热处理对Mg-45Zn-1.5Nd合金组织及性能的影响

Effects of heat treatment on microstructure and properties of Mg-45Zn-1.5Nd alloy

采用常规铸造法制备了Mg-45Zn-1.5Nd三元合金,利用SEM、EDS、XRD、硬度及拉伸实验等方法,研究了热处理对Mg-45Zn-1.5Nd合金组织及性能的影响规律。结果表明:铸态组织由Mg7Zn3基体、α-Mg枝晶、α-Mg+MgZn共晶组织以及极少量的球状准晶相组成;退火后α-Mg枝晶和共晶组织溶入基体中,析出了球状准晶相,组织均匀化程度显著提高;热处理使Mg-45Zn-1.5Nd合金的性能大幅度提高,硬度和抗拉强度最高分别达到141.9 HB和168 MPa,比铸态合金提高了14.3%和48.7%,最佳热处理工艺为330℃×6 h;热处理后拉伸断口中尽管出现少量韧窝,但仍是以解理为主的脆性断裂。

Mg-45Zn-1.5Nd alloy was prepared by conventional casting method.Effects of heat treatment on microstructure and properties of the alloy were investigated by means of SEM,EDS,XRD,hardness tests and tensile tests.The results show that microstructure of the as-cast alloy consists of Mg7Zn3 matrix,α-Mg dendrite,α-Mg + MgZn eutectic structure and a very few spherical quasicrystal phase,and then the α-Mg dendrite and eutectic structure dissolve into the matrix,spherical quasicrystal phase precipitates and the homogenization degree of microstructure is significantly improved after annealing treatment.Compared with that of the as-cast alloy,the properties of Mg-45Zn-1.5Nd alloy are further improved by heat treatment.The hardness and the tensile strength of the alloy can be up to 141.9 HB and168 MPa,respectively,which are increased by 41.3% and 48.7% compared with that of the as-cast alloy.The best heat treatment process of Mg-45Zn-1.5Nd alloy is annealing at 330 ℃ for 6 h.The tensile fracture surfaces still exhibit cleavage brittle fracture although some dimples are observed.