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金属学报  2020, Vol. 56 Issue (2): 212-220    DOI: 10.11900/0412.1961.2019.00192
  研究论文 本期目录 | 过刊浏览 |
Ag-Ni偏晶合金凝固过程研究
邓聪坤1,2,江鸿翔1,赵九洲1(),何杰1,赵雷3
1. 中国科学院金属研究所 沈阳 110016
2. 中国科学院大学 北京 100049
3. 辽宁石油化工大学机械工程学院 抚顺 113001
Study on the Solidification of Ag-Ni Monotectic Alloy
DENG Congkun1,2,JIANG Hongxiang1,ZHAO Jiuzhou1(),HE Jie1,ZHAO Lei3
1. Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China
2. University of Chinese Academy of Sciences, Beijing 100049, China
3. School of Mechanical Engineering, Liaoning Shihua University, Fushun 113001, China
全文: PDF(8344 KB)   HTML
摘要: 

对Ag-Ni偏晶合金开展了快速/亚快速凝固实验,获得了富Ni相粒子均匀弥散分布于Ag基体的合金样品,Ag-Ni合金显微硬度随着合金Ni含量增加和试样凝固过程冷却速率升高而增大,当Ag-4.0%Ni合金液-液相变开始阶段熔体冷却速率达1800 K/s时,其显微硬度接近粉末冶金生产的Ag-10.0%Ni片状电触头的硬度。建立了描述Ag-Ni合金凝固组织演变的动力学模型,模拟计算了Ag-Ni合金凝固组织形成过程,分析讨论了合金成分和试样直径(冷却速率)对Ag-Ni合金凝固组织形成过程的影响。结果表明:富Ni相液滴/粒子形核阶段熔体的冷却速率对合金凝固组织弥散度具有决定性影响;合金的Ni含量越高、试样冷却速率越低,凝固组织中富Ni相粒子平均尺寸越大;Ag-Ni合金熔体冷却凝固时,富Ni相液滴/粒子的尺寸主要受形核和长大控制,Ostwald粗化作用很弱。

关键词 Ag-Ni偏晶合金液-液相分离凝固组织显微硬度模拟计算    
Abstract

The Ag-Ni alloy has high electrical conductivity, good thermal conductivity, high specific heat capacity, and excellent electrical wear resistance if the Ni-rich phase is dispersedly distributed in the Ag-based matrix. It has been widely used in the medium load contactors, magnetic starters, relays, etc. However, Ag-Ni alloy is a typical monotectic system. Generally, the liquid-liquid phase transformation leads to the formation of a solidification microstructure with serious phase segregation. So far, there have been few studies on the solidification process of Ag-Ni alloys and powder-metallurgical techniques are commonly used to prepare Ag-Ni alloys in industry. In this work, casting experiments and microhardness test were carried out with the Ag-Ni monotectic alloy. The samples with composite microstructure, in which the Ni-rich particles dispersed homogeneously in Ag matrix, were obtained. The microhardness of Ag-Ni alloy increases with the increase of nickel content and the cooling rate of the sample during solidification. When the cooling rate during the liquid-liquid phase transition of the Ag-4.0%Ni alloy reaches 1800 K/s, the microhardness of the Ag-4.0%Ni alloy is close to that of the Ag-10.0%Ni sheet electrical contacts produced by powder metallurgy. A model describing the microstructure evolution during cooling Ag-Ni monotectic alloy melt has been proposed. The process of microstructure formation has been simulated and discussed in details. The results indicate that the cooling rate during the nucleation of the Ni-rich droplets/particles has a dominant influence on the solidification microstructure. The average radius of the Ni-rich particles increases with the increase of nickel content, while it decreases with the increase of the cooling rate during solidification. The average radius of the Ni-rich particles shows an inverse square root dependence on the cooling rate during the nucleation of the Ni-rich droplets/particles. The Ostwald coarsening of the Ni-rich droplets/particles is very weak during cooling Ag-Ni monotectic alloy melt. Rapid/sub-rapid solidification has a good application prospect in the preparation of the high-performance Ag-Ni contact materials.

Key wordsAg-Ni monotectic alloy    liquid-liquid phase separation    solidification microstructure    microhardness    simulation
收稿日期: 2019-06-13     
ZTFLH:  TG111.4  
基金资助:国家自然科学基金项目(51771210);国家自然科学基金项目(51574216);国家自然科学基金项目(51774264);辽宁省教育厅基本科研项目(L2017LQN022)
通讯作者: 赵九洲     E-mail: jzzhao@imr.ac.cn
Corresponding author: Jiuzhou ZHAO     E-mail: jzzhao@imr.ac.cn
作者简介: 邓聪坤,男,1991年生,博士生

引用本文:

邓聪坤,江鸿翔,赵九洲,何杰,赵雷. Ag-Ni偏晶合金凝固过程研究[J]. 金属学报, 2020, 56(2): 212-220.
Congkun DENG, Hongxiang JIANG, Jiuzhou ZHAO, Jie HE, Lei ZHAO. Study on the Solidification of Ag-Ni Monotectic Alloy. Acta Metall Sin, 2020, 56(2): 212-220.

链接本文:

https://www.ams.org.cn/CN/10.11900/0412.1961.2019.00192      或      https://www.ams.org.cn/CN/Y2020/V56/I2/212

图1  不同直径(d) Ag-4.0%Ni合金试样心部的冷却曲线
图2  直径为8 mm的Ag-4.0%Ni合金中富Ni相粒子分布示意图及实测富Ni相粒子体积分数(φsβ)沿试样轴向和径向分布
图3  直径为5 mm的Ag-xNi合金显微组织的SEM像
Fig.4  2D size distributions of the Ni-rich particles in Ag-xNi alloys for the samples of 5 mm in diameter with x=1.25% (a), x=2.24% (b), x=3.0% (c) and x=4.0% (d)图4直径为5 mm的Ag-xNi合金中富Ni相粒子的二维尺寸分布
图5  Ag-Ni合金中富Ni相粒子二维平均半径(<R>2D)随合金成分的变化
图6  不同直径Ag-4.0%Ni合金试样凝固组织的SEM像
图7  Ag-4.0%Ni合金中富Ni相粒子<R>2D和富Ni相液滴形核阶段熔体冷却速率(T.nuc)随试样直径的变化
图8  Ag-Ni合金显微硬度随合金成分和试样直径的变化
ParameterValueUnit
Thermal conductivity of liquid Ag klAg122.29093+0.04259TW·K-1·m-1
Thermal conductivity of liquid Ni klNi57W·K-1·m-1
Thermal conductivity of solid Ag ksAg429W·K-1·m-1
Thermal conductivity of solid Ni ksNi90.7W·K-1·m-1
Density of liquid Ag ρlAg9330-0.91(T-1233.7)kg·m-3
Density of liquid Ni ρlNi7905-1.19(T-1727)kg·m-3
Density of solid Ag ρsAg10500kg·m-3
Density of solid Ni ρsNi8900kg·m-3
Specific heat of liquid Ag cpl,Ag283J·kg-1·K-1
Specific heat of liquid Ni cpl,Ni620J·kg-1·K-1
Specific heat of solid Ag cps,Ag235J·kg-1·K-1
Specific heat of solid Ni cps,Ni444J·kg-1·K-1
Latent heat of solidification of pure Ag LAg102809J·kg-1
Latent heat of solidification of pure Ni LNi292334J·kg-1
表1  Ag-Ni体系的热物性参数[31,32]
图9  Ag-2.24%Ni和Ag-4.0%Ni合金试样心部基体过饱和度,富Ni相液滴/粒子形核率、数量密度和二维平均半径随凝固时间的变化曲线
图10  不同直径Ag-4.0%Ni合金试样冷却时试样心部冷却速率、基体熔体过饱和度和富Ni相液滴形核率随凝固时间的变化曲线
图11  不同成分Ag-Ni合金凝固组织中富Ni相粒子平均半径(<R>)随富Ni相液滴/粒子T.nuc的变化
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