Microstructural basis for improved corrosion resistance of laser surface processed AZ31 Mg alloy

• DOI: 10.1016/j.corsci.2021.109707
• Publication Date: 2021-07-21T17:40:24Z
• Authors: Saumyadeep Jana; Matt Olszta; Danny Edwards; Mark Engelhard; Avik Samanta; Hongtao Ding; Pratik Murkute; O. Burkan Isgor; Aashish Rohatgi
• Keywords: 02 engineering and technology; 0210 nano-technology

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.