Short communication Refinement and characterisation of a thermodynamically stable β-[Ni(Al,Ti)]–β′-[Ni₂ AlTi]–γ′-[Ni₃ (Al,Ti)] metal–metal composite

Abstract

The Ni–Al–Ti system contains three intermetallic phases, γ′, β, and β′ which have complementary properties. The objective of the present investigation was to coextrude these three phases to form a metal–metal composite (MeMeC) and investigate the mechanical properties and failure mechanisms of such a material. High strengths, comparable with that of the strongest constituent phase, have been recorded for the MeMeC material. Strength is maintained at a constant level up to 500°C above which it falls progressively. The compressive strain to failure is considerably greater that that expected for monolithic β or β ′ phases. It has been shown that the interfaces between nominally single phase regions provide lines of weakness along which cracks propagate during compressive loading. Preliminary attempts to strengthen the interfaces by a 24 h heat treatment at 900°C have been carried out.