Microstructural basis for improved corrosion resistance of laser surface processed AZ31 Mg alloy. (October 2021)

• Record Type: Journal Article
• Authors: Jana, Saumyadeep; Olszta, Matt; Edwards, Danny; Engelhard, Mark; Samanta, Avik; Ding, Hongtao; Murkute, Pratik; Isgor, O. Burkan; Rohatgi, Aashish
• Is Part Of: Corrosion science. Volume 191(2021)
• Publication Date: 2021-10
• Subjects: Magnesium -- SEM -- STEM -- EIS -- XPS -- Localized corrosion; Corrosion and anti-corrosives -- Periodicals; 620.11223
• DOI: 10.1016/j.corsci.2021.109707
• Languages: English
• ISSNs: 0010-938X

Abstract

Highlights: Mg alloy (AZ31) shows better corrosion resistance after laser surface processing. Laser surface processing changes mode of corrosion from localized to uniform. Laser surface processing creates ∼0.5 μm thick mixed-metal oxide surface film. Mixed-metal oxide surface film converts to layered double hydroxide film later. Abstract: Despite their excellent strength-to-weight ratio, wider use of magnesium (Mg) alloys for light-weight applications is limited by their poor corrosion resistance, especially in chloride-containing environments. The present study shows improved corrosion resistance imparted by laser surface processing (LSP) of a commercial AZ31 (Mg-3Al-1Zn) alloy. Nanosecond laser processing at three different power settings was carried out on the surface of a 1-mm-thick rolled AZ31 sheet. Electrochemical studies and salt spray testing (ASTM B117) indicate substantial enhancement of corrosion resistance in LSP-treated AZ31. The underlying reasons behind improved corrosion resistance of the LSP-AZ31 surface have been studied through detailed microstructural characterization and chemical analysis by SEM, TEM, and XPS. Formation of a ∼0.5 μm thick mixed metal (Mg, Al) oxide surface film, together with refinement in the size and number density of Al-Mn intermetallic particles, are shown to play a major role toward improved corrosion resistance after LSP treatment of the AZ31 alloy.