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Microstructures and corrosion behaviors of squeeze‐cast Mg‐4Al‐2RE and Mg‐4Al‐0.5RE‐ x Ca ( x = 0.3, 0.8, and 1.5) alloys
Author(s) -
Chen Yun,
Wang Zhiping,
Xiong Xinhong,
Zhu Chao,
Yan Pan
Publication year - 2018
Publication title -
materials and corrosion
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.487
H-Index - 55
eISSN - 1521-4176
pISSN - 0947-5117
DOI - 10.1002/maco.201810036
Subject(s) - acicular , microstructure , metallurgy , corrosion , alloy , materials science , oxide , grain boundary
To develop low‐cost and ultrahigh strength magnesium alloys, AE42 (Mg‐4Al‐2RE) alloy is modified by adding Ca (Mg‐4Al‐0.5RE (RE = Y, Ce)‐ x Ca ( x = 0.3, 0.8, and 1.5)) to replace the majority of rare earth elements. The microstructures of squeeze‐cast AE42 and Mg‐4Al‐0.5RE‐xCa alloys are investigated by XRD, EPMA, and SEM, respectively. The corrosion behaviors of all alloys are studied by gravimetric measurements and electrochemical tests. Results show that the microstructure difference between AE42 and Mg‐4Al‐0.5RE‐xCa alloys is that with the addition of Ca, dendritic and acicular Al‐RE phases are suppressed and thin acicular Al 2 Ca or bone‐shaped (Mg, Al) 2 Ca phases are formed. Because the reduction of Al‐RE phases can decrease the number of cathode and the Ca‐containing phases have lower potential, the corrosion resistance of Mg‐Al‐0.5RE‐xCa alloys is significantly better than that of AE42 alloy. The alloy with 0.8 wt% Ca addition shows the best corrosion resistance, which can be attributed to the effect of mixed oxide film of RE and Ca and moderate Al 2 Ca phase discontinuously distributed on the grain boundaries.