Improving Aging Behavior and Corrosion Resistance of Mg-5Ga Alloy by Ca Alloying

Aging behavior, mechanical behaviors and corrosion resistance of Mg-5Ga-xCa (x = 0, 0.2 wt.%) alloys have been researched. Rod-shaped and lump-shaped Mg₅Ga₂ precipitates are both observed in two peak-aged alloys, while few nano-sized Mg₂Ca phase exists in the Ca-containing alloy. There are some rod-shaped Mg₅Ga₂ that have a certain orientation of [001] _Mg5Ga2||[11 \(\overline{2 }\) $\overline{2}$ 0]_Mg in Mg-5Ga and [ \(\overline{1 }\overline{1 }\overline{1 }\) $\overline{1}\overline{1}\overline{1}$ ]_Mg5Ga2||[11 \(\overline{2 }\) $\overline{2}$ 0]_Mg in Mg-5Ga-0.2Ca. The peak-aged Mg-5Ga-0.2Ca alloy shows favorable mechanical properties (103 MPa for YS, 229 MPa for UTS, and 12.5% for El), which could be attributed to the reinforcement of more finely dispersed Mg₅Ga₂ precipitates and grain refinement, and superior corrosion resistance (with the P_w of 1.273 mm/year), which may be associated with the type and morphology of the phases to corrosion resistance, and well-protected corrosion product films and the small grain size are also effective.