中间层厚度对TLP扩散连接TC4组织和性能的影响

Effects of interlayer thickness on interfacial microstructure and joint performance of transient liquid phase bonded TC4 titanium alloy

摘要:

采用电沉积Ni/Cu层作为中间层实现了TC4钛合金瞬时液相（TLP）扩散连接，采用扫描电子显微镜、能谱仪和X射线衍射仪研究了Cu层厚度对TC4钛合金接头界面微观组织和力学性能的影响，并结合Ti-Cu和Ti-Ni二元相图阐明了反应机制。结果表明，瞬时液相扩散连接接头的典型界面组织为TC4/α-Ti+Ti2(Cu, Ni)/TC4，其中Ni元素均以固溶体的形式存在于接头中。随着电沉积Cu层厚度增加，扩散层和焊缝宽度增加，接头中央未焊合的孔洞消失，反应层中开始出现连续的Ti2(Cu, Ni)金属间化合物层且宽度逐渐增加。接头抗拉强度在电沉积Cu层厚度为15 μm时达到最大值500 MPa。断裂分析表明，所有TLP扩散连接接头均以解理断裂方式在焊缝处断裂。

Abstract:

Transient liquid phase (TLP) diffusion bonding of TC4 titanium alloy was realized using an electrodeposited Ni/Cu layer as interlayer. The effects of Cu interlayer thickness on interfacial microstructure and mechanical property of TC4 joint were studied by scanning electron microscopy, energy disperse spectroscopy and X-ray diffractometer, and the reaction mechanism was clarified by Ti-Cu and Ti-Ni binary phase diagram. The results show that the typical interfacial microstructure of the joint is TC4/α-Ti+Ti2(Cu, Ni)/TC4, and Ni element exists in the form of solid solution. With the increase of the thickness of electrodeposited Cu layer, the width of diffusion layer and welding seam increased, and the voids in the center of the joint disappeared. Continuous Ti2(Cu, Ni) intermetallic layer appeared in the reaction layer and its width increased gradually. The tensile strength of the joint increased first and then decreased, reaching the maximum value of 500 MPa when the thickness of Cu layer was 15 μm. Fracture analysis showed that all of the bonded joints fractured at the welding seams in the form of cleavage modes.