Size effect of the width of beta-Li phase on the ductility of magnesium-lithium dual-phase alloys

摘要

The size effect on ductility is not sufficiently understood and developed to be calculated by equations like that of the well-known Hall-Petch relationship for the size effect on strength. To improve the understanding of the size effect on ductility, in this work, small amount of rare earth (Sc and Y) elements were submitted to Mg-Li dual-phase alloys, possessing hexagonal-close-packed alpha-magnesium (α-Mg) and body-centra-cubic beta-lithium (β-Li) phases. An abnormally high elongation of 43%, more than two times as those of common magnesium alloys, was acquired in an as-cast Mg-Li dual-phase alloy. The abnormally high ductility possessed by Mg-Li dual-phase alloys in both this work and previous literatures, during tension and compression, was attributed to the size effect of the width of β-Li phase in this kind of alloys. The critical value of this size effect, which is believed to be twice of the interface-affected zone (IAZ), presented to lay in the range of 3-8 μm. Based on this size effect, a duplex Mg-Li alloy, after the working process, is expected to achieve a high elongation via making the width of β-Li phase to satisfy the critical value presented in this work.