Insights into the assessment of the magnetic-field-induced precipitation behavior of alloy carbides M7C3 in steels

Abstract

A combination of first-principles calculations, Weiss molecular field theory and density functional perturbation theory is combined to systematically evaluate the magnetic-field-induced thermodynamic properties of the alloy carbide M7C3 in steel. Special emphasis is focused on the self-magnetic and the external magnetic-field-induced magnetic contribution determined by extending the magnetic heat capacity. The self-magnetism origins from the 3d orbit contribution of the Fe atoms which constituted the carbon-containing trigonal prism. The magnetic-field-induced Curie temperature which triggers the boundary of the long and short-range magnetic order closely related to the Cr content and the magnetic field strengths. The higher external magnetic-field-induced Gibbs energy change provides a potential precipitation strategy in advance for the alloy carbides M7C3 which is well in agreement with the experimental results. Our insights further will extend the mechanistic understanding of magnetic-field-induced phase transformation in ferromagnetic Fe-based alloys, emphasizing the role of external field in minimizing energy and guiding new alloy design.

Keywords

• Alloy carbides M7C3
• Thermodynamic properties
• High magnetic field
• Steel