T4处理后AZ91镁合金焊接接头组织演变规律

Evolution rule of microstructure of AZ91 magnesium alloy welded joint after T4 treatment

为了明确固溶(T4)处理工艺参数对AZ91镁合金焊接接头组织演变规律的影响,需要进行T4处理优化设计,确定最佳热处理工艺.热处理后分别采用光学显微镜、扫描电子显微镜和拉伸试验机对焊接接头的显微组织和力学性能进行分析.结果表明,T4处理可以改变接头的组织形态,影响第二相β-Mg17Al12的位置,增大晶粒尺寸,特别是粗晶区;较为合理的T4参数可以提高抗拉强度,提高塑性,降低硬度;AZ91镁合金固溶处理的最佳工艺条件为420℃×15 h,抗拉强度为274.28 MPa.

In order to clarify the effect of technological parameters of solid solution( T4) treatment on the evolution rule of microstructure of AZ91 magnesium alloy welded joint,the optimization design for T4 treatment technological parameters is necessary to determine the optimal heat treatment technology. After the heat treatment,the microstructure and mechanical properties of welded joint were investigated with the optical microscope( OM),scanning electron microscope( SEM) and tensile testing machine. The results showthat the T4 treatment can change the microsrtructural morphologies of welded joint,affect the location of second phase β-M g17Al12,and increase the grain size specifically in the coarse-grained zone. The reasonable T4 technological parameters can improve the ultimate tensile strength and plasticity,but decrease the hardness. The optimum technological conditions of solid solution treatment for the AZ91 magnesium alloy is 420 ℃ × 15 h,and the ultimate tensile strength is 274. 28 M Pa.