Fundamental Research on Precision Hot Forming of TiAl Alloys
Prof Yuyong Chen, Harbin Institute of Technology, China
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TiAl alloys are considered as one of the most promising novel light-weight, high-temperature structure materials applied to aerospace and automotive industry due to their low density, high specific strength and modulus, excellent high temperature oxidation resistance and creep resistance. This paper reviews the investment casting, forging and rolling of TiAl alloys based on the research in Harbin Institute of Technology. Aimed at the development of key technologies and research advances of investment casting of TiAl alloys, the fabrication of unique ceramic moulds for investment casting of TiAl alloys, interface reaction mechanisms between TiAl melt and ceramic moulds, casting properties of TiAl alloys, simulation and process optimization of gating system and the microstructure adjustment of castings were carried out and identified. The results indicated that the addition of polymer into the ceramic moulds could solve the hot tearing problem in TiAl castings and the TiAl parts were casted by investment casting successfully. In order to improve the hot-working character, the wrought processes of TiAl alloys were summarized. Recently, the homogenous TiAl ingots which maximum diameter was Φ290mm were fabricated by VAR technology. The near isothermal forging technology of TiAl ingots was systemically studied and as-forged TiAl pancakes with largest diameter of 780mm were obtained. Based on the thermal mechanical treatment technology of TiAl alloys, the thin TiAl sheet with a size of 700mm × 160mm × 2mm was rolled successfully. Also the TiAl alloy parts were fabricated by isothermal die forging using wrought TiAl alloy.
Yuyong Chen is a professor at Harbin Institute of Technology, China. He earned a bachelor degree in Dalian University of Technology in 1978, a Masters degree in 1981 and PhD degree in 1985 at the Harbin Institute of Technology. He was a senior visiting scholar in State University of New York at Buffalo from 1992 to 1994 and senior research scholar in University of Sheffield in 2005.
Prof Chen's main research interests focus on the solidification process and solidification structure control, precision casting and precision hot forming of TiAl alloys, Ti alloys and Ti based composites. He is a member of a council of the Foundry Institution of the Chinese Mechanical Engineering Society, the member of a council of the National Titanium Association executive committee, the member of a council of the China Society for Materials Research-Intermetallic and Amorphous Alloy Branch, the member of the council of Chinese Society for Materials Research-Solidification Science branch, and the chairman of the Heilongjiang Foundry Society. Prof Chen served as the Chief Scientist of “973” project, has taken more than 40 research projects, including national key projects of science and technology and national natural science foundation of China. He has also received two first-class and eight second-class prizes at provincial and ministerial levels. Prof Chen has published more than 280 academic papers, and applied for more than 40 national invention patents, 35 of which have been authorized.