Study On Optimization Of Isothermal Forging Process Parameter Of TA15 Titanium Alloy

TA15 with medium strength of room-temperature and high-temperature and good thermal stability is a kind of near α alloy of high aluminum equivalent. This alloy was introduced from Russia in the 1990s (the brand of Russia was BT20), according to the need of selecting suitable materials in the aircraft industry of our country. This alloy is designed for components plane and engine under 500℃.This paper studied the effect of isothermal forging and heat treatment on the microstnicture and mechanical properties of TA15 titanium alloy, and focused on the effect of deformation temperature, deformation degree, strain rate, fire time and different heat treatment on the microstructure and mechanical properties of TA15 titanium alloy. By discussing the relationship among the technology, microstructures and the mechanical properties, better processing parameters of isothermal forging and heat treatment have been obtained which can be referred for experiments of isothermal forging and technology of heat treatment of large-scale forging.The experiment showed that we could get axle organization with good mechanical performance when forging in the range from 900℃ to 980℃, especially at 980℃, with isothermal forging of 60% and one fire shaping. Room temperature intensity of TA15 alloy was reducing with the rising of anneal temperature. TA15 alloy can be solution-aging strengthened.The refining effect of multiple deformation heat treatment on the microstructure of the TA15 titanium alloy have been also studied in this paper. The results indicated that the multiple .deformations heat treatment could obviously refine the microstructure of TA15 alloy, and the comprehensive mechanical properties of TA15 alloy could be improved to some extent. In single phase region, the high-temperature deformation heat-treatment could refine β grains and get fine-acicular martensite α' and meta-stable β phase. The low-temperature deformation heat-treatment could further refine fine-acicular α + β phase dissolved from martensite α' and meta-stable β phase. The multiple deformation heat-treatment is an effective way of refining microstructure of titanium alloy.In this paper the test of the isothermal compression with constant strain rate of TA15 alloy has also been studied at the α + β phase region and 3 phase region The stress-strain curves have been obtained , changing laws of the flow strenss and microstructure have been discussed. The results showed that the strain rate obviously affected the flow stress of TA15;the extent of the effect of deformation temperature on flow stress was related to the measure of strain rate;the uniform , fine and equiaxed α phase structure was achieved at lower temperature and faster strain rate, but the structure was coarsened definitely at slow strain rate. The optimum isothermal compression temperature is between 980℃ and 900℃, the strain rate may be selected within the constant range according to the need of forging forming,structure properties and productivity .Under good forming condition of forgings, strain rate may be appropriately raised.