Mg-6Gd-(2-4)Y-1Zn变形镁合金的组织与性能

Microstructures and mechanical properties of Mg-6Gd-(2-4)Y-1Zn alloys

制备了3种不同成分的Mg-Gd-Y-Zn四元合金,并对其显微组织和力学性能进行了系统的研究.结果显示,Mg-6Gd-2Y-1Zn和Mg-6Gd-3Y-1Zn合金的铸态组织主要由α-Mg,(Mg,Zn)3Gd和18R-LPSO结构的Mg12Y1Zn1相组成.而Mg-6Gd-4Y-1Zn合金的铸态组织则主要由α-Mg,Mg24(YGdZn)5和Mg12Y1Zn1相组成.合金退火后,3种合金的退火组织均由α-Mg,Mg12Y1Zn1和14H-LPSO相组成.热挤压过程中Mg12Y1Zn1相被拉长,呈长条状沿挤压方向排列,而14H-LPSO相则分布于条状分布的Mg12Y1Zn1之间.挤压态合金经固溶和225℃时效(T6)处理后,显微组织中呈现14H-LPSO结构和β'沉淀相共存.对挤压后的合金直接进行时效处理(T5)过程中也发生了β'沉淀相,但14H-LPSO相体积分数少于T6态.3种合金中Mg-6Gd-4Y-1Zn合金在T6态的性能最好.

Three quaternary alloys with composition of Mg-6Gd-（2-4）Y-1Zn were prepared and their microstructure and mechanical properties were investigated. The results show that the as-cast microstructure of the Mg-6Gd-2Y-1Zn and Mg-6Gd-3Y-1Zn alloys studied consists of o^-Mg matrix, （ Mg, Zn） 3 Gd eutectic and Mg12 Y1 Zn1 phase which is 18R long-period staking ordered. The as-cast microstructure of the Mg-6Gd-4Y-1Zn alloy studied consists of α-Mg matrix, Mg24 （YGdZn） 5 eutectic and Mg12Y1 Zn1phase. After extrusion, the Mg12 Y1 Zn1 phase is stretched along the direction of extrusion, and the 14H-LPSO phase distributes between Mg12Y1Zn1 strips. When solution-treated alloys are aged at temperature of 225 ℃ （T6 treatment）, the 14H-LPSO phase and β＇ precipitates appear in the microstructure. Aging of as extruded alloys （T5 treatment） also causes the formation of β＇ precipitates but the volume fraction of the 14H-LPSO phase in the T5 treated specimens is lower than that in specimens after T6 treatment. High tensile strength combined with good ductility is achieved in Mg-6Gd-4Y-1Zn alloy after T6 aging.