Inclusion Analysis Of AZ91D Magnesium Smelting Directly With Crude Magnesium

In order to respond the appeal of the nation policy in the "eleventh five-year" plan of"energy conservation and emission reduction", the process of AZ91magnesium alloyssmelting directly with crude magnesium was studied in this paper. The AZ91alloy wasfabricated directly using refining, filtering and alloying from crude magnesium in thispaper. The optimal processing parameters were obtained with the help of inspection ofmicrostructures and mechanical properties, which provided experimental data forapplication of magnesium alloy smelting directly with crude magnesium.The optimal smelting processing parameters of crude magnesium obtained are asfollows: smelting temperature is740℃, pouring temperature is720℃, filter method isfiltering by barbed wire, refining way are refining by scouring agent and blow argon,protection way is mixed gas protection with SF6+N2, and the actual gains rate of crudemagnesium in purification is ninety percent under the experimental condition. In themelting process, adopt the method of grain refinement with ultrasonic stir to deal with theliquid metal, and respectively pouring the melt metal before and after the ultrasonic stirred.Compared the two groups of AZ91magnesium alloys to the commercial AZ91Dmagnesium alloys smelting directly with crude magnesium through tensile test, impact testand salt fog corrosion test, it analyzed the fracture morphology and inclusion composition.The following conclusion was obtained: The average tensile strength of commercialAZ91D magnesium alloys smelting directly with crude magnesium is155.84MPa,theaverage impact toughness is2.517J/cm2; The average tensile strength of alloys withoutultrasonic stir is79.74MPa,the average impact toughness is2.119J/cm2; The averagetensile strength of alloys after ultrasonic stir is174.74MPa, he average impact toughness is4.539J/cm2; All fracture way belong to brittle fracture; The performance of alloys on saltfog corrosion which were smelted in laboratory was a little more than that of commercialAZ91D alloys. The tensile and impact mechanical properties of AZ91alloys haveimproved significantly after ultrasonic stir which smelted in laboratory, and the internal defects of the alloys have reduced obviously. But there is little effect on alloys corrosiontest and inclusion removed after ultrasonic stir.The main elements of impurities are C, O and Si in magnesium alloys smeltingdirectly with crude magnesium, and they are the main accounts which affect themechanical properties. The key of improve alloys quality is reduce the content of C, O andSi through the purification treatment. It can be reduce the energy consumption of twicesmelting by smelting directly of crude magnesium. It is practically significant to achievedthe purpose of reduce process and cost, improve production efficiency.