(北京科技大學(xué) 新材料技術(shù)研究院，北京 100083)
摘 要: 利用定向凝固法制備藕狀多孔鎂，采用GLEEBLE-1500型材料模擬實(shí)驗(yàn)機(jī)和分離式霍普金森壓桿(SHPB)裝置，在以1×10-3~1650 s-1的應(yīng)變速率范圍內(nèi)沿垂直于氣孔方向進(jìn)行壓縮實(shí)驗(yàn)，研究應(yīng)變速率對(duì)藕狀多孔鎂壓縮變形行為和力學(xué)性能的影響。結(jié)果表明：當(dāng)垂直于氣孔方向壓縮時(shí)，藕狀多孔鎂的應(yīng)力-應(yīng)變曲線分為應(yīng)力線性增加的彈性階段、應(yīng)力緩慢增加的平臺(tái)階段和應(yīng)力急劇增加的密實(shí)化階段，應(yīng)力隨應(yīng)變的增加持續(xù)增大，無(wú)應(yīng)力峰值的出現(xiàn)。而當(dāng)垂直于氣孔方向壓縮時(shí)，應(yīng)變速率對(duì)藕狀多孔鎂的變形行為影響顯著，在應(yīng)變速率 <60 s-1條件下，主要變形方式為氣孔先發(fā)生橢圓化變形，然后部分氣孔的孔壁率先向氣孔內(nèi)發(fā)生彎月形塌陷并形成垂直于壓縮方向的先變形帶，隨后變形帶不斷產(chǎn)生，從而逐步實(shí)現(xiàn)密實(shí)化；而較高應(yīng)變速率( =450~1650 s-1)下的變形方式雖然氣孔也是先后發(fā)生橢圓化、孔壁向氣孔內(nèi)的彎曲塌陷等變形并形成先變形帶，但先變形帶沿試樣對(duì)角線方向率先形成，并隨壓縮進(jìn)行不斷向與對(duì)角線垂直的方向擴(kuò)展。應(yīng)變速率對(duì)藕狀多孔鎂的力學(xué)性能有較明顯的影響，其影響機(jī)制主要是由于不同應(yīng)變速率時(shí)氣孔的變形方式發(fā)生了變化。
關(guān)鍵字: 藕狀多孔鎂；應(yīng)變速率；變形行為；力學(xué)性能；變形機(jī)制
（Institute for advanced Materials and Technology, University of Science and Technology Beijing, Beijing 100083, China）
Abstract: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.
Key words: lotus-type porous magnesium; strain rate; deformation behaviors; mechanical property; deformation mechanism
