Site-dependent Ga substitution in FeAl: Elastic and thermal transport properties

FeAl intermetallics have very high potential in structural and thermal applications at high temperatures due to their light-weight and oxidation resistance. However, they have low mechanical strength and poorly understood thermal behavior when alloyed with other elements. Gallium substitution has not been studied in detail, particularly with respect to its influence on structure, elasticity, and thermal transport in FeAl. In this study, we used density functional theory to study the properties of alloyed FeAl when gallium substitutes for either aluminum or iron. We performed structural, elastic, and thermal property calculations. It was found out that gallium substitution onto aluminum sites causes only a small lattice expansion and preserves the stability of the structure, but reduces both its stiffness thermal conductivity. Gallium on the iron sites, on the other hand, caused a significant jump in the lattice parameter, which led to mechanical instability and lower thermal conductivity. Most of the thermal transport was found to be dominated by electrons. This shows that gallium doesn’t just tweak FeAl’s properties, but it provides a way to tune them, depending on the site where the substitution is done. However, it is necessary to check intermediate substitution levels that yield ideal materials for structural applications.