Phase transformation and amorphization resistance in high-entropy MAX phase M2SnC (M = Ti, V, Nb, Zr, Hf) under in-situ ion irradiation

Chemical complexity significantly affects structures and properties in materials, such as high-entropy alloys and oxides. In this study, we firstly studied the radiation effects in high-entropy MAX phases, M 2 SnC ( M= Ti, V, Nb, Zr, Hf), irradiated by 800 keV Kr 2+ ions coupling with an in-situ transmission electron microscopy. Phase transformation of the initial hexagonal phase to intermediate γ phase and amorphization was observed during irradiation in both Ti 2 SnC and (TiVNbZrHf) 2 SnC using selected area electron diffraction (SAED) and high-resolution TEM (HRTEM) imaging. By comparing the structural evolution in these two materials under the same irradiation condition, the high-entropy MAX phase exhibits better tolerance to irradiation-induced phase transformation and amorphization than Ti 2 SnC. The roles of chemical complexity on the susceptibilities of these materials to structural evolution were elucidated by ab initio calculations. The M -Sn ( M = Ti, V, Nb, Zr, Hf) antisite defect formation energy in the (TiVNbZrHf) 2 SnC is lower than that in Ti 2 SnC due to the chemical complexity. Thus, (TiVNbZrHf) 2 SnC is prone to accommodate more point defects and maintain the lattice structure during irradiation. This study provides a comprehensive understanding of structural evolution in high-entropy MAX phases and proposes a new approach to searching MAX phases with outstanding radiation tolerance.