Softening Al₁₃Fe₄ intermetallic compound through Fe-site multi-principal-element doping

Designing transition materials that can reduce the brittleness/hardness of interface intermetallic compound (IMC) is of practical significance to accelerate the integration of Al-steel hybrid component into car bodies. Bearing the IMC-induced predicament in mind, in this study we investigate the possibility to intrinsically softening Al₁₃Fe₄ through Fe-site multi-principal-element doping. Our density functional theory (DFT) calculations and experiments show that, pronounced softening is achievable through binary FeNi, ternary FeNiCo, quaternary FeNiCoCr and quinary FeNiCoCrMn equiatomic doping. Among the so-generated IMCs, Al₁₃(FeNi)₄ and Al₁₃(FeNiCo)₄ exhibit the most significant softening effect. This is closely related to the weakening of chemical bonds through the filling of extra electrons induced by doping Ni and Co with more valence electrons to the anti-bonding orbitals. Our works suggest the promise of applying high/medium entropy alloys as transition materials during Al-steel dissimilar metal welding/joining and paves the avenue of designing transition materials with desirable compositions.