Plasticity in multiphase intermetallics

We have studied the mechanical behavior of model NiAl-based eutectic compos ites to gain insight on micromechanisms of plasticity in multiphase interme tallics. We show that in composites where the NiAl matrix and the reinforci ng ductile second phase can deform compatibly due to easy slip transfer acr oss interfaces, high room temperature tensile ductility and fracture toughn ess are obtained. In composites where interfaces are strong barriers to sli p transfer and the metallic second phase has high strength and limited duct ility, incompatible deformation of the two phases results in negligible ten sile ductility and limited toughness enhance ment. Factors that affect ease of slip transfer across interfaces are discussed. Calculations of dislocat ion pile-up stresses are used to predict whether slip is activated prior to cleavage or vice-versa for a given set of respective yield strengths and c rystallographic orientation relationships between the two phases. (C) 2000 Elsevier Science Ltd. All rights reserved.