HIP処理したFe,V,B添加TiAl合金の熱処理組織と常温引張特性の検討
1997 年 83 巻 4 号 p. 275-280
詳細
1997 年 83 巻 4 号 p. 275-280
A gamma alloy, Ti-46.7Al-1.3Fe-1.1V-0.35B(mol%), has been developed as a casting materials for turbine components, replacing superalloys. This alloy is characterized by the addition of Fe and V which improve castability. In order to use this alloy widely, improvements of mechanical properties are required. Thus, microstructural evaluation of various HIP treatments was studied to decrease amounts of casting defects. HIP treatment made a large contribution to improve tensile properties and to reduce a scatter of mechanical value. As compared with other TiAl alloys, the grain growth of an alpha phase during heat treatment at higher temperatures than alpha transus temperature in the TiAl-Fe-V-B alloy was slower. Moreover, the optimum conditions of HIP treatment and heat treatment were determined to further improve the room temperature strength and ductility in this study. As a result, we developed heat treatment process to produce a duplex structure which improves ductility. The alloy with the duplex structure by the HIP and heat treatments had 550MPa tensile strength and 1.8% elongation at room temperature. These results show that the HIP and heat treatments improve both of strength and ductility. The stage 5 blades for use of low pressure turbine were cast and its engineering applicability was demonstrated by 500 flight cycles test in a CF6 engine at GEAE, in November, 1994.
