高应变速率下Mg-3Zn-1Y镁合金的各向异性及变形机制

Anisotropy and Deformation Mechanisms of As-Extruded Mg-3Zn-1Y Magnesium Alloy Under High Strain Rates

采用分离式Hopkinson压杆装置(SHPB)测试了挤压态Mg-3Zn^(-1)Y稀土镁合金在应变速率分别为1000、1500和2200 s^(-1)时的动态真应力-真应变曲线;采用OM和SEM等分析了其高速变形过程中的组织演变规律及断口形貌,从微观变形机制的角度探讨了具有强烈初始基面织构的挤压态镁合金产生各向异性的原因。分析结果表明:在高速变形条件下,由于加载方向不同,挤压态Mg-3Zn^(-1)Y镁合金的压缩行为表现出较明显的各向异性。挤压态Mg-3Zn^(-1)Y镁合金宏观上的各向异性是由于不同的微观变形机制所引起的。沿挤压方向压缩时,当应变较小时,变形机制主要为拉伸孪晶,当应变增加时,会有柱面滑移参与变形,当应变达到一定值时滑移成为其主要的变形方式。而沿挤压横向压缩时,随着应变速率增加,变形方式由压缩孪生为主变为基面滑移和二次锥面滑移协同变形。

As a very important design principle, the dynamic properties of materials attracted extensive attention in resent years and a bunch of works have been done concerning with the materials deformation behaviors under high strain rates. However, the dynamic behaviors of magnesium alloys are not through understood, especially the rare earth based magnesium alloys. In order to investigate the dynamic and anisotropic behavior under high strain rates deformation of as-extruded Mg-3 Zn^（-1） Y magnesium alloy, the split Hopkinson pressure bar（SHPB） apparatus was used to testing the true stress-true strain curves under the high strain rates of 1000, 1500 and 2200 s^（-1） of as-extruded Mg-3 Zn^（-1） Y magnesium alloy. The OM and SEM were used to analysis the micorstructure evolution and fracture surface morphology of the alloy. The true reason behind the anisotropic phenomenon was revealed based on the deformation mechanism of highly basal-textured magnesium alloy. The results demonstrate that the as-extruded Mg-3 Zn^（-1） Y magnesium alloy exhibits pronounced anisotropy during compression according to the loading direction. The anisotropy of the as-extruded Mg-3 Zn^（-1） Y magnesium alloy are arised from the variety of the deformation mechanisms. When the loading direction is along extrusion direction, the predominant deformation mode changes from extension twinning at a lower strain to prismatic slip at a higher strain.While compressed along extrusion radial direction（ERD）, the predominant deformation mode changes from contraction twinning to a coordination of basal and second order pyramidal slip with the increasing of strain.