Study On Hot Deformation Behavior Of TA15 Titanium Alloy

TA15 alloy is a kind of titanium alloy of high Al equivalent near?type widely used in aviation field,and its phase transition point is 990±5?.This alloy has not only excellent mechanical properties,but also good machining properties and welding properties.In order to extend the service life of forging work,improve the efficiency of the whole structure,the new aircraft in use in the design and manufacture a lot of large titanium forgings,and put forward the demand of the large size bar,titanium alloy materials specifications for?300 mm?350 mm.TA15 large size materials??300?350 mm?production,since poor uniformity of the exposed group and 500?the problem such as low tensile properties.In this paper,the true stress-strain curve with the strain rate of 0.01 s^-1,0.1 s^-1,1.0 s^-1,10.0 s^-1 and the strain variable of 60%was obtained by the Gleeble3800 thermal simulation machine with the deformation temperature of 850?,900?,950?,1050?,1100?and 1150?.The influence of thermal deformation parameters on the rheological stress and microcosmic stress in the plastic deformation of the alloy was analyzed,and the constitutive relationship and the thermal process ing diagram were established based on the true stress-strain curve,which provided a theoretical basis for the process improvement.The main findings are as follows:?1?When the strain rate is constant,the rheological stress of TA15 titanium alloy is negatively correlated with the deformation temperature.When the temperature increases,the rheological stress decreases.When the deformation temperature is constant,the rheological stress of TA15 titanium alloy is positively correlated with the deformation rate,and the deformation rate increases,so does the rheological stress.In addition,the TA15 alloy was thermally deformed in the two-phase region at 850?and 950?.With the decrease of the strain rate,the rheological stress curve tended to be gentle,and the dynamic recovery softening mechanism was relatively strengthened during the deformation process.At 1050?and 1150?in single-phase zone,the rheological stress is relatively gentle no matter the high strain rate or the low strain rate.?2?Through the analysis of the relationship between deformation parameters and microstructure,it is concluded that:the deformation of TA15 titanium alloy is below the phase transition point,and the content of?gradually decreases with the increase of deformation temperature.Compared with the deformation at 950?,the temperature decreased,and the content of the primary lustrum increased.Compared with the deformation at 1150?,the temperature decreased,and the size of original margin of?grain decreased,and the aspect ratio of the transformed margin of?grain increased.When deforming at 850?,different strain rates have little effect on the tissue.The degree of recrystallization increases with the increase of temperature.The strain rate has an effect not only on the content of?phase,but also on the form of young?phase.With the decrease of strain rate,the degree of equalization of the primary?phase increased.At the strain rate of 0.01s-1,the degree of equalization of the nascent luen phase was the highest.But the effect on content and size is relatively smal.?3?Based on the dynamic material model?DMM?,the hot processing map of TA15titanium alloy was established.It can be seen that there are two unstable regions in the thermal deformation process of TA15 titanium alloy:one is 1075?<T<1150?and the>2 s^-1 region,and the other is T<975?and 0.014 s^-1<<2.72 s^-1 region.?4?In this paper,the Arrhenius hyperbolic sinusoid model was used to establish the constitutive relationship of thermal deformation of TA15 titanium al oy:The constitutive relationship of?+?facies region:???=e^58.18898121[sinh?0.00932??]^3.7198exp?-588.7455857/RT?The constitutive relationship of the?facies region:???=e^13.32762[sinh?0.03959??]^2.78563exp?-176.1834606/RT??5?Through process optimization,developed a uniform organization,performance,excellent?300 mm?350 mm bar,physical quality is not lower than similar foreign products,meet the needs of the aviation sector.