Microstructure and mechanical properties of Ni3Al-based alloy joint transient liquid phase bonded using Ni/Ti interlayer

Ni3Al-based alloy joints were fabricated by transient liquid phase (TLP) bonding with Ni/Ti composite inter-layer. The typical interfacial microstructure of the bonded joint was primarily composed of three zones: isothermal solidification zone, athermal solidification zone and base metal. Various reaction products were observed in the bonded joint, including gamma'-Ni-3(Al, Ti), TiNi3, Cr-Mo-Fe rich precipitates and beta-Ti. The TiNi3 phase in the athermal solidification zone was gradually reduced and eventually vanished by increasing the bonding parameters. The maximum room temperature shear strength of 828 MPa was obtained when the joint was bonded at 1220 degrees C for 60 min, while it was 625 MPa and 533 MPa at 650 degrees C and 800 degrees C, respectively. Cracks propagated primarily along the Ni3Al base metal and partially at the bonding interface when the joint was bonded at 1220 degrees C for 60 min, indicating the shear strength of the joint was almost equal to that of the base metal.