The Research On Prediction Model For Dynamic And Static Recrystallization Of As-cast TC21 Titanium Alloy

In recent years,with the rapid development of social science and technology,titanium alloy,is a lightweight alloy material with excellent performance and great development prospects.It has the advantages of high specific strength,chemical resistance,low density,good low temperature resistance,and high thermal strength.And it has been widely used in aerospace,automobile manufacturing,ships,nuclear energy and chemical industries.However,during the titanium alloy forging production process,especially in the titanium alloy forging-cogging process,the method of manual repeated trial and error correction is still used to optimize its process,which is difficult to meet the high-efficiency,economical,high-quality production requirements.And,titanium alloy is a difficult-to-deform metal,its resistance to deformation during the forging process is large,and it is difficult to completely forge the central tissue,which eventually leads to uneven tissue and unstable performance,which seriously restricts the quality of the finished product.Therefore,in order to better understand the thermoplastic deformation behavior and mechanism of titanium alloys,the dynamic and static recrystallization of titanium alloy center structure is predicted.Based on this,the forgeability of the material during the forging-cogging process is judged,and it helps to develop and optimize the process designing of actual titanium alloy forging process.In this paper,the as-cast TC21 titanium alloy was used as the research object.The thermal deformation behavior of the as-cast TC21 titanium alloy was studied in detail and systematically by using thermal simulation compression experiments.On this basis,the heat treatment experiment of thermal simulation compression sample was carried out,extracted the dynamic and static recrystallization volume fraction,built the prediction model of dynamic and static recrystallization on the basis of recrystallization kinetics curve of ascast TC21 titanium alloy.And simulation verification and correlation analysis were carried out by DEFORM-3D software.The details are as follows:(1)Through Gleeble thermal simulation compression experiments,the flow stress-strain curves under different deformation conditions were obtained,and the thermal deformation behavior of the alloy was analyzed.at the same time,a constitutive model,strain rate sensitivity exponent,and strain hardening exponent were established.And finally the hot working drawing of as-cast TC21 titanium alloy was plotted and the rheological instability of this alloy was analyzed.(2)The sample subjected to the thermal simulation compression experiment was subjected to a heat treatment experiment,the dynamic and static recrystallization volume fraction under different deformation conditions was extracted by various means,and the kinetics curve of the as-cast TC21 titanium alloy was drawn.And based on this,a prediction model of dynamic and static recrystallization of as-cast TC21 titanium alloy was constructed.(3)Developed the secondary programming of DEFORM-3D software to make it have the simulation function of dynamic and static recrystallization volume fraction.(4)DEFORM-3D software was used to simulate the dynamic and static recrystallization model of as-cast TC21 titanium alloy,and compared with the experimental results to analyze its reliability and accuracy,hoping to provide some help to actual production.Finally,the thermal simulation compression process under a certain deformation condition is analyzed,which has reference significance for the development of the forging-cogging process of titanium alloy.