Ultrasonic properties of Mg₂₃Al₃Y₄ alloy with LPSO structures

Ultrasonic properties of Mg₂₃Al₃Y₄ alloy, which has a synchronized long-period stacking ordered (LPSO) structure, were examined in terms of valence electron concentration (VEC), and real and complex elasticities. The alloy locates to a point (2.54, 436.5 K) near a critical amorphous alloy composition, and a point with largest Poisson's ratio (0.322) and lower G/K (0.404) in metal group, showing a metastable like metallic alloy. The addition of small amounts of Al and Y elements, i.e. appearance of excess electrons induces an increase in c/a ratio and cell expansion of hcp Mg lattice, and stabilization of cluster structures, leading to formation of LPSO phases with L1₂ typed Al₆Y₈ clusters. The elasticity and viscoelasticity of the alloy is predominated by three-dimensional volumetric motion, i.e., high rigidity.