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金属学报  2018, Vol. 54 Issue (5): 824-830    DOI: 10.11900/0412.1961.2017.00312
  金属材料的凝固专刊 本期目录 | 过刊浏览 |
自由落体条件下Ti-6Al-4V合金微液滴的快速凝固研究
翟斌, 周凯, 吕鹏, 王海鹏()
西北工业大学应用物理系 西安 710072
Rapid Solidification of Ti-6Al-4V Alloy Micro-Droplets Under Free Fall Condition
Bin ZHAI, Kai ZHOU, Peng Lü, Haipeng WANG()
Department of Applied Physics, Northwestern Polytechnical University, Xi'an 710072, China
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摘要: 

在自由落体条件下实现了Ti-6Al-4V合金微液滴的深过冷与快速凝固,研究了合金的相组成、凝固组织和显微硬度。计算出落管中不同直径微液滴的过冷度和冷却速率,揭示了Ti-6Al-4V合金凝固组织随过冷度及冷却速率的变化规律。结果表明,深过冷与快冷速的耦合作用使凝固组织不断细化且形貌发生转变:层片α+β→枝晶α→网篮状α'+β→针状α'→针状α'+不规则β。当液滴直径小于400 μm时,位于原始等轴β晶的晶界及晶内的针状马氏体α'转化为大量连续分布且形状不规则的次生β相,发生α'β固态转变。不同直径范围内的Ti-6Al-4V合金凝固组织的显微硬度与组织形貌有关,“层片组织”、“ 针状α'组织”和“针状α'+不规则β组织”的显微硬度随液滴直径的减小而增大,“网篮组织”的显微硬度随液滴直径的减小而减小。其中,枝晶组织的显微硬度可高达785 kg/mm2,是母合金硬度的2.6倍。

关键词 钛合金深过冷快速凝固微观组织显微硬度    
Abstract

Especially in the past decades, Ti-6Al-4V alloy has received much attention, not only due to its high melting temperature, good corrosion resistance, low density and high hardness, but also because of the diverse and complicated microstructures formed under different conditions. This makes Ti-6Al-4V a potential candidate in both aerospace industries and fundamental research. It is well known that the solidified microstructures of alloy have a great influence on their mechanical properties. Therefore, it is crucial to investigate the mechanical properties of Ti-6Al-4V solidified under different conditions, in particular in the undercooling conditions. However, it is noted that most research on the solidification of Ti-6Al-4V alloy was carried out under equilibrium condition. With respect to Ti-6Al-4V alloy solidified under substantial undercooling conditions, few studies could be found. Thus, it is interesting to study two points: (1) the feature of the microstructure of Ti-6Al-4V alloy solidified under highly undercooled conditions and large cooling rate, (2) the influence of undercooling and cooling rate on the mechanical property of Ti-6Al-4V alloy. To address these two problems, Ti-6Al-4V alloy was rapidly solidified in a drop tube. The main results are summarized as follows. The microstructure of the Ti-6Al-4V alloy solidified under free fall condition displays "lamellar α+βα dendrites→basket-weave α'+β→ needle-like α'→ needle-like α'+ anomalous β " transformation with decreasing the droplets diameter. And the needle-like α' phase in the original boundaries of equiaxed β grains is transformed into a continuous distribution and anomalous structure of β phase when the droplet size is less than about 400 μm. The microhardness of this alloy ranges from 506 kg/mm2 to 785 kg/mm2 when the droplet diameter decreases from 1420 μm to 88 μm, which is much higher than that of the master alloy. For "lamellar structure of α+β phases", "needle-like α' phase" and "needle-like α' phase+ anomalous β phase", the microhardness increases with the decrease of droplet diameter. But for 'basket-weave' microstructure, the microhardness diminishes with the decrease of droplet diameter.

Key wordstitanium alloy    high undercooling    rapid solidification    microstructure    microhardness
收稿日期: 2017-07-25     
ZTFLH:  TG113.12  
基金资助:资助项目 国家自然科学基金项目Nos.51474175、51522102、51506182和51734008,以及航空科学基金项目No.2016ZF53060
作者简介:

作者简介 翟 斌,男,1993年生,硕士生

引用本文:

翟斌, 周凯, 吕鹏, 王海鹏. 自由落体条件下Ti-6Al-4V合金微液滴的快速凝固研究[J]. 金属学报, 2018, 54(5): 824-830.
Bin ZHAI, Kai ZHOU, Peng Lü, Haipeng WANG. Rapid Solidification of Ti-6Al-4V Alloy Micro-Droplets Under Free Fall Condition. Acta Metall Sin, 2018, 54(5): 824-830.

链接本文:

https://www.ams.org.cn/CN/10.11900/0412.1961.2017.00312      或      https://www.ams.org.cn/CN/Y2018/V54/I5/824

图1  Ti-6Al-4V母合金的XRD谱和DSC曲线
图2  Ti-6Al-4V合金微液滴过冷度与冷却速率随直径变化的曲线
图3  Ti-6Al-4V母合金典型凝固组织和直径D=1330 μm合金微液滴的凝固组织
图4  不同直径Ti-6Al-4V合金微液滴的凝固组织
图5  Ti-6Al-4V合金β相含量与液滴直径的关系
图6  Ti-6Al-4V合金微液滴凝固组织显微硬度与直径的关系
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