A comparison of AA2024 and AA7150 subjected to ultrasonic shot peening: Microstructure, surface segregation and corrosion

The influence of ultrasonic shot peening (USSP) on microstructure, surface segregation, localized and electrochemical corrosion of AA2024 was investigated using immersion test, OCP, EIS, polarization, XRD and SEM-EDS methods. The results are compared with those of AA7150. Like AA7150, second phase p...

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Bibliographic Details
Published in:Surface & coatings technology 2018-03, Vol.337, p.552-560
Main Authors: Sun, Qingqing, Liu, Xingtao, Han, Qingyou, Li, Jie, Xu, Rong, Zhao, Kejie
Format: Article
Language:English
Subjects:
AA2024
AA7150
Alloys
Aluminum base alloys
Comparative analysis
Corrosion
Corrosion rate
Corrosion resistance
Electrochemical corrosion
Grain refinement
Immersion tests (corrosion)
Intergranular corrosion
Localized corrosion
Microstructure
Shot peening
Sodium chloride
Solid solubility
Surface layers
Surface nanocrystallization
Surface segregation
Ultrasonic shot peening
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Summary:The influence of ultrasonic shot peening (USSP) on microstructure, surface segregation, localized and electrochemical corrosion of AA2024 was investigated using immersion test, OCP, EIS, polarization, XRD and SEM-EDS methods. The results are compared with those of AA7150. Like AA7150, second phase particles of AA2024 peened surface layer dissolved into Al matrix due to the extended solid solubility caused by USSP. After USSP, corrosion rate of AA2024 increased by 2–3 times due to surface contamination, however, intergranular corrosion (IGC) resistance of AA2024 is significantly enhanced by USSP treatment. The improvement in localized corrosion resistance is mainly attributed to grain refinement and microstructure homogenization. As opposed to AA7150, OCP of AA2024 in 3.5 wt% NaCl solution (pH = 5.8) shifts to more noble direction after USSP. This is due to the different surface segregation behaviours of the two studied alloys. The mechanism of surface segregation is also briefly discussed. [Display omitted] •IGC resistance of AA2024 and AA7150 was significantly improved by USSP.•Second phase particles dissolved after USSP for both alloys.•Shifting of XRD peak and OCP value caused by USSP was different for alloys.•Different surface segregation behaviours for the two peened alloys
ISSN:0257-8972
1879-3347
DOI:10.1016/j.surfcoat.2018.01.072