Understanding the mechanical properties of reduced activation steels

Highlights: • A comprehensive guide for optimizing elastic properties and intrinsic ductility of ferritic, Fe-rich, FeCrWVMn alloys is provided. • The superposition of individual solute effects in Fe₉₁Cr₉ accurately describes micro-mechanical properties of FeCrWVMn alloys. • The charge transfer and change in partial d-pressure explains strong solute effect of W on bulk modulus and lattice parameter of Fe₉₁Cr₉. • The intrinsic ductility of Fe₉₁Cr₉ is enhanced by W or V addition and deteriorated by Cr or Mn addition. Reduced activation ferritic/martensitic (RAFM) steels are structural materials with potential application in Generation-IV fission and fusion reactors. We use density-functional theory to scrutinize the micro-mechanical properties of the main alloy phases of three RAFM steels based on the body-centered cubic FeCrWVMn solid solution. We assess the lattice parameters and elastic properties of ferromagnetic α-Fe and Fe₉₁Cr₉, which are the main building blocks of the RAFM steels, and present a detailed analysis of the calculated alloying effects of V, Cr, Mn, and W on the mechanical properties of Fe₉₁Cr₉. The composition dependence of the elastic parameters is decomposed into electronic and volumetric contributions and studied for alloying levels that cover the typical intervals in RAFM steels. A linear superposition of the individual solute effects on the properties of Fe₉₁Cr₉ is shown to provide an excellent approximation for the ab initio values obtained for the RAFM steels. The intrinsic ductility is evaluated through Rice's phenomenological theory using the surface and unstable stacking fault energies, and the predictions are contrasted with those obtained by empirical criteria. Alloying with V or W is found to enhance the ductility, whereas additional Cr or Mn turns the RAFM base alloys more brittle.