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, M2SnC (M=Ti, V, Nb, Zr, Hf), irradiated by 800 keV Kr2+ 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 Ti2SnC and (TiVNbZrHf)2SnC 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 Ti2SnC. 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)2SnC is lower than that in Ti2SnC due to the chemical complexity. Thus, (TiVNbZrHf)2SnC 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.