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本文选用大晶粒和微细晶粒两种镁合金,利用现代测试手段进行超塑性变形机制的研究.结果表明,在超塑性变形条件下,两种合金都显示以晶界滑动为主的,由扩散蠕变和位错滑移所协调的复合变形机制.作者提出一个包括三种变形机制在内的复合机制模型.在超塑性变形中,下层金属晶粒通过晶界滑动不断涌现到试样表面横向晶界发生宽化及空洞的地方,从而不断增加沿拉伸轴方向上的晶粒数.这是试样在拉伸变形中获得非常大的伸长量的原因.
In this paper, two types of magnesium alloys, large grains and fine grains, were selected to study the mechanism of superplastic deformation by means of modern testing methods. The results show that both superplastic deformations show that the grain boundary sliding is dominated by Diffusion creep and dislocation slip coordination mechanism.The author proposed a composite mechanism model including three deformation mechanisms.In the superplastic deformation, the lower metal grains continue to slip through the grain boundary to the surface of the specimen The lateral grain boundaries are widened and hollow, increasing the number of grains in the direction of the stretching axis, which is why the specimen attains a very large elongation in the tensile deformation.