Mechanoelectrochemical behavior of magnesium alloys

The mechanochemical effect (the effect of mechanical deformation on electrochemical polarization) was investigated for Mg-Al based alloys AZ91D, AM50 and AS21. The correlation between the mechanoelectrochemical behaviour and strain hardening stages is observed during plastic deformation. Potentiodynamic polarization and immersion tests were carried out at 25 °C in the borate buffer aqueous solution (pH 9.3) and in borate buffer aqueous solution + NaCl 3.5%. It was found that the mechanochemical effect depends on the Al content in the alloy as well as higher corrosion rate of AZ91D alloy was observed compared to AM50 alloy. In order to understand the reason for the advantages of AM50 alloy under stress corrosion, TEM analysis was investigated and succeeded to locate dislocation pile-ups at a further stage in the stressed AM50 alloy which were found to be beneficial to it's resistance to stress corrosion cracking. Corrosion creep was studied at 25 °C in the borate buffer aqueous solution in order to find a correlation between the crack propagation to the electrochemical behavior.