The role of Ca on the microstructure and corrosion behavior of Mg–8Sn–1Al–1Zn–Ca alloys

• TAZ811-(x)Ca is mainly composed of α-Mg, Mg2Sn, CaMgSn and Mg2Ca phase. After Ca addition, the grain size was refined.
• The TAZ811 alloys with 1 wt.% Ca addition presents the best corrosion resistant behavior.
• As the Ca content exceeds 1 wt.%, coarse ternary CaMgSn phase was formed.

The influence of Ca (1–3 wt.%) content on the microstructure and corrosion behavior of Mg–8Sn–1Al–1Zn–Ca alloys have been investigated by OM, XRD, SEM and potentio-dynamic measurements and salt spray tester. The average grain size of studied alloys decreased from 79 μm to 52 μm with increasing Ca content. The morphology, number and size of second phase particles are found to be the Ca content dependence. After Ca addition, the new phases of CaMgSn and Mg2Ca can be found, with the CaMgSn phase presenting neddle-like or particle-like shape. And both of the Mg2Ca and the CaMgSn phases showed severe segregation as the Ca content exceed 2 wt.%. The corrosion resistance of the studied alloys increased firstly and then decreased as the Ca content increased. The Mg–8Sn–1Al–1Zn–1Ca alloy exhibited the best corrosion resistance behavior with the corrosion rate of 8.1 mm/a.