Method for increasing AZ91D magnesium alloy corrosion-resistant property

The invention relates to a method for improving corrosion-resistant performance of AZ91D magnesium alloy, comprising the steps of: heating to melt AZ91D magnesium alloy ingot, introducing protective CO2 and SF6 mixed gas at 590-610 DEG C, heating to 720-740 DEG C, adding boron to the magnesium alloy liquid in the Al-4B intermediate alloy form, stirring, standing to obtain boron-magnesium complex liquid, cooling to 680-700 DEG C, pouring the boron-magnesium complex liquid into a preheated metal mould (200-400 DEG C), and placing the mould into a rotating magnetic field; and powering on to start up a rotating magnetic field generating device, allowing the boron-magnesium complex liquid to solidify under the action of rotating magnetic field, cooling at room temperature, powering off the rotating magnetic field generating device, and demoulding. The inventive method can improve the corrosion-resistant performance of AZ91D magnesium alloy; and has the advantages of no pollution, low energy consumption, and remark