Abstract
Cast Mg-9Li alloy was successfully solid-solution (SS) treated via heating at 575 °C for 4.5 h and rapidly quenched with ice-water mixture. The mechanical property and corrosion resistance of the SS alloy were simultaneously improved. Rapid bcc/hcp phase transition of the alloy occurred during the quenching process, creating the newly precipitated needle-like fine α-Mg phase, uniformly distributed in the β-Li phase matrix. Dramatic grain refinement and uniform distribution of the α-Mg phase, as well as the massively increased α/β phase interfaces, are factors leading to the improved mechanical property of the SS alloy. Meanwhile, due to the modified duplex-phase structure, the SS alloy has a uniform corrosion-resistant surface film on the β-Li phase, which completely covers the entire alloy surface and efficiently protects the substrate. In addition, the SS alloy has fewer difference in the elements concentration and corrosion activity of the duplex phases, which reduces the pitting sensitivity and improves the corrosion resistance of the alloy matrix. The findings in this binary Mg-Li alloy can also serve as a benchmark for other more practical and complicated Mg-Li alloys.
Highlights
Magnesium-lithium (Mg-Li) alloys are the lightest structural metallic materials with a density of about 1.35–1.65 g·cm−3 and are usually regarded as ultra-light alloys [1]
When the Li content increases by 5.7 wt.%, the hcp-structured Mg matrix will be partially transformed into a Li-rich phase with a body-centered cubic structure, creating the duplex phase structure of Mg-Li alloy with a hcp Mg-enriched α phase and bcc Li-enriched β phase
The satisfactory SS-treated Mg-9Li alloy sample can be achieved with alloys bore the high risk of burnout via a higher heating temperature (580 °C) and longer heating a minimum surface burnout and most uniform is noteworthy that the SS-treated time under current equipment
Summary
Magnesium-lithium (Mg-Li) alloys are the lightest structural metallic materials with a density of about 1.35–1.65 g·cm−3 and are usually regarded as ultra-light alloys [1]. Li does reduce the density of Mg alloys, and changes the phase structure and the mechanical properties of alloys with a different Li content [4,5]. Duplex-phase Mg-Li alloys have been studied extensively among all the Mg-Li alloy series due to their outstanding comprehensive mechanical properties. Their insufficient absolute strength still needs to be further improved [8,9]. Solid-solution (SS) treatment may be the potential way to improve the mechanical property of the binary Mg-Li alloys.
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