Mg-3Zn-2Gd合金轧制态和退火态的组织与力学性能

Microstructure and Mechanical Properties of Rolled-and Annealed-Mg-3Zn-2Gd Alloy

利用光学显微镜和扫描电子显微镜分析了热轧态及退火态Mg-3Zn-2Gd合金的组织,并测试了其室温拉伸力学性能。结果表明：合金板材经应变为23%~67%的轧制后组织得到细化,平均晶粒尺寸由10μm减至轧制应变为67%时的4μm。初始组织中的大量孪晶和剪切带逐渐减少;随着轧制应变增至67%,剪切带消失,组织由动态再结晶晶粒和少量孪晶组成。拉伸力学性能显著提高,抗拉强度σb和屈服强度σ0.2分别由未轧制时的255 MPa和215 MPa提高至轧制应变为67%时的305 MPa和300 MPa,而伸长率δ先提高后降低。再经573 K退火处理1 h后,合金组织发生静态再结晶,变形不均匀区域消失,由细小均匀等轴晶组成;σb和σ0.2分别降至265 MPa和235 MPa,δ提高至19.0%;拉伸断口呈现大量韧窝,表现为韧性断裂。

Microstructure of hot rolled and annealed Mg-3Zn-2Gd alloy was characterized by optical microscopy and scanning electron microscopy.Meanwhile,their tensile mechanical properties at ambient temperature were tested.The results show that the microstructure of the alloy sheet is refined after rolling by the strain range from 23% to 67% and the average grain size decreases from 10 μm to 4 μm by the rolling strain of 67%.Lots of twins and shear bands in the initial microstructure decrease gradually.When the rolling strain increases to 67%,the shear bands disappear,and meanwhile the dynamic recrystalliza-tion grains and few twins exist,while the tensile mechanical properties of the alloy are enhanced significantly.Tensile strength σband yield strength σ0.2increase from 255 MPa and 215 MPa for the non-rolled alloy to 305 MPa and 300 MPa for the rolled alloy by strain 67% respectively,while the elongation δ first increases,and then decreases.After annealed at 573 K for 1 h,the rolled alloy experienced static recrystallization,in the meanwhile,the non-uniform deformation areas disappeared and finally showed a microstructure of fine and uniform equiaxed grains,and the relevant σband σ0.2decreased to 265 MPa and235 MPa,respectively,while δ slightly increases to 19.0%.The tensile fracture consists of a large number of dimples presenting the typical characteristic of ductile fracture.