锻压技术

车体用挤压态Al-6.5Zn-1.55Mg-0.25Cr-0.1Zr合金晶粒取向及应力腐蚀性分析

英文标题：Analysis on grain orientation and stress corrosion for extruded Al-6.5Zn-1.55Mg-0.25Cr-0.1Zr alloy used in vehicle body

作者：白云唐明

单位：重庆工业职业技术学院长沙冶金设计研究院有限公司

关键词：Al-Zn铝合金晶粒组织腐蚀性能微观组织晶界

分类号：TG146.2

出版年,卷(期):页码：2020,45(3):174-178

摘要：

对含有不同显微组织形态的Al-6.5Zn-1.55Mg-0.25Cr-0.1Zr铝合金开展耐应力腐蚀表征，利用EBSD和TEM处理方法深入探讨了试样发生应力腐蚀开裂的特性。研究结果表明：晶粒形成了许多小角度晶界，大角度晶界基本都是由纤维状晶界构成。以挤压工艺制备的Al-Zn铝合金可以对再结晶过程起到抑制作用，由此减小大角度晶界的比例。有大量亚稳态球形MgZn2颗粒分布于等轴晶组织以及纤维组织晶粒中，还有大量纤维组织出现在亚晶结构中；在纤维组织中还可以观察到一些非常细小的亚晶界析出相，颗粒尺寸只有12 nm。原始组织会减小应力耐腐性，在不同时间的裂纹扩展方向也存在较大差异，在临界深度处变成横向排布的裂纹。大角度晶界成为应力腐蚀裂纹的高效扩展通道，当形成小角度亚晶界后则能够对裂纹扩展发挥抑制作用。

The stress corrosion resistance of Al-6.5Zn-1.55Mg-0.25Cr-0.1Zr aluminum alloy with different microstructures was characterized, and the stress corrosion cracking characteristics of sample were investigated by EBSD and TEM treatment. The results show that many grain boundaries of small angle are formed in grain, while the grain boundaries of large angle are basically composed of fibrous grain boundaries. However, Al-Zn aluminum alloy prepared by extrusion process inhibits the recrystallization process, and the proportion of grain boundary of large angle reduces. There are a lot of metastable spherical MgZn2 particle distributing in the isometric tissue and fibrous tissue of grain, and there are many fibrous tissue appeared in the crystal structure. In the fibrous tissue, some very small subgrain boundary precipitates with the particle sizes of 12 nm are observed. Furthermore, primary grain microstructure reduces the stress corrosion resistance, and the direction of crack propagation at different times also has great difference to become transverse crack at the critical depth. Thus, the grain boundary of large angle is the efficient propagation channel of stress corrosion crack, and the subgrain boundary of small angle inhibits the crack propagation.

基金项目：

湖南技术创新项目(2016252010)

白云(1983-)，女，硕士，副教授 E-mail：youtuozhaobei@126.com

参考文献：

［1］Dursun T, Soutis C. Recent developments in advanced aircraft aluminium alloys
［J］. Materials & Design (1980-2015), 2014, 56: 862-871.

［2］Xiao Y P, Pan Q L, Li W B, et al. Influence of retrogression and re-aging treatment on corrosion behaviour of an Al-Zn-Mg-Cu alloy
［J］. Materials & Design, 2011, 32(4): 2149-2156.

［3］Li J F, Peng Z, Li C X, et al. Mechanical properties, corrosion behaviors and microstructures of 7075 aluminium alloy with various aging treatments
［J］. Transactions of Nonferrous Metals Society of China, 2008, 18(4): 755-762.

［4］Shi Y, Pan Q, Li M, et al. Influence of alloyed Sc and Zr, and heat treatment on microstructures and stress corrosion cracking of Al-Zn-Mg-Cu alloys
［J］. Materials Science and Engineering: A, 2015, 621: 173-181.

［5］Fang H C, Chao H, Chen K H. Effect of recrystallization on intergranular fracture and corrosion of Al-Zn-Mg-Cu-Zr alloy
［J］. Journal of Alloys and Compounds, 2015, 622: 166-173.

［6］Deng Y, Yin Z, Zhao K, et al. Effects of Sc and Zr microalloying additions and aging time at 120 ℃ on the corrosion behaviour of an Al-Zn-Mg alloy
［J］. Corrosion Science, 2012, 65: 288-298.

［7］Li Z, Jiang H, Wang Y, et al. Effect of minor Sc addition on microstructure and stress corrosion cracking behavior of medium strength Al-Zn-Mg alloy
［J］. Journal of Materials Science & Technology, 2018, 34(7): 1172-1179.

［8］Brunner J G, Birbilis N, Ralston K D, et al. Impact of ultrafine-grained microstructure on the corrosion of aluminium alloy AA2024
［J］. Corrosion Science, 2012, 57: 209-214.

［9］Ralston K D, Birbilis N, Davies C H J. Revealing the relationship between grain size and corrosion rate of metals
［J］. Scripta Materialia, 2010, 63(12): 1201-1204.

［10］Ralston K D, Fabijanic D, Birbilis N. Effect of grain size on corrosion of high purity aluminium
［J］. Electrochimica Acta, 2011, 56(4): 1729-1736.

［11］Knight S P, Birbilis N, Muddle B C, et al. Correlations between intergranular stress corrosion cracking, grain-boundary microchemistry, and grain-boundary electrochemistry for Al-Zn-Mg-Cu alloys
［J］. Corrosion Science, 2010, 52(12): 4073-4080.

［12］Zuo J, Hou L, Shi J, et al. Enhanced plasticity and corrosion resistance of high strength Al-Zn-Mg-Cu alloy processed by an improved thermomechanical processing
［J］. Journal of Alloys and Compounds, 2017, 716: 220-230.

［13］Wang M, Huang L, Chen K, et al. Influence of minor combined addition of Cr and Pr on microstructure, mechanical properties and corrosion behaviors of an ultrahigh strength Al-Zn-Mg-Cu-Zr alloy
［J］. Micron, 2018, 104: 80-88.

［14］Chen J, Zhang X, Zou L, et al. Effect of precipitate state on the stress corrosion behavior of 7050 aluminum alloy
［J］. Materials Characterization, 2016, 114: 1-8.

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