Effects of alloying elements on the microstructure and corrosion behavior of Mg-Li-Al-Y alloys

The effects of lithium, aluminum and yttrium elements on the microstructure and corrosion behavior of the Mg-Li-Al-(Y) alloys were studied by signal-to-ratio (S/N) analyses. The sequence of alloying elements (Li, Al and Y) affecting the corrosion behavior of the Mg-Li-Al-(Y) alloys from strong to weak is Al > Li > Y. The addition of Al affects the size and area fraction of Al-rich intermetallics. As the Li content increases, the crystal structures of Mg-Li alloys can be transfer from hcp (single a phase), hcp + bcc (alpha + beta dual-phase), to bcc (single beta phase). The addition of Y refines the grains and hinders the formation of AlLi compound. The Mg-10Li-3Al-0.6Y alloy has a better corrosion resistance mainly due to the homogeneous microstructure and uniformly distribution of short rod-like alpha-Mg phase with a relatively high area fraction as a corrosion barrier inhibits the severe localized dissolution of beta-Li matrix. The corrosion rate of the optimized alloy of approximately 2.14 mm/y is still higher than the intrinsic corrosion rate of ultra-pure Mg of 0.3 mm/y. (C) 2020 Elsevier B.V. All rights reserved.