Room temperature spallation of α-alumina films grown by oxidation

Tolpygo and Clarke (2000) presented an excellent experimental study on the room temperature circular spallation of α-alumina films grown by oxidation on Fe-Cr-Al alloy. Their observations are remarkable and thought-provoking and are worthy of mechanical interpretation. The present work hypothesizes that pockets of energy concentration (PECs) exist due to dynamic and non-uniform plastic relaxation or creep in the film and Fe-Cr-Al alloy substrate during cooling. PECs may be the driving energy for room temperature spallation failure. Based on this hypothesis, an analytical mechanical model is developed in this work to predict the spallation behavior, including the separation nucleation, stable and unstable growth, and final spallation and kinking off. The predictions from the developed model are compared against experimental results and excellent agreement is observed. The work reveals a completely new failure mechanism of thin layer materials.