Stacking fault energy calculation of pure metals used in high entropy alloys by the density functional theory

Abstract

Multicomponent alloys, high or medium entropy alloys or complex and concentrated alloys are designations of a new class of metal alloys, marked by the presence of several main elements. As the possible compositions are numerous, these alloys have a wide range of properties, especially mechanical, when compared to traditional alloys. Thus, the development of methods that allow to know in advance the effect of the composition on the properties of these alloys is essential to enable their development with an optimized experimental effort. In particular, several alloys exhibit the effect of phase transformation (TRIP) and twinning (TWIP) during deformation, these alloys tend to exhibit very high combinations of strength and ductility. In the present project, a route to calculate the driving force for these effects using the density functional theory method will be tested in the CrCoNi system. As the stacking fault energy (SFE) is what tends to control these mechanisms, this energy will be calculated by two methods, that of the difference in free energy between the face centered cubic (FCC) and hexagonal compact (HCP) phases and a supercell method in pure Cr, Ni and Co metals. The values will be compared to literature values and extrapolations for binary and ternary compositions will be tested via combination with the CALPHAD method. The important results to guide future developments of high entropy alloys with TWIP / TRIP effects. (AU)