Cu-Sn-Ti/Cu foam/Cu-Sn-Ti multi-layer composite fillers to modulate the microstructure and shear strength of YG18/Cu-Sn-Ti/40Cr joints

In this study, the Cu-Sn-Ti/Cu foam/Cu-Sn-Ti multi-layer composite fillers were designed to reduce the proportion of intermetallic compounds in YG18/Cu-Sn-Ti/40Cr joints, so as to modulate the microstructure and shear strength . The introduction of Cu foam effectively inhibited the Co solubilization in YG18 into the filler layer and reduced the content and proportion of intermetallic compounds such as Co 2 SnTi and CuSn 3 Ti 5 in the filler layer. At Cu foam thicknesses of 50 and 100 μm, the foam Cu would interact with the filler metal , which promoted the uniform distribution of the phase inside the filler layer and formed a stable composite structure. However, the liquid filler metal was difficult to fill completely due to the increase in the total volume of the pores when the thickness of the Cu foam was 200 μm, resulting in the formation of defects such as lack of weld and holes. The typical microstructure of the joint was YG18/“wedge” structure (WC + TiC)/TiC layer/Cu [s, s] + eutectic (CuSn 3 Ti 5 + Cu [s, s])/TiC layer/40Cr. The Cu foam effectively enhanced the shear strength of the joints. In comparison to the joint without Cu foam, 100 μm Cu foam enhanced the shear strength of the joint by 32 % to 284 MPa. • Cu-Sn-Ti/Cu foam/Cu-Sn-Ti multi-layer composite filler was designed to braze the YG18/40Cr joints. • The introduction of Cu foam effectively inhibited the Co solubilization in YG18 into the filler layer. • The addition of Cu foam effectively reduced the content and proportion of intermetallic compounds in the filler layer. • Compared to the joint without Cu foam, 100 μm Cu foam enhanced the shear strength of the joint by 32 % to 284 MPa.