Li对快速凝固Mg--_(96.5)Gd_(2.5)Zn_1合金微观组织和力学性能的影响

Effects of Li Addition on Microstructure and Mechanical Properties of Rapidly Solidified Mg_(96.5)Gd_(2.5)Zn_1 Alloy

考察了快速凝固条件下不同含量Li元素添加对长周期有序结构相增强Mg_(96.5)Gd_(2.5)Zn_1合金微观组织和力学性能的影响。结果表明,随着Li元素的添加,铸态合金中Gd、Zn溶质原子在镁基体晶粒中的过饱和度降低、(Mg,Zn)_3Gd晶界析出相增加、镁基体晶粒尺寸减小。而固溶处理后,随着Li含量的增加,合金中14H型长周期堆垛有序结构相(LPSO)的形成受到抑制,同时纳米/亚微米(Mg,Zn)_3Gd颗粒相大量析出,当Li为7.6 at%时合金中LPSO相急剧减少。经热挤压变形后,合金中块状14H相发生扭折分层开裂、层片状14H相发生不同程度溶解、(Mg,Zn)_3Gd相破碎细化、基体发生不同程度再结晶;不加Li的Mg_(96.5)Gd_(2.5)Zn_1表现出最佳的力学性能(R_m=325 MPa,δ=9.5%),而含Li合金则随Li含量的增加,力学性能逐步下降。对合金在不同条件下的组织转变机理及力学行为变化进行了分析。

The effects of different amounts of Li addition on the microstructure and mechanical properties of rapidly solidified Mg96.5Gd2.5Zn1 alloy were investigated.The results indicate that the supersaturation of Gd and Zn solute atoms of the as-cast alloys decreases in the Mg matrix grains,and the（Mg,Zn）3Gd precipitates located at the grain boundaries increase and the grain size of Mg matrix decreases with the Li addition.After solid-solution treatment,the formation of 14H type of long-period stacking phase in the alloys is inhibited and the nano-or submicron（Mg,Zn）3Gd phase precipitates in large amounts with the increase of Li addition.And as the Li content is 7.6 at%,the volume fraction of LPSO phase in the alloy declines dramatically.After hot extrusion deformation,the block 14H phase in the alloys is kinked and delaminated,and the lamellar14H dissolves to some extent in the matrix.（Mg,Zn）3Gd phase is fragmented and refined,and different degrees of recrystallization occur in the matrix.Mg96.5Gd2.5Zn1 alloy exhibits the best comprehensive mechanical properties with the Rm=325 MPa and theδ=9.5%,whereas the mechanical properties of the alloys with Li addition decline gradually with the increase of Li addition.The microstructure evolution mechanism and mechanical behavior response under various conditions were analyzed.