利用碳和碱土金属(Ca和Sr)对Mg-3Al合金进行单独或复合细化处理,研究其品粒细化效果及其晶粒细化对Mg-3Al合金抗拉强度特性的影响规律.结果表明:0.2%C(质量分数,下同)、0.2%Ca及0.2%Sr均可显著细化Mg-3Al合金,而经0.2%C与0.2%Ca或0.2%Sr复合细化可进一步提高细化效果.细化后Mg-3Al合金的拉伸性能明显提高,经复合细化后合金的极限抗拉强度和断裂伸长率分别提高了20%和40%.晶粒细化影响Mg-3Al合金的断裂机制,由具有粗大解理面的解理断裂模式转变为解理和准解理的混合断裂模式.%The Mg-3A1 alloy was modified by 0. 2%C(mass fraction) and/or alkaline-earth elements of 0. 2%Ca or 0. 29%Sr to refine its grain size. The effect of grain refinement on the tensile properties of the Mg-3A1 alloy was investigated. The results show that higher grain refining efficiency can be obtained for the Mg-3Al alloy modified by the combination of carbon and alkaline-earth elements. Compared to the Mg-3Al alloy without any treatment, the tensile properties of the Mg-3A1 alloy are remarkably improved after being modified by the combination of carbon and a little addition of alkaline-earth elements. The ultimate tensile strength and elongation to failure are improved by about 20% and 40%, respectively. After being refined either by carbon or by the combination of carbon and a little addition of alkaline-earth elements, the main fracture mechanism is changed from cleavage mode with large cleavage planes for the unrefined Mg-3A1 alloy to mixed mode of cleavage and quasi-cleavage fracture. The fracture surfaces are almost composed of small cleavage planes with thin river patterns and quasi-cleavage planes with severe plastic deformation.
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