Lead


Lay summary
Magnetism is a fundamental property of ferritic steels that needs to be understood to obtain insight into mechanical and plastic properties. Thus, in this project, synergistic XMCD and ab initio calculations investigate the magnetic properties of the Fe-Cr system.Background:Magnetism is inherent in the nature of ferritic materials. The inclusion of antiferromagnetic Cr in the ferromagnetic Fe matrix leads to anisotropy in the system due to spin-orbit coupling. The Fe-Cr alloy is the fundamental building block of many structural materials design due to superior properties of increased strength and hardness, low oxidation rate, corrosion resistance and retention of strength at high temperatures. However, the influence of the magnetism present in the Fe-Cr alloy has until recently been ignored in its development as a material exposed to extreme conditions. Our recent X-ray magnetic circular dichroism (XMCD) and extended X-ray absorption fine structure (EXAFS) measurements as well as ab initio calculations on two Fe-Cr alloys indicate the significant dependence between magnetism and structure. These results highlight that magnetism affects the properties of the alloy by altering stability, defect mobility and the dynamics of dislocations which in turn influence the material’s lifetime.Aim:This proposal aims to understand the magnetic structure of Fe-Cr alloys and, hence, it’s fundamental mechanical properties change with Cr content as a result of its anisotropic behaviour and in the long term determine optimal Cr concentrations in these alloys. Impact: From XMCD spectra, the orbital and spin moments of Fe and Cr will be determined and directly compared to ab initio calculation results. Trends will track the influence of Cr content, which is important within the search for optimal Fe-Cr alloys. This coupled approach will validate the modelling scheme while bringing forth a better knowledge of the atomistic mechanisms which influence Fe-Cr alloy properties. We expect the insights obtained in the role of magnetism in such mechanisms to impact a broad spectrum of materials users and developers including fission, fusion, aeronautics, space and magnetic storage device technologists.