Formation of intermetallic compound layer in multi-laminated Ni-(TiB2/Al) composite sheets during annealing treatment

Solid-state reactive diffusion between Ni and Al was investigated during annealing at 650°C by employing multi-laminated Ni-(TiB(2)/Al) composite sheets. In multi-laminated Ni-(TiB(2)/Al) composite sheets annealed up to 5min NiAl(3) was the only phase observed in the diffusion zone, and Ni(2)Al(3) appeared after longer annealing time. Most grains of Ni(2)Al(3) showed equiaxed morphology rather than columnar microstructures like NiAl(3), due to the low concentration gradients of Al and Ni at the Ni/NiAl(3) interface. The preferential formation of this intermetallic compound NiAl(3) in multi-laminated Ni-(TiB(2)/Al) composite sheets was predicted using an effective heat of formation model. The present work indicated that both Ni and Al interdiffused, and the formation of NiAl(3) was a reaction-diffusion process.