Distinct amorphization resistance in high-entropy MAX-phases (Ti, M)2AlC (M=Nb, Ta, V, Zr) under in situ irradiation

High-entropy materials have been proposed for applications in nuclear systems recently due to their outstanding properties in extreme environments. Chemical complexity in these materials plays an important role in irradiation tolerance since it significantly affects energy dissipation and defect behaviors under particle bombardment. Indeed, better resistance to irradiation-induced amorphization was observed in the high-entropy MAX (HE-MAX) phase (Ti, M)2SnC (M = V, Nb, Zr, Hf). However, in this work, we report an opposite trend in another series of HE-MAX phases (Ti, M)2AlC (M = Nb, Ta, V, Zr). It is demonstrated that the amorphization resistance is sequentially reduced as the number of components increases from single-component Ti2AlC to (TiNbTa)2AlC and (TiNbTaVZr)2AlC. These phenomena are verified through AIMD simulations and interpreted by analyzing the underlying properties combining lattice distortion and bonding characteristics through the first-principle calculation. By developing a machine-learning (ML) model, we can directly predict lattice distortion to screen HE-MAX phases with excellent resistance to irradiation-induced amorphization. We highlight that the elemental species plays a more crucial role in the irradiation tolerance of these MAX phases than the number of constituent elements. Knowledge gained from this study will enable an improved understanding of the irradiation tolerance in HE-MAX phases and other multi-elemental ceramics.