Influence of Pre-Aging on Microhardness and Corrosion Resistance of AA6061 Processed by ECAP and NECAP

Document Type : Research Paper

Authors

Department of Mechanical Engineering, Faculty of Engineering, University of Kurdistan, Sanandaj 15175-66177, Iran

Abstract

This study investigates the initial heat treatment, namely annealing versus the peak-aged T6 condition, and subsequent severe plastic deformation (SPD) via equal-channel angular pressing (ECAP) and non-equal-channel angular pressing (NECAP), on the microhardness and corrosion resistance of AA6061 aluminum alloy. Samples in both the annealed and peak-aged conditions were subjected to a single pass of ECAP or NECAP, respectively. Microhardness was characterized using Vickers measurements on planes oriented perpendicular to the pressing (PPD) and extrusion (PED) directions. Corrosion behavior was evaluated using electrochemical impedance spectroscopy (EIS) conducted in a 3.5% NaCl solution. The results revealed that initial peak-aging substantially enhanced hardness while concurrently diminishing corrosion resistance relative to the annealed state. Both ECAP and NECAP processing resulted in significant improvements in hardness and corrosion resistance for both initial material conditions. A comparison of the SPD routes indicated that NECAP yielded slightly higher hardness values, particularly for the peak-aged material, whereas ECAP provided superior hardness uniformity between the PPD and PED planes and slightly enhanced corrosion resistance. Notably, the beneficial impact of SPD processing on hardness (relative increase) and corrosion resistance (final attained value) was more pronounced for the material initially in the annealed condition. These findings highlight the significant interplay between the initial microstructure and the chosen SPD methodology in tailoring the resultant mechanical and electrochemical characteristics of the AA6061 alloy.

Keywords

References

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Iranian Journal of Materials Forming
Volume 13, Issue 4
October 2026
Pages 15-23

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