高应变下挤压态Mg-8Zn-2.5Nd-0.8Y镁合金的力学性能和组织演变分析

Mechanical properties and tissue evolution analysis of Mg-8Zn-2.5Nd-0.8Y magnesium alloys under high strain

采用分离式霍普金森压杆,测试挤压态Mg-8Zn-2.5Nd-0.8Y镁合金在不同应变速率下的真应力-真应变曲线,并分析其高应变压缩时的组织演变。结果表明:横向压缩曲线未形成明显屈服,表现出连续屈服的特点,当应变速率增大,最大流变应力随之增大。纵向压缩曲线具有连续屈服的特点,表现出明显的正应变速率强化特征。横向与纵向屈服强度都随应变速率的增大而增大。挤压态镁合金基体中生成了明显的再结晶组织,晶粒平均尺寸约为25μm。试样进行横向压缩后,基体中生成了很多孪晶组织,孪晶之间相互平行。纵向压缩变形组织中生成了更多细小的孪晶组织。

The true stress-true strain curves of the extruded Mg-8Zn-2.5 Nd-0.8 Y magnesium alloy with different strain rates were measured with separated hopkinson pressure bar,and the structural evolution of the extruded Mg-8 Zn-2.5 Nd-0.8 Y magnesium alloy with high strain compression was analyzed. The results show that the transverse compression curve has not formed obvious yield,and the deformation is continuous yield. As the strain rate increases,the maximum rheological stress also increases. The longitudinal compression curve has the characteristics of continuous yield and shows obvious positive strain rate enhancement. Both transverse specimen and longitudinal yield strength increase with the increase of strain rate. In the extruded magnesium alloy matrix,an obvious recrystallization structure is formed,and the average size of the grain is about 25 μm. Many twin structures are formed in the matrix after transverse compression of the sample,and these twin crystals usually remain parallel to each other. More fine twin structures are formed after longitudinal compression deformation.