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Nb42Ti21Co37包共晶合金定向凝固组织演化规律研究
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桂林电子科技大学

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国家自然科学(51761009和51701048)、广西自然科学(2020GXNSFAA159163)、桂林电子科技大学研究生教育创新计划项目(2019YCXS109)和广西信息材料重点实验室(191021-Z)资助


Evolution law of directional solidification structure of Nb42Ti21Co37 ternary quasiperitectic alloy
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    摘要:

    包共晶转变兼具共晶转变和包晶转变双重特征,存在于众多的工业合金中。然而,迄今为止尚未建立起相对完整的包共晶凝固理论模型,关于其凝固机理的相关研究较少。基于此,本文针对Nb42Ti21Co37包共晶合金开展了不同抽拉速度(V=1, 3, 5, 15, 30, 70 μm/s)下的定向凝固实验,旨在研究不同抽拉速度下合金的微观组织演化规律,并构建相应的凝固机制。研究结果表明:Nb42Ti21Co37包共晶合金常规铸态和定向凝固组织中均含有α-Nb、Co6Nb7和TiCo+Co6Nb7包共晶相,随着抽拉速率的逐渐增加,初生相α-Nb依次经历了圆球状→花瓣状→团簇状→枝晶状的转变;伴随着上述过程,淬火界面经历了胞状界面到胞枝晶状界面的转变,并且,在抽拉速率V=70 μm/s时固/液界面消失;其次,定向凝固稳态生长区内包共晶的组织逐渐细化,其层间距与生长速率呈指数线性关系,即λ=-1+5×e2.5;当抽拉速率低于5μm/s时,合金的定向凝固过程与平衡凝固相类似;另外,各相在稳定生长区的生长机制为共生生长,随着抽拉速率的增加,包共晶组织的定向排列性逐渐变差。

    Abstract:

    The quasiperitecticcoated transformation has the dual characteristics of eutectic transformation and peritectic transformation, and it exists in many industrial alloys. However, a relatively complete theoretical model of peritectic solidification has not been established so far, and there are few related studies on its solidification mechanism. Based on this, this article carried out directional solidification experiments at different drawing speeds (v=1, 3, 5, 15, 30, 70 μm/s) for the Nb42Ti21Co37 quasiperitectic alloy, aiming to study the alloy"s performance at different drawing speeds. Microstructure evolution law, and build the corresponding solidification mechanism. The research results show that the conventional as-cast and directional solidification structures of Nb42Ti21Co37 quasiperitectic alloy contain α-Nb,Co6Nb7 and TiCo+Co6Nb7 quasiperitectic phases. With the gradual increase of the drawing rate, the primary α-Nb phase undergoes a spherical shape →petal-like →cluster-like →dendrite-like transformation; along with the above process, the quenched interface has undergone the transformation from cellular interface to cellular dendrite-like interface, and at the pulling rate v=70 μm/s, solid/liquid The interface disappears; secondly, the quasiperitectic structure in the steady-state growth zone of directional solidification is gradually refined, and the interlayer spacing has an exponential linear relationship with the growth rate, that is, λ=1+5×e2.5V;when the pulling rate is lower than 5μm/s the directional solidification process of the alloy is similar to equilibrium solidification; in addition, the growth mechanism of each phase in the stable growth zone is symbiotic growth. With the increase of the pulling rate, the directional arrangement of the quasiperitectic structure gradually deteriorates.

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王金华,闫二虎,狄翀博,陈运灿,刘威,王豪,葛晓宇,程健,黄仁君,孙立贤. Nb42Ti21Co37包共晶合金定向凝固组织演化规律研究[J].稀有金属材料与工程,2021,50(10):3577~3584.[Wang Jinhua,闫二虎,Di Chongbo, Chen Yuncan, Liu Wei, Wang Hao, Ge Xiaoyu, Cheng Jian, Huang Renjun, Sun Lixian. Evolution law of directional solidification structure of Nb42Ti21Co37 ternary quasiperitectic alloy[J]. Rare Metal Materials and Engineering,2021,50(10):3577~3584.]
DOI:10.12442/j. issn.1002-185X.20200786

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  • 收稿日期:2020-10-12
  • 最后修改日期:2020-12-11
  • 录用日期:2020-12-22
  • 在线发布日期: 2021-10-28
  • 出版日期: 2021-10-25