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.