An investigation of fracture and fatigue crack growth behavior of cast niobium aluminide intermetallics

This paper presents the results of a combined experimental and theoretical study of fracture toughness and fatigue crack growth in cast Nb-15Al-xTi (x = 10, 25 and 40 at%) niobium aluminide-based intermetallics. Fracture toug hness and fatigue crack growth resistance are shown to improve sigificantly in the cast alloy containing 40 at% Ti. The improvements in the fracture t oughness of the 40Ti alloy are shown to be due to the combined effects of l igament toughening, crack-tip plasticity and crack-tip blunting. The atomis tic simulations show that the increased plasticity in these alloys is assoc iated with their higher Ti content. The micromechanisms of fatigue crack gr owth are also elucidated. The implications of the results are discussed for potential structural application of niobium aluminide intermetallics. (C) 1999 Elsevier Science S.A. All rights reserved.