Effects of Nd/YAl₂ on aging behavior of Mg-8Li-3Al-RE alloys

In this study, two Mg-Li alloys, LAY831–1.5YAl_2p and LAY831–0.4Nd0.3YAl_2p, with nice comprehensive mechanical properties were prepared. The differences in microstructure and mechanical properties, such as grain size, phase composition, hardness, tensile strength between the two alloys under different aging temperatures were analyzed comparatively to explore the correlation and micro-mechanism between the fine-tuning of Nd/YAl₂ contents and the inhibition of over-aging in multiphase Mg-Li alloys. Our results indicate that both alloys underwent varying levels of β-phase decomposition and precipitation during aging, weakening lattice distortion and causing different magnitudes of strength attenuation. This means strength enhancement as well as lattice distortion caused by solution strengthening of rare earth elements are not stable, significantly affected by the aging temperatures and will gradually be weakened with the aging process. While the external added YAl₂ particles, persistently dispersed in the matrix and bear the load, will not decompose during aging, playing a determining role in enhancing stability of the mechanical properties of Mg-Li alloys.