Ultrafine Magnesium Alloy Extrusions Forming Process And Properties

Magnesium is a rich kind element of crustal, and accounts about2.5%of the elementsof the crust. Magnesium alloy has good dimensional stability, excellent dampingperformance, lower density, good casting properties, high specific strength and stiffnessand process ability, etc. And it is easy to recycle, environmentally friendly features,because magnesium alloy with a series of excellent performance in the automobile industryand have received increasing attention in order to reduce the quality of the car and lowerfuel consumption, to achieve the purpose of energy saving.In the paper, extrusion process and structure characteristics of AZ31magnesium alloyautomotive profiles were studied, before the extrusion, firstly, with solution temperature of400℃, the ingot was holding for10hours under solution treatment. AZ31Magnesiumalloy profile extrusion process parameters: Extrusion temperature400℃, temperature ofthe mold and the ingot430℃, extrusion speed1.5mm/s, the tensile strength of extrudedsections257MPa, elongation up to18.1%.By the solution treatment of the AZ31magnesium alloy profiles, extruded metal flowline disappears and β-Mg17Al12phase substantially matrixes into Mg. At the same time,400℃insulation8h, the tensile strength achieves244.05MPa, and the elongation rate ofprofiles is16.8%.By means of the AZ31magnesium alloy profiles the heat treatment and the cryogenictreatment for different parameters, the tensile strength and the elongation of AZ31magnesium alloy after the direct cryogenic treatment are better than those after T4treatment+cryogenic treatment, cryogenic treatment+T5treatment and T6treatment+cryogenic treatment. Under-196℃, cryogenic treatment directly after8hours, the tensilestrength gets the maximum274.14MPa. With cryogenic time increasing, the elongation ofdirect cryogenic treatment shows a rising trend in the72hours immediately after cryogenictreatment reaching the maximum elongation of28.8%. During the cryogenic treatmentsince the temperature falling sharply, the volume of AZ31magnesium alloy extrudedprofile organization shrinks, and its crystal lattice has tending of narrowing, it also can produce the compressive stress within the crystal organization, in order to lead producingtiny crystal in local, to achieve to get fine grains.