A method for improving the medium-temperature mechanical properties of mg‑al magnesium alloy die castings

Abstract

The invention discloses a method for improving the medium-temperature mechanical property of Mg-Al series magnesium alloy pressure castings. The method comprises the steps of die-cast formation of magnesium alloy subjected to smelting and aging treatment of the pressure castings subjected to die-cast formation and is characterized in that the aging treatment is directly carried out on the pressure castings after die-cast formation; Pb and Sn are added in the smelting process of the magnesium alloy. The method has the advantages that the Pb and the Sn have the grain refinement effect on structures of the Mg-Al series magnesium alloy pressure castings, the Pb can reduce precipitation of harmful discontinuous second-phase Mg17Al12 and enhance precipitation of beneficial continuous second-phase Mg17Al12 after the aging treatment, and the Sn can form high-melting-point Mg2Sn particles for being precipitated with Mg in the aging process. According to the method, the aging heat treatment is directly carried out instead of being carried out after solution treatment, and therefore the problem that bubbles are generated on the surfaces of the magnesium alloy pressure castings because the temperature is excessively high in the solution treatment process can be avoided.

Description

technical field [0001] The invention relates to the field of metal material science, in particular to a method for improving the medium temperature mechanical properties of Mg-Al series magnesium alloy die castings. Background technique [0002] Magnesium alloy is currently the lightest commercial metal structural material, with good damping and vibration reduction performance, excellent thermal and electrical conductivity, good casting and machining process, etc., and has good application prospects in ground vehicles, aerospace and other fields. Die casting is currently the most important forming method for magnesium alloys, and more than 90% of magnesium alloy parts are die castings. The Mg-Al series (including AZ and AM series) cast magnesium alloys that are most used in the engineering field have relatively low mechanical properties in the die-cast state, especially in the medium and high temperature environment above 100oC, the mechanical properties decay rapidly and ar...

AI Technical Summary

Problems solved by technology

However, for ordinary magnesium alloy die castings, due to the gas entrainment behavior in the die casting process, the internal gas content is high, and it is not suitable for solution treatment at a temperature as high as about 400oC, because this will lead to the near surface of the die casting. The gas expands when heated, causing "bubbling" defects on the surface of the die casting

Therefore, the conventional T6 treatment cannot be applied to ordinary die-cast magnesium alloy parts