Study On Experiment And Numerical Simulation Of Equal Channelangular Press For7075Aluminum Alloy

ECAP (Equal Channel Angular Press, ECAP) is one of the severe plasticdeformation technology, which is most widely studied.7075-T651aluminum alloy isone of super hard material widely used in aviation aviation, aerospace and automotiveapplications and other fields. Since the poor plastic forming ability, using grainrefinement is one of the hotpots to improve low plastic material forming ability.In this paper, applying experiment and simulation method study the materialdeformation mechanism and grain refinement effect. Using7075-T651aluminumalloy material for the study of the process of ECAP process test applicationsDeform-3D finite element analysis software simulation process parameters andorganizational modeling, analysis metallographic and hardness test sample afterprocess test.In the process of testing, select the die corner, extrusion speed and friction of thethree process parameters as variables, according to the orthogonal design ideas, werenine single-pass ECAP process test. Since the7075-T651is a hard deformablematerial, samples with different levels of a crack. Hardness of9samples were tested,results tells the hardness increased, the distribution in cross-section at roughly themiddle of the highest hardness, followed by the upper and lower hardness minimum,is coincided the effective strain laws. The simulation result of sample No.1load-stroke curves and deformation were similar to the experiment. Establishing thereliability of the numerical simulation.Parameter simulation of corner angular, temperature, extrusion speed, frictionresult shows that the equivalent strain will decrease with the increase the angular ofthe corner; internal equivalent strain and mises stress distribution uniformity willimprove as the temperature rises, temperature increases will accelerate the recoveryprocess of the organization, is not conducive to refined grains; improve extrusionspeed may increase the efficiency, but temperature increase significantly; more friction led to surface stress concentration, temperature rise. Sample No.6processwas simulated, exist within the three-state area to tensile stress, axial tensile stress istoo large, exceeding the tensile strength of the material, causing the material fracture,consistent with the experimental results.Grain evolution simulation was proceed of sample No.1, which is the best grainrefinement of experimental process. The result shows the entire progress of the graingrowth and recrystallization. The head, middle and tail of sample, respectively, of theaverage grain size of3.5μm,2.4μm,29.1μm. Compared with the initial grain size of40μm, preferably, the central material thinning effect.Taking into account the effects of hydrostatic pressure on the plasticity, backpressure of the deformation process and variable back pressure given under simulatedload analysis and comparison. The results show that extrusion force increase with theincreasing back pressure, but the final load-time curves tended towards stability, butin ordinary ECAP, the final load-time curves tended towards decreasing; the absolutevalue of the hydrostatic stress at the corner increased which is beneficial to refinegrain and improve the plasticity; the back pressure makes the distribution of strainrate in plastic deformation area more uniform and improve the uniformity ofdeformation.