Simulation Of ECAP-FE Combined Extrusion Process For Magnesium Alloy Based On Material Point Method

Grain refinement is an important way to improve the deformation capacity of magnesium alloys at room temperature.The degree of single pass extrusion deformation of magnesium alloy is limited.And the multi-pass machining is easy to make the billet fracture which is difficult to obtain high-performance materials.The ECAP-FE composite extrusion process enables the magnesium alloy to obtain a large cumulative strain which results in dynamic recrystallization of the material and grain refinement.Material point method(MPM)is a novel meshless algorithm with the advantages of both Euler method and Lagrangian method.It avoids the defects of finite element mesh distortion,discrete element convergence and large computation when dealing with large deformation problems.In this paper,the ECAP-FE composite extrusion process of magnesium alloy was simulated based on the material point method.A material point method program for ECAP-FE composite extrusion process was written in FORTRAN language.The extrusion pressure and equivalent strain obtained by the simulation of AZ31 magnesium alloy ECAP-FE composite extrusion are in good agreement with the results in the literature.The results show that the numerical simulation of ecap-fe composite extrusion process of AZ31 magnesium alloy by MPM is feasible.The extrusion process of AZ31 magnesium alloy ecap-fe was numerically simulated by material point method.The influence of die structure parameters(transition distance,extrusion ratio,die Angle,punch shape,etc.)and forming process parameters(extrusion temperature,friction coefficient,extrusion speed,etc.)on AZ31 magnesium alloy ECAP-FE composite extrusion process was analyzed.Through the research on the structure parameters of the die,it is shown that:The transition distance has little effect on the peak value of extrusion load,but with the increase of transition distance,the peak time of extrusion load has obvious hysteresis.With the increase of the die Angle,the peak value of the extrusion load was larger and the peak appeared earlier.The larger the extrusion ratio is,the larger the peak value of extrusion load is.The shape of the punch causes a change in the internal friction of the material channel,thus resulting in a change in the peak extrusion load.The results show that theextrusion pressure decreases with the increase of extrusion temperature and velocity.The extrusion pressure increases with the increase of friction factor.In order to predict the deformation effect of AZ31 in ECAP-FE process under the influence of comprehensive factors,orthogonal analysis and numerical simulation of ECAP-FE composite extrusion process of AZ31 magnesium alloy were carried out based on material point method.The peak value of extrusion load in AZ31 extrusion process was selected as the experimental index.Three different experimental factors,namely extrusion temperature T,friction factor M and extrusion ratio,were selected through range and variance analysis.The results show that the parameters that have the greatest influence on the peak load of extrusion are extrusion ratio with 2,friction coefficient with 0.1,and extrusion temperature with 300℃.The significant horizontal relationship of the three factors was: extrusion ratio > friction factor > extrusion temperature.The research in this paper has provided a novel method to simulate magnesium alloy ECAP-FE composite extrusion.There is some guidance for the selection of technological parameters of magnesium alloy ECAP-FE composite extrusion.