Regulating the precipitation behavior of Mg alloys to overcome the strength-ductility trade-off puzzle is a long-thought pursuit in the materials community.With this purpose,external stress has been recently applied d...Regulating the precipitation behavior of Mg alloys to overcome the strength-ductility trade-off puzzle is a long-thought pursuit in the materials community.With this purpose,external stress has been recently applied during aging and shows immense potential in affecting atomic diffusion,and regulating the coherence of the phase boundaries.In this study,elastic tensile(TSA)and compressive stress aging(CSA)of Mg-1.1Gd-0.6Zn-0.3Mn alloy are carried out and the competition of precipitation between multiple precipitates occurs during stress aging.A significant quantity ofβ’precipitates primarily distribute along grain boundaries in conventional peak aging alloy.Whereas high density ofγ’phases rather thanβ’phase precipitate in both TSA and CSA alloys.The first-principle calculations reveal that the application of external stress introduces shear strain,which decreases unstable stacking fault energies,and thereby promoting the precipitation ofγ’phase and impeding the precipitation ofβ’phase.Furthermore,the sequential transformation fromγ’phase to Long Period Stacking Ordered(LPSO)phase occurs in CSA sample,due to the release of elastic local strain at phase boundaries.After subjected to TSA treatment,the sample possesses an ultimate tensile strength of 356 MPa,a yield strength of 294 MPa,and a total elongation of~14.3%.The excellent strength-ductility synergy of TSA sample is primarily contributed to the profuseγ’precipitates hindering the motion of large number of pyramidal(c+a) dislocations during tensile deformation.This study offers new insights on regulating the precipitation behavior of Mg alloys containing multiple types of precipitates through the application of external stress,and extends the potential window for obtaining an excellent strength-ductility synergy in age-hardenable Mg alloys.展开更多
青藏高原在末次冰期晚期(30—40 ka B.P.,相当于MIS3a阶段)出现的暖湿气候事件强烈地影响了川西高原东缘河流地质生态环境。表现在深切河谷中普遍发育大型滑坡、泥石流、冲洪积扇体等灾变事件和古堰塞湖沉积。本文重点剖析了岷江上游、...青藏高原在末次冰期晚期(30—40 ka B.P.,相当于MIS3a阶段)出现的暖湿气候事件强烈地影响了川西高原东缘河流地质生态环境。表现在深切河谷中普遍发育大型滑坡、泥石流、冲洪积扇体等灾变事件和古堰塞湖沉积。本文重点剖析了岷江上游、大渡河中游大型堵江事件的地形地貌特点、沉积物发育特征、沉积年代学、新构造背景等,同时分析了黄河上游玛曲段大型冲-洪积扇体的沉积特征与时代。结果表明在川西高原东缘深切河谷普遍存在距今30—40 ka时期的堵江事件,而这一时期在黄河上游发生大型冲-洪积事件和黄河袭夺若尔盖古湖事件,二者均与青藏高原末次冰期暖湿事件同步。研究认为这期急剧气温变化增强了河谷侵蚀和卸载能力,而东缘强烈的地震断层活动又触发了突发事件的发生,暖湿气候事件与新构造运动在时空上的耦合共同塑造了晚更新世晚期川西高原东缘深切河谷系统特殊的地质生态环境及其演变。展开更多
基金the financial supports from the University Natural Science Research Project of Anhui Province(No.2022AH050316)the National Natural Science Foundation of China,China(No.51901144)the Anhui Provincial Natural Science Foundation,China(No.2108085QE185)。
文摘Regulating the precipitation behavior of Mg alloys to overcome the strength-ductility trade-off puzzle is a long-thought pursuit in the materials community.With this purpose,external stress has been recently applied during aging and shows immense potential in affecting atomic diffusion,and regulating the coherence of the phase boundaries.In this study,elastic tensile(TSA)and compressive stress aging(CSA)of Mg-1.1Gd-0.6Zn-0.3Mn alloy are carried out and the competition of precipitation between multiple precipitates occurs during stress aging.A significant quantity ofβ’precipitates primarily distribute along grain boundaries in conventional peak aging alloy.Whereas high density ofγ’phases rather thanβ’phase precipitate in both TSA and CSA alloys.The first-principle calculations reveal that the application of external stress introduces shear strain,which decreases unstable stacking fault energies,and thereby promoting the precipitation ofγ’phase and impeding the precipitation ofβ’phase.Furthermore,the sequential transformation fromγ’phase to Long Period Stacking Ordered(LPSO)phase occurs in CSA sample,due to the release of elastic local strain at phase boundaries.After subjected to TSA treatment,the sample possesses an ultimate tensile strength of 356 MPa,a yield strength of 294 MPa,and a total elongation of~14.3%.The excellent strength-ductility synergy of TSA sample is primarily contributed to the profuseγ’precipitates hindering the motion of large number of pyramidal(c+a) dislocations during tensile deformation.This study offers new insights on regulating the precipitation behavior of Mg alloys containing multiple types of precipitates through the application of external stress,and extends the potential window for obtaining an excellent strength-ductility synergy in age-hardenable Mg alloys.
文摘青藏高原在末次冰期晚期(30—40 ka B.P.,相当于MIS3a阶段)出现的暖湿气候事件强烈地影响了川西高原东缘河流地质生态环境。表现在深切河谷中普遍发育大型滑坡、泥石流、冲洪积扇体等灾变事件和古堰塞湖沉积。本文重点剖析了岷江上游、大渡河中游大型堵江事件的地形地貌特点、沉积物发育特征、沉积年代学、新构造背景等,同时分析了黄河上游玛曲段大型冲-洪积扇体的沉积特征与时代。结果表明在川西高原东缘深切河谷普遍存在距今30—40 ka时期的堵江事件,而这一时期在黄河上游发生大型冲-洪积事件和黄河袭夺若尔盖古湖事件,二者均与青藏高原末次冰期暖湿事件同步。研究认为这期急剧气温变化增强了河谷侵蚀和卸载能力,而东缘强烈的地震断层活动又触发了突发事件的发生,暖湿气候事件与新构造运动在时空上的耦合共同塑造了晚更新世晚期川西高原东缘深切河谷系统特殊的地质生态环境及其演变。
