Correlation between microstructure and tensile behavior of metal–intermetallic laminate compound with different initial Ni foil thickness

Abstract

Ni-base metal–intermetallic laminate composites were obtained from in situ reaction synthesis between Ni and Al foils by utilizing plasma activated sintering. The effects of Ni foil thickness on the microstructure and tensile properties of the composites were investigated. The results show that the phases forming during reaction synthesis are independent of the starting thickness of the Ni foils. However, thicker reacted layers are obtained in the samples fabricated from 100 μm Ni foils (Ni100) than those obtained in the samples from 50 μm Ni foils (Ni50) when treated at the same process. The tensile strength of Ni100 samples increases with the temperature increasing at the expense of ductility. Dissimilarly, Ni50 composites treated at higher temperatures exhibit enhanced strength and ductility. Both Ni50 and Ni100 laminate fracture in a similar mechanism. Cracking first occurs in the brittle intermetallic layers. These original cracks result in shear bands in Ni layers emitted from the crack tips, and thus producing local stress concentration, which initiates new cracks in adjacent intermetallic layers. The multiplication of cracks and shear bands leads to the failure of the laminates.