Mould for refining magnesium alloy structure and enhancing mechanical property

Abstract

The invention discloses a mold for refining the microstructure of magnesium alloy and improving its mechanical properties, which belongs to the technical field of alloy material development. It includes an upper mold with a vertical mold cavity in the middle and an upper half of the horizontal mold cavity below, and a lower mold with the lower half of the horizontal mold cavity on the upper mold and matched with the horizontal mold cavity of the upper mold. The extrusion rod that exits automatically is characterized in that the cross-section shape of the horizontal die cavity formed by the cooperation of the upper and lower dies is a square cross-section that gradually shrinks from the inside to the outside, and the extrusion ratio is 25-1.21. In addition, a graphite pressure head is installed at the lower end of the extruding rod, and a retracting rod spring is installed on the upper die. The advantages of the present invention are ①. Since the cross-section of the horizontal die cavity is changed from large to small, the billet is deformed by extrusion after large shear deformation, which can achieve the purpose of refining grains and improving mechanical properties. ②. A graphite indenter is installed at the end of the extrusion head to avoid sticking of alloy materials. ③. Equipped with a retracting rod spring, it is convenient to retract the rod.

Description

technical field [0001] The invention belongs to the technical field of alloy material development, and in particular relates to a mold for refining magnesium alloy structure and improving mechanical properties. Background technique [0002] Grain refinement has always been a hot topic in the field of materials science, especially for green engineering magnesium alloy materials. Extrusion deformation is an ideal deformation method to refine grains and improve its mechanical properties. At present, the refinement of magnesium alloy materials adopts an equal channel angular extrusion deformation technology (ECAP), which is a one-way extrusion process in two die cavities with the same cross-sectional area and crossing each other at an angle of 90 degrees. Pressing is completed, that is, a vertical mold cavity and a horizontal mold cavity are made in a special mold, the vertical mold cavity and the horizontal mold cavity are equal in section and perpendicular to each other, and...

AI Technical Summary

Problems solved by technology

The principle is to accumulate large strains through repeated extrusion, so as to achieve grain refinement. Compared with traditional cold rolling, extrusion, drawing, and forging technologies, it has made great progress, but its disadvantage is that after one pass After extrusion, the strain distribution of the material section is extremely uneven, and it is necessary to change the mode and angle for many times before extrusion to obtain a large strain and a uniform distribution of strain, and the stress on the material during the extrusion process The state is not ideal, especially the strong tensile stress exists on the upper surface of the sample after passing through a 90° angle, which leads to premature cracking of the sample, and it is difficult to control the strain of the section uniformly, thus limiting the degree of grain refinement and increasing Reduced scrap rate and increased production costs

In addition, the pressure head of the extrusion rod used to pressurize the material in the mold is made of metal materials such as steel. This metal pressure head has high thermal expansion, so a large gap must be left between the pressure head and the mold wall. The gap, and the large gap leaves a dead zone after the extrusion of the magnesium alloy billet, and when the indenter contacts the billet for extrusion, the billet will wrap on the surface of the indenter, which is difficult to remove, and it will be difficult to remove it after the extrusion is completed. The lever is also very inconvenient

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