5A90铝锂合金电子束焊接头超塑性变形组织演变

Microstructure evolution of electron beam welded 5A90 aluminum lithium alloy during superplastic deformation

关键词:  铝锂合金  电子束焊  超塑性成形  组织演变

Key words:  aluminum lithium alloy  electron beam weld  superplastic deformation  microstructure evolution

摘要:

对5A90铝锂合金电子束焊接头进行高温拉伸试验，使用光学显微镜观察试样变形过程中的组织演变，并对变形机理进行分析.结果表明，超塑性变形初期，接头超塑性变形机制以扩散导致的晶界迁移为主，焊缝细小等轴晶粒迅速长大.当应变大于100%时，接头中大晶粒开始发生动态再结晶，超塑性变形机制转变为动态再结晶机制.在超塑性变形过程中热影响区平均晶粒尺寸与焊缝平均晶粒尺寸逐渐接近，组织存在耦合均匀化过程.提出采用均匀化系数K来表征焊缝与热影响区的组织均匀化程度，随着变形的进行，K值逐渐升高.

Abstract:

High temperature tensile test of 5A90 aluminum lithium alloy electron beam welding joints was carried out, using optical microscope to observe the microstructure evolution of the sample during deformation, and the deformation mechanism was analyzed. The results showed that the superplastic deformation mechanism at the initial stage of superplastic deformation mainly depended on the grain boundary migration caused by diffusion, and the fine equiaxed grains of the weld seam grew rapidly. When strain was greater than 100%, large grains in the joint began to arise dynamic recrystallization, and superplastic deformation mechanism changed into dynamic recrystallization mechanism. During superplastic deformation, the average grain size of the heat affected zone was close to the average grain size of the weld, and there was a homogenization process in the microstructure. Homogenization coefficient K was used to characterize the degree of homogenization of the weld and heat affected zone. With the deformation, the K value increased gradually.