The effect of temperature and time on the precipitation of κ-carbides in Fe-28Mn-10Al-0.8C low-density steels: aging mechanism and its impact on material properties

This study investigates the second phase evolution mechanism of κ-carbides during the aging process of Fe-28Mn-10Al-0.8C low-density steel (wt%) and its impact on the material's properties. Under different heat treatment conditions, intragranular κ-carbides exhibit various morphologies and crystallographic characteristics, such as acicular, spherical, and short rod-like shapes. At the initial stage of aging, κ-carbides primarily precipitate in acicular forms, accompanied by a few spherical carbides. With the extension of aging time, κ-carbides grow and coarsen, the spherical carbides significantly reduce, and the rod-like carbides become noticeably coarser. In the literature on low-density steel, κ-carbides primarily precipitate in the form of nanoscale particles from within austenite grains, with limited mention within ferrite matrix grains; furthermore, the second-phase evolution mechanism during the aging process remains unclear in the observations made in this experiment. By adjusting the aging temperature and time, this study thoroughly analyzed the crystallographic characteristics and morphological evolution of κ-carbides and investigated the impact of these changes on the material's microhardness. It comprehensively assessed the influence of different aging conditions on material properties and, based on these findings, proposed potential strategies for improving material strength.