The effect of electromagnetic stirring on the microstructure and corrosion of mischmetal modified AZ91D magnesium alloy

The microstructure and corrosion behaviour of mischmetal modified AZ91D magnesium alloy in the presence or absence of a rotating electromagnetic field have been investigated. The study suggests that the size and volume fraction of the beta (Mg17Al12) phase in the alloy decreases as magnetic field intensity increases. The immersion test results show that the mass loss for the alloy solidified in the absence of a magnetic filed is always larger than that for the alloy solidified under magnetic field. The electrochemical corrosion experiments indicate that the corrosion potential of the alloys increases from -1.56 to -1.51 V, while the corrosion current density decreases from 6.31 to 1.58 mA.cm(-2), and the charge transfer resistance increases from 3.17 to 11.32 k Omega.cm(2) as the excitation voltage increases from 0 to 120 V. The enhancement of the corrosion resistance is attributed to the grain refinement, and to the volume fraction reduction of the beta (Mg17Al12) phase under a rotating electromagnetic field.