The preparation process of large size fine crystal monolithic blade disc of high uniformity Ti55 high temperature titanium alloy includes the opening forging of alloy ingot at 1150℃ ~ 1250℃, and then the resulting billet is upsetting and drawing deformation at 1015℃ ~ 1035℃, and water cooling after forging. Then the billet is heated to 890℃ ~ 920℃ for 12h ~ 20h, and then forged with the furnace temperature to 940℃ ~ 980℃, and then the billet is upset and deformed at 950℃ ~ 970℃ for 6 ~ 8 times, and then the billet is formed at 950℃ ~ 960℃ to obtain the forging billet. Finally, solid solution + aging heat treatment is carried out to obtain the monolithic disc forging blank. The process is suitable for preparing monolithic disc forgings from 700mm to 1200mm and from 60mm to 150mm in height. The microstructure uniformity and performance of the forgings are superior to the traditional process.
Ti-55 titanium alloy is a nearly α-shaped high-temperature titanium alloy designed according to the electron concentration law of Ti3X phase precipitation. It has good thermal strength and thermal stability, and long-term working temperature can reach 550℃. It is mainly used for the whole blade disc, drum, blade and other parts of the high-pressure compressor in the aero engine, and has good process plasticity at room temperature and high temperature.
With the increase of the thrust-to-weight ratio of aero-engine, the working conditions of compressor are more complex. While relying on the overall blade disc and the overall blade ring structure design, it is also necessary to replace steel and nickel-based superalloys with high-temperature titanium alloys with higher strength, lower density and high temperature resistance to achieve the purpose of reducing the weight of the structure.
Due to the high alloying degree of Ti-55 and the α phase at room temperature, the deformation resistance is greater than that of traditional two-phase titanium alloys such as TC4 and TC11. This makes the forging of the integral blade disk of the alloy, especially the forging of the large-size integral blade disk, more difficult. It is not only easy to crack in the forging process, but also poor hardenability, which makes it difficult to obtain the required organization and comprehensive properties.
