On the Mechanisms of Ductility Enhancement in β+γ′- Ni70Al30 and β+(γ+γ)-Ni50Fe30Al20In Situ Composites

Abstract

ABSTRACTDuctile phase reinforcement is an attractive approach for improving room temperature ductility and toughness of intermetallics. Two alloys of nominal composition (at.%) Ni70Al30 and Ni50Fe30Al20 were directionally solidified to produce quasi-lamellar microstructures. Both alloys exhibit ∼10% tensile ductility at 300 K when the ductile phase is continuous, while the Ni70Al30 alloy has a tensile ductility of ∼4% when the γ′ phase is discontinuous. Observations of slip traces and dislocation substructures indicate that a substantial portion of the ductility enhancement is a result of slip transfer from the ductile phase to the brittle matrix. The details of slip transfer in the two model materials and the effect of the volume fraction and morphology of the ductile phase on the ductility enhancement in the composite are discussed.