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金属学报  2018, Vol. 54 Issue (6): 844-850    DOI: 10.11900/0412.1961.2017.00402
  本期目录 | 过刊浏览 |
过热温度和冷却速率对过冷Ti熔体凝固过程的影响
樊丹丹, 许军锋, 钟亚男, 坚增运()
西安工业大学材料与化工学院 西安 710021
Effect of Superheated Temperature and Cooling Rate on the Solidification of Undercooled Ti Melt
Dandan FAN, Junfeng XU, Yanan ZHONG, Zengyun JIAN()
School of Materials and Chemical Engineering, Xi'an Technological University, Xi'an 710021, China
全文: PDF(4930 KB)   HTML
摘要: 

采用分子动力学方法研究了金属Ti熔体的凝固过程,通过径向分布函数、H-A键型结构以及最大原子团簇方法分析了Ti的凝固组织。结果表明,金属Ti熔体的凝固过冷度随过热温度的升高而增大,且过冷度与过热温度的变化曲线上出现2次转折:T1=2100 K和T2=2490 K,分别对应于形核团簇的原子键破坏起始温度和破坏终了温度。在此温度区间,过热熔体中微观晶核团簇随温度升高而减少。当过热温度增大到一定程度(大于T2),其过冷度将维持定值;同时,金属Ti熔体的过冷度也随冷速的增大而增大,直到非晶结构形成;金属Ti形成非晶的临界冷速为1.0×1013 K/s。

关键词 过冷度凝固均质形核分子动力学    
Abstract

Undercooling is an important parameter to characterize the process of solidification and the physical properties of the melt. However, the traditional experimental conditions do not provide mature technical conditions and experimental platforms for the study of this subject. Molecular dynamics simulation method can not only study the experimental process and the organization structure, but also break through the limited conditions of the laboratory, and provide advanced prediction for scientific research. In order to study the influences of superheated temperature and cooling rate on the undercooling of the homogeneous nucleation and the solidified structure, the solidification of undercooled Ti melt was studied by molecular dynamics simulation in this work; and the solidified structure was then analyzed by the radial analysis, the H-A key type analysis and the largest groups of cluster analysis. The results show that, the nucleation undercooling of Ti melt increases with the rise of superheated temperature. In the undercooling vs temperature curve there are two inflection points at 2100 K (T1) and 2490 K (T2), which correspond to the breaking-start temperature and breaking-end temperature for bond pair of nucleation cluster. In this temperature range, the number of nucleation clusters decreases with rise of temperature. When the superheated temperature is higher than T2, the nucleation undercooling approaches a constant. On the other hand, the nucleation undercooling of Ti melt increases with the accelerate of cooling rate until an anomalous structure is formed, and in the numbers of the bonds of the structure vs different cooling rate curves, the number of 1541, 1551 and 1431 bond types gradually adds with cooling rate going up. In addition, when the cooling rate is less than 1.0×1011 K/s, the hcp and bcc inlaid crystalline structures are obtained after the solidification of Ti melt. When the cooling rate is greater than or equal to 1.0×1013 K/s, two kinds of crystalline structure are reduced, and the microstructures are mainly amorphous. When the cooling rate ranges between 1.0×1011 K/s and 1.0×1013 K/s, its structure is a mixture of crystalline and amorphous. From the results of radial distribution, H-A bond type and atomic cluster analysis, it was found that the critical cooling rate for amorphous structure is determined as 1.0×1013 K/s.

Key wordsundercooling    solidification    homogeneous nucleation    molecular dynamics
收稿日期: 2017-09-25     
ZTFLH:  TG113.12  
基金资助:国家自然科学基金项目No.51671151和陕西省科技项目No.2016KJXX-87
作者简介:

作者简介 樊丹丹,女,1993年生,硕士生

引用本文:

樊丹丹, 许军锋, 钟亚男, 坚增运. 过热温度和冷却速率对过冷Ti熔体凝固过程的影响[J]. 金属学报, 2018, 54(6): 844-850.
Dandan FAN, Junfeng XU, Yanan ZHONG, Zengyun JIAN. Effect of Superheated Temperature and Cooling Rate on the Solidification of Undercooled Ti Melt. Acta Metall Sin, 2018, 54(6): 844-850.

链接本文:

https://www.ams.org.cn/CN/10.11900/0412.1961.2017.00402      或      https://www.ams.org.cn/CN/Y2018/V54/I6/844

图1  采用嵌入原子法(EAM)模拟计算的熔点温度
Ts Tc ΔT
2006 917 1023
2036 910 1030
2100 904 1036
2250 899 1041
2320 896 1044
2350 894 1046
2400 888 1052
2450 879 1061
2490 874 1066
2540 874 1066
2600 874 1066
表1  金属Ti熔体从不同Ts快冷后的结晶温度Tc和过冷度ΔT
图2  不同过热温度Ts下Ti体系能量随温度的变化曲线
图3  Ti熔体过冷度与过热温度的关系
图4  Ti熔体在不同的冷速Rc下能量随温度变化的曲线
图5  Ti熔体ΔT-lgRc曲线
图6  Ti熔体在不同冷速下的径向分布函数曲线
图7  以不同冷速冷却后金属Ti最终构型中各键型个数
Rc / (Ks-1) Tc / K ΔT / K
1.0×109.8 913.37 1026.63
1.0×1010 907.26 1032.74
1.0×1010.5 882.83 1057.17
1.0×1011 876.79 1063.21
1.0×1011.5 857.17 1082.83
1.0×1012 799.76 1140.24
表2  Ti熔体在不同Rc下的Tc 和ΔT
Rc / (Ks-1) Nc Nbcc Nfcc Nhcp
1.0×109.8 22300 1852 0 20448
1.0×1010 17276 8349 0 8927
1.0×1010.5 17283 11770 0 5513
1.0×1011 13697 8298 0 5399
1.0×1011.5 21586 6781 0 14805
1.0×1012 18743 5384 0 12909
1.0×1012.5 6315 3150 0 3165
1.0×1013 579 162 0 417
1.0×1013.5 216 58 0 158
1.0×1014 96 17 0 79
1.0×1014.5 43 6 0 37
1.0×1015 35 4 0 31
1.0×1015.5 4 1 0 3
1.0×1016 2 1 0 1
表3  不同冷速冷却后最大原子团簇中总原子数以及各晶态结构原子数
图8  不同冷速冷却后最大团簇微观结构
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