Amorphous and quasi-crystalline phases in rapidly solidified MgAlZn alloys

The formation of amorphous and icosahedral phases and approximants has been identified in rapidly solidified MgAlZn alloys. The icosahedral phase is located at the composition range between those of the amorphous phase and approximants. Mg₄₀Al₄₀Zn₂₀ is a cubic 1 1 approximant in the equilibrium state and a cubic 5 3 rational approximant in the rapidly solidified state. Rapidly solidified Mg₅₀Al₃₀Zn₂₀ and Mg₅₀Al₂₀Zn₃₀ have a disordered icosahedral structure with a high density of random phason strain. The valence concentration e/a plays an important role in the selections of rapidly solidified structure between the amorphous and the icosahedral phases and of phason strains between isotropic and anisotropic.