Research On The Microstructure Evolution And Simulation Of TC21 Titanium Alloy In The Hot Working Process

TC21 is a new kind of damage tolerantα+βtwo-phase titanium alloy,so it has great prospect in manufacturing high performance aerocraft structural parts. Due to its characteristics of high yield to tensile strength, the main manufacture method for this material is hot working including high temperature forging, superplastic forming, hot forming etc. Different hot working process can result in different microstructure and the microstructure of a hot working part determines its performance and usage,so in order to obtain the ideal microstructure that can meet the performance requirement,it is necessary to know the microstructure evolution at different hot working conditions such as heat preservation, strain rate and deformation extent. Based on the above reason,this paper studied the microstructure evolution and conducted correlative computer simulation of TC21 titanium alloy in the hot working process, and the main work is as follows:Firstly,on the basis of analyzing phase transformation theory of titanium alloys, the heating and soaking experiment was performed according to the characteristics and the possible hot working (forging) technologies of of TC21 titanium alloy in actual production. Through analysis of the metallographic pictures under different heating temperatures and holding time , some conclusions concerningαtoβphase transformation were reached, which could provide reference to the optimization of hot working technological parameters of this alloy.Secondly,the hot compression experiments at different temperatures and strain rates were carried out on Gleeble 3500 hot simulator for TC21 titanium alloy. The microstructures after deformation indicated that dynamic recrystallization occurred at certain strain rates aboveβ-transus temperature. And material performance parameters related with hot working process such as deformation activation energy,stress exponent etc. in different temperature ranges were obtained through regression analysis.Lastly,the cellular automaton method was introduced, a 2-D cellular automaton model for dynamic recrystallization was established and the program for the process was developed with Visual C++ 6.0. The elementary simulation for the dynamic recrystallization of TC21 titanium alloy in theβsingle phase was conducted,and the existing problems were analyzed, which has laid foundation for the later microstructure simulation of TC21 titanium alloy in the hot plastic deformation.