TC4钛合金激光焊接头微观组织和硬度

Microstructure and microhardness of laser welding joints in TC4 alloy

采用光学显微镜和场发射扫描电镜观察了TC4钛合金激光焊接接头的显微组织,测量了接头焊缝中心到母材的显微硬度。结果表明,母材由α相和其相界上断续分布的粒状β相组成。焊接接头组织由粗大等轴晶区、柱状晶区、细等轴晶区和热影响区过热组织组成。粗大等轴晶区组织形态有层片状α+β、魏氏体α和网篮状α+β3种,其显微硬度略低于柱状晶区和细等轴晶区,但比母材高;柱状晶区和细等轴晶区组织为针状马氏体,柱状晶区显微硬度相对较高。热影响区显微硬度与母材相差不大。

Microstructure of welding joints in TC4 alloy manufactured by laser processing was investigated by optical microscope and scanning electron microscopy. The microhardness from weld center of the joint to base metal was measured. The results show that,in the base metal,the microstructure is consisted of α phase and dispersed granular β. Microstructure of the welding joint is composed of coarse equiaxed zone,columnar grain zone,fine equiaxed zone and reheat microstructure. The structure in the coarse equiaxed zone is consisted of platelet α + β,widmanstatten structure α and basket weave α + β,which microhardness is lower than that of the columnar grain zone and fine equiaxed zone,but higher than the base metal. The structure in the columnar grain zone and fine equiaxed zone is mainly needle-shaped martensite.The microhardness of the columnar grain is the highest in the joint. The microhardness of HAZ is close to that of base metal.