Development of the highly corrosion resistant AZ31 magnesium alloy by the addition of a trace amount of Ti

The addition of a trace amount of Ti (<0.01 wt.%) to AZ31 alloy refined the dendritic structure and grain size, supressed the formation of β phase and promoted the formation of the dense and tight network structure of the divorced eutectic α phase with a high aluminium content ≥ 6.3 wt. % along the grain boundaries and interdendritic interfaces in the as-cast microstructure. This network structure made of Al-rich α phase, which resembles the morphology of continuous β phase structure in the cast AZ91 alloy, significantly enhanced the corrosion resistance of AZ31 alloy by playing a role as an effective barrier to corrosion in NaCl solution.