Mechanism for abnormal thermal shock behavior of Cr2AlC

Some MAX phases exhibit abnormal thermal shock behavior, i.e. the residual strength of as-quenched MAX phases decreases gradually with increasing quenching temperatures and then unbelievably increases after quenching from even higher temperatures. To date, the abnormal thermal shock behavior has been found in some MAX ceramics for about 17 years and has resisted interpretation. Herein Cr2AlC as a representative member of the MAX phases is chosen to investigate such unique behavior. Thermal shock tests show that the abnormal thermal shock phenomenon for Cr2AlC occurs at above 1200 °C. The main mechanism for this phenomenon is that the thermal shock induced cracks are instantly healed by the formation of reactants well adhering to the crack faces during quenching. The mechanism demonstrated here can be applied to other materials with the abnormal thermal shock behavior. Such materials may find applications in environments where temperature changes abruptly.