Interfacial microstructure and mechanical properties of Ti/Cu joint manufactured by Ni-Al thermal explosion reaction

The dissimilar metals joining of Ti/Cu was conducted using a rapid thermal explosion (TE) reaction. The Ni-Al powder mixture was used as TE reaction system, and the effect of temperature (600, 700, 800 and 900 degrees C) on interfacial diffusions, microstructure and mechanical properties of Ti/Cu joint were investigated. The maximum combustion temperature of Ni-Al interlayer during heating process was 720 degrees C and a significant exothermic phenomenon was observed for 5 s. The infiltration of melted Al into the Ti/Cu substrate and formed a continuous transition region at the interface of the joints were the dominant joining mechanisms. Microhardness of the interlayer after heated at 900 degrees C for 30 min possessed prominent improvement from 32.6 to 101.7 HV due to the completely phase transformation of Ni-Al interlayer, which composed of main phase NiAl and minor phase Ni3Al. The bond strength of the joint was checked to assess the joint quality. For the joint processed by 900 degrees C for 30 min, the maximum shear strength of Ti/NiAl and Cu/NiAl were 33.4 MPa and 39 MPa, respectively.