Finite Element Simulation And Experiment Of Alternate High Pressure Torsion For ZrTiAlV Alloys

High pressure torsion(HPT)is a successful and effective method for severe plastic deformation(SPD)deformability,The process mainly uses high pressure and torsion to produce shear strain to refine the grain size of the material,so that the grain size can be reduced to submicron or even nanometer level,thus improving the physical properties and mechanical properties of the material.However,the tissue properties and thickness of samples prepared by high pressure torsion are easy to be unevenly distributed in radial and axial directions.Based on the traditional unidirectional high pressure torsion technology,the alternate high pressure torsion technology is put forward in this paper,This technology was simulated by finite element simulation and compared with unidirectional high-pressure torsion process,and the advantage of repeated high pressure torsion technology is proved.Finally,the simulation results are verified by taking ZrTiAlV alloy as an example.Using Abaqus finite element software,the unidirectional high-pressure torsion process with different pressure and different torsion angle was simulated.The deformation size,thickness distribution and equivalent strain cloud map of the sample were obtained.By comparing the changes of sample under different technological parameters and analyzing the changes of size and thickness,the distribution of equivalent strain of sample after unidirectional high-pressure torsion was obtained.In addition,the strain formulae of the constraint and quasi-constraint high pressure torsion are derived,and the formula for equivalent strain calculation of the sample was obtained.The technology of alternate high pressure torsion is put forward on the basis of unidirectional high pressure torsion,four alternate high pressure torsion techniques were set up by controlling the torsion angle and direction of the down mould.the equivalent strain and thickness distribution of the sample were obtained,and the effect of alternate high pressure torsion on the uniformity of the sample's deformation was studied.On the basis of this,the technique of codirectional asynchronous and reverse synchronous high pressure torsion is put forward.The effect on the strain and thickness distribution of the sample was studied by changing the direction and speed of the torsion of the upper and down molds.By comparing the simulation results of several high pressure torsion process,the thickness and equivalent strain distribution of the sample after deformation were analyzed.The results show that the thickness distribution and the equivalent strain distribution in axial and radial direction are more uniform under alternate high pressure torsion.Unidirectional high pressure torsion and alternate high pressure torsion experiments were carried out by using a single ? phase ZrTiAlV alloy which was subjected to electric field assisted heat treatment as the experimental material.The shape size,hardness and microstructure of the deformed samples were compared,which was consistent with the simulation results.The results show that the alternate high pressure torsion process can greatly improve the uniformity of the microstructure and properties of the alloy.