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

Highlights • Shot peening produced a deformation zone on the top of a TiAl based alloy. • γ/α 2 lamellar structure was collapsed and grains refined in the deformation zone. • Shot peening catalyzed formation of a submicron-thick α-Al 2 O 3 film. • The prior Al 2 O 3 formation prohibited Ti of the alloy from oxidation at 900 °C. Abstract 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 TiO 2 -Al 2 O 3 mixed oxides to an exclusive Al 2 O 3 in air at 900 °C. The basic reason for this is that the shot peening catalyzes formation of an α-Al 2 O 3 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. [ABSTRACT FROM AUTHOR]