Pre-Exposure Embrittlement and Stress Corrosion Cracking of Magnesium Alloy AZ31B in Chloride Solutions

Abstract

Stress corrosion cracking of the Mg-Al-Zn AZ31B (UNS M11311) alloy was studied in sodium chloride (NaCl) solutions at different potentials and NaCl concentrations using the slow strain rate technique. Results showed that stress-strain curves were similar despite changes in potential and chloride concentration. In addition, pre-exposure tests were performed in NaCl solutions at the open-circuit potential followed by immediate straining or straining after a dry-air exposure delay. The dependence of ductility with pre-exposure time, the reversibility of embrittlement, and the fracture surface of pre-exposed samples suggested that the AZ31B alloy was susceptible to internal hydrogen embrittlement. Stress corrosion cracking and the pre-exposure embrittlement of this alloy in NaCl environments are explained assuming that crack growth rate was controlled by hydrogen diffusion.