Effect Of Hot Working Temperature On Microstructure And Properties Of Ti6242S Alloy Small Size Bar

Ti6242S alloy is a high-temperature titanium alloy with high creep resistance developed by American Timet company in 1974. Its nominal composition is Ti-6Al-2Sn-4Zr-2Mo-0.1Si, and the maximum use temperature is about 550 . It is mainly used for high-pressure compressor disc and blade of the aero engine. In foreign countries, especially in European and American countries, the application of Ti6242S alloy is very mature. It has been successfully applied to advanced military and civil aviation engines such as F414, F119, TRENT800 and so on. It is the first titanium alloy material for the compressor disc and blade below 550 . According to the published literature, the research on Ti6242S alloys is mainly based on the study of the relationship between heat treatment and microstructure and properties, but little research on the effect of heat processing temperature on Microstructure and properties, especially for small size bars used for blades. With the continuous development of China's aviation industry, higher requirements for the small size bar used for high-pressure compressor blades are put forward. Therefore, it is imperative to develop high-quality high-temperature titanium alloy small size bar.

The researchers used three kinds of hot working temperatures to prepare Ti6242S alloy bars. The effects of temperature on the microstructure, mechanical properties, and detection of the clutter were compared and analyzed. The purpose was to provide the basis for making and optimizing the technology for the industrial production of small Ti6242S alloy bars.


High quality Ti6242S alloy ingots was selected for the experimental materials, and their chemical composition conforms to the requirements of AMS4975 standard. The phase transition point of the alloy was measured by the metallographic method, which was 1010~1015 . The billet was forged at high temperature and the precision bar for the forging was obtained with a size of 85mm. The forged microstructure of the edge, 1/2R and core of the bar is equiaxed. The SXP-16 precision forging machine is used to make the Ti6242S alloy rod billet of 85mm from 920, 940 and 960 centigrade respectively. The mechanical properties of the samples were treated at 980 X 1h/AC+595 X 8h/AC. The test results show that:

(1) the microstructures of Ti6242S alloy bars obtained by precision forging at 920, 940, 960  respectively, with the increase of forging temperature, the content of the alpha phase decreases, the distorted alpha phase decreases, and the equiaxed degree of the alpha phase is increased.

(2) the microstructure of the three bars after heat treatment at 980 * 1h/AC+595 * 8h/AC has almost no difference in microstructure and mechanical properties.

(3) with the increase of forging temperature, the clutter level of Ti6242S alloy precision forging bar is improved.