应变速率对藕状多孔镁垂直于气孔方向压缩变形行为与力学性能的影响

摘要

Lotus-type porous magnesium was fabricated by unidirectional solidification, and the compressive experiments were subsequently conducted in the compressive direction vertical to the pores at strain rate in range of 1× 10−3−1650 s−1 using GLEEBLE−1500 materials simulation system and split Hopkinson pressure bar (SHPB). The effects of strain rate on the compressive deformation behaviors and mechanical properties of lotus-type porous magnesium were investigated. The results indicate that the compressive deformation process of lotus-type porous magnesium consists of a linear elastic stage, a plateau stage and a densification stage at various strain rates, and the stress increases with the increase of strain without the stress peak. The strain rates have significant effects on the compressive deformation behaviors of lotus-type magnesium in the compressive direction vertical to the pores. When compressed at a lower strain rate less than 60 s−1, lotus-type magnesium deforms mainly in the way, the round pore was firstly flatten to ellipse, then the wall of some pores earlier starts to collapse into the hole by a crescent-shaped bending and forms a first deformation band which is vertical to compressed direction. When compression continues, the deformation band forms continually. However, when compressed at high strain rates between 450 s−1 and 1650 s−1, the deformation band first forms along the diagonal direction and expands along the direction vertical to the diagonal. The strain rates have obvious influence on the mechanical property, and the main mechanism is that the deformation way of pore at lower strain rate is different from that at high strain rate.%利用定向凝固法制备藕状多孔镁，采用GLEEBLE−1500型材料模拟实验机和分离式霍普金森压杆(SHPB)装置，在以1×10−3~1650 s−1的应变速率范围内沿垂直于气孔方向进行压缩实验，研究应变速率对藕状多孔镁压缩变形行为和力学性能的影响。结果表明：当垂直于气孔方向压缩时，藕状多孔镁的应力−应变曲线分为应力线性增加的弹性阶段、应力缓慢增加的平台阶段和应力急剧增加的密实化阶段，应力随应变的增加持续增大，无应力峰值的出现。而当垂直于气孔方向压缩时，应变速率对藕状多孔镁的变形行为影响显著，在应变速率ε。<60 s−1条件下，主要变形方式为气孔先发生椭圆化变形，然后部分气孔的孔壁率先向气孔内发生弯月形塌陷并形成垂直于压缩方向的先变形带，随后变形带不断产生，从而逐步实现密实化；而较高应变速率(ε。=450~1650 s−1)下的变形方式虽然气孔也是先后发生椭圆化、孔壁向气孔内的弯曲塌陷等变形并形成先变形带，但先变形带沿试样对角线方向率先形成，并随压缩进行不断向与对角线垂直的方向扩展。应变速率对藕状多孔镁的力学性能有较明显的影响，其影响机制主要是由于不同应变速率时气孔的变形方式发生了变化。