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采用高温拉伸试验法对5A90铝锂合金电子束对接板超塑性变形行为进行了研究,并用显微镜对焊缝变形前后的显微组织进行观察。结果表明,随温度升高和初始应变速率增大,焊板的伸长率先增大后减小,在450℃,5×10~(-3)s~(-1)时达到最大为168%;焊板接头部分的塑性变形率随初始应变速率增大而增大,随温度升高先增大后减小,在变形参数为475℃,1×10~(-2)s~(-1)时达到最大为92%。随变形进行,焊缝中共晶组织逐渐消失,枝状晶不断长大并“熔解”在粗大等轴晶内。元素扩散导致的晶界迁移参与协调了接头的变形,温度升高和应变速率增加都可提高晶界迁移速率。
The superplastic deformation behavior of 5A90 Al-Li alloy electron beam butt joint was investigated by high temperature tensile test. Microstructures before and after deformation of the weld were observed with a microscope. The results show that as the temperature increases and the initial strain rate increases, the elongation of the welded plate firstly increases and then decreases, reaching a maximum of 168% at 450 ℃ and 5 × 10 -3 s -1, The plastic deformation rate of the welded joint increases with the increase of the initial strain rate and then increases with the increase of temperature, then decreases. When the deformation parameter is 475 ℃ and 1 × 10 -2 s -1 The maximum is 92%. With the deformation, the eutectic weld gradually disappeared, dendrites continue to grow and “melting ” in the coarse equiaxed. The grain boundary migration caused by the element diffusion is involved in coordinating the deformation of the joint. The increase of the temperature and the increase of the strain rate can increase the grain boundary migration rate.