Effect Of Al-Mg Coated Reverse Isothermal Extrusion Process On Microstructure And Properties Of Products

Among metal materials,magnesium alloys have the advantages of high specific strength,stiffness,low density,good damping and shock absorption performance,and have attracted much attention in industrial production,especially the current lack of resources and environmental damage caused by economic development.Magnesium alloy is considered to be the most promising lightweight material in the 21st century.Because magnesium alloys are easy to corrode,this paper uses reverse hot extrusion process to study the mechanical properties,corrosion resistance and corrosion resistance of aluminum-magnesium-coated rods prepared by casting 2A12 aluminum alloy coated AZ31 magnesium alloy Mechanism and other content.The research results of the thesis are as follows:In this paper,DeForm-3D finite element simulation software is used to establish the aluminum-magnesium reverse extrusion geometric model,and the extrusion process is determined as follows:the extrusion speed is 5.199 mm/s,the billet temperature is 380?,and the mold and extrusion barrel temperature is 400?,The extrusion ratio is 10.82.The 2A12aluminum alloy with an extruded blank size of?120 mm×300 mm is coated with an AZ31magnesium alloy of?95 mm×300 mm.The metal deformation and equivalent plasticity of the aluminum-magnesium composite billet in the process of preparing composite rods by the reverse isothermal extrusion process are studied.The changes of stress-strain and temperature fields are demonstrated through experiments.The results show that the aluminum-magnesium composite rod of?38 mm×2690 mm is extruded,the average thickness of the 2A12 aluminum alloy coating is 4mm,the diameter of the AZ31 magnesium alloy core material is?30 mm,the bonding interface is formed between the aluminum-magnesium metal,and the extrusion-coated rod The molding condition is good.Through the study of the structure of the extruded coated bar,it is found that the grains are obviously refined after extrusion,and the texture of the structure shows a preferred orientation distribution.The mechanical properties of the extruded magnesium alloy bar were analyzed,and the effects of different aging treatment systems on the phase change and mechanical properties of the AZ31 magnesium alloy before and after cladding and extrusion were mainly studied.Through phase analysis and mechanical property testing,it was found that the extrusion process was helpful for grain refinement to generate Al₁₂Mg₁₇ phase,and through aging treatment it was found that Al₁₂Mg₁₇ phase affects the mechanical properties of the alloy,and it was found that cladding extrusion helps improve the alloy Mechanical properties.Corrosion analysis was carried out by immersion test?GB10124-88?and electrochemical workstation.The comparative study of 2A12 aluminum alloy,as-cast AZ31 magnesium alloy,extruded AZ31 magnesium alloy,AZ31/2A12 composite rod,aluminum-magnesium composite intermediate interface Microstructure,weight loss rate,polarization curve,impedance spectrum in 3.5%wt.NaCl solution.The results showed that recrystallization was happened during the indirect extrusion process for the profiles with precipitated phases of??Al₃Mg₂?and?(Mg₁₇Al₁₂),while only?(Mg₁₇Al₁₂)phases were precipitated along the grain boundaries for that without coating.It is always happened that a passivation layer was formed on the surface of that extruded profile with the aluminum cover during corrosion process,so that the extruded profiles were prevented from further corrosion by the passivation layer.Therefore,research shows that the indirect co-extrusion technology is beneficial to improve the corrosion resistance of the magnesium alloy AZ31 coated by aluminum.