Mechanical effects of Cr and V substitutions in AlFe₂B₂ by first-principles calculations

MAB phase AlFe₂B₂ has attracted a lot of attention as a ternary transition metal boride with layered structure due to its near-room temperature magneto-caloric effect (MCE), composed of earth-abundant elements and other properties. In this work the electronic structure, chemical bonding characteristics, mechanical stability, elastic properties, and elastic anisotropy of AlFe₂B₂-based compounds (borides) have been investigated using first-principles calculations based on density functional theory (DFT). The substitution effect of transition metals (TM) Cr and V in AlFe_(2-x)TM_xB₂ (x = 0–1), (TM = Cr, V) compounds have been investigated. It was determined that all the elements added instead of the removed Fe element in the borides increased the mechanical properties such as hardness, brittleness, and isotropy. Moreover, it has been observed that hardness, brittleness, and isotropy increase with the increasing amount of the fourth alloying element. In AlFe_(2-x)TM_xB₂, it has been observed that for x = 0.25 and 0.5 values, V causes an increase in stiffness more than Cr; however, for x = 1, while the increase in Cr continues to have an effect, a reverse trend is observed for V. Additionally, it has been observed that an increase in isotropy is significantly more influenced by Cr than by V. Among borides, it has been determined that AlFeCrB₂ exhibits the highest elastic moduli (bulk, shear, and Young's modulus), hardness, and isotropy.