Selective oxidation of aluminium in Mo(Al, Si)2. (February 2023) - Ding, Zhaoying
Abstract: Mo(Al x Si1- 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-Al2 O3 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 Al2 O3 scale is responsible for the equiaxed and columnar grain growth based on a two-layered microstructure. The formation of a dense equiaxed α-Al2 O3 layer contributes to excellent oxidation resistance. Highlights: High Al containing Mo(Alx Si1-x )2 alloys (x up to 0.65) were prepared by a one-step spark plasma sintering. Counter-diffusion process of O and Al along grain boundaries resulted in the equiaxed and columnar grain growth of α-Al2 O3 . Direct exposure to a high oxygen partial pressure ambient (0.21 atm.) leads to a denser and more protective α-Al2 O3 scale.