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金属学报  2018, Vol. 54 Issue (1): 100-108    DOI: 10.11900/0412.1961.2017.00203
  本期目录 | 过刊浏览 |
非等温回归再时效对Al-8Zn-2Mg-2Cu合金厚板组织及性能的影响
冯迪1(), 张新明2, 陈洪美1, 金云学1, 王国迎1
1 江苏科技大学材料科学与工程学院 镇江 212003
2 中南大学材料科学与工程学院 长沙 410083
Effect of Non-Isothermal Retrogression and Re-Ageing on Microstructure and Properties of Al-8Zn-2Mg-2Cu Alloy Thick Plate
Di FENG1(), Xinming ZHANG2, Hongmei CHEN1, Yunxue JIN1, Guoying WANG1
1 School of Materials Science and Engineering, Jiangsu University of Science and Technology, Zhenjiang 212003, China
2 School of Materials Science and Engineering, Central South University, Changsha 410083, China
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摘要: 

基于铝合金厚板热处理时客观存在的非等温现象,利用非等温回归动力学模型、力学性能测试、电导率测试及TEM观察,研究了非等温回归温度场和时间的耦合效应对Al-8Zn-2Mg-2Cu (质量分数,%)合金厚板组织及性能的影响。结果表明,随着非等温回归时间的延长,合金的电导率逐渐升高,硬度和强度逐渐下降。优化的非等温回归再时效制度使MgZn2相的尺寸分布范围宽化。因此,位错切过和位错绕过强化机制的合理匹配有效地降低了硬度的损失,同时合金的电导率得到显著提升。以105 ℃、24 h为预时效制度,经过慢速升温非等温回归处理120 min后再经120 ℃、24 h峰时效,Al-8Zn-2Mg-2Cu铝合金厚板的抗拉强度、屈服强度及电导率分别为620 MPa、593 MPa和21.1 MS/m,其综合性能优于单级峰时效(T6)及双级过时效(T73),且包含慢速升温的非等温回归再时效技术更适用于厚板的时效热处理。

关键词 Al-Zn-Mg-Cu合金厚板非等温回归再时效时效动力学    
Abstract

7000 series Al alloy has been widely used in aeronautical structural materials because of its high strength, high stress corrosion cracking resistance and good fatigue resistance when treated by retrogression and re-ageing (RRA). Al-8Zn-2Mg-2Cu (mass fraction, %) thick plate is supposed to manufacture the aircraft wing in Chinese big plane project. Due to the non-isothermal environment in the process of heat treatment for aluminum alloy thick plate, the influence of coupling effect of non-isothermal retrogression temperature field and time on the microstructure and properties of Al-8Zn-2Mg-2Cu alloy thick plate was investigated by the non-isothermal kinetic model, mechanical properties tests, electrical conductivity test and TEM observations. The results show that, the electrical conductivity increases while the hardness and strength decrease with the non-isothermal retrogression time increasing. The optimized non-isothermal retrogression and re-ageing (NRRA) treatment makes the size distribution range of MgZn2 phase wider. Therefore,the logical matching between the dislocation cutting off mechanism and the dislocation by-passing mechanism effectively reduces the loss of hardness. Meanwhile, the electrical conductivity is significantly improved. After the treatment of 105 ℃, 24 h (pre-ageing) and non-isothermal regression (120 min) with slow heating rate and 120 ℃, 24 h re-ageing, the Al-8Zn-2Mg-2Cu alloy thick plate possesses an excellent comprehensive performance than those of T6 and T73 states. The tensile strength, yield strength and electrical conductivity are 620 MPa, 593 MPa and 21.1 MS/m, respectively. The NRRA treatment with slow heating rate is more suitable for the ageing treatment of thick plate.

Key wordsAl-Zn-Mg-Cu alloy    thick plate    non-isothermal retrogression and re-ageing    ageing kinetics
收稿日期: 2017-05-25      出版日期: 2017-11-01
ZTFLH:  TG146.2  
基金资助:国家重点基础研究发展计划项目No.2012CB619500,江苏省自然科学基金项目No.BK20160560,江苏省高校自然科学基金项目No.16KJB430010,江苏高校优势学科建设工程资助项目
作者简介:

作者简介 冯 迪,1984年生,博士

引用本文:

冯迪, 张新明, 陈洪美, 金云学, 王国迎. 非等温回归再时效对Al-8Zn-2Mg-2Cu合金厚板组织及性能的影响[J]. 金属学报, 2018, 54(1): 100-108.
Di FENG, Xinming ZHANG, Hongmei CHEN, Yunxue JIN, Guoying WANG. Effect of Non-Isothermal Retrogression and Re-Ageing on Microstructure and Properties of Al-8Zn-2Mg-2Cu Alloy Thick Plate. Acta Metall, 2018, 54(1): 100-108.

链接本文:

http://www.ams.org.cn/CN/10.11900/0412.1961.2017.00203      或      http://www.ams.org.cn/CN/Y2018/V54/I1/100

图1  Al-8Zn-2Mg-2Cu合金(厚板)非等温回归示意图
Treatment Pre-ageing Retrogression Re-ageing
NRRA-i 105 ℃, 24 h 5 ℃min-1 and 190 ℃, i min 120 ℃, 24 h
T6 120 ℃, 24 h - -
T73 120 ℃, 6 h - 160 ℃, 24 h
表1  热处理工艺参数
图2  Al-8Zn-2Mg-2Cu合金30 mm厚板的时效温度曲线(回归阶段)
图3  不同时效状态下Al-8Zn-2Mg-2Cu合金30 mm厚板的硬度和电导率
图4  不同时效状态下Al-8Zn-2Mg-2Cu合金厚板的拉伸性能
图5  不同时效状态下Al-8Zn-2Mg-2Cu合金厚板晶内析出相的TEM明场像、SAED花样及衍射斑点示意图[19]
图6  不同时效状态下Al-8Zn-2Mg-2Cu合金厚板晶界析出相的TEM明场像
图7  Al-8Zn-2Mg-2Cu合金厚板中心层的Scheil积分-时间关系曲线
图8  不同时效状态下晶内析出相的尺寸分布统计图
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