微重力下Fe-Al-Nb合金液滴的快速凝固机理及其对显微硬度的影响

发布时间：2018-04-20 00:06

本文选题：共晶生长 + 快速凝固　；参考：《物理学报》2017年10期

【摘要】：采用落管无容器处理技术实现了Fe_(67.5)Al_(22.8)Nb_(9.7)三元合金在微重力条件下的快速凝固,获得了直径为40—1000μm的合金液滴.实验中合金液滴的过冷度范围为50—216 K,冷却速率随着液滴直径的减小由1.23×10~3K·s~(-1)增大到5.53×10~5K·s~(-1).研究发现,Fe_(67.5)Al_(22.8)Nb_(9.7)合金液滴的凝固组织均由Nb(Fe,Al)_2相和(αFe)相组成,且随着液滴直径的减小,初生Nb(Fe,Al)_2相由树枝晶转变为等轴晶,共晶组织发生了约3倍的细化且生长特征由层片共晶向碎断共晶转变;硬质初生Nb(Fe,Al)_2相的析出有效提高了合金的显微硬度.与电磁悬浮条件下同过冷合金的凝固组织对比发现,落管条件下的合金液滴凝固组织更细化,使得合金显微硬度提高了2%—6%.
[Abstract]:The rapid solidification of Fe _ S _ 2O _ (67.5) Alac _ (22. 8) NbSZ _ (9. 7) ternary alloy under microgravity conditions has been realized by using the technology of tube-dropping without container. The droplets of the alloy with diameter of 40-1000 渭 m have been obtained. The supercooling range of the alloy droplets is 50-216 K, and the cooling rate increases from 1.23 脳 10 ~ (3) K ~ (-1) to 5.53 脳 10 ~ (5) K ~ (-1) ~ (-1) with the decrease of the droplet diameter. It is found that the solidification structure of the alloy droplets is composed of the (伪 Fe) phase and the (伪 Fe) phase, and with the decrease of the diameter of the droplet, the primary NbFeFeAlN / AlN phase changes from dendrite to equiaxed crystal. The eutectic structure was refined by about 3 times and the growth characteristics were changed from lamellar eutectic to broken eutectic, and the microhardness of the alloy was improved effectively by the precipitation of hard primary NB _ 2O _ (Fe) Al _ 2O _ 2 phase. Compared with the solidified microstructure of the supercooled alloy under the condition of electric magnetic levitation, it is found that the solidified microstructure of the alloy droplet under the condition of falling tube is more refined, which makes the microhardness of the alloy increase by 2-6.
【作者单位】：西北工业大学应用物理系;
【基金】：国家自然科学基金(批准号:51327901,U1660108,51671161) 航空科学基金(批准号:2014ZF53069) 陕西省科学技术研究发展计划工业科技攻关项目(批准号:2016GY-247)资助的课题~~
【分类号】：TG111.4

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