Mechanical properties and deformation behavior of laminated Ni-(Ni2Al3+NiAl3) and Ni-(Ni3Al+NiAl) composites

The Ni-(Ni2Al3+NiAl3) and Ni-(Ni3Al+NiAl) laminated composites have been fabricated by reaction synthesis in vacuum using 0.40 mm thick Ni sheets and 0.08 or 0.15 mm thick Al foils. The aluminum layers were completely consumed owing to the formation of intermetallics. It was shown that the composites could be easily designed because the structures of the composites depended only on the treating time and temperature. Reaction synthesis at 620 °C for 2 h resulted in a microstructure consisting of Ni and Ni2Al3+NiAl3 layers. Heat treatment at 620 °C for 2 h and then at 1150 °C for 4 h resulted in composites comprising Ni and Ni3Al+NiAl layers. Compressive strength, flexural strength and impact toughness measurements were performed on the materials with different microstructures to establish their mechanical properties and deformation behavior. The results showed that the composition of intermetallic layers was the main factor determining properties. The Ni-(Ni3Al+NiAl) composites generally had higher mechanical properties than the Ni-(Ni2Al3+NiAl3) composites. The fracture behavior of the Ni-(Ni2Al3+NiAl3) laminates in all accomplished tests exhibited a mixture of brittle transverse cracking of intermetallics and ductile one of Ni layers. The Ni-(Ni3Al+NiAl) laminated composites behaved different. A non-catastrophic fracture was observed due to the micro-debonding along the Ni3Al/Ni3Al interfaces containing inclusions of Al2O3. The Ni3Al layers co-operatively deformed with the Ni layers during testing. As a result, the Ni-(Ni3Al+NiAl) composites behaved like a ductile alloy and exhibited considerable strain-hardening.