| Through alloying introducing high temperature disorder bcc β, beta-gamma TiAl alloys can greatly improve the hot deformability. This paper selected the Ti-43A1-9V-Y(at.%) alloy, and investigated systematicly the microstructure evolution, high temperature deformation behavior and hot working performance.The deformation behavior of as-cast and HIPed Ti-43A1-9V-Y(at.%) alloy was investigated in the temperature of1100-1225℃and stain rate range of0.01-1.Os-1using thermal physical simulation. The effect mechanism of temperature and strain rate and microstructrue volution were explained. as-cast Ti-43A1-9V-Y alloy showed positive strain rate sensitive and negative temperature sensitive. Phase change β→γ and dynamic recrystallization happened are the main microstructure evolution mechanisms of deformation.The stress exponent n and the apparent activation energy of deformation Q were determined as2.83and492.22kJ mol-1, respectively.Based on the theory of the dynamic materials model(DMM), the hot processing map of the alloy was established, determining the temperature interval of the β→γ phase transformation, the dynamic recrystallization and local cracking instability. respectively. The quantitative relationship between microstructure evolution and power dissipation efficiency and hot processing parameters was analyzed, it found that phaes change β→γ will happen in the strain rate of0.01s-1and temperature higher than1150℃, and the dynamic recrystallization happened at the same time. which were the main mechanisms of power dissipation. revealing the deformation mechanism of the alloy in different temperature interval, acquired optimizing parameter scope of the hot working, that is, the strain rate of0.01s-1and temperature higher than1200℃, achieved the purpose of the optimum control of the hot working performance.Microstructure evolution of different parts of samples was analysed. And the temperature, the strain rate, the strain in the thermal deformation process were analysed using ABAQUS software. the results showed that the rise of adiabatic temperature and stress uneven phenomenon were the two major factors of the deformation uniformity. High quality pancake of the alloy was obtained at strain rate0.01s-1and temperature1200℃, using two-step canned forging technology.Different quenching process were investigated, showed that many β phase exist in temperature1200℃or higher than1240℃. The deformation behavior of as-forged Ti-43A1-9V-Y(at.%) alloy in the temperature range of1100-1225℃, and strain rate range of0.01-1.Os-1was analysed using thermal physical simulation. As with as-cast, β phase precipitated out fine needle γ and the dynamic recrystallization will happen in deformation process. The apparent activation energy Q and stress exponent n of the alloy were determined as342.27kJ mol-1and3.02respectively. Based on the theory of DMM, established the hot working map of the as-forged alloy, In the low strain rate0.01s-1and temperature range higher than1225℃, dissipative efficiency higher than60%. Combining analysis microstructure evolution and dissipation efficiency value, obtained the optimum hot working parameters:temperature higher than1225℃, strain rate is0.01s-1. |
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