Phenomenological understanding of kappa-carbides on strengthening mechanism of low-density steel

Abstract

We elucidate here the phenomenological understanding of deformation mechanisms over a wide range of strain rates (5.5 × 10–4s–1 to 5.5 × 10–1s–1) based on the evolution of microstructure. Atom probe tomography (APT), transmission electron microscopy (TEM) and electron back-scattered diffraction (EBSD) experiments were conducted to reveal the spatial distribution of precipitates and microstructure evolution. The ordered kappa-carbides were characterised by a layered-type structure, which made it difficult for dislocations to by-pass kappa-carbides in the same layer individually and the corresponding strengthening mechanism was cutting mechanism. Dislocations and microbands evolution analysis shows that compared to dislocations, slip band width was the key factor that governed the strength of the experimental steel at different strain rates.