Research On Microstructure And Properties Of AZ80 Magnesium Alloy By Solid State Recycling And Extrusion Shear Composite Forming

Magnesium alloy is an important metal structural material in industrial production.It has the advantages of high specific strength,good shock absorption,free cutting,no pollution,easy recycling and so on.It is called "the green engineering material in the 21 st century" and is widely used in the fields of automobile,communication,electronics,aerospace,national defense and military industry.The wide application of magnesium alloy products also causes the waste of magnesium alloy in the production process.The wide application of magnesium alloy products also causes the waste of magnesium alloy in the production process.The use of reasonable methods to regenerate magnesium alloy scrap is of great significance for protecting the environment and promoting the sustainable development of the magnesium industry.At present,the traditional method of magnesium alloy regeneration is mainly liquid regeneration,which classifies and processes magnesium alloy wastes and then throws them into the furnace for smelting.This recycling method is complicated,energy consuming,environmental pollution and low recycling rate.In this paper,the solid state recycling of AZ80 magnesium alloy scraps is firstly carried out by pressing technology,and then the extrusion-shear composite forming process of regenerative magnesium alloy was numerically simulated by using DEFORM-3D finite element analysis software,and strong plastic deformation experiments of extrusion-shear of regenerative magnesium alloy and as-cast magnesium alloy were conducted to eliminate microstructure defects and improve the properties of the alloy.The magnesium alloy solid-state recycling experiment adopts a two-step forming scheme of cold press forming and hot press sintering.The cold press forming is carried out at room temperature and constant pressure,and different sintering pressures and different sintering temperatures are used in the hot pressing sintering process.The microstructure analysis and mechanical properties of the regenerated magnesium alloy were tested.The results show that the relative density of cold-pressed alloy is 78.64%,and the density of the regenerated alloy after sintering is significantly improved.When the sintering temperature is above 300°C,the alloy will undergo dynamic recrystallization.The regenerated alloy obtained at the sintering temperature of 350 °C and the sintering pressure of 300 MPa has the highest mechanical properties,the relative density of the alloy is 99.62%,and the compressive strength is 17.35% higher than that of the as-cast alloy,but the ultimate compressive strain is only 83.86% of the as-cast alloy.The extrusion-shear composite forming process of regenerative magnesium alloy was simulated by finite element method,and the influences of extrusion temperature,extrusion speed,friction coefficient and other parameters on the temperature distribution of samples,the distribution of equivalent stress and equivalent strain,and the extrusion load required by the experiment were studied,which provided a basis for the determination of subsequent extrusion experiment parameters.The extrusion-shear composite forming experiment was carried out on the reclaimed magnesium alloy,and the microstructure analysis and mechanical properties test were carried out on the extrusion samples.The results show that the magnesium alloy undergoes dynamic recrystallization and the grains become smaller.When the extrusion temperature is 300°C and the extrusion speed is 0.6 mm/s,the sample grain size is the smallest.As the extrusion temperature increases,the sample grains will grow and the internal ? phase morphology will change.When the extrusion temperature is high,a granular and lamellar ? phase precipitates during the cooling of the material.When the extrusion temperature is 300 ° C and the extrusion speed is 0.6 mm / s,the sample has the best plasticity and the elongation is 10.06 times that of the as-cast alloy.When the extrusion temperature is 400 ° C and the extrusion speed is 1.0 mm / s,the tensile strength of the sample is the highest,which is 128.26% higher than that of the as-cast alloy.Extrusion-shear composite forming experiments were carried out on as-cast magnesium alloys,and the microstructure and mechanical properties of the samples were analyzed and compared with the extruded alloy extruded samples.The results show that the yield strength of the as-cast alloy extruded specimen is higher,the tensile strength and elongation are not much different,the tensile strength is about 335 MPa,which is 128% higher than that of the as-cast alloy,and the elongation is about 19%,which is about 8.44 times that of the as-cast alloy.