Phase-Species-Dependent Electrochemical and Corrosion Behaviors of Wrought Mg-Y-Zn-Based Alloys
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JMEPEG https://doi.org/10.1007/s11665-020-05034-y
Phase-Species-Dependent Electrochemical and Corrosion Behaviors of Wrought Mg-Y-Zn-Based Alloys Xuan Liu, Shengyuan Li, and Jilai Xue (Submitted March 22, 2020; in revised form June 29, 2020) The electrochemical and corrosion behaviors of the wrought Mg-Y-Zn-based alloys with different phase species have been systematically investigated to compare the role of phase species in the corrosion performance. The X-Mg12YZn phase contributes a superior corrosion inhibiting effect over the W-Mg3Y2Zn3 phase. The corrosion rate of Mg-Y-Zn alloy bearing X-Mg12YZn phase is 13.09 mm year21, which is lower than that of the alloy bearing W-Mg3Y2Zn3 phase (16.67 mm year21). This is because the X-Mg12YZn platelike phase plates are more effective and durable than W-phase particles to release Y element during surface film formation. The small W-Mg3Y2Zn3 phase particles may drop out from the corrosion scale, resulting in the mass loss and breakdown of the protective surface film during the propagation of corrosion into inner layers. The related corrosion mechanism has been discussed in detail. Keywords
Mg-Y-Zn alloys, corrosion resistance, electrochemical behaviors, phase species, surface film
1. Introduction Magnesium alloys are promising lightweight structural materials dedicated to the energy saving and fuel economy of modern vehicles, due to their low density, high specific strength and stiffness (Ref 1, 2). However, the shortcomings [such as low strength and poor corrosion resistance (Ref 3-5)] make the Mgbased alloys far from the high-volume automotive applications. For decades, the Mg-Y-Zn-based wrought alloys greatly motivated the research interests to pursue high-strength Mgbased alloys around the world, due to the effective strengthening ternary Mg-Y-Zn phases [long period stacking ordered (LPSO) X-phase (Mg12YZn), the icosahedral quasicrystal I-phase (Mg3Zn6Y) and the cubic W-phase (Mg3Y2Zn3)] (Ref 6-14). In addition, the LPSO phase has also been considered for toughening the Mg-Li-based alloys (Ref 15, 16). Also, the corrosion behaviors of these Mg-Y-Zn-based alloys have received great attention. Popov et al. early investigated the initial corrosion of Mg-Zn-Y-Zr alloy bearing grain boundary I-phase in 1 g L 1 NaCl solution (Ref 17). Izumi et al. studied on the relation between the corrosion behavior and microstructure of Mg97Zn0.75Y2 and Mg97Zn0.75Y2Al0.5 alloys (containing Xphase) prepared by cooling-rate-controlled solidification (Ref 18, 19). The corrosion rate of Mg-Y-Zn alloys bearing X-phase mainly depended on the volume fraction and arrangements of Xphase (Ref 20-22). Meanwhile, the post-heat treatment could improve the corrosion resistance of the as-forged Mg-Y-Zn alloy bearing I- and W-phases (Ref 23). Furthermore, Song et al. and Xuan Liu, Shengyuan Li, and Jilai Xue, State Key Laboratory of Advanced Metallurgy, School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China. Contact e-mails: [email protected]
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