Low temperature mechanical behavior of Ni-15Cr-Ai-Ti-Mo alloys

Abstract

A series of Ni-15 Cr-Al-Ti-Mo alloys with varying γy-γ’ mismatch, Ti/Al atomic ratio, and weight fraction of γ’ were tension tested at ambient temperature after aging to peak yield strength at 760°C. After subtracting the alloy yield stress in the solution treated condition, σss, the increment in yield stress due to precipitation of γ’, Δσy, was found to be principally influenced by the weight fraction of γ’ and the measured γ-γ’ mismatch. Only a small contribution of APBE to alloy strength was observed between two compositions of similar mismatch and differing measured APBE. The work hardening behavior of the alloys was similarly influenced by weight fraction of γ’ and γy-γ’ mismatch. Alloys with low mismatch exhibited sheared γ’ precipitates following tensile deformation. A model for shear of ordered γ’ precipitates by residual dislocation loops in low γ-γ’ mismatch alloys is proposed to account for the low work hardening rates observed.