Research On Numerical Simulation Of High-pressure Torsion(HPT) Of Titanium Alloy

The titanium alloy was used widely in various fields as a light material.High-pressure torsion(HPT)is a special plastic deformation method,which is also severe plastic deformation(SPD).Effects of different deformation factors on the HPT of the titanium alloy were studied,which is of great mean for the concrete implementation of HPT of the titanium alloy.HPT forming process of TC4 alloy was studied by Deform-3D software.First,the UG modeling software is used to build the 3D model,and then the model is imported into Deform-3D software,thus establishing the three-dimensional model of the high-pressure torsion of the titanium alloy.Deform-3D software was used to simulate the influence of different process factors on HPT deformation process of titanium alloy.Effect of friction factor on equivalent strain and relative torsion angle of the three typical titanium alloys TA11 α-type titanium alloy,TB6 β-type titanium alloy and TC4 α + β-type titanium alloy was analyzed during HPT.In this paper,the influence of friction and deformation temperature factors on the high-pressure torsion forming process of TC4 titanium alloy was analyzed,and the damage,effective strain,effective stress,surface expansion ratio,velocity vector distribution and variation law of titanium alloy during high-pressure torsion were obtained.The numerical simulation results show that for the TA11α-type titanium alloy,the effective strain decreases first and then increases with the increase of the friction factor.,the relative torsion angle increases first and then decrease.For the TB6 β-type titanium alloy,the effective strain and the relative torsion angle of the HPT process was same to TA11 α-type titanium alloy.For TC4 α + β-type titanium alloy,with the increase of friction factor,the effective strain gradually increases,the relative torsion angle increases first and then decrease,finally increase again.For the TC4 titanium alloy,with the increase of the friction factor,the upper surface damage of the specimen is about 0.5 ~ 0.6,the effective strain and the surface expansion ratio increase during the HPT process,and the size of the velocity vector are decreasing.The effective strain is distributed unevenly in the radial and axial directions,and the distribution of the effective stress in the radial and axial directions is relatively uniform and remains almost on a horizontal line.With the increase of deformation temperature,the change of the damage of the upper surface of the specimens are maintained at about 0.6 ~ 0.9,the size of effective strain and velocity vector increases gradually,and the size of effective stress and surface expansion ratio decreases.The effective strain is not evenly distributed in the radial and axial directions,and the effective stress is more uniform in the radial and axial directions,almost on a horizontal line.Hydrogen can improve the TC4 titanium alloy HPT surface quality,can make the deformation deep into the blank,and make the deformation evenly.The simulation results show that the deformation process of different types of titanium alloy is different.The higher the friction factor is more conducive to the process of HPT process,the higher the deformation temperature is conducive to the plastic deformation,which is hard to achieve high temperature in real life.Hydrogen was helpful to HPT.