Zr添加量对Mg-6Zn镁合金组织的影响

Effects of addition amount of Zr on microstructure of Mg-6Zn magnesium alloys

采用光学显微镜及万能力学拉伸试验机研究Zr质量分数(0.3%,0.6%,0.9%)对Mg-6Zn合金铸态、热处理后显微组织及力学性能的影响.研究结果表明:加入Zr元素后,合金的组织由树枝状转为颗粒状并分布于晶界,Zr质量分数增加到0.9%时,晶粒边界出现组织富集,质量分数为0.6%时合金则分布均匀.铸态及热处理条件下,合金的抗拉强度均呈现先上升后下降的变化趋势,含Zr质量分数0.6%时,合金的力学性能最高,铸态拉伸强度达到249 MPa,热处理后则为274 MPa.采用等温热处理法研究合金非枝晶组织随保温温度及保温时间的变化规律,保温温度620℃,保温时间30min时,含Zr质量分数0.6%的合金非枝晶组织圆整、细小.

The optical microscope and universal mechanical tensile testing machine were utilized to study the effect of Zr content（0.3%,0.6%,0.9%）on microstructure and mechanical properties of the as-cast and heat-treated Mg-6Zn alloy.The results showed that after addition of Zr,the microstructure of Mg-6Zn alloy would transform from dendritic into granular and element Zr would distribute at the grain boundary.When the mass-fraction of Zr increased to 0.9%,the enrichment of the microstructure around the grain boundary occurred,while the mass fraction of 0.6% alloy would distribute uniformly.Under the condition of the as-cast and heat treatment,the tensile strength of the alloy would increase at first and then descend.When the mass fraction of Zr was 0.6%,the mechanical properties would be the highest,and the tensile strength of the as-cast alloy reached 249 MPa,after heat treatment,the tensile strength of the alloy reached 274 MPa.Isothermal heat treatment method was utilized to investigate the changing pattern of the alloy non-dendritic structure with the heat preservation temperatures and time.When this temperature and time was 620 ℃ and 30 min respectively,the non-dendritic structure of alloy with 0.6% mass fraction of Zr would be round and fine.