低于β相相变温度时TC4钛合金搅拌摩擦焊接头的成形及拉伸性能

摘要

利用轴肩直径为15 mm的钨铼合金搅拌头对2.5 mm厚TC4钛合金进行搅拌摩擦焊,重点分析接头成形、显微组织与拉伸性能.结果表明:焊核区的横截面形貌呈现典型的"碗形";当转速小于200 r/min时,焊接过程中的温度峰值低于β相相变温度.组成焊核的搅拌针作用区常出现"撕裂"型缺陷,其主要与焊接过程中的焊接拉应力有关;降低搅拌头的旋转速度有利于减小、甚至消除"撕裂"型缺陷.低于相变温度下获得的无缺陷焊接接头的抗拉强度几乎与母材的等同,拉伸测试后的断口由大量韧窝组成,为典型的韧性断裂.%TC4 titanium alloy with thickness of 2.5 mm was friction stir welded using W-Re rotational tool with shoulder diameter of 15 mm. The formation, microstructure and tensile property of FSW joint were mainly discussed. The results show that nugget zone (NZ) of cross section presents typical bowl-like shape. When rotating speed is lower than 200 r/min, the peak temperature during welding is below β-phase transus temperature. The tearing defect often appears in pin affected zone of NZ, which results from the welding tensile stress during welding. Decreasing the rotating speed is beneficial to reduce and even eliminate the tearing defect. The defect-free FSW joint attained below β-phase transus temperature owns high tensile strength, which is almost equal to that of base metal. The fracture surface is composed of plenty dimples, presenting the typical ductile fracture.