High-temperature Deformation Behavior And Multi-directional Forging Process Of （TiB₂+TiB）/Ti₂AlNb Composites

Ti₂AlNb-based alloy is a kind of light superalloy,whose service temperature is between650 and 750℃.Its low density makes it stand out among superalloys,and it is widely used in the aerospace field.However,the sintered Ti₂AlNb-based alloy has poor thermal workability,and the high-temperature mechanical properties cannot meet the needs of the aerospace field.It is necessary to improve the workability and high-temperature mechanical properties of Ti₂AlNb-based alloy by other means.For metals,the increase in deformation temperature will improve plasticity and reduce the performance after processing.To clarify the high-temperature deformation mechanism and balance the relationship between workability and the properties of processed samples,this paper studies the hot deformation behavior of single phase B2 based on（Ti B₂+Ti B）/Ti₂AlNb composites and expounds the influence of deformation parameters on the workability,dynamic recrystallization,and reinforcement.The effects of different process parameters on the deformation behavior of（Ti B₂+Ti B）/Ti₂AlNb composites were investigated by finite element simulation of a multidirectional forging process.The constitutive model and dynamic recrystallization dynamic model of（Ti B₂+Ti B）/Ti₂AlNb composites were constructed through the isothermal hot compression experiment,and the hot working diagram was drawn to discuss the hot workability under different parameters.The microstructure evolution during the hot deformation of materials was analyzed.The results showed that the increase in strain rate and the decrease in deformation temperature can inhibit the dynamic recrystallization behavior.The average grain size of dynamic recrystallization is 4.02μm at 1060℃and 5s^-1.The decrease in strain rate and the increase in deformation temperature promote the transition of Ti B₂ to the Ti B phase,and the Ti B phase is more evenly distributed in the matrix.By using DEFORM-3D finite element software,the finite element simulation of the multi-direction forging process at different temperatures（1060℃,1090℃,1120℃,1150℃）and different passes（1 pass,2 pass,3 pass）was carried out,and the influence of process parameters on the equivalent strain,dynamic recrystallization degree and grain size of the deformed billet was analyzed.The results show that the dynamic recrystallization degree is positively correlated with the deformation pass and deformation temperature,and the equivalent strain is positively correlated with the deformation pass and is not sensitive to the change in deformation temperature.The grain size is negatively correlated with the deformation pass and positively correlated with the deformation temperature.