置氢TC4钛合金线性摩擦焊接头组织

采用线性摩擦焊技术对置氢TC4钛合金进行了焊接。利用金相显微镜、扫描电镜和透射电镜等对不同氢含量试样接头各区的显微组织进行分析,并探讨氢致钛合金高温塑性的微观机理。结果表明:置氢钛合金试样接头的焊缝宽度比未置氢试样的明显减小;随着氢含量的增加,试样母材和热力影响区组织中β相的含量增加;氢使得钛合金试样焊缝附近的位错密度降低,说明氢促进了位错运动;置氢钛合金接头组织中层错和孪晶的数量明显增加;在氢含量为0.4%和0.6%(质量分数)的TC4钛合金接头组织中发现了面心立方结构(FCC)的片状氢化物δ。氢主要是通过改变钛合金中的两相比例,促进位错运动和动态再结晶等机制来增强钛合金的高温塑性,从而改善线性摩擦焊的连接性能。

Microstructure of linear friction welded joints of hydrogenated TC4 titanium alloy

The linear friction welding of hydrogenated TC4 titanium alloy was carried out,and the microstructures in different zones of joints were investigated by optical microscopy(OM),scanning electron microscopy(SEM) and transmission electron microscopy(TEM).The micro mechanism of improving high temperature plasticity of titanium alloy induced by hydrogen was also analyzed.The results show that the weld width of hydrogenated specimen decreases evidently compared with that of the non-hydrogenated one.The β phase fraction of the base metal and thermomechanically affected zone(TMAZ) increases with the increase of hydrogen content.The dislocation density near the weld bead of the joint is decreased by hydrogen,which shows that the dislocation motion is promoted by hydrogen.The amounts of faults and twins increase significantly in the joint of hydrogenated alloy.There are δ titanium hydride(FCC structure) plates precipitated in the joints containing hydrogen 0.4% and 0.6%(mass fraction).The high temperature plasticity of titanium alloy is enhanced by hydrogen mainly through mechanisms as: changing phase proportion of α and β,promoting dislocation movement and dynamic recrystallization,inducing twin in alloy.As a result,the linear friction welding performance is improved by hydrogenation.