Synergistic impact of ECAP and thermal treatments on the corrosion performance of AZ91 Mg alloy

This research examines the synergistic action of Equal-Channel-Angular-Pressing (ECAP) and heat treatments on the corrosion characteristics of AZ91 Mg alloy, a metal that is renowned for its mechanical and light weight properties but flawed by susceptibility to corrosion. The AZ91 alloy was ECAP for two and four passes to reduce its microstructure and afterwards, followed by the treatment of annealing and aging at the temperature of 523 K, 623 K and 723 K with treatment times of 6 and 12 hours. In order to investigate grain structure and secondary phase distribution, microstructural analysis was carried out using energy dispersive X-ray spectroscopy (EDX), optical microscopy (OM), and scanning electron microscopy (SEM). Potentiodynamic polarization experiments in a 3.5 wt. % NaCl environment were performed to assess corrosion behavior and found that the ECAP and subsequent heat treatments greatly improved corrosion resistance. Tests found that a combination of ECAP followed by annealing at 723 K for 12 hours produced a uniform distribution of secondary phases, with resultant smaller corrosion current densities and better electrochemical stability. The results show that the coupled processing methods successfully enhance the corrosion performance of AZ91 Mg alloy, which offers significant findings for its use in corrosive environments.