采用高功率碟片激光器焊接8 mm厚TC4钛合金, 研究了激光焊接接头的显微组织和力学性能。结果表明, 焊缝组织为晶界明显的粗大原始β柱状晶, 晶内为针状马氏体, 随着激光功率的增加, 马氏体分布更加密集; 近焊缝侧的热影响区组织为残余α相＋针状马氏体, 近母材侧的热影响区只发生α相向β相转变。焊接接头的显微硬度从母材到焊缝呈增加趋势, 至焊缝处达到最高, 不同功率下的焊缝显微硬度相当; 8 mm厚 TC4钛合金在速度为2.7 m/min, 7.3～7.9 kW高功率工艺参数下可获得质量良好的焊缝, 焊接接头的抗拉强度、延伸率与母材相当, 断裂在母材; 在速度为2.7 m/min, 7.0 kW低功率工艺参数下, 焊缝有气孔倾向, 焊接接头的延伸率只有母材的24%, 断裂在焊缝。断在母材和焊缝的断口都呈韧窝形貌, 断在焊缝的断口韧窝数目更少。

The TC4 titanium alloys with a thickness of 8 mm were welded by high power disk laser, the microstructure and mechanical properties of the laser beam welded TC4 titanium alloy were researched. Results show the microstructure of weld metal consists of clear-boundary course primary β columnar with intragranular acicular martensite. With increasing laser power, the distribution of martensite becomes more dispersive. The heat affected zone close to the weld metal is characterized by retained α phase and acicular martensite. The transformation of α to β phase is the only phase change in the heat affected zone close to the base metal. The microhardness increases from the base metal to the weld metal, and reaches the highest in the weld metal. The microhardness of the weld metal at different power is almost equivalent. Under the welding speed of 2.7 m/min and laser power 7.3~7.9 kW, the sound welds of 8 mm TC4 titanium alloy were obtained, the tensile strength and elongation of the welded joints are equivalent to the base metal, and the welded joints rupture in the base metal. Under the welding speed of 2.7 m/min and laser power 7.0 kW, the weld metal has a porosity tendency, and the elongation of welded joints reaches 24% of that of the base metal, and the welded joints rupture in the weld metal. The micrograph of fracture in the base metal and in the weld metal both shows dimple character, and the number of the dimple at the weld metal fracture is less than that at the base metal fracture.