Spallation of alpha alumina due to non-uniform creep relaxation

A cooling and time rate dependent function is devised first to measure the level of dynamic creep relaxation of thermally grown oxide (TGO) α-Al₂O₃ on the Fe-Cr-Al alloy substrate during cooling [1,2]. It explains the cooling rate dependent spallation of the alumina scales at room temperature very well and proves that the dynamic creep relaxation is the cause of scale spallation. Then, the work develops a pocket of non-uniform creep relaxation model which gives accurate predictions of spallation radius. The work [3,4] is significantly advanced.