Transactions of Materials and Heat Treatment

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

Authors： Bai Yun Tang Ming

Unit： Chongqing Polytechnic Changsha Metallurgical Design & Research Institute Co. Ltd.

KeyWords： Al-Zn aluminum alloy grain structure corrosion property microstructure grain boundary

ClassificationCode：TG146.2

year,vol(issue):pagenumber：2020,45(3):174-178

Abstract：

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.

Funds：

湖南技术创新项目(2016252010)

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

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