Microstructure and tensile behavior of Ni-base metal-intermetallic laminate composites prepared by plasma activated sintering

Ni-base metal-intermetallic laminate (MIL) composites were obtained from in-situ combustion reaction between the Ni and Al foils by a plasma activated sintering (PAS). Microstructural observation reveals that the laminates consist of alternate residual Ni layers and reacted layers which can be further divided into multiple layers of Ni-aluminides. The compositional gradient series of these intermetallic phases change in a stepwise fashion from Al-rich phases to Ni-rich phases with the increasing of the treatment temperature. Accordingly, the tensile strength of the composite increases steadily with the increase of temperature. The composites fabricated at 1473 K have the highest tensile strength and elongation. The fractographies of the tensile samples indicate that the failure of the composites treated at lower temperatures (1073 K and 1173 K) result from the interaction between the transversal cracks in the intermetallic layers and the shear bands in the Ni layers. When the treatment temperature increases, a transition from multiple cracking to a single cracking of the intermetallic layers can be observed.