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

Abstract

Abstract 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 α phase), hcp + bcc (α + β dual-phase), to bcc (single β 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 α-Mg phase with a relatively high area fraction as a corrosion barrier inhibits the severe localized dissolution of β-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.