临时合金元素氢对TC4钛合金搅拌摩擦焊接头微观组织和力学性能的影响

Effect of Hydrogen as a Temporary Alloying Element on Microstructure and Mechanical Properties of TC4 Titanium Alloy Friction Stir Welded Joints

摘要:

采用钨铼合金搅拌头对置氢0.1%，0.3%和0.5% (质量分数) 的α+β双相TC4钛合金进行搅拌摩擦焊，通过焊后真空退火将氢从焊态接头中除去，研究了氢作为临时合金元素对TC4钛合金搅拌摩擦焊接头微观组织和力学性能的影响。结果表明，氢含量对置氢钛合金焊态接头的微观组织和力学性能有很大影响。氢在焊接过程中几乎未从置氢钛合金中逸出并可以通过焊后真空退火除去。焊态接头中的亚稳相和含氢相在除氢过程中发生分解及转变，除氢后接头只由α及β两相组成，但焊态接头微观组织会影响除氢态接头中α和β两相比例及形态。氢含量越高，置氢钛合金本身的力学性能越低，其焊态接头的力学性能也越低。经过除氢处理后，不同氢含量的置氢钛合金性能得到恢复且趋向一致，其接头的性能差异也明显减小，而且除氢态接头的性能与未置氢钛合金接头的性能相当

关键词:搅拌摩擦焊;钛合金;热氢处理;微观组织;力学性能

Abstract:

The α+β dual phase TC4 titanium alloy hydrogenated with 0.1 wt%, 0.3 wt% and 0.5 wt% hydrogen was friction stir welded using a W-Re pin tool. Hydrogen was removed from the as-welded joints through post-weld vacuum annealing. Effects of hydrogen as a temporary alloying element on microstructure and mechanical properties of TC4 titanium alloy friction stir welded joints were investigated. Results show that hydrogen content has a significant influence on microstructure and mechanical properties in hydrogenated titanium alloy as-weld joints. Hydrogen almost does not escape from the hydrogenated titanium alloy during the friction stir welding and can be removed through post-weld vacuum annealing. The hydrogen-induced metastable phases and hydrogen-rich phases in as-welded joints decompose and transform during the dehydrogenation process. Mechanical properties of as-welded joints are also significantly recovered after dehydrogenation and the mechanical properties of dehydrogenated joints basically reach the level of the as-received unhydrogenated titanium alloy joints.

Key words:friction stir welding; titanium alloy; thermohydrogen processing; microstructure; mechanical property