Research On Magnesium Alloy Vacuum Die Casting Technology And Organization Performance

Nowadays, it is important and necessary to coordinate the relation between thesustainable development of the automotive industry and energy saving and emissionreduction. In recent years, automobile lightweight gradually attracted much attention, thevehicle lightweight can not only improve the vehicle performance, but also has obviousadvantages in energy saving and consumption reduction. Therefore, automobile materiallightweight is one of the hot research areas. Steel and iron can be changed into aluminum（Al） or magnesium （Mg） alloys, especially Mg alloy materials whose proportion is1/3ofsteel,2/3of Al. Mg alloys are considered to be the best automotive structure material, butthe advantages are limited due to the lower mechanical properties.In order to improve the mechanical properties of Mg alloy on automobile, AZ andAM series alloys are researched using vacuum die casting. The influence of vacuumexhaust system, vacuum degree, alloying and heat treatment on Mg alloy die casting andproperties is studied by means of numerical simulation, microstructure observation andmechanical testing system, and the mechanism of strength-toughness is discussed in thispaper. The test results show that the gas that is inside the mold cavity can be eliminatedadequately with the help of computer numerical simulation to optimize casting exhaustsystem and process parameters and add exhaust passage to the overflow groove in thecentral of flank to reduce internal gas of the casting. When the mold cavity vacuum degreereaches to5KPa, the minimal gas and higher density can be obtained in the liquid metalduring filling. Besides, the microstructure and mechanical properties of the test results andsimulation results are consistent. The content of Al is decreased on the basis of AZ91,thetensile strength of the alloy is reduced, while the elongation is increased; after joining the2%Sn in basic of AZ71alloy, the microstructure of alloy is refined, and the granularMg₂Sn phase is formed, the strength and toughness are improved. Especially after beingT4heat treated, microstructure is more uniform and Mg₂Sn phase disperses, themechanical properties of AT72alloy is effectively improved. Tensile strength, yield strength and elongation reach to276.01MPa,202.55MPa and10.6%, respectively. Theproperties are increased17%,34.4%and135.6%respectively compared with AZ91alloy.The tensile strength of AM70alloy is increased compared with AM50alloy, but theelongation is reduced; the tensile strength of AM70-0.5Nd-0.5Ca alloy is further improved,while the plasticity is dropped. The microstructure of the alloy is refined after a smallamount of Nd and Ca elements are added which are mainly dissolved in Mg17Al12phases,while new phases are not formed. The mechanical properties of AM70-0.5Nd-0.5Ca alloycan be improved after being T4heat treated. The tensile strength, yield strength andelongation can reach to243.62MPa,145.2MPa and6.7%, respectively.