Microscopic Elastic Properties of Polycrystalline Mg₈₅Zn₆Y₉ Alloy with Long-Period Stacking Ordered 18R Phase Investigated by Inelastic X-ray Scattering

Abstract

Inelastic X-ray scattering measurements were performed on polycrystalline Mg₈₅Zn₆Y₉ alloy with long-period stacking ordered 18R phase to clarify the microscopic elastic properties. Tiny but clear excitation signals of longitudinal acoustic (LA) modes are observed in the whole Q range measured (Q < ∼16 nm⁻¹). In addition, the transverse acoustic and unknown modes are detectable in the second Brillouin zone (∼13 < Q < ∼26 nm⁻¹). The microscopic sound velocity of the LA modes is similar to the macroscopic value. The microscopic Poisson ratio is 0.22 ± 0.04, slightly smaller than the macroscopic value of 0.26 and usual metal values of ∼0.3, indicating a hard stiffness of the bond angles.