Microstructure, mechanical properties and bio-corrosion behavior of Mg–2Zn-0.3Ca-x (x= 0, 0.5, 1.0) Y alloys

Microstructure, mechanical properties, and bio-corrosion behavior of Mg–2Zn-0.3Ca-x (x = 0, 0.5, 1.0) wt.% Y series alloy have been investigated using microstructure observation, microhardness testing, tensile testing, immersion tests, and electrochemical measurements in simulated body fluid (SBF). The results show that the second phase's type, volume fraction, and distribution change with Y microalloying in the Mg–Ca–Zn alloys. The Mg–2Zn-0.3Ca (alloy 1) mainly comprises α-Mg and Ca2Mg6Zn3 phases. However, the amount of the Ca2Mg6Zn3 phase gradually decreases, and phases I (Mg3YZn6) and W (Mg3Y2Zn3) are also formed in Mg–2Zn-0.3Ca-0.5Y (alloy 2) and Mg–2Zn-0.3Ca–1Y (alloy 3), respectively. Furthermore, an increase in Y content to 1% refines the grains of alloy 1 leading to the improvement of microhardness (66.7 ± 4.2 HV), yield strength (141 ± 7 MPa), and ultimate tensile strength (385.7 ± 18 MPa) in alloy 3. The coarse and discontinuous eutectic phases (α-Mg + Ca2Mg6Zn3) in alloy 1 leads to accelerating the galvanic corrosion near the grain boundary. Moreover, polarization tests show that the addition of the rare earth element Y up to 0.5% in the alloy 2 leads to decreased corrosion current density (4.04 × 10−3 A cm−2) and the best anti-corrosion property as the result of formation of a protective corrosion product film.