Influence of the microstructure on the corrosion behaviour of cast Mg-Al alloys.

• Chemical stability of homogeneous α-phase increases with rising Al-content. • Impact of continuity of β-phase on corrosion depends on the surrounding α-Matrix. • Al content of α-phase is more important for control corrosion than β-phase network. The influence of α-phase and β-phase (Mg 17 Al 12) on corrosion of cast binary Mg-Al alloys was investigated by immersion testing in 5 wt.-% NaCl solution saturated with Mg(OH) 2 and by measuring the corrosion potential E corr. The microstructure of the alloys regarding Al-content of α-phase and amount of β-phase was adjusted by solution heat treatments at various temperatures. Subsequently the continuity of β-phase (C β) was measured. With increasing Al-content in the α-phase, the impact of C β decreases. The results show that the Al-content of the α-phase is a very important factor to influence the corrosion resistance. [ABSTRACT FROM AUTHOR]