Strengthening $\kappa$-carbide steels using residual dislocation content

TL;DR

This study shows that hot rolling at lower temperatures increases residual dislocation density in Fe-Mn-Al-C steel, significantly enhancing strength without sacrificing ductility, and does so without hindering precipitation of κ-carbides.

Contribution

It demonstrates that optimizing hot rolling temperature can improve steel strength through residual dislocation retention without affecting κ-carbide precipitation.

Findings

Lower temperature rolling increased yield strength by 299 MPa.

Residual dislocation density remained high after aging.

Precipitation kinetics of κ-carbides were unaffected by dislocation density.

Abstract

A steel with nominal composition Fe-28Mn-8Al-1.0C in mass percent was hot rolled at two temperatures, 1100 \degree C and 850 \degree C and subsequently aged at 550 \degree C for 24 h. The lower temperature rolling resulted in a yield strength increment of 299 MPa while still retaining an elongation to failure of over 30\%. The large improvement in strength was attributed to an increase in residual dislocation density which was retained even after the ageing heat treatment. A homogeneous precipitation of $\kappa$-carbides in both samples also showed that the high residual dislocation density did not adversely affect precipitation kinetics. These findings demonstrate that the tensile properties of this class of steel can yet be improved by optimising hot rolling process parameters.