交叉轧制对AZ31镁合金边部组织及成形性的影响

Effect of Cross Rolling on the Edge Microstructure and Formability of AZ31 Magnesium Alloy

摘要:

为了改善镁合金变形组织及弱化基面织构强度,提高边部的成形性能。将AZ31B镁合金板在250℃~400℃的温度下以0.5m/s的速度进行热轧试验,设置四种不同交叉轧制路径,利用扫描电镜(SEM)、电子背散射(EBSD)技术详细分析了不同轧制工艺得到的镁合金板上边裂的宏观形貌、微观结构和织构。研究结果表明：镁板边部裂纹随着温度的升高呈减小趋势,在400℃条件下通过RII轧制路径得到的镁合金板几乎没有裂纹的出现。边部裂纹与轧制方向大致为45度,且RII路径下镁板边部为“O”形态的封闭裂纹,很难向两端进一步扩展,裂纹最宽部分为129μm。经过交叉工艺轧制后晶粒明显细化,大部分晶粒已发生完全动态再结晶,小角度晶界数量减少,基面织构也从23.68最低可降为7.62。更加细小的晶粒不仅可以产生更大面积的晶界,同时弱化基面织构,明显抑制裂纹的扩展,控制边裂的生成。

Abstract:

The AZ31B magnesium alloy sheet was subjected to a hot rolling test at a temperature of 250℃ to 400℃ at a rate of 0.5 m/s, and four different cross rolling paths were selected to reduce the edge cracks during the deformation. The hot rolling structures and textures were modified for controlling the edge crack generation. The macroscopic morphology, microstructure and texture of the magnesium alloy plate obtained by different rolling processes were analyzed by scanning electron microscopy (SEM) and electron backscattering (EBSD). The results show that, the edge crack of the magnesium plate decreases with the increase of the temperature, and there was almost no crack appearance in the magnesium alloy plate obtained by the RII rolling path at 400℃. The angles between Edge crack and rolling direction were approximately 45 degrees, and the edge of the magnesium plate formed a “O” with the widest part of 129μm under rolling path II, which meant that It will difficult to further expand to both sides. After the multi-cross rolling, the grains were obviously refined, and most of the grains had a completely dynamic recrystallization. The number of low-angle-grain-boundaries decreased with the changes of different rolling path, and the intensity of the base texture was reduced from 23.68 to 7.62. More fine grains can not only produce a larger grain boundary, but also weaken the base texture, and obviously inhibit the expansion of the crack, control the formation of edge crack.