TiNi形状记忆合金与不锈钢的瞬时液相扩散焊

Transient Liquid Phase Diffusion Bonding of TiNi Shape Memory Alloy and Stainless Steel

摘要:

采用AgCu金属箔作中间过渡层，对TiNi形状记忆合金与不锈钢进行了瞬时液相扩散焊，分析了接头的显微组织、元素分布和物相组成等，研究了接头的抗剪强度和断裂方式。结果表明：接头界面区由TiNi侧过渡区，中间区，不锈钢侧过渡区组成，主要相分别为Ti（Cu，Ni，Fe），AgCu，TiFe等。连接温度为860 ℃，保温时间为60 min，连接压力为0.05 MPa时，接头最大抗剪强度为239 MPa。断裂发生在TiNi母材和AgCu中间层扩散界面上，断口为混合断裂形貌。通过中间层等温凝固过程动力学模型，结合界面形貌和元素扩散分析，认为TiNi SMA与不锈钢异种材料瞬时液相扩散焊过程存在明显的非对称性。

Abstract:

TiNi shape memory alloy (SMA) and stainless steel (SUS304) were joined by transient liquid phase (TLP) diffusion bonding using Ag-Cu foil as interlayer. The microstructure, the element profile and the phase composition of the joint were analyzed, and the shear strength and the fracture mode of the joint were also investigated. The results show that the interface zone of the joint is composed of TiNi transition zone, middle zone and stainless steel transition zone, and their main phases are Ti(Cu,Ni,Fe), AgCu and TiFe, respectively. The maximum shear strength is about 239 MPa for the specimens joined at 860 °C for 60 min under a specific pressure of 0.05 MPa. The fracture occurs at the diffusion interface between TiNi alloy and AgCu interlayer, and the joint presents a characteristic of ductile-brittle mixed fracture. Based on interface morphology and element diffusion analysis, the kinetics of isothermal solidification was studied. It indicates that the process of TLP diffusion bonding of TiNi SMA and stainless steel shows a typical characteristic of asymmetry.