Atomistic Insight of Stability of MAX Phase: A Molecular Dynamics Study

Thermal stability of Ti 3 SiC 2 , a prototypical MAX phase, is investigated using molecular dynamics (MD) simulation. At high temperature (2000 K), Ti 3 SiC 2 structure tends to destabilize due to outward diffusion of Si, and it partly dissociates into (Ti,Si)C phases. This effect is accelerated at higher heating/ramp rates. Thermal instability of Ti 3 SiC 2 stems from a topotactic degradation mechanism, where Si layers progressively diffuse out between the layers of Ti 6 C octahedral slabs, yielding Ti 0.78 Si 0.18 C. Overall, the high‐temperature instability of Ti 3 SiC 2 originates from dynamic Si sublattice disorder and volatility, combined with high‐temperature spikes and carbon‐rich environment rather than collapse of the Ti–C framework. MD results are further corroborated experimentally for both Ti–Si–C and Ti–Al–C systems, where higher heating rate during spark plasma sintering results in dissociation of as‐formed MAX phases. Phase pure MAX phase results from quasi‐equilibrium heating experiment. The integration of atomistic diffusion and bond disorder with macroscopic decomposition data provides a coherent picture of Ti 3 SiC 2 thermochemical fragility, which offers design insights for processing conditions that maximize structural retention at elevated temperatures and can be served as a general processing guideline for phase pure MAX‐phase formation.