TC4钛合金搅拌摩擦焊微观组织演变机制及影响

Mechanism and effects of microstructure evolution of TC4 titanium alloy in friction stir welding

采用搅拌摩擦焊技术在保护气氛下对单块TC4钛合金板材施焊,并获得良好成形。重点研究搅拌区α+β双相微观组织演变机制及不同工艺参数对组织硬度的影响。结果表明,经优化后的工艺参数条件下,搅拌区组织经历了α/β相变,最终形成基于β相区的α+β双态组织,搅拌头行走过后冷却析出的层片状α相沿β相区界面及内部分布,α相及β相晶粒细化明显,α/β层片间距的缩小可增强α+β复相强化效应,提高搅拌区硬度。搅拌头转速的提高增加了β相区的长大倾向,行进速度的提高降低了α相比例,并可生成针状马氏体。

The friction stir welding was employed for the processing of TC4 titanium alloy with good-formability,under the protective atmosphere. Evolution mechanism of α＋β dual phase microstructure in stirred zone and their effects of processing parameters were researched.The α/β transformation behaviors were completed to produce the microstructure of β-regions with acicular-α phase among interface and internal distribution. Grain refinement of α and β phase was obvious,the shortening of the α/β lamellar spacing distance could strengthen the α＋β phase reinforcement effect,improve the stir zone hardness. The improvement of the tool rotation speed could increase the tendency to grow up of β-regions,while the elevating of travel speed could reduce the α phase ratio and generate needle-type martensites.