Research On High Temperature Deformation Mechanism And Heat Treatment Process Of TA15 Titanium Alloy

TA15 titanium alloy is a significant structural and damage tolerance type titanium alloy which is widely used in China’s aerospace and military industries. In order to obtain semi-finished products or parts with uniform microstructure and excellent mechanical properties TA15 titanium alloy has to go through series of complex thermomechanical treatment and heat treatment. A lot of studies on hot deformation behavior, heat treatment process, influencing factors of microstructure and properties, evolution of sub-structure and microscopic texture of TA15 titanium alloy have been made by many domestic and foreign researchers. But in order to control the microstructure and mechanical properties of TA15 titanium alloy accurately to meet the increasing strict requirement of service conditions, there are important theoretical and engineering value to do systematic and in-depth research on the deformation mechanism, evolution of sub-structure and microscopic orientation during thermomechanical treatment process, the metastable phase decomposition mechanism and evolution of microstructure and texture during the heat treatment process, as well as the quantitative analysis of microstructure and performance, intelligent optimization and so on.Based on the constant strain rate isothermal compression tests and vacuum annealing experiments of TA15 titanium alloy the qualitative and quantitative research on phase transition, recrystallization behavior, evolution of microscopic orientation, sub-structure and microstructure during thermal deformation process and annealing process were made by using a variety of modern material characterization techniques and quantitative calculation theories. The results which reveal the thermal deformation mechanism and strengthening mechanism of annealing comprehensively can provide a theoretical basis for the development of rational thermal deformation and heat treatment program. The accurate prediction models between characteristic parameters of microstructure and thermal deformation parameters were established based on response surface methodology. The influences of thermal processing parameters on the microstructure characteristic parameters were studied deeply to reveal the intrinsic relations between them. The reasonable range of thermal processing parameters of ternary microstructure with excellent integrated mechanical properties and lamellar microstructure with high damage tolerance property in the current program were obtained by multi-objective visual optimization and verification. The results of this study will be of great significance in the revelation of essential characteristics of titanium, optimization of process parameters, prediction and controlling of the microstructure of titanium and improving the performance of titanium alloy products.