Study On Structure And Properties Of Heat-Proof Wrought Magnesium Alloys With High Strength

In the present paper,heat-proof wrought magnesium alloys with high performance is taken as the research object,and the addition of Ca element into magnesium alloy is taken as the main research content, the rule and relationship among alloy composition,structure,deformation and performance were studied systematically on the base of our previous work.The main conclusions are presented as follows.(1)When A1 element content is in the range of 10～11%and Zn is 2～3%,the tensile strength of as-extrused magnesium alloys increases with the increase or Al,Zn content,but the elongation decreases. The tensile strength of AZ113 is highest,352.6MPa,and the elongation 9.5%.(2)With an increase of the content of Ca element,both the tensile strength and the elongation of AZ113 magnesium alloy fall down followed by a rising step.When the conten of Ca is 2.0%,the tensile strength at room temperature reach the maximum value 351.4 MPa,whcih is only 0.34%lower than the matirx alloy; When the Ca content is 0.7%,the elongation reache the maximum value 8.86%.(3)The tensile strength of AZ113 magnesium alloy at 250℃can be improved by the addition of Ca element.The tensile strength at elevated temperature increases about 1.7%and 10.0%when the Ca content is 0.7%and 2.0%respectively.The elongation at elevated temperature is a little lower than the matrix alloy. When the addition of Ca is 0.7%and 2.0%,whose elongation at elevated temperature is 17.8%and 16.9% respectively.(4)With the precipitation of bar-likeβ-Mg₁₇Al₁₂phase,the tensile strength of X20 magnesium alloy enhances further,but the elongation reduces after T5 treatment.After T4 treatment at the same temperature, the grains of X20 are much smaller than AZ113,whereβ-Mg₁₇Al₁₂phase cann't fully dissolve but Al₂Ca phase with high-melting point forms reversely.(5)There is a compact CaO/MgO layer formed on the surface of magnesium alloy with the addition of Ca,which improves the cellular structure of the oxide film,eliminates the ruptured phenomenon of the oxide film and enhances the antioxidant properties of AZ113 magnesium alloy at elevated temperature evidently.(6)The analyses on the microstructure and the performance of AZ113+xCa magnesium alloys show that the X20 magnesium alloy have a good over-all properties,both the tensile strength at ambient and elevated temperature exceed AZ80A,ZK60A which are considered to have the highest tensile strength at present,and whose elongation can also reach 7.29%.