X-ray diffraction (transmission-XRD) measurement, transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), energy dispersive X-ray spectroscopy (EDS). The approximate proof stress of the LZ91 Mg alloy sample was found that the lattice strain retained the expanded state from 0.6% nominal strain, and the transmission-XRD measurement characterized the crystalline behavior during the transition by the integrated intensity of crystal group hcp(100). The lattice strain of bcc(110) decreased from the 0.6% nominal strain due to dislocation activity, which occurred near β/β grain boundary. In addition, we performed the analyses of electron energy loss spectroscopy (EELS) modes, the Li-K peak disappeared from the segregated Li regions of 10–60 nm near β/β grain boundary at the nominal strain of 0.8%. Understanding this mechanical behavior during the elastic to plastic deformation transition by transmission-XRD is crucial for the development of Mg-Li alloys.
{"title":"Characterization of deformation transition in the rolled LZ91 magnesium alloy under tensile loading","authors":"","doi":"10.1016/j.jma.2024.07.029","DOIUrl":"10.1016/j.jma.2024.07.029","url":null,"abstract":"<div><div>In this study, the mechanical behavior of crystal group of hexagonal close-packed (<em>hcp</em>; α phase) and body-centered cubic (<em>bcc</em>; β phase) during tensile loading was investigated to elucidate the mechanism from elastic to plastic deformation transition of the rolled LZ91 Mg alloy using transmission-X-ray diffraction (transmission-XRD) measurement, transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), energy dispersive X-ray spectroscopy (EDS). The approximate proof stress of the LZ91 Mg alloy sample was found that the lattice strain retained the expanded state from 0.6% nominal strain, and the transmission-XRD measurement characterized the crystalline behavior during the transition by the integrated intensity of crystal group <em>hcp</em>(100). The lattice strain of <em>bcc</em>(110) decreased from the 0.6% nominal strain due to dislocation activity, which occurred near β/β grain boundary. In addition, we performed the analyses of electron energy loss spectroscopy (EELS) modes, the Li-K peak disappeared from the segregated Li regions of 10–60 nm near β/β grain boundary at the nominal strain of 0.8%. Understanding this mechanical behavior during the elastic to plastic deformation transition by transmission-XRD is crucial for the development of Mg-Li alloys.</div></div>","PeriodicalId":16214,"journal":{"name":"Journal of Magnesium and Alloys","volume":null,"pages":null},"PeriodicalIF":15.8,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S221395672400272X/pdfft?md5=523fef3a80c8721d474fe20bb3e35741&pid=1-s2.0-S221395672400272X-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142312091","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-01DOI: 10.1016/j.jma.2024.07.030
Understanding the interaction between cyclic stresses and corrosion of magnesium (Mg) and its alloys is increasingly in demand due to the continuous expansion of structural applications of these materials. This review is dedicated to exploring the corrosion-fatigue mechanisms of these materials, with an emphasis on microscale processes, and the possibility of expanding current knowledge on this topic using scanning electrochemical techniques. The interaction between fatigue and corrosion of Mg alloys is analyzed by considering the microstructural aspects (grain size, precipitates, deformation twins), as well as the formation of pits. Furthermore, in the case of coated alloys, the role of coating defects in these phenomena is also described. In this context, the feasibility of using scanning electrochemical microscopy (SECM), scanning vibrating electrode technique (SVET), scanning ion-selective electrode technique (SIET), localized electrochemical impedance spectroscopy (LEIS) and scanning Kelvin probe (SKP) methods to study the corrosion-fatigue interaction of Mg alloys is examined. A comprehensive review of the current literature in this field is presented, and the opportunities and limitations of consolidating the use of these techniques to study the microscale processes involved in Mg corrosion-fatigue are discussed.
{"title":"A review on the synergism between corrosion and fatigue of magnesium alloys: Mechanisms and processes on the micro-scale","authors":"","doi":"10.1016/j.jma.2024.07.030","DOIUrl":"10.1016/j.jma.2024.07.030","url":null,"abstract":"<div><div>Understanding the interaction between cyclic stresses and corrosion of magnesium (Mg) and its alloys is increasingly in demand due to the continuous expansion of structural applications of these materials. This review is dedicated to exploring the corrosion-fatigue mechanisms of these materials, with an emphasis on microscale processes, and the possibility of expanding current knowledge on this topic using scanning electrochemical techniques. The interaction between fatigue and corrosion of Mg alloys is analyzed by considering the microstructural aspects (grain size, precipitates, deformation twins), as well as the formation of pits. Furthermore, in the case of coated alloys, the role of coating defects in these phenomena is also described. In this context, the feasibility of using scanning electrochemical microscopy (SECM), scanning vibrating electrode technique (SVET), scanning ion-selective electrode technique (SIET), localized electrochemical impedance spectroscopy (LEIS) and scanning Kelvin probe (SKP) methods to study the corrosion-fatigue interaction of Mg alloys is examined. A comprehensive review of the current literature in this field is presented, and the opportunities and limitations of consolidating the use of these techniques to study the microscale processes involved in Mg corrosion-fatigue are discussed.</div></div>","PeriodicalId":16214,"journal":{"name":"Journal of Magnesium and Alloys","volume":null,"pages":null},"PeriodicalIF":15.8,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2213956724002780/pdfft?md5=c0288e6af95cff2622373c2d61c6c10f&pid=1-s2.0-S2213956724002780-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142312076","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-01DOI: 10.1016/j.jma.2024.08.016
Mg-Gd-Zn based alloys have better creep resistance than other Mg alloys and attract more attention at elevated temperatures. However, the multiple alloying elements and various heat treatment conditions, combined with complex microstructural evolution during creep tests, bring great challenges in understanding and predicting creep behaviors. In this study, we proposed to predict the creep properties and reveal the creep mechanisms of Mg-Gd-Zn based alloys by machine learning. On the one hand, the minimum creep rates were effectively predicted by using a support vector regression model. The complex and nonmonotonic effects of test temperature, test stress, alloying elements, and heat treatment conditions on the creep properties were revealed. On the other hand, the creep stress exponents and creep activation energies were calculated by machine learning to analyze the variation of creep mechanisms, based on which the constitutive equations of Mg-Gd-Zn based alloys were obtained. This study introduces an efficient method to comprehend creep behaviors through machine learning, offering valuable insights for the future design and selection of Mg alloys.
{"title":"Understanding the creep behaviors and mechanisms of Mg-Gd-Zn alloys via machine learning","authors":"","doi":"10.1016/j.jma.2024.08.016","DOIUrl":"10.1016/j.jma.2024.08.016","url":null,"abstract":"<div><div>Mg-Gd-Zn based alloys have better creep resistance than other Mg alloys and attract more attention at elevated temperatures. However, the multiple alloying elements and various heat treatment conditions, combined with complex microstructural evolution during creep tests, bring great challenges in understanding and predicting creep behaviors. In this study, we proposed to predict the creep properties and reveal the creep mechanisms of Mg-Gd-Zn based alloys by machine learning. On the one hand, the minimum creep rates were effectively predicted by using a support vector regression model. The complex and nonmonotonic effects of test temperature, test stress, alloying elements, and heat treatment conditions on the creep properties were revealed. On the other hand, the creep stress exponents and creep activation energies were calculated by machine learning to analyze the variation of creep mechanisms, based on which the constitutive equations of Mg-Gd-Zn based alloys were obtained. This study introduces an efficient method to comprehend creep behaviors through machine learning, offering valuable insights for the future design and selection of Mg alloys.</div></div>","PeriodicalId":16214,"journal":{"name":"Journal of Magnesium and Alloys","volume":null,"pages":null},"PeriodicalIF":15.8,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2213956724002895/pdfft?md5=8a636cfa054af42fdfa99496b0f7694e&pid=1-s2.0-S2213956724002895-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142268958","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-01DOI: 10.1016/j.jma.2023.02.011
In this study, the nano-TiC/AZ61 composites with different heterogeneous bimodal grain (HBG) structures and uniform structure are obtained by regulating the extrusion speed. The effect of HBG structure on the mechanical properties of the composites is investigated. The increasing ductility and toughening mechanism of HBG magnesium matrix composites are carefully discussed. When the extrusion speed increases from 0.75 mm/s to 2.5 mm/s or 3.5 mm/s, the microstructure transforms from uniform to HBG structure. Compared with Uniform-0.75 mm/s composite, Heterogeneous-3.5 mm/s composite achieves a 116.7% increase in ductility in the plastic deformation stage and almost no reduction in ultimate tensile strength. This is mainly because the lower plastic deformation inhomogeneity and higher strain hardening due to hetero-deformation induced (HDI) hardening. Moreover, Heterogeneous-3.5 mm/s composite achieves a 108.3% increase in toughness compared with the Uniform-0.75 mm/s composite. It is mainly because coarse grain (CG) bands can capture and blunt cracks, thereby increasing the energy dissipation for crack propagation and improving toughness. In addition, the CG band of the Heterogeneous-3.5 mm/s composite with larger grain size and lower dislocation density is more conducive to obtaining higher strain hardening and superior blunting crack capability. Thus, the increased ductility and toughness of the Heterogeneous-3.5 mm/s composite is more significant than that Heterogeneous-2.5 mm/s composite.
{"title":"Improving the ductility and toughness of nano-TiC/AZ61 composite by optimizing bimodal grain microstructure via extrusion speed","authors":"","doi":"10.1016/j.jma.2023.02.011","DOIUrl":"10.1016/j.jma.2023.02.011","url":null,"abstract":"<div><div>In this study, the nano-TiC/AZ61 composites with different heterogeneous bimodal grain (HBG) structures and uniform structure are obtained by regulating the extrusion speed. The effect of HBG structure on the mechanical properties of the composites is investigated. The increasing ductility and toughening mechanism of HBG magnesium matrix composites are carefully discussed. When the extrusion speed increases from 0.75 mm/s to 2.5 mm/s or 3.5 mm/s, the microstructure transforms from uniform to HBG structure. Compared with Uniform-0.75 mm/s composite, Heterogeneous-3.5 mm/s composite achieves a 116.7% increase in ductility in the plastic deformation stage and almost no reduction in ultimate tensile strength. This is mainly because the lower plastic deformation inhomogeneity and higher strain hardening due to hetero-deformation induced (HDI) hardening. Moreover, Heterogeneous-3.5 mm/s composite achieves a 108.3% increase in toughness compared with the Uniform-0.75 mm/s composite. It is mainly because coarse grain (CG) bands can capture and blunt cracks, thereby increasing the energy dissipation for crack propagation and improving toughness. In addition, the CG band of the Heterogeneous-3.5 mm/s composite with larger grain size and lower dislocation density is more conducive to obtaining higher strain hardening and superior blunting crack capability. Thus, the increased ductility and toughness of the Heterogeneous-3.5 mm/s composite is more significant than that Heterogeneous-2.5 mm/s composite.</div></div>","PeriodicalId":16214,"journal":{"name":"Journal of Magnesium and Alloys","volume":null,"pages":null},"PeriodicalIF":15.8,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2213956723000592/pdfft?md5=8a0a34e076c7fc11377210d5a72ff323&pid=1-s2.0-S2213956723000592-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43624188","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-01DOI: 10.1016/j.jma.2024.07.027
While magnesium (Mg) is a promising material for personalized temporary implants, the lack of a digital manufacturing solution for Mg implants impedes its potential progress. This study introduces a hybrid manufacturing process that integrates binder jet additive manufacturing with automated dry post-machining to enable end-to-end digital manufacturing of personalized Mg implants. Spherical cap-shaped Mg implants were additively manufactured through binder jetting. These implants were placed on graphite flakes during sintering as a potential non-reactive support material, allowing unrestricted shrinkage of 15.2 % to a relative density of 87 %. Microstructural and dimensional analysis revealed consistent interconnected porous microstructures with a shrinkage distortion within ± 0.2 mm of the original digital drawing. High-speed dry milling of the sintered samples, assessed via an orthogonal cutting test, identified the optimized cutting parameters. A three-step machining process for automated 5-axis machining, along with clamping strategies, referencing, and an adaptive plug-in, were successfully implemented. The automated dry machining on binder-jet printed Mg implants resulted in an average roughness of < 1.3 µm with no defects. In summary, this work introduces a robust digital manufacturing solution to advance the transformative landscape of Mg implants and scaffolds.
{"title":"Digital manufacturing of personalized magnesium implants through binder jet additive manufacturing and automated post machining","authors":"","doi":"10.1016/j.jma.2024.07.027","DOIUrl":"10.1016/j.jma.2024.07.027","url":null,"abstract":"<div><div>While magnesium (Mg) is a promising material for personalized temporary implants, the lack of a digital manufacturing solution for Mg implants impedes its potential progress. This study introduces a hybrid manufacturing process that integrates binder jet additive manufacturing with automated dry post-machining to enable end-to-end digital manufacturing of personalized Mg implants. Spherical cap-shaped Mg implants were additively manufactured through binder jetting. These implants were placed on graphite flakes during sintering as a potential non-reactive support material, allowing unrestricted shrinkage of 15.2 % to a relative density of 87 %. Microstructural and dimensional analysis revealed consistent interconnected porous microstructures with a shrinkage distortion within ± 0.2 mm of the original digital drawing. High-speed dry milling of the sintered samples, assessed via an orthogonal cutting test, identified the optimized cutting parameters. A three-step machining process for automated 5-axis machining, along with clamping strategies, referencing, and an adaptive plug-in, were successfully implemented. The automated dry machining on binder-jet printed Mg implants resulted in an average roughness of < 1.3 µm with no defects. In summary, this work introduces a robust digital manufacturing solution to advance the transformative landscape of Mg implants and scaffolds.</div></div>","PeriodicalId":16214,"journal":{"name":"Journal of Magnesium and Alloys","volume":null,"pages":null},"PeriodicalIF":15.8,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2213956724002743/pdfft?md5=c89c7492abbbd0f3367550a465b11bec&pid=1-s2.0-S2213956724002743-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142312184","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-01DOI: 10.1016/j.jma.2024.08.009
The mechanical properties of an extruded Mg-10Gd sample, specifically designed for vascular stents, are crucial for predicting its behavior under service conditions. Achieving homogeneous stresses in the hoop direction, essential for characterizing vascular stents, poses challenges in experimental testing based on standard specimens featuring a reduced cross section. This study utilizes an elasto-visco-plastic self-consistent polycrystal model (ΔEVPSC) with the predominant twinning reorientation (PTR) scheme as a numerical tool, offering an alternative to mechanical testing. For verification, various mechanical experiments, such as uniaxial tension, compression, notched-bar tension, three-point bending, and C-ring compression tests, were conducted. The resulting force vs. displacement curves and textures were then compared with those based on the ΔEVPSC model. The computational model's significance is highlighted by simulation results demonstrating that the differential hardening along with a weak strength differential effect observed in the Mg-10Gd sample is a result of the interplay between micromechanical deformation mechanisms and deformation-induced texture evolution. Furthermore, the study highlights that incorporating the axisymmetric texture from the as-received material incorporating the measured texture gradient significantly improves predictive accuracy on the strength in the hoop direction. Ultimately, the findings suggest that the ΔEVPSC model can effectively predict the mechanical behavior resulting from loading scenarios that are impossible to realize experimentally, emphasizing its valuable contribution as a digital twin.
专为血管支架设计的挤压 Mg-10Gd 样品的机械性能对于预测其在使用条件下的行为至关重要。实现环向均匀应力是鉴定血管支架特性的关键，但在基于横截面缩小的标准试样的实验测试中却面临挑战。本研究利用弹性-粘弹性自洽多晶体模型（ΔEVPSC）和主要孪晶重新定向（PTR）方案作为数值工具，为机械测试提供了一种替代方法。为进行验证，进行了各种机械试验，如单轴拉、压、缺口杆拉、三点弯曲和 C 环压缩试验。然后将得出的力与位移曲线和纹理与基于 ΔEVPSC 模型的曲线和纹理进行比较。模拟结果表明，在 Mg-10Gd 样品中观察到的差异硬化和微弱的强度差异效应是微机械变形机制和变形诱导的纹理演变之间相互作用的结果，这凸显了计算模型的重要性。此外，该研究还强调，结合测量到的纹理梯度，从接收材料中提取轴对称纹理可显著提高箍向强度的预测精度。最终，研究结果表明，ΔEVPSC 模型可以有效预测实验中不可能实现的加载情况下产生的力学行为，强调了其作为数字孪生模型的宝贵贡献。
{"title":"Crystal plasticity finite element simulations on extruded Mg-10Gd rod with texture gradient","authors":"","doi":"10.1016/j.jma.2024.08.009","DOIUrl":"10.1016/j.jma.2024.08.009","url":null,"abstract":"<div><div>The mechanical properties of an extruded Mg-10Gd sample, specifically designed for vascular stents, are crucial for predicting its behavior under service conditions. Achieving homogeneous stresses in the hoop direction, essential for characterizing vascular stents, poses challenges in experimental testing based on standard specimens featuring a reduced cross section. This study utilizes an elasto-visco-plastic self-consistent polycrystal model (ΔEVPSC) with the predominant twinning reorientation (PTR) scheme as a numerical tool, offering an alternative to mechanical testing. For verification, various mechanical experiments, such as uniaxial tension, compression, notched-bar tension, three-point bending, and C-ring compression tests, were conducted. The resulting force vs. displacement curves and textures were then compared with those based on the ΔEVPSC model. The computational model's significance is highlighted by simulation results demonstrating that the differential hardening along with a weak strength differential effect observed in the Mg-10Gd sample is a result of the interplay between micromechanical deformation mechanisms and deformation-induced texture evolution. Furthermore, the study highlights that incorporating the axisymmetric texture from the as-received material incorporating the measured texture gradient significantly improves predictive accuracy on the strength in the hoop direction. Ultimately, the findings suggest that the ΔEVPSC model can effectively predict the mechanical behavior resulting from loading scenarios that are impossible to realize experimentally, emphasizing its valuable contribution as a digital twin.</div></div>","PeriodicalId":16214,"journal":{"name":"Journal of Magnesium and Alloys","volume":null,"pages":null},"PeriodicalIF":15.8,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2213956724002810/pdfft?md5=8267ddd6a5db08a12120ca12f592bd79&pid=1-s2.0-S2213956724002810-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142312073","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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