Effect of hot-dip tin coating treatment on the CuSn10Pb10/45 steel joint fabricated by diffusion bonding

The present study investigates the diffusion bonding of leaded-tin bronze (CuSn10Pb10) and 45 steel via surface modification method, i.e., hot-dip tin coating (HDTC) treatment, so as to provide guidance for the application of copper/steel joints. The effect of HDTC treatment on the interfacial microstructure and mechanical performance of CuSn10Pb10/45 steel joint is established. The results show that the interfacial crack is formed during diffusion bonding of CuSn10Pb10 and 45 steel without HDTC treatment. However, HDTC treatment evidently promotes the mutual diffusion of elements between CuSn10Pb10 and 45 steel, and a metallurgical CuSn10Pb10/HDTC 45 steel joint with a transition layer consisting of Fe-enriched solid solution, Cu-enriched solid solution and Cu10Sn3 intermetallic compound is obtained. The CuSn10Pb10/HDTC 45 steel joint at a bonding temperature of 900 °C shows higher shear strength and better ductility than that of CuSn10Pb10/45 steel joint. With the increasing of bonding temperature, the promoted occurrence and aggregation of Cu10Sn3 intermetallic compound in the CuSn10Pb10/HDTC 45 steel bonding interface results in the increase in shear strength, but the decrease in ductility of joint.