Effect of brazing temperature on interfacial microstructure and mechanical property of 316L/AuSi/NiTi joint

The NiTi shape memory alloy was successfully brazed with 316L stainless steel by AuSi filler metal. The interfacial microstructures of brazed joints at different temperatures were analyzed by scanning electron microscope and energy dispersive spectrometer. The results showed that the typical interfacial microstructure of 316L/AuSi/NiTi joint was 316L/(Fe,Cr)₅Si₃/Au(s,s)+Ti₁₄Ni₄₉Si₃₇(+Si)/Ni₄Si₇Ti₄+NiSiTi/NiTi. With the rising of temperature, the (Fe,Cr)₅Si₃ layer on 316L stainless steel side was gradually formed and grew thicker, while the NiSiTi layer on NiTi alloy side was thick at first and then became thinner. Meanwhile, the content of Si in the braze seam decreased gradually. The shear test indicated that the brazed joint at 600 ℃ for 30 min exhibited the highest shear strength of 34 MPa. The path of fracture analysis showed that the joint tended to fracture along the solid solution in the brazing seam.