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A New Heat Treatment Process for Titanium Alloy Forgings

BT25 titanium alloy is a Ti Al Sn Zr Mo W-Si alloy system with excellent comprehensive properties α+β Type heat resistant titanium alloy. It combines the high thermal strength of BT9 alloy and the thermal stability of BT8 alloy, suitable for long-term operation at 500-550 ℃.
According to reports, the working time can reach 6000 hours below 500 ℃ and 3000 hours at 550 ℃. Therefore, BT25 titanium alloy is an ideal thermal strength titanium alloy for engines and can be used to manufacture compressor parts for aircraft engines. This alloy can be processed into forgings, die forgings, bars, and other forms of products. In the former Soviet Union, it has been included in relevant standards such as OCT for large-scale production.
Researchers from Baoji Titanium Industry Co., Ltd. studied the effects of different solid solution temperatures and cooling methods on the microstructure and properties of BT25 titanium alloy forgings. The results indicate that at the same solid solution temperature, the microstructure of air-cooled samples is finer than that of furnace cooled samples. The solid solution temperature is above the phase transition temperature, and the room temperature strength of air-cooled is higher than that of furnace cooled, but the plasticity index and impact toughness do not change much. The solid solution temperature is below the phase transition temperature. At the same solid solution temperature, the room temperature strength of air-cooled materials is slightly higher than that of furnace cooled materials, with much higher cross-sectional shrinkage and impact toughness, and little change in elongation. However, the yield strength slightly decreases. The high-temperature strength shows a slight increase trend with the increase of cooling rate, and the change in plasticity index is not significant. The optimal combination of alloy strength and plasticity can be ensured by selecting a solid solution temperature of 30-40 ℃ below the phase transition point, holding for 2 hours and air cooling at 550 ℃, and a 6-hour air cooling heat treatment system

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