Microstructures and mechanical properties of a L12-structured precipitation strengthened Co-based superalloy

Abstract

A L12-structured precipitation (γˊ) strengthened Co-based superalloy is identified based on thermodynamic calculation and experimental validation. An alloy with composition of Co9Al5Mo30Ni2Ta10Cr is fabricated to explore the relationships among processing, microstructures and mechanical properties. Typical γ/γˊ two-phase microstructures have been obtained after heat treatments, where the spherical γˊ phase with diameter of ∼100 nm is uniformly distributed in the face centered cubic (FCC) matrix. The L12 structured γʹ-(Ni, Co)3(Al, Ta) phase can be stabilized, which coherently precipitates in the FCC matrix (γ) during aging treatment. The alloy exhibits promising strength with comparison to traditional Co-based superalloys at a temperature range from room temperature (RT) to 1000 °C. The predominant deformation mechanism transits from shearing of dislocation pairs to dislocations bypassing γʹ phase when deformation temperature increases from RT to 1000 °C.