Research On Dynamic Recrystallization Microstructure Evolution Under Hot Deformation Of TC4-DT Ti-Alloy

TC4-DT alloy is our country self-developed new damage-tolerant alloys under the concept ofmodern damage tolerance design criteria. It is a new type of two phase α+β titanium alloy, which hastremendous prospect in the high-performance structural parts in aerospace applications. Because usedas aerospace structural parts, its mainly processing is hot forming process. Since the internalmicrostructure of the workpiece determine its mechanical properties and mechanical behaviors, so thehot forming process needs to be determinated and the evolution of the microstructure of the parts hasto be studied to get the higher required product quality. In this paper, basic research of hotdeformation behaviors and microstructure evolution, and computer simulation work based on CellularAutomaton methos under certain conditions of TC4-DT alloy has been done. The major content canbe summarized as follows:Hot compressive deformation of TC4-DT titanium alloy was carried out with the hot-simulationmachine of Gleeble-3500. The deformation behavior and microstructure have been analyzed. Theresults reveal that when TC4-DT alloy deforms at temperatures below950℃, the deformationmechanism and deformation activation energy is different from the deformation mechanism above950℃high temperatures; when the alloy deforms athigh temperatures and low strain rates contributeto the occurrence of dynamic recrystallization behavior, while at higher strain rates generally onlydynamic recovery occurs. At the mean time, Arrhenius constitutive equation of TC4-DT alloy underthis experimental condition was constructed.Using the metallographic experimental technoiques, the microstructure evolution under this hotdeformation conditions of TC4-DT alloy was analysed. The result shows that microstructure after thedeformation of950℃and lower strain rate clearly contained dynamic recrystallization grain.Thesituation of the microstructure and the impact of process parameters such as thermal deformationtemperature, strain rate and deformation degree were studied which provided an essential foundationfor microstructure simulation.Based on the Callular Automaton method, the2D dynamic recrystallization model wasestablished and the program was developed with MATLAB. Efficient simulations on one-phase andtwo-phase normal2D grain growth were complished, and the simulated microstructure was similar toactual alloy. Also, the simulation of the dynamic recrystallization of TC4-DT alloy in the β phase wasfinished. Compared with the experimental results, it shows the simulated microstructures are similar to the actual ones.