The Effect of Stacking-Fault Energy on the Stress/Strain Curve of Dispersion-Hardened Ni-Co Alloys

Abstract

The 0.1% proof stress and strain-hardening rates of four Ni-Co-2½ vol.-% Al₂O₃ alloys, which varied in matrix stacking-fault energy from 24 × 10⁻² to 1 × 10⁻² J/m², have been studied in the temperature range 77–1000 K. The proof stress of the 0, 30, and 60% Co alloys was shown to be independent of temperature and strain rate below 600 K. However, that of the 67% Co alloy was temperature-sensitive, as a result of the temperature-dependence of stacking-fault energy which markedly affects the stability of Orowan loops at low fault energies. At temperatures above 600 K the strain-hardening rate of all the alloys became temperature- and strain-rate dependent, because of a recovery process that is dependent on stacking-fault energy.