Mg-Gd-Y-Nd-Zr合金热压缩变形的动态再结晶机制（英文）

Dynamic recrystallization mechanisms during hot compression of Mg-Gd-Y-Nd-Zr alloy

在变形温度为450°C和应变速率为2 s-1的条件下对均匀化退火后的Mg-7Gd-4Y-1Nd-0.5Zr合金进行热压缩试验。采用金相显微镜(OM)、扫描电镜(SEM)和透射电镜(TEM)综合分析合金变形过程中的动态再结晶机制。采用电子背散射衍射(EBSD)获得晶体微取向信息。结果表明:随应变逐渐增加到-1.88,合金流变应力先快速升高到某个峰值,随后下降到最低值,最后又开始逐渐上升。在低应变下,大量{1 012}拉伸孪晶诱发形核形成动态再结晶晶粒,导致晶粒明显细化。动态再结晶晶粒首先在孪晶边界进行形核,且与孪晶母体存在30°<0001>的取向差。在大应变下,合金组织中在原始大晶粒附近形成细小动态再结晶晶粒,且从原始大晶粒内部到其晶界处的累积微取向连续增加,从而确定合金发生了连续动态再结晶。合金中也发现了粒子激发形核的动态再结晶机制。

Hot compression tests were conducted on a homogenized Mg-7Gd-4Y-1Nd-0.5Zr alloy at 450 ℃ and a strain rate of 2 s-1. Dynamic recrystallization （DRX） mechanisms were investigated by optical microscope （OM）, scanning electron microscope （SEM） and transmission electron microscope （TEM） systematically. The crystallographic orientation information is obtained through electron back-scattering diffraction （EBSD）. The result shows that the flow stress firstly reaches a peak rapidly followed by declining to a valley, and then increases gradually again when the alloy is compressed to a strain of-1.88. DRX related to {10]2} tensile twins is extensively observed at small strains, resulting in an evident grain refinement. DRX grains first nucleate along the edges of twin boundaries with about 30~ （0001） off the twin parents. While at large strains, conventional continuous DRX （CDRX） is frequently identified by the formation of small DRX grains along the original grain boundaries and the continuously increasing misorientation from the centre of large original grains to the grain boundaries. Evidence of particle-stimulated nucleation （PSN） is also observed in the present alloy.