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.