Thermal growth of exclusive alumina scale on a TiAl based alloy: Shot peening effect

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Shot peening, although generally accepted as a useful surface treatment method to improve oxidation resistance of Ni-, Co- and Fe-based alloys, has been less applied to TiAl based alloys. This work shows that a shot peening treatment converts the Ti-45Al-2Nb-2Mn-1B alloy from thermally growing TiO2-Al2O3 mixed oxides to an exclusive Al2O3 in air at 900 °C. The basic reason for this is that the shot peening catalyzes formation of an α-Al2O3 thin film, which prevents Ti of the alloy from oxidation at the high temperature. The slow oxidation of the shot-peened alloy mitigates the degradation of typical γ/α2 lamellar microstructure.