Study On High Temperature Deformation Behavior And Evolution Of The Micro Structure Of TB5Titanium Alloy

This subject is the branch of project of plates and strips rolling technology of special steel and alloys. The project was proposed to combine with the construction of plates and strips project ofbaosteel special steel branch. The main purpose of the project is to ensure the plates and strips project to proceed smoothly and the production proceed smoothly, carry out hot rolling process researched on Stickle mill, research on temperature schedule and rolling schedule and control of structure property as well as control of shape of strip.In this paper, with the aids of OM, TEM and EBSD, the hot deformation behavior, evolution of the micro structure and softening mechanisms of TB5titanium have been studied on thermal simulator testing machine. The processing maps of TB5titanium alloy was established by dynamic model and the high temperature deformation characteristics have been analyzed using processing map in detail, and provide a theoretical reference for the thermal processing technology. The conclusions drawn were shown as follows:(1) The true stress-true strain curve of TB5alloy was drawn using the data selected, and the characteristics of the curve were analyzed. The influence of hot deformation parameters on flow stress of TB5titanium alloy was analyzed. By comparing the different deformation resistance models, a new hyperbolic sine constitutive equation has been established using the parameters of Zener-Holloman, and we calculated the material constants and hot deformation activation energy. The values of the material constants and the hot deformation activation energy were evaluated at various strains. A fourth order polynomial was found to represent the compensation of strains.(2) Through the metallographic observation photos that obtained from the microstructure after water quenching, the test discovered the influence of hot deformation parameters on the microstructure of TB5alloy. The test discovered the conditions of dynamic recovery for TB5alloy through TEM. The test also discovered the conditions and the mechanism of the dynamic recrystallization through EBSD and OM photos. At the grain boundary it was continuous dynamic recrystallization; at the intragranular it was non continuous dynamic recrystallization. (3) According to the processing map theory, the processing map of TB5alloy was established using dynamic material model. We analysis the different areas of the processing map. The deformation mechanism of the micro structure for the stable areas and unstable areas was obtained by the comparison of the OM photos. The results were shown as follows:under this experimental condition, there were five peak areas and two "trough" regions in the power dissipation map and the strain rate sensitivity coefficient map of TB5alloy. From the metallographic observation, obvious dynamic recrystallization was found in the peak areas, this deformation mechanism was better, it was better to the subsequent processing. Rheological instability was found at the "trough" regions, it was just about local plastic flow and adiabatic shear band. So when thermal processing technology was formulated, it was not conducive to the subsequent processing, so the rheological instability areas should be avoided.