Probing the effect of intragranular premature kappa-carbide on incipient plasticity behavior in austenite-based Fe-Win-Al-(Cr)-C steels

The effect of nanoscale intragranular premature kappa-carbide precipitates, having an ordered structure but without chemical partitioning, on the incipient plasticity behavior of austenite in Fe-Mn-Al-(Cr)-C low-density steels was investigated by nanoindentation. We found that the incipient plasticity was dominated by a heterogeneous dislocation nucleation mechanism via atom-vacancy exchange. Although the content of kappa-carbide decreased with Cr addition, its negligible effect on incipient plasticity strength was witnessed by the slightly increased shear stress for dislocation nucleation. Comparatively, the increased interstitial C atoms with Cr content in austenite enhanced lattice cohesions which impeded the nucleation events by increasing the requisite shear stress. IMPACT STATEMENT Despite being one of the most important strengthening phases, nanoscale premature kappa-carbide precipitates surprisingly have a negligible effect on incipient plasticity of austenite in Fe-Mn-Al-(Cr)-C low-density steels.