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金属学报  2019, Vol. 55 Issue (5): 611-618    DOI: 10.11900/0412.1961.2018.00504
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脉冲电流作用下TiAl合金凝固组织演变及形成机理
陈占兴,丁宏升(),陈瑞润,郭景杰,傅恒志
1. 哈尔滨工业大学材料科学与工程学院金属精密热加工国家级重点实验室 哈尔滨 150001
Microstructural Evolution and Mechanism of Solidified TiAl Alloy Applied Electric Current Pulse
Zhanxing CHEN,Hongsheng DING(),Ruirun CHEN,Jingjie GUO,Hengzhi FU
1. National Key Laboratory for Precision Hot Processing of Metals, School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China
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摘要: 

利用OM和TEM研究了脉冲电流作用下Ti-48Al-2Cr-2Nb合金的凝固组织,并分析了其微观组织演变及形成机理。结果表明,脉冲电流细化了TiAl合金的一次枝晶臂间距、柱状晶尺寸和片层间距。未加载电流的TiAl合金凝固的初生相为α相,TiAl合金的片层取向与柱状晶生长方向夹角较大,甚至垂直于生长方向。脉冲电流作用导致枝晶发生熔断和破碎,促进了β枝晶相的析出及增多,片层取向与晶体生长方向夹角较小或成45°生长的片层进一步增多。脉冲电流降低了固-液相之间的自由能及原子扩散激活能,减少形核位垒及晶核的形核功,从而在一定程度上促进原子扩散,增大了形核率,细化一次枝晶臂间距及柱状晶;初生相的转变析出及其特殊的位向关系是片层取向变化的主要原因。

关键词 脉冲电流TiAl合金组织演变片层取向    
Abstract

As a new type of lightweight and high temperature structural material, TiAl alloy has become the most ideal candidate in the fields of aerospace, military and civil products, and it has a good perspective in the industrialization. Refining and improving the microstructure of TiAl alloys has higher theoretical significance and engineering value. In this work, the solidified Ti-48Al-2Cr-2Nb alloy applied electric current pulse is studied, and its microstructural evolution and mechanism are analyzed. The results show that the electric current pulse refines the primary dendrite arm spacing, columnar crystal size and interlamellar spacing of the Ti-48Al-2Cr-2Nb alloy. The primary phase is α without electric current pulse, the angle of the Ti-48Al-2Cr-2Nb alloy that between the lamellar orientation and the growth direction is usually bigger, even perpendicular to the growth direction approximately. The applied electric current pulse causes the dendrite to melt and break, and promotes the occurrence and increase of the primary β phase, the lamellae orientation having a small angle or 45° between the growth direction is further increasing. The electric current pulse reduces the solid-liquid phase free energy and atomic diffusion activation energy, reduces the nucleation barrier and the critical nucleation energy, thereby atomic diffusion and the crystallization nucleation is promoted to a certain extent, the primary dendritic spacing and columnar crystals are remarkably refined. The electric current pulse causes the transformation of the primary phase and its corresponding crystal orientation relationship is the main reason for the change of lamellar orientation.

Key wordselectric current pulse    TiAl alloy    microstructural evolution    lamellar orientation
收稿日期: 2018-11-07      出版日期: 2019-03-15
ZTFLH:  TG113.12  
基金资助:国家自然科学基金项目(51171053);国家自然科学基金项目(51471062);国家自然科学基金项目(51671072)
通讯作者: 丁宏升     E-mail: dinghsh@hit.edu.cn
Corresponding author: Hongsheng DING     E-mail: dinghsh@hit.edu.cn
作者简介: 陈占兴,男,1985年生,博士生

引用本文:

陈占兴,丁宏升,陈瑞润,郭景杰,傅恒志. 脉冲电流作用下TiAl合金凝固组织演变及形成机理[J]. 金属学报, 2019, 55(5): 611-618.
Zhanxing CHEN,Hongsheng DING,Ruirun CHEN,Jingjie GUO,Hengzhi FU. Microstructural Evolution and Mechanism of Solidified TiAl Alloy Applied Electric Current Pulse. Acta Metall Sin, 2019, 55(5): 611-618.

链接本文:

http://www.ams.org.cn/CN/10.11900/0412.1961.2018.00504      或      http://www.ams.org.cn/CN/Y2019/V55/I5/611

Sample No.ip / (mA·mm-2)f / Hz
10-
232100
364100
496100
56450
664200
表1  脉冲电流作用下Ti-48Al-2Cr-2Nb合金凝固实验参数
图1  脉冲电流作用下Ti-48Al-2Cr-2Nb合金柱状枝晶的生长形态
图2  脉冲电流作用下Ti-48Al-2Cr-2Nb合金的一次枝晶臂间距
图3  脉冲电流作用下Ti-48Al-2Cr-2Nb合金的凝固组织
图4  脉冲电流作用下Ti-48Al-2Cr-2Nb合金片层取向的正态分布
图5  脉冲电流影响下的Ti-48Al-2Cr-2Nb合金片层结构
图6  脉冲电流对Ti-48Al-2Cr-2Nb合金片层间距的影响
图7  TiAl合金中不同初生相的晶体生长方向与片层取向的关系
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