高应变速率下AZ31镁合金的各向异性及拉压不对称性

采用分离式霍普金森拉杆及压杆装置,研究挤压态AZ31镁合金高速变形下的各向异性及拉压不对称性,并从微观变形机制的角度探讨具有强烈初始基面织构的挤压态镁合金各向异性及拉压不对称性产生的原因。结果表明:在高速变形条件下,依据加载方向及应力状态挤压态AZ31镁合金的拉伸行为表现出很强的各向异性,但压缩行为的各向异性不明显;在挤压方向表现出很强的拉压不对称性,而在垂直于挤压方向的拉压不对称性很低。挤压态AZ31镁合金宏观上的各向异性及拉压不对称性是由于不同的微观变形机制所引起的。沿挤压方向拉伸的主要变形机制为柱面滑移,沿垂直于挤压方向拉伸及压缩的主要变形机制为锥面滑移;沿挤压方向压缩时初始变形机制为拉伸孪晶,当变形量为0.08(8%)左右时由于孪晶消耗殆尽,变形变而以滑移的方式进行。

Anisotropy and asymmetry of as-extruded AZ31 magnesium alloy deformed under high strain rate

The anisotropy and asymmetry of an as-extruded AZ31 magnesium alloy deformed under high strain rate were investigated by split Hopkison tension(SHTB) and pressure bar(SHPB).The reasons for the anisotropy and asymmetry were analyzed in terms of deformation mechanisms.The tension and compression were conducted along the extrusion direction and transverse direction,respectively.The results demonstrate that the as-extruded AZ31 magnesium alloy exhibits pronounced anisotropy in tension,but the anisotropic behavior is not obvious in compression according to the loading direction and stress state.The anisotropy is considerably apparent rather in tension than in compression and the asymmetry is more pronounced in extrusion direction than in transverse direction.The anisotropy and asymmetry of the as-extruded magnesium alloy are caused by the variety of the deformation mechanisms: the prismatic slip is the main activation system if tension stress is along the extrusion direction,while the pyramidal slip is the control deformation mechanism for tension and compression along the transverse direction.The initial deformation mechanism of compression along the extrusion direction is the tension twinning;when the strain is about 0.08(8%) the tension twinning is exhausted.At this time the main deformation mechanism is changed to be slipping.