The effect of Sn addition on the microstructures and mechanical properties of Mg-5Al-2Si alloys was investigated with variations of Sn contents （3 and 6 wt pct）. The microstructure of the alloy was characterized by ...The effect of Sn addition on the microstructures and mechanical properties of Mg-5Al-2Si alloys was investigated with variations of Sn contents （3 and 6 wt pct）. The microstructure of the alloy was characterized by the presence of Mg2Sn particles within matrix and at grain boundaries. As the Sn contents increased, yield and ultimate tensile strength were increased at room temperatures and 150℃. Creep properties were improved with the increasing amount of Sn due to the fine precipitation of Mg2Sn phases within grain during creep.展开更多
High-entropy alloys(HEAs)consisting of CoCrFeNiAlTi systems,with a face-centered cubic(FCC)matrix reinforced by ordered L12 precipitates,have demonstrated exceptional strength-ductility combinations.However,the curren...High-entropy alloys(HEAs)consisting of CoCrFeNiAlTi systems,with a face-centered cubic(FCC)matrix reinforced by ordered L12 precipitates,have demonstrated exceptional strength-ductility combinations.However,the current compositional design of HEAs heavily relies on high Ni and Co contents,compro-mising the balance between properties and cost.Thus,it is crucial to optimize the cost-performance trade-offby fine-tuning the range of Fe,Co,and Ni,while maintaining excellent strength-ductility com-bination.In this study,we propose a novel Fe-based HEA with nanosized precipitates and a heteroge-neous grain distribution,achieving a strength-ductility combination comparable to state-of-the-art Ni-or Co-based HEAs.The alloy benefits from both precipitation hardening and hetero-deformation-induced strengthening attributed to the heterogeneous grain distribution,resulting in excellent yield strength of 1433 MPa,tensile strength of 1599 MPa,and ductility of 22%.The microstructural evolution and its in-fluence on mechanical properties are unraveled with respect to the observation of precipitate-dislocation interaction and hetero-deformation-induced stress(HDI stress)evaluation.This study suggests that the challenge of balancing properties and cost can be addressed through optimized compositional and mi-crostructural design.展开更多
Herein,the evolution of long-period stacking ordered(LPSO)phases in the as-cast Mg-6Gd-1Zn-0.6Zr(wt.%)alloy are investigated via transmission electron microscopy(TEM)and atom probe tomography(APT).The TEM results reve...Herein,the evolution of long-period stacking ordered(LPSO)phases in the as-cast Mg-6Gd-1Zn-0.6Zr(wt.%)alloy are investigated via transmission electron microscopy(TEM)and atom probe tomography(APT).The TEM results reveal that two types of LPSO phase(a bulky interdendritic phase and a plate-like matrix LPSO phase)are formed in the as-cast sample.Most of the LPSO phases are confirmed to be of the 14H type,with a smaller proportion being of the 18R LPSO.Further,the APT results reveal that the composition of the interdendritic LPSO phase is closer to that of the ideal 14H phase compared to the matrix LPSO phase,and both the interdendritic and matrix LPSO phases exhibit a Gd/Zn ratio of 2.5,thereby indicating a deficient Zn content compared to the ideal 14H phase(i.e.,1.3).In addition,the influence of the LPSO phases on the deformation behavior is investigated at different compressive plastic strains using electron backscatter diffraction(EBSD)analysis to reveal twinning and slip behavior during deformation.The results indicate that the LPSO phase induces additional work hardening in the late stage of deformation via the suppression of{1011}compressive twinning and the activation of non-basal slip systems.展开更多
Martensitic-based microstructures in low-density steels offer high strength and improved specific strength,combined with the lightweight effect of aluminum(Al).However,while Al effectively reduces density,it simultane...Martensitic-based microstructures in low-density steels offer high strength and improved specific strength,combined with the lightweight effect of aluminum(Al).However,while Al effectively reduces density,it simultaneously promotes the formation of coarse ferrite and expands the two-phase(α+γ)intercritical temperature range.Thus,increasing the Al content for higher weight reduction inevitably leads to ferrite formation and impedes further strengthening.To achieve both high strength and duc-tility while incorporating ferrite,it is crucial to elucidate the effects of ferrite fraction,size,and dis-tribution on mechanical properties and deformation behavior,particularly in relation to phase interac-tions.In this study,three model steels were developed through controlled annealing temperatures,pro-ducing distinct triplex microstructures comprising ferrite,martensite,and retained austenite(RA).The role of each phase in strain partitioning was investigated using ex-situ microscopic digital image cor-relation and electron back-scattered diffraction analysis.Key findings reveal that the martensitic matrix ensures an ultrahigh strength level(1758 MPa),while a moderate fraction(∼17%)and homogeneous dis-tribution of intercritical-ferrite(IC-ferrite)enable sustainable strain-hardening behavior by delaying the transformation-induced plasticity(TRIP)effect.Strain partitioning into IC-ferrite reduces local strains in the martensitic matrix,preventing early exhaustion of the TRIP effect and facilitating ductile fracture behavior.This strategy leverages the presence of ferrite,offering significant advantages for applications requiring both ultrahigh strength and ductility.展开更多
文摘The effect of Sn addition on the microstructures and mechanical properties of Mg-5Al-2Si alloys was investigated with variations of Sn contents （3 and 6 wt pct）. The microstructure of the alloy was characterized by the presence of Mg2Sn particles within matrix and at grain boundaries. As the Sn contents increased, yield and ultimate tensile strength were increased at room temperatures and 150℃. Creep properties were improved with the increasing amount of Sn due to the fine precipitation of Mg2Sn phases within grain during creep.
基金supported by the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIT)(Nos.NRF-2022R1A5A1030054,NRF-2023M3H4A6A01058096).
文摘High-entropy alloys(HEAs)consisting of CoCrFeNiAlTi systems,with a face-centered cubic(FCC)matrix reinforced by ordered L12 precipitates,have demonstrated exceptional strength-ductility combinations.However,the current compositional design of HEAs heavily relies on high Ni and Co contents,compro-mising the balance between properties and cost.Thus,it is crucial to optimize the cost-performance trade-offby fine-tuning the range of Fe,Co,and Ni,while maintaining excellent strength-ductility com-bination.In this study,we propose a novel Fe-based HEA with nanosized precipitates and a heteroge-neous grain distribution,achieving a strength-ductility combination comparable to state-of-the-art Ni-or Co-based HEAs.The alloy benefits from both precipitation hardening and hetero-deformation-induced strengthening attributed to the heterogeneous grain distribution,resulting in excellent yield strength of 1433 MPa,tensile strength of 1599 MPa,and ductility of 22%.The microstructural evolution and its in-fluence on mechanical properties are unraveled with respect to the observation of precipitate-dislocation interaction and hetero-deformation-induced stress(HDI stress)evaluation.This study suggests that the challenge of balancing properties and cost can be addressed through optimized compositional and mi-crostructural design.
基金This work was supported by the National Research Foundation of Korea(Grant number:NRF-2019K1A3A1A18116059 and NRF-2023R1A2C200529811)Austrian Science Fund(FWF)(P 32378-N37)Federal Ministry of Austria Education,Science and Research(BMBWF)(KR 06/2020).
文摘Herein,the evolution of long-period stacking ordered(LPSO)phases in the as-cast Mg-6Gd-1Zn-0.6Zr(wt.%)alloy are investigated via transmission electron microscopy(TEM)and atom probe tomography(APT).The TEM results reveal that two types of LPSO phase(a bulky interdendritic phase and a plate-like matrix LPSO phase)are formed in the as-cast sample.Most of the LPSO phases are confirmed to be of the 14H type,with a smaller proportion being of the 18R LPSO.Further,the APT results reveal that the composition of the interdendritic LPSO phase is closer to that of the ideal 14H phase compared to the matrix LPSO phase,and both the interdendritic and matrix LPSO phases exhibit a Gd/Zn ratio of 2.5,thereby indicating a deficient Zn content compared to the ideal 14H phase(i.e.,1.3).In addition,the influence of the LPSO phases on the deformation behavior is investigated at different compressive plastic strains using electron backscatter diffraction(EBSD)analysis to reveal twinning and slip behavior during deformation.The results indicate that the LPSO phase induces additional work hardening in the late stage of deformation via the suppression of{1011}compressive twinning and the activation of non-basal slip systems.
基金financially supported by Korea Institute for Advancement of Technology(KIAT)grant funded by the Ko-rea Government(MOTIE)(HRD Program for Industrial Innova-tion)(P0023676)the National Research Foundation of Ko-rea(NRF)grant funded by the Korea government(MSIT)(NRF-2022R1A5A1030054,RS-2023-00281508,NRF-RS-2024-00345498).
文摘Martensitic-based microstructures in low-density steels offer high strength and improved specific strength,combined with the lightweight effect of aluminum(Al).However,while Al effectively reduces density,it simultaneously promotes the formation of coarse ferrite and expands the two-phase(α+γ)intercritical temperature range.Thus,increasing the Al content for higher weight reduction inevitably leads to ferrite formation and impedes further strengthening.To achieve both high strength and duc-tility while incorporating ferrite,it is crucial to elucidate the effects of ferrite fraction,size,and dis-tribution on mechanical properties and deformation behavior,particularly in relation to phase interac-tions.In this study,three model steels were developed through controlled annealing temperatures,pro-ducing distinct triplex microstructures comprising ferrite,martensite,and retained austenite(RA).The role of each phase in strain partitioning was investigated using ex-situ microscopic digital image cor-relation and electron back-scattered diffraction analysis.Key findings reveal that the martensitic matrix ensures an ultrahigh strength level(1758 MPa),while a moderate fraction(∼17%)and homogeneous dis-tribution of intercritical-ferrite(IC-ferrite)enable sustainable strain-hardening behavior by delaying the transformation-induced plasticity(TRIP)effect.Strain partitioning into IC-ferrite reduces local strains in the martensitic matrix,preventing early exhaustion of the TRIP effect and facilitating ductile fracture behavior.This strategy leverages the presence of ferrite,offering significant advantages for applications requiring both ultrahigh strength and ductility.
