Development of a new AgCuZnSn filler metal for brazing TiNi shape memory alloy and stainless steel

A new-type AgCuZnSn filler metal suitable for brazing TiNi shape memory alloy and stainless steel and applying in biomedicine field has been developed. The melting characteristics, microstructure and brazing properties of AgCuZnSn filler metals were investigated and mechanical properties of the joints of TiNi shape memory alloy and stainless steel brazed with AgCuZnSn filler metals were evaluated. The results showed that the liquidus and solidus temperatures of the novel Ag51~53Cu21~23Zn17~19Sn7~9 filler metal were 590.0℃ and 635.3℃, respectively. The filler metal mainly consisted of α-Ag solid solution, α-Cu solid solution and Ag-Cu eutectic phase as well as a little Cu₄₁Sn₁₁, AgZn, Ag₃Sn and Cu₅Zn₈ compounds. The tensile strength of the brazed joint of TiNi shape memory alloy and stainless steel using the filler metal reached to 320~360 MPa while the loss of shape memory effect and superelasticity of TiNi shape memory alloy was low. The developed AgCuZnSn filler metal had advantage of low melting point, brazing metallurgy characteristics and interface metallurgy unity and the brazed joint had good tenacity and plasticity.