Mg-(RE)-Zn合金不同状态下的物相构成、显微组织及性能

Phase Composition, Microstructure and Properties of Mg-(RE)-Zn Alloys in different states

摘要:

比较研究了Mg-(RE)-Zn合金铸态和经560 ℃扩散退火后的显微组织、物相及性能，发现铸态的Mg-(RE)-Zn合金经560 ℃保温7 h扩散退火，原晶界区的共晶组织消失，晶界净化，材料成分和显微组织均匀，扩散退火的过程中合金的物相构成和分布均发生显著变化， 由铸态下的Mg-(Me)固溶体+GdMg转变为均匀分布的Mg-(Me)固溶体+ MgGd3+MgZn2，经扩散退火后的合金平均硬度、抗拉强度和延伸率均提高，单向拉伸断裂方式由铸态下的沿晶断裂转变为微孔聚集型的穿晶断裂

Abstract:

The microstructure, phase composition and properties of Mg-(RE)-Zn alloys under different conditions were investigated, i.e. as-cast alloys and annealed alloys at 560 oC for 7 h. The results show that the as-cast Mg-(RE)-Zn alloy contains mainly the α-Mg(RE) solid solution and the GdMg phase, which distributes predominantly in the eutectic structure, but the eutectic microstructure completely disappears and there is no deposition in the grain boundary after annealing at 560 oC for 7 h. The annealed Mg-(RE)-Zn alloy involving the α-Mg (RE) phase, the MgGd3 phase and the MgZn2 phase, has a higher hardness, a higher ultimate tensile strength and a better elongation compared with the as-cast Mg-(RE)-Zn alloy. There is a significant difference in the fracture mode for the two alloys after a uniaxial tensile test. The fracture of the as-cast Mg-(RE)-Zn alloy exhibits an intergranular mode, while the fracture of the annealed Mg-(RE)-Zn alloy shows a transgranular mode induced by microvoid coalescence