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金属学报  2022, Vol. 58 Issue (9): 1169-1178    DOI: 10.11900/0412.1961.2021.00272
  研究论文 本期目录 | 过刊浏览 |
快速凝固Ti-Al-Nb合金B2相形成机制与显微力学性能
梁琛, 王小娟, 王海鹏()
西北工业大学 物理科学与技术学院 西安 710072
Formation Mechanism of B2 Phase and Micro-Mechanical Property of Rapidly Solidified Ti-Al-Nb Alloy
LIANG Chen, WANG Xiaojuan, WANG Haipeng()
School of Physical Science and Technology, Northwestern Polytechnical University, Xi'an 710072, China
引用本文:

梁琛, 王小娟, 王海鹏. 快速凝固Ti-Al-Nb合金B2相形成机制与显微力学性能[J]. 金属学报, 2022, 58(9): 1169-1178.
Chen LIANG, Xiaojuan WANG, Haipeng WANG. Formation Mechanism of B2 Phase and Micro-Mechanical Property of Rapidly Solidified Ti-Al-Nb Alloy[J]. Acta Metall Sin, 2022, 58(9): 1169-1178.

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摘要: 

采用急冷和深过冷快速凝固技术,研究了冷却速率与过冷度对Ti75 - x Al x Nb25 (x = 22、45,原子分数,%)合金相组成、凝固组织演变、B2相形成机制及显微力学性能的作用。在自由落体条件下,随着液滴直径减小,Ti53Al22Nb25合金凝固液滴中B2相由粗大枝晶向等轴晶转变,Ti30Al45Nb25合金凝固液滴的B2相形核位置由γ-TiAl相晶粒内部向晶界处转移,B2相的体积分数逐渐减小。在电弧熔炼和真空吸铸条件下,随着冷却速率的增加,Ti53Al22Nb25合金B2相枝晶尺寸显著减小,Ti30Al45Nb25合金凝固组织发生了由非规则(γ + B2)相层片→规则(γ + B2)相层片→针状(γ + B2)的转变。自由落体条件下Ti75 - x Al x Nb25合金显微硬度随液滴直径的减小逐渐增加,显微硬度的最大值分别为11.57和7.7 GPa,分别较吸铸样品增加了64%和22%,表明深过冷耦合大冷速能有效提高合金的显微力学性能。

关键词 Ti-Al-Nb合金快速凝固组织演变显微硬度    
Abstract

Ti-Al-Nb alloys are widely used in the aerospace industry and are promising candidate materials for turbine engines owing to their relatively low density, high specific strength, and good oxidation resistance. Here, the effects of the cooling rate and undercooling on phase constitution, microstructure evolution, B2 phase formation, and micromechanical properties of the rapidly solidified Ti75 - x Al x Nb25 (x = 22, 45, atomic fraction, %) alloy were investigated. With a decrease in the droplet diameter, the primary B2 phase of Ti53Al22Nb25 alloy transforms from coarse dendrite to equiaxed grain under free fall. For the rapidly solidified Ti30Al45Nb25 alloy droplet, the nucleation and growth of the B2 phase transforms from the center of the γ dendrite to γ-grain boundaries, and the volume fraction of the B2 phase decreases with the droplet diameter. Under the condition of arc melting and vacuum suction casting (VSC), with an increase in the cooling rate, the average diameter of the B2 dendrite of the Ti53Al22Nb25 alloy decreases from 515 to 370 μm. For the Ti30Al45Nb25 alloy, the solidified microstructure changes from irregular (γ + B2) lamellae to regular (γ + B2) lamellar, to acicular (γ + B2) microstructure, and Al segregation is inhibited. The microhardness of Ti75 - x Al x Nb25 alloy increases with a decrease in the droplet diameter, and the maximum microhardness of each alloy is 11.57 GPa and 7.7 GPa, respectively, which are 64% and 22% higher than that of VSC, respectively, thereby indicating that the coupled effect of a large cooling rate and high undercooling can effectively enhance the microhardness of the Ti-Al-Nb alloy.

Key wordsTi-Al-Nb alloy    rapid solidification    microstructure evolution    microhardness
收稿日期: 2021-07-02     
ZTFLH:  TG146.2  
基金资助:国家自然科学基金项目(51734008);国家自然科学基金项目(51871185);国家重点研发计划项目(2018YFB2001800)
作者简介: 梁 琛,男,1989年生,博士生
图1  落管无容器条件下Ti75 - x Al x Nb25合金的冷却速率及过冷度
图2  电弧熔炼和真空吸铸条件下Ti53Al22Nb25的温度分布
图3  电弧熔炼与吸铸条件下Ti75 - x Al x Nb25合金的冷却速率
图4  自由落体条件下Ti75 - x Al x Nb25合金凝固液滴的XRD谱
图5  自由落体条件下不同直径Ti53Al22Nb25合金液滴的凝固组织演变
图6  自由落体条件下不同直径的Ti30Al45Nb25合金液滴的凝固组织演变
图7  电弧熔炼条件下Ti75 - x Al x Nb25合金的XRD谱
图8  电弧熔炼与吸铸条件下Ti75 - x Al x Nb25合金的凝固组织演变
图9  电弧熔炼Ti30Al45Nb25合金的显微组织及元素分布
图10  电弧熔炼与吸铸条件下Ti75 - x Al x Nb25合金的显微硬度
图11  Ti75 - x Al x Nb25合金凝固液滴的显微硬度与直径的关系
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