低应变速率下AZ31镁合金热形变过程的取向成像分析

An Oim Analysis on the Deformation Mechanism in Hot Compressed AZ31 Magnesium Alloy

利用EBSD取向成像技术,分析了低应变速率下具有三种不同初始织构的AZ31镁合金在340℃伪平面应变压缩时的晶粒取向演变规律,目标在于揭示在超塑变形条件下塑性滑移进行的程度和不同类型滑移机制进行的程度。结果表明,不仅在 1(10 - 2s - 1应变速率下,即使在 4(10 -4s - 1应变速率(超塑变性条件)下,不同初始织构的试样中晶粒都以不同方式逐渐转到基面取向(｛0 0 0 2 ｝∥挤压面)附近,随应变量增大,基面织构变强。这说明塑性滑移在高温变形时起着重要作用。而基面初始织构的试样在变形过程中一直保持基面的取向,从织构演变规律上并没有观察到明显的非基面的 a +c 滑移发生,说明了常见的基面滑移仍是主要的塑性滑移机制。另外,在基面初始取向的试样中检测到晶粒发生粘滞性层流现象。

Orientation mapping based on EBSD technique was applied to analyze the rules of orientation evolution of grains in AZ31 magnesium alloy. The samples with three initial textures were deformed in the way of quasi-plain strain compression at low strain rate of 4(10-4 s-1. The aim is to reveal the extent of plastic slip and inhomogeneous mechanism of slip process under superplastic deformation condition. Results show that not only under 1(10-2s-1, but under 4(10-4 s-1(superplastic deformation condition), grains in all samples with initial textures rotate gradually to near basal orientation ({0002} ∥ compression plane) through different ways, and basal texture becomes stronger with increased strain, which indicates an important role of plastic slip during hot deformation. Otherwise, no evident non-basal slip of <a+c>as observed by referring texture evolution in the sample with initial basal texture, which keeps basal orientation all through deformation process. It was suggested that basal slip is still the uppermost plastic slip mechanism in hot deformation. In addition, the phenomenon of viscous laminar flow was observed in the sample with initial basal texture.