Effect of nano-CaO particle on the microstructure, mechanical properties and corrosion behavior of lean Mg-1Zn alloy

Abstract

The effects of nano-CaO contents on the microstructure, mechanical properties and corrosion resistance of lean Mg-1Zn alloy were investigated. The results showed that the addition of nano-CaO significantly refined the grain size and improved mechanical properties of the Mg-1Zn alloy. At the same time, CaO reacted with molten Mg in situ to form nano-MgO, whose corrosion product in SBF solution was the same with the degradation product of Mg matrix, resulting in the enhanced compactness of the Mg(OH)2 layer and reduced corrosion rate of matrix. The Mg-1Zn alloy had lower corrosion resistance due to excessively large grain size and shedding of corrosion products. The composite with 0.5 wt.% CaO had the best corrosion resistance with a weight loss of 9.875 mg·y−1·mm−2 due to the small number of Ca2Mg6Zn3 phase and suitable grain size. While for composites with high content of CaO (0.7 wt.% and 1.0 wt.%), they had lower corrosion resistance due to the coexistence of large number of Ca2Mg6Zn3 and Mg2Ca at grain boundaries, especially for 1.0 wt.% CaO composite, resulting from the strong micro-galvanic corrosion.