船用TA5钛合金激光焊接接头组织和性能研究

采用IPG光纤激光器对8 mm厚的TA5钛合金进行激光自熔焊接，并对焊接接头的微观组织和力学性能进行分析。结果表明，激光焊接接头表面成形连续、均匀、无飞溅，内部无气孔和裂纹等缺陷。母材组织为细小均匀的等轴α相；焊缝区组织主要由粗大的β柱状晶粒、大量的针状马氏体α'以及少量的板条马氏体组成；热影响区组织主要由等轴α相、少量的针状马氏体α'和少量的残余β组成；在熔合线的边界，柱状晶粒与等轴晶粒联生结晶、外延生长，保证了焊接接头的稳定连接。焊接接头各区域的显微硬度差异较大，最高硬度出现在熔合线附近，焊缝区和热影响区的显微硬度明显高于母材的。对拉伸断裂部位进行观察，拉伸断裂发生在远离焊缝的母材处，这说明激光焊接接头的抗拉强度与母材等强或者略高于母材的，这与大量针状马氏体形成的网篮组织有直接的关系。 

Microstructure and Mechanical Properties of Laser Welded Joint of TA5 Titanium Alloy

The 8 mm thick TA5 titanium alloy is welded by IPG fiber laser, and the microstructure and mechanical properties of the welded joint analyzed. The result shows that the surface of the laser welded joint is continuous, uniform and with no splash, and there are no such internal defects as pores and cracks. The microstructure of base metal is equiaxed α phase, fine and uniform. The microstructure of weld zone is mainly composed of coarse β columnar grains, a large amount of acicular martensite α' and a small amount of lath martensite. The structure of heat affected zone is mainly composed of equiaxed α phase, a small amount of acicular martensite α' and a small amount of residue β. At the boundary of the fusion line, columnar grains and equiaxed grains are crossly crystallized and epitaxially grown, so as to ensure the stable connection of the welded joint. The Vickers hardness of each area of the welded joint varies greatly, the highest hardness exists near the fusion line, and the hardness of weld zone and heat affected zone is significantly higher than that of base metal. The tensile fracture exists at the base metal, away from the weld, indicating the tensile strength of the laser welded joint is equal to or slightly higher than that of the base metal. The high tensile strength of the weld is due to the net-basket structure formed by a large amount of acicular martensite.