Microstructures and properties of in situ synthesis Ni/Ni-Al multilayer composites

Full-density Ni/Ni-Al multilayer composites were successfully fabricated by in - situ reaction of Ni and Al foils at 620°C for 1 hour under 1 MPa pressure, and then diffusion annealing for 4 hours at 750°C , 950°C and 1150°C respectively under 5 MPa pressure in vacuum. Ductile Ni layer in composites can greatly improve room-temperature fracture toughness by microcracks bridging and blunting. After annealing at 750°C and 950°C , Al₂O₃ at the surface of Al foils before reaction remains at the interface of bilayer Ni₂Al₃ as inclusions, which makes interface poorly bonded. But after annealing at 1150°C , Ni₃Al layer is well-bonded with Ni and NiAl layer. So, the composites show significantly strain-hardening and plastic flow, its mean fracture strength and strain are 786 MPa and 12.8% respectively.