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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。
The microstructures of hot-rolled and annealed Mg-3Zn-2Gd alloy were analyzed by optical microscope and scanning electron microscope. The tensile mechanical properties at room temperature were tested. The results show that the microstructure of the alloy sheet is refined with the strain of 23% ~ 67%. The average grain size decreases from 10μm to 4μm when the rolling strain is 67%. Large numbers of twins and shear bands in the initial tissue gradually decrease; as the strain increases to 67%, the shear band disappears and the microstructure consists of dynamic recrystallized grains and a few twins. Tensile mechanical properties were significantly improved, the tensile strength σb and yield strength σ0.2 increased from 255 MPa and 215 MPa without rolling to 305 MPa and 300 MPa when the rolling strain was 67%, while the elongation δ First increase and then decrease. After annealed at 573 K for 1 h, the microstructure of the alloy recrystallizes with static deformation and the non-uniform deformation area disappears, which is composed of fine uniform equiaxed grains. The σb and σ0.2 decrease to 265 MPa and 235 MPa, respectively, and the δ increase to 19.0% Tensile fracture shows a large number of dimples, showing ductile fracture.