Strain hardening behaviour of an Fe-Ni-Cr-Al alloy

Strain hardening behaviour of Fe-Ni-Cr-Al alloys, in both solution treated and aged conditions, has been investigated at ambient temperature. The alloy in both solution treated and aged conditions exhibits three fairly distinct stages of strain hardening. The strain hardening rate decreases in regime I, remains constant in regime II and begins to fall again in regime III. The three regimes shift to lower strain levels upon ageing and then shift to higher strain levels with over-ageing. While interaction of slip and deformation twinning is responsible for the constant strain hardening rate in solution treated specimens, dislocation-dislocation interaction (forest interaction) leading to the formation of dislocation tangled networks contributes to such a behaviour in aged specimens. Although the precipitate size effects on work hardening behaviour are clearly discernible for both theta versus sigma and theta(d)sigma(d) versus sigma(d) plots, as compared to theta versus epsilon plots, the hybrid model (theta(d)sigma(d) versus sigma(d) plots) provides a quantitative description of precipitate size effects on the work hardening behaviour of the alloy in aged conditions.