Effect of Al on Grain Refinement and Mechanical Properties of Mg-3Nd Casting Alloy

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Effect of Al on Grain Refinement and Mechanical Properties of Mg-3Nd Casting Alloy Lei Wang, Yicheng Feng, Liping Wang, Yanhong Chen, and Erjun Guo (Submitted November 18, 2017; in revised form February 05, 2018) The effect of Al on the grain reﬁnement and mechanical properties of as-cast Mg-3Nd alloy was investigated systematically by a series of microstructural analysis, solidiﬁcation analysis and tensile tests. The results show that Al has an obvious reﬁning effect on the as-cast Mg-3Nd alloy. With increasing Al content, the grain size of the as-cast Mg-3Nd alloy decreases ﬁrstly, then increases slightly after the Al content reaching 3 wt.%, and the minimum grain size of the Mg-3Nd alloy is 48 ± 4.0 lm. The reﬁning mechanism can be attributed to the formation of Al2Nd particles, which play an important role in the heterogeneous nucleation. The strength and elongation of the Mg-3Nd alloy reﬁned by Al also increase with increasing Al content and slightly decrease when the Al content is more than 3 wt.%, and the strengthening mechanism is attributed to the grain reﬁnement as well as dispersed intermetallic particles. Furthermore, the microstructural thermal stability of the Mg-3Nd-3Al alloy is higher than that of the Mg-3Nd-0.5Zr alloy. Overall, the Mg-3Nd alloy with Al addition is a novel alloy with wide and potential application prospects. Keywords

grain reﬁnement, mechanical properties, Mg-3Nd alloy, thermal stability

1. Introduction Magnesium and its alloys are especially suitable for lightweight structural parts due to their low density, high speciﬁc strength, high speciﬁc rigidity, easy processing and recovery. Among these alloys, Mg-RE alloy possesses high strength at elevated temperature, good creep resistance and excellent casting ability, which make it widely used in aerospace ﬁeld (Ref 1-4). It is well known that grain reﬁnement is an important method to improve the strength and plasticity of metallic materials. Due to the higher Hall-Petch coefﬁcient of magnesium alloys, the effect of ﬁne-grained strengthening is better than other metallic materials (Ref 5). Zr has a good reﬁnement effect in Mg-RE alloy (Ref 6); however, the high manufacturing costs and easy deposition in reﬁning process limit its application (Ref 7). It is very necessary to seek a new effective reﬁner for Mg-RE alloy (Ref 8). Qiu found that the addition of Al can signiﬁcantly reﬁne the grain of Mg-10Y alloy and illustrated that Al2Y particle had an orientation relationship with a-Mg matrix. When the size of Al2Y particle is larger than 2 lm, grain reﬁning effect can be obtained due to the Al2Y particle acting as heterogeneous nucleation site for a-Mg matrix (Ref 9-11). Subsequently, the effects of Al on Mg-Gd, Mg-Gd-Y, Mg-Sm and Mg-Ce alloys were studied (Ref 12-15). The results showed that Al2Gd, Al2(Gd0.5Y0.5), Al2Sm and Al2Ce can also effectively reﬁne the grain of magnesium alloys and the reﬁning effect is equivalent

Lei Wang, Yicheng Feng, Liping Wang, Yanhong Chen, and Erjun Guo, School of

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