Ti6Al4V薄板脉冲激光拼焊焊缝成形及力学性能

Formation of weld and mechanical properties of Ti6Al4V thin plate by pulse laser welding

为了改善钛合金薄板激光焊接过程中因工装误差或存在毛刺造成的焊穿、焊漏等缺陷,采用光纤激光器对1.2 mm厚的Ti6Al4V薄板进行脉冲激光焊接试验。分析脉冲频率、对接间隙及激光峰值功率3个工艺条件对焊缝成形的影响,针对外观成形较好的焊缝进行显微组织与力学性能测试,确定了适合Ti6Al4V薄板拼焊的最佳焊接工艺参数。结果表明,采用脉冲频率40 Hz,占空比60%,激光峰值功率2.0 kW,光斑直径0.7 mm,焊接速度1.8 m/min的脉冲激光焊接工艺可以获得质量优异的焊缝;焊缝由粗大的柱状β晶粒和针状α′相组成,热影响区形成了短针状α′相;随着峰值功率的增大,焊缝的显微硬度明显增大,抗拉强度逐渐减小。最优焊接工艺参数下的焊缝强度可以达到母材的98%,拉伸断口表面平整、规则,断面与拉伸轴线方向呈45°,断口含有大量韧窝。

In order to improve defects such as welding burn through and leakage caused by tooling error or burr in laser welding of titanium alloy sheet,a pulse laser welding experiment was carried out on 1.2 mm thick Ti6Al4V sheet with a fiber laser.Effects of pulse frequency,butt clearance and laser peak power on formation of weld were analyzed.Microstructure and mechanical properties of welds with good appearance were tested,and the best welding parameters suitable for butt welding of Ti6Al4V thin plate were determined.The results showed that excellent weld quality could be obtained by a pulse laser welding process with a pulse frequency of 40 Hz,a duty cycle of 60%,a laser peak power of 2.0 kW,a spot diameter of 0.7 mm and welding speed of 1.8 m/min.The weld consisted of thick columnarβgrains and acicularα′phase,and short needle shapeα′phase formed in heat-affected zone.With increase of peak power,microhardness of weld increased obviously,but tensile strength decreased gradually.Strength of weld under the optimal welding parameters could reach 98%that of base metal.The surface of tensile fracture was flat and regular,fracture surface to direction of tensile axis showed 45°,and fracture contained a large number of dimples.