Microplasticity in Elgiloy

Abstract

The room temperature microstrain characteristics of Elgiloy (composition in wt%, 40 Co, 20 Cr, 15 Ni, 7 Mo, 2 Mn, 0.1 C, balance Fe) have been determined for a range of microstructures corresponding to various alloy treatments reported previously. The friction stress was found to be constant (σ _F=12±3 MN m⁻²) for the solution treated (after prestrain), cold-worked and cold-worked plus aged at 500° C conditions, but decreased toσ _f=5±3 MN m⁻² after ageing at 800° C. The microscopic yield stress (MYS) increased with cold-working and subsequent ageing at 500° C to a maximum value of 210 MN m⁻² reflecting the increase in the long range internal stress field. An increase in the MYS of the solution treated strip was noted with ageing at 800° C, whereas the MYS of the cold-worked samples was decreased by this treatment. The solution treated and aged at 800° C samples exhibited a two-stage stress-plastic microstrain curve, whereas the cold-worked and cold-worked plus aged at 500° C conditions showed a three-stage stress-plastic microstrain behaviour.