Significant effects of adding trace amounts of Ti on the microstructure and corrosion properties of Mg–6Al–1Zn magnesium alloy

•Adding trace amounts of Ti significantly altered the microstructure of AZ61.•The morphology, volume fraction and size of β-Mg17Al12 phase were changed.•Adding trace amounts of Ti changed the corrosion properties in significance.

Adding trace amounts of Ti (0.01–0.02 wt.%) significantly changed the volume fraction, morphology and size of the β phase in the microstructure of as-cast AZ61 alloy, despite its effect on grain size and texture being small, and strongly affected the corrosion properties of the alloy. The addition of 0.01 wt.% Ti drastically increased the corrosion rate in sodium chloride solution due to breaking up of the semi-continuous β phase, which destroyed the barrier effect of the β phase against corrosion attack. The addition of a larger amount of Ti (0.02 wt.%) also increased the corrosion rate, but the AZ61 alloy with 0.02 wt.% Ti exhibited a much better corrosion resistance than the AZ61 alloy with 0.01 wt.% Ti. This was because adding 0.02 wt.% Ti greatly decreased the volume fraction and size of the β phase, which reduced the galvanic corrosion effect. The current results suggest that a proper control of trace amounts of Ti has a potential to improve the corrosion properties of cast Mg–Al alloys by modifying the microstructure of the β phase.