Improving the strength and SCC resistance of an Al-5Mg-3Zn alloy with low-angle grain boundary structure

• Published in: Journal of materials science & technology Vol. 161; pp. 63 - 73
• Main Authors: Tang, Z.C., Xu, W., Zhao, D.Y., Zhang, B.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 20.10.2023
• Subjects: Al-5Mg-3 Zn alloy; Dynamic plastic deformation; Low angle grain boundary; Nanostructured; Stress corrosion cracking; Nanostructured; Stress corrosion cracking; Al-5Mg-3 Zn alloy; Dynamic plastic deformation; Low angle grain boundary
• ISSN: 1005-0302; 1941-1162
• DOI: 10.1016/j.jmst.2023.02.063

•The anodic dissolution of active T' phases at GBs promotes the SCC crack growth of CG Al-5Mg-3Zn.•A high proportion of LAGBs was introduced into NS Al-5Mg-3Zn by DPD and annealing treatment.•The active precipitates at GBs were greatly suppressed in the sensitized NS Al-5Mg-3Zn alloy.•The sensitized NS alloy possesses excellent SCC resistance with high yield strength. The strength of traditional Al-Mg alloys is relatively low because it mainly relies on solid solution strengthening. Adding a third component to form precipitation can improve their strength, but it usually leads to high-stress corrosion cracking (SCC) sensitivity due to the formation of high-density precipitates at grain boundaries (GBs). So far, it is still challenging to improve the strength of Al-Mg alloys without reducing SCC resistance. Herein, a nanostructured Al-5Mg-3 Zn alloy with a good yield strength of 336 MPa and good elongation was successfully produced. By dynamic plastic deformation and appropriate annealing treatment, near-equiaxed nanograins were introduced in the nanostructured Al-5Mg-3 Zn alloy with a high proportion (71%) of the low-angle grain boundary. TEM statistical investigations show that the precipitation of active T' phase at GBs has been greatly suppressed in the nanostructured Al-5Mg-3 Zn alloy at sensitized conditions, and the area fraction of GB precipitates is reduced from 72% to 21%, which significantly decreases the SCC susceptibility. This study provides guidance for developing advanced Al-Mg alloy with high SCC resistance. [Display omitted]