Abstract
This paper presents the results of recent studies on the ambient temperature fracture toughness and cyclic crack growth characteristics of a ductile-phase toughened gamma-titanium aluminide intermetallic alloy reinforced with TiNb particles. Under monotonic loading, substantial toughening is achieved in the composite microstructure and is ascribed to bridging of the crack by uncracked TiNb particle reinforcements in the wake of the crack tip. Crack-particle interactions such as crack bridging, bifurcation, deflection and crack renucleation contribute to an enhancement in toughness. Under cyclic loading, ductile phase toughening was found to be less effective resulting in an inferior fatigue crack growth resistance of the composite when compared to the monolithic counterpart. The lower cyclic fatigue resistance is attributed to an increased susceptibility of the ductile phase to fatigue failure, coupled with the mutually interactive influences of an absence of bridging contributions to crack-tip shielding, higher crack-tip opening displacements and the intrinsic effects of inelastic strains that are developed in the ductile phase-reinforced composite matrix.
Published Version
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