仿空间条件下Mg-25at%Zn亚包晶合金的快速凝固组织与微观力学性能  

Microstructural evolution and micromechanical property of rapidly solidified Mg-25at%Zn hypoperitectic alloy under simulated space conditions

作　　者：龙强 胡亮[1] 糜晓磊 武博文 魏炳波[1] LONG Qiang;HU Liang;MI XiaoLei;WU BoWen;WEI BingBo(School of Physical Science and Technology,Northwestern Polytechnical University,Xi’an 710072,China)

机构地区：[1]西北工业大学物理科学与技术学院,西安710072

出　　处：《中国科学:技术科学》2025年第2期270-280,共11页Scientia Sinica(Technologica)

基　　金：国家重点研发计划(编号:2021YFA0716301);国家自然科学基金(批准号:52088101);陕西省自然科学基金(编号:2023JCJQ30)资助项目。

摘　　要：采用自由落体实验技术,实现了Mg-25at%Zn亚包晶合金在仿空间条件下的快速凝固和组织调控,揭示了微观组织随过冷度的演变规律,分析了Mg_(51)Zn_(20)包晶相对合金力学性能的影响.在近平衡条件下,合金微观组织由初生α-Mg枝晶和(α-Mg+MgZn)共析组织构成.当过冷度增大到44 K时,微观组织中开始出现Mg_(51)Zn_(20)包晶相.过冷度达到124 K时,α-Mg初生相的形核和生长被抑制,微观组织呈现壳核结构特征,核区为Mg_(51)Zn_(20)包晶相,壳区为(α-Mg+MgZn)共析组织.相比于共析组织,Mg_(51)Zn_(20)包晶相具有高硬度、低弹性模量和高抗磨性.随着过冷度的增大,Mg_(51)Zn_(20)包晶相体积分数逐渐提升,共析组织片层间距不断减小,合金平均维氏硬度显著提高,最高可达283 HV,提升了39%.若合金液滴过冷度升至154 K(0.23TL),共析转变被完全抑制,形成单一亚稳Mg_(51)Zn_(20)包晶相的凝固组织.The rapid solidification mechanism of Mg-25at%Zn hypoperitectic alloy under simulated space conditions was studied by the drop tube technique.The microstructure of near-equilibrium solidification was characterized by primaryα-Mg dendrite and interdendritic(α-Mg+MgZn)eutectoid structure.In the case of freely falling alloy droplets,theoretical calculations revealed that both cooling rate and liquid undercooling increased exponentially with the decrease of droplet diameter,and their maximums attained 9.78×10^(3)K s^(−1)and 154 K(0.23TL),respectively.As liquid undercooling increased,the nucleation and growth of the primaryα-Mg phase and the following eutectoid transition were both suppressed,leading to the formation of metastable Mg_(51)Zn_(20)peritectic phase.The nanoindentation measurements indicated that both hardness and Young’s modulus of(α-Mg+MgZn)eutectoid structure showed an increasing trend with the enhancement of liquid undercooling.The hardness of the eutectoid structure rose monotonously from 2.8 to 3.5 GPa,whereas that of Mg_(51)Zn_(20)phase decreased slightly below 3.9 GPa.The Vickers hardness of alloy particles was enhanced from 203 to 283 HV with the rise of undercooling,which was attributed to the increased volume fraction of metastable Mg_(51)Zn_(20)peritectic phase.Such a metastable phase with high hardness and low Young’s modulus can only be derived from rapid solidification which is quite senseful for improving mechanical properties.

关 键 词：快速凝固 镁合金 亚包晶合金 力学性能 

分 类 号：TG146.22[一般工业技术—材料科学与工程]