应变速率对TC18钛合金厚板电子束焊接接头组织和力学性能的影响

Effect of strain rate on microstructure and mechanical properties of TC18 thick plate by electron beam welding

摘要:

研究了在优化后的焊接工艺参数下, TC18钛合金厚板电子束焊接接头沿板厚方向(上层、中层、下层)应变速率对显微组织、拉伸性能和应变硬化行为的影响。结果表明：焊接后焊缝微观结构发生了明显变化,熔合区显微组织由粗大的β相和次生α相组成。与母材相比,沿厚度方向的焊接接头表现出较低的强度和塑性,但其硬化能力增强。焊缝下层的强度和延伸率高于中层和上层。当应变速率为1×10-2 s-1时,焊缝的最大屈服强度和极限拉伸强度达到母材的83％。随着应变速率的增加,焊缝的硬化能力下降。拉伸断裂发生在焊缝区,上层的断裂过程为解理断裂,中下层为准解理断裂。

Abstract:

The influence of strain rate of Microstructures, tensile properties and strain hardening behavior of the electron beam welded joint for TC18 titanium alloy under optimized welding parameters were investigated with three slices (top, middle and bottom). The results showed that the welding led to significant microstructural changes across the joint. The microstructure of fusion zone is composed of coarsened β phase and secondary α-phase. Compared with the base metal, the joint slices along the thickness exhibited a lower strength and plasticity but a further higher hardening capacity. The strength and ductility of the bottom slices are higher than those of the middle and top slices. The maximum yield strength and ultimate tensile strength of the welding slices reached the base metal 83% at the strain rate of 1×10_-2 s_-1. The hardening capacity of welding slices decreased with increasing strain rate. It was significantly enhanced at the middle and bottom slices than the top slice. Tensile fracture occurred in the weld zone.The fracture process of the top slice is cleavage fracture. However, the middle and bottom slices are quasi-cleavage crack.