HIGH SPEED PROCESSING OF NI-ALUMINIDES-REINFORCED NI-MATRIX COMPOSITES BY PULSED-CURRENT HOT PRESSING (PCHP)

Abstract

Nickel-aluminides-reinforced nickel-matrix composites were fabricated from 0.05mm-thick nickel foils and 0.012mm-thick aluminum foils, in a process using a pulsed-current hot pressing (PCHP) equipment, and the effect of reaction temperature on mechanical properties of the composites was investigated. The composites were of laminated structure and composed of Ni and reacted layers containing Ni -aluminides. The chemical composition of the reacted layers was dependent on reaction temperature in the temperature range employed. Tensile testing at room temperature revealed that the reaction temperature evidently influences mechanical properties, including tensile strength, elongation and fracture mode, of the composites. The tensile strength and elongation of composites fabricated at 1373K were 500MPa and 3.8%, respectively. Microstructure observations of fractured specimens revealed that Ni layers of the composite played a significant role in prohibiting the growth of numerous cracks emanating from Ni -aluminides. In the case of composites fabricated at 1373K, in addition, crack propagation between Ni -rich Al -solid-solution layers and cellular Ni 3 Al in the Ni -aluminides were prevented by mutual interaction.