Effect Of Sm Addition On Microstructure And Properties Of Mg-gd-Y-Zr Alloy

Magnesium alloys have increasing attracted scientific interest for potential applications. High specific strength and stiffness and good electromagnetic shielding characteristics combined with quite low density make them very attractive as structural materials in applications where weight saving is of great importance. Such ares are aircraft and space machinery, but ground transport, including automobiles and3C products. Rare earths can greatly improve the strength properties. Recent reports showed that Mg-Gd-Y-Zr alloys exhibit high properties. Therefore, using low cost rare earths elements to reduce consumption of Gd or Y have become an advanced research project in magnesium alloys areas.Mg-Gd-Y-Sm-Zr alloys are successfully prepared in electric resistance furnace with shielding gas. Strength properties and microstructure were analyzed by tensile testing, X-ray diffraction, scanning electron microscope. The main contents of research are as follows:1. As-cast Mg-6Gd-3Y-xSm-0.5Zr (x=0,1,3,6) alloys of different Sm addition were studied.The result showed that second phase multiplied with Sm contents increasing.The second phase were composed of Mg24Y5、Mg5Gd、Mg41Sm5.The eutectic phase has skeleton-like shape. The ultimate tensile strength increased fistly, then decreased and finally recovered a little. And the elongation exhibited opposite trends.2. The Mg-6Gd-3Y-xSm-0.5Zr (x=0,1,3,6) in different solid solution treatment were analized. The primary eutectic phase had been dissolved and RE-rich particulate phase emerged with increasing time of solid solution. The increasing of RE-rich particulate phase may diminish elongation. The strength properties were the highest after8hour of solid solution treatment. The ultimate tensile strength raise with Sm addition. The ultimate tensile strength of Mg-6Gd-3Y-6Sm-0.5Zr was231.87MPa and elongation was2.24%.3. The aged Mg-6Gd-3Y-6Sm-0.5Zr was investigated. Vickers-hardness firstly increased, and then decreased a little with the extension of aging time. Peak aging time was20h. The rod-like eutectic phase precipitates dramatically after peak aging.The component of rod-like eutectic phase was same as as-cast alloys. The ultimate tensile strength was improved greatly, about130MPa higher than as-cast alloy. But the elongation decreased.