Corrosion behavior of as-cast Mg–8Li–3Al+xCe alloy in 3.5wt% NaCl solution

Abstract

Mg–8Li–3Al+xCe alloys (x = 0.5wt%, 1.0wt%, and 1.5wt%) were prepared through a casting route in an electric resistance furnace under a controlled atmosphere. The cast alloys were characterized by X-ray diffraction, optical microscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The corrosion behavior of the as-cast Mg–8Li–3Al+xCe alloys were studied under salt spray tests in 3.5wt% NaCl solution at 35°C, in accordance with standard ASTM B–117, in conjunction with potentiodynamic polarization (PDP) tests. The results show that the addition of Ce to Mg–8Li–3Al (LA83) alloy results in the formation of Al₂Ce intermetallic phase, refines both the α-Mg phase and the Mg₁₇Al₁₂ intermetallic phase, and then increases the microhardness of the alloys. The results of PDP and salt spray tests reveal that an increase in Ce content to 1.5wt% decreases the corrosion rate. The best corrosion resistance is observed for the LA83 alloy sample with 1.0wt% Ce.

Keywords

magnesium lithium alloys / cerium / sodium chloride solutions / corrosion rate / polarization

References

[1] Wang T., Zhang M.L., Wu R.Z. Microstructure and properties of Mg–8Li–1Al–1Ce alloy. Mater. Lett., 2008, 62(12-13): 1846.

[2] Crawford P., Barrosa R., Mendez J., Foyos J., Es-Said O.S. On the transformation characteristics of LA141A (Mg–Li–Al) alloy. J. Mater. Process. Technol., 1996, 56(1-4): 108.

[3] Haferkamp H., Niemeyer M., Boehm R., Holzkamp U., Jaschik C., Kaese V. Development, processing and applications range of magnesium lithium alloys. Mater. Sci. Forum, 2000, 350-351(7): 31.

[4] Wang T., Zhang M.L., Niu Z.Y., Liu B. Influence of rare earth elements on microstructure and mechanical properties of Mg−Li alloys. J. Rare Earths, 2006, 24(6): 797.

[5] Jensen J.A., Chumbley L.S. Processing and mechanical properties of magnesium−lithium composites containing steel fibers. Metall. Mater. Trans. A, 1998, 29, 863.

[6] Takuda H., Kikuchi S., Tsukada T., Kubota K., Hatta N. Effect of strain rate on deformation behaviour of a Mg–8.5Li–1Zn alloy sheet at room temperature. Mater. Sci. Eng. A, 1999, 271(1-2): 251.

[7] Takuda H., Enami T., Kubota K., Hatta N. The formability of a thin sheet of Mg–8.5Li–1Zn alloy. J. Mater. Process. Technol., 2000, 101(1-3): 281.

[8] Hara N., Kobayashi Y., Kagaya D., Akao N. Formation and breakdown of surface films on magnesium and its alloys in aqueous solutions. Corros. Sci., 2007, 49(1): 166.

[9] Nordlien J.H., Nisancioglu K., Ono S., Masuko N. Morphology and structure of water-formed oxides on ternary MgAl alloys. J. Electrochem. Soc., 1997, 144(2): 461.

[10] Wang J.L., Liao R.L., Wang L.D., Wu Y.M., Cao Z.Y., Wang L.M. Investigations of the properties of Mg−5Al−0.3Mn−xCe (x=0−3,wt.%) alloys. J. Alloys Compd., 2009, 477(1): 341.

[11] Zhang M.L., Wu R.Z., Wang T. Microstructure and mechanical properties of Mg−8Li−(0−3)Ce alloys. J. Mater. Sci., 2009, 44(5): 1237.

[12] Yan H., Chen R.S., Han E.H. Microstructures and mechanical properties of cold rolled Mg−8Li and Mg−8Li−2Al−2RE alloys. Trans. Nonferrous Met. Soc. China, 2010, 20(2): s550.

[13] Liu B., Zhang M.L., Wu R.Z. Influence of Ce on microstructure and mechanical properties of LA141 alloys. Trans. Nonferrous Met. Soc. China, 2007, 17(1): s376.

[14] Qu Z.K., Wu L.B., Wu R.Z., Zhang J.H., Zhang M.L., Liu B. Microstructures and tensile properties of hot extruded Mg–5Li–3Al–2Zn–xRE (rare earths) alloys. Mater. Des., 2014, 54, 792.

[15] Song Y.W., Shan D.Y., Chen R.S., Han E. Corrosion characterization of Mg–8Li alloy in NaCl solution. Corros. Sci., 2009, 51(5): 1087.

[16] Wu L.B., Liu X.H., Wu R.Z., Cui C.L., Zhang J.H., Zhang M.L. Microstructure and tensile properties of Mg−Li−Al− Zn based alloys with Ce addition. Trans. Nonferrous Met. Soc. China, 2012, 22(4): 779.

[17] ASTM B117–11. Standard Practice for Operating Salt Spray (Fog) Apparatus, 2011

[18] ASTM G31–72. Standard Practices for Laboratory Immersion Corrosion Testing of Metals, 2004

[19] Wu L.B., Cui C.L., Wu R.Z., Li J.Q., Zhan H.B., Zhang M.L. Effects of Ce-rich RE additions and heat treatment on the microstructure and tensile properties of Mg–Li–Al–Zn-based alloy. Mater. Sci. Eng. A, 2011, 528(4-5): 2174.

[20] Easton M., StJohn D. Grain refinement of aluminum alloys: Part II. Confirmation of, and a mechanism for, the solute paradigm. Metall. Mater. Trans. A, 1999, 30(6): 1625.

[21] Uhlig H.H., Revie R.W. Corrosion and Corrosion Control, 1985 3 New York, John Wiley and Sons