The Study Of Casting Magnesium Alloy Grain Refinement

Although magnesium alloy has many unique advantages, but because of defects in mechanics magnesium alloy, making its practical application in the industry much less than aluminum. To find an effective grain refiner and appropriate processing method is an effective way to expand the scope of application of magnesium alloy, but the current study the grain refinement of magnesium alloys have a technical bottleneck. The current grain refinement of magnesium alloy mainly in ZL114 A, AM60 and AZ91, refiners mainly Mn CO3, Al-Ti-C and rare earth Y, La, for AZ91 and AZ31 aluminum grain refiners lack of systematic research, and the use of Al-5Ti-2C, Al-4Ti-B, rare earth Sm, Gd, Y and other comparative study more rare.To study the Al-Ti-B, Al-Ti-C and magnesium alloy rare earth elements Refinement of Grain, under inert gas conditions smelting AZ91, AZ31 alloy, and Al-4Ti-B was added in the molten state, Al-5Ti-2C refiner and rare earth elements, magnesium alloy samples prepared. Studied before and after thinning, cast and solid solution AZ91 and AZ31 alloy microstructure and grain size, grain refinement compared the effects of different thinning agents. Hardness testing using the method of the alloy mechanical testing experiments to compare the effects of different amounts of incorporation refiner alloy properties tested. From the experimental results show, Al-4Ti-B, Al-5Ti-0.8C master alloy is added to help refine AZ91 magnesium alloy increases the amount added, the refining effect and mechanical properties has been improved; but adding an excess of Al-4Ti-B and Al-5Ti-0.8C master alloys, grain size becomes large, reduce the mechanical properties. Thus, there is an intermediate alloy optimum amount of Al-4Ti-B is about 0.1875%, Al-5Ti-0.8C is about 0.2%. Rare earth elements Sm, Gd, Y added help refine AZ31 magnesium alloy, with the added amount, the effect of the good or bad, wherein the optimum amount of Sm about 0.4%, Gd was about 1.5%, Y It is about 1.0%. By the refiner to refine the grain size statistics show that after joining Al-4Ti-B and Al-5Ti-0.8C refiner, grain size has been significantly reduced, but the effect of thinning to Al-5Ti-0.8C than adding Al-4Ti-B to Mg-Al alloy cast larger average grain size, effective as add Al-Ti-B refiner. After the addition of rare earth refining agent, grain size has been significantly reduced, but thinning effect than adding Al-4Ti-B and Al-5Ti-0.8C of Mg-Al alloy cast larger average grain size, on rare earth elements, the refining effect of Gd best. After refinement of the alloy hardness and tensile strength tests showed that grain refinement of Al-4Ti-B mechanical properties superior to the Al-5Ti-0.8C and rare earths.