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Mg-Zn-Gd铸造镁合金凝固组织及准晶相调控研究
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西北工业大学

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国家科技重大专项(J2019-VI-0004-0118);国家自然科学基金(51771152);国家重点研发计划(2018YFB1106800)


Study on Solidification Structure and Quasicrystal Regulation of Mg-Zn-Gd Casting Alloys
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1.State Key Laboratory of Solidification Processing,Northwestern Polytechnical University,Xi’an 710072;2.China

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    摘要:

    利用Thermo-Calc软件计算了Mg-xZn-2Gd(x=0~12, wt.%)合金的平衡凝固和Scheil凝固路径,研究了冷却速率和合金成分对准晶I相含量的影响规律。结果表明,Zn/Gd原子比6.0的合金平衡凝固组织中仅包含准晶I相,而在非平衡凝固时因固相中的溶质扩散受限,W相难以转变为I相,形成W相与I相混合的组织。冷却速率和合金成分的变化均会通过影响初生相α-Mg凝固过程中液相的溶质富集速率,改变次生相结晶时残余液相的溶质含量和温度,并通过影响凝固驱动力来影响次生相的类型及含量。Mg-Zn-Gd铸造合金制备时,提高凝固冷却速率和增加Zn/Gd原子比均会抑制W相并促进I相的形成,获得具有更高准晶I相含量的合金。

    Abstract:

    The I phase (Mg3GdZn6, icosahedral quasicrystal phase) is widely considered as the strengthening phase in Mg-Zn-Gd system alloys, offering more significant improvements in the mechanical properties compared to the W phase (Mg3Gd2Zn3, cubic phase). However, both the W phase and the I phase typically coexist in the as-cast Mg-Zn-Gd alloy, thereby weakening its mechanical properties. There has been limited systematic research dedicated to investigating the crystallization mechanism of these phases during solidification. In this study, the equilibrium solidification and Scheil solidification paths of Mg-xZn-2Gd (x = 0~12, wt.%) alloys were calculated using Thermo-Calc software. The effects of cooling rate and alloy composition on the fraction of the I phase were studied. The results show that the equilibrium solidification structure of the alloy with a Zn/Gd atomic ratio of 6.0 only contains the I phase. In contrast, limited solute diffusion in the solid phase hampers the transformation of the W phase into the I phase during non-equilibrium solidification, forming a mixed structure composed of both the W phase and the I phase. The variation of cooling rate and alloy composition affects the solute enrichment rate in the Liquid during the solidification process of the primary α-Mg phase, alters the solute content and temperature of the residual Liquid when the secondary phase begins to crystallize, and influences the type and fraction of the secondary phase as determined by the solidification driving force. Higher solidification cooling rates and an increased Zn/Gd atomic ratio inhibit the W phase and promote the formation of the I phase during Mg-Zn-Gd alloy preparation, resulting in the alloy with a higher proportion of the I phase.

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王春辉,杨光昱,秦贺,阚志勇. Mg-Zn-Gd铸造镁合金凝固组织及准晶相调控研究[J].稀有金属材料与工程,,().[Wang Chunhui, Yang Guangyu, Qin He, Kan Zhiyong. Study on Solidification Structure and Quasicrystal Regulation of Mg-Zn-Gd Casting Alloys[J]. Rare Metal Materials and Engineering,,().]
DOI:10.12442/j. issn.1002-185X.20240112

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  • 收稿日期:2024-03-04
  • 最后修改日期:2024-05-06
  • 录用日期:2024-05-08
  • 在线发布日期: 2024-06-26
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