Investigation On The Hot Deformation And The Dynamic Mechanical Behavior Of TA32 Titanium Alloy

As a new near-?titanium,TA32 has high specific strength,creep resistance,and fine weldability,was a kind of high temperature titanium alloys with great application potential.It has great significance for the further application of TA32 titanium alloy to study the hot deformation and the dynamic mechanical behaviors of TA32 titanium alloy.In this paper,the hot deformation behavior of TA32 under quasi-static loading at high temperature and the dynamic mechanical behavior of TA32 under high strain rate at room temperature were researched,respectively.High temperature tensile test of TA32 titanium alloy sheet were carried out in the temperature range of 650-850?and strain rate range of 0.001-0.1s^-1.The curves of true stress-strain under quasi-static loading at high temperature were obtained,and the rheological constitute model of TA32 titanium alloy at high temperature were established.The results indicated that TA32 was a kind of temperature sensitive and strain rate sensitive material at high temperature.At above 750?,the elongation increased and the strength decreased obviously,which can be used for plastic forming.The constitute model based on the Hooke's law and Grosman equation could describe the rheological behaviour of TA32 alloy at high temperature.Microscopic observation and analysis of the high temperature tensile specimens were conducted by metallographic microscope and scanning electronic microscopy.The results showed that the grain size of alloy was strip at lower temperature and the micro-fracture morphology was equiaxed dimples,which present the typical characteristic of ductile fracture.The recrystallized grains were appeared on the edge of grain at above 750?.High temperature and low strain rate could contribute to the occurrence of dynamic recrystallization.The serpentine slip micro-morphology was showed on the edge of equiaxed dimples at higher temperature.At room temperature,dynamic compression experiments of TA32 were performed at a range of strain rate from 1000s^-1 to 5000s^-1 by split Hopkinson pressure bar,The curves of true stress-strain under high strain rate were obtained,and the dynamic constitute model of TA32 titanium alloy were established.The results showed that TA32 have obvious strain working-hardening and effects of strain rate at strengthening,plasticity-increasing.With the increasing of strain rate,it has stronger effects of strain rate at strengthening,plasticity-increasing.The dynamic constitute model based on the improved Johnson-Cook model could describe the dynamic rheological behaviour of TA32 alloy.Microscopic observation and analysis of SHPB specimens were carried out.Obvious adiabatic shear bands were observed in TA32 alloy at above 2000s^-1 and their width increased from 7?m to 20?m with strain rate ranging from 2000s^-1 to 8000s^-1.Lots of parabolic dimple were observed on the fracture surface.The dimensions of dimple increased slightly with the increase of strain rate.