Microstructure Design for Reliability of Turbocharger Blade of Cast TiAl Based Alloy

Based on the application background of turbocharger wheel, the mechanical properties reflecting the damage resistance of turbocharger wheel blade, including RT ductility and fracture toughness together with residual RT ductility after thermal exposure were analyzed in details for a cast TiAl alloy with the directional lamellar microstructure, and the feasibility of cast process for obtaining this microstructure in the blade was also discussed, upon which a new idea of microstructure design was proposed for the reliability of turbocharger wheel. The results indicate that the directional lamellar structure exhibits excellent RT ductility and fracture toughness, and also can retain relatively higher RT ductility after thermal exposure at high temperature, and these good performances rely on the orientation uniformity of the directional lamellar structure. More importantly, by controlling the cooling condition during solidification and atomic ratio of Ti and Al, this directional lamellar structure with the lamellar boundary nearly parallel to the blade surface can be obtained in the blade of turbocharger wheel. This special structure is good to improve the damage resistance of the blade and the reliability of turbocharger.