The critical role of irradiated intermediate state lattice distortion on the amorphization resistance in MAX phases.

Many ceramic materials transform to a solid-solution intermediate state before amorphization under extreme conditions. Combining in-situ irradiation experiments and ab initio molecular dynamics simulations, we performed a comparative study of the defect accumulation process in MAX phases, Ti 2 AlC, Cr 2 AlC, and Ti 2 SnC, to clarify the correlation between solid-solution intermediate phase properties and phase instability. It is found that phase stability strongly depends on the lattice distortion of the solid-solution intermediate state, rather than the defect energies in the initial phases that were previously believed as the indicator of the resistance to the irradiation-induced amorphization. Larger lattice distortions of the solid-solution intermediate state can hinder defect recombination and lead to faster collapse to an amorphous state. This work provides a new research insight into phase instability for ceramic materials under extreme conditions. [ABSTRACT FROM AUTHOR]