Selective oxidation of aluminium in Mo(Al,Si)2

Mo(AlxSi1-x)2 alloy with x in the range of 0.35–0.65 were prepared by a one-step spark plasma sintering. To study the exclusive formation of an α-Al2O3 scale, oxidation experiments were conducted in low and high oxygen partial pressure ambient at 1373 K; viz.: 10−14 and 0.21 atm. The oxidation kinetics follows a parabolic rate law after a transient period. A counter-diffusion process of O and Al along grain boundaries of Al2O3 scale is responsible for the equiaxed and columnar grain growth based on a two-layered microstructure. The formation of a dense equiaxed α-Al2O3 layer contributes to excellent oxidation resistance.