Preparation method of high-strength low-cost magnesium alloy bar

The invention discloses a preparation method of a high-strength low-cost magnesium alloy bar. A magnesium alloy comprises the following raw materials in percentage by mass: 3-7% of Y, 1-2% of Zn, 0.5-1.5% of Mn and the balance of magnesium and inevitable impurities. According to the invention, by adopting a mode of accurately controlling the content of each element of the alloy and combining a solid solution aging treatment process, the original LPSO phase structure is changed before extrusion through solid solution aging treatment; and then the LPSO phase and the gamma'phase influence the dynamic recrystallization process in the extrusion process, the double-peak grain structure is regulated and controlled, the strength of the wrought magnesium alloy is remarkably improved, high plasticity is kept, and a new thought is provided for research on preparation of the high-performance magnesium alloy. The method has the advantages of simple equipment, low alloy element content, low cost, simple and convenient proc