Viscosity, undercoolability and short-range order in quasicrystal-forming Al-Cu-Fe melts

Abstract

Understanding the mechanisms which relate properties of liquid and solid phases is crucial for fabricating new advanced solid materials, such as glasses, quasicrystals and high-entropy alloys. Here we address this issue for Al-Cu-Fe alloys which can serve as a model for studying microscopic mechanisms of quasicrystal formation. We study experimentally two structural-sensitive properties of the liquid – viscosity and undercoolability – and compare results with ab initio investigations of short-range order (SRO). It is shown that the main features of interatomic interaction in Al-Cu-Fe system, extracted from radial distribution function and bong-angle distribution function, are the same for both liquid and solid states. In particular, the system demonstrates pronounced effective repulsion between Fe and Cu as well as strong chemical interaction between Fe and Al. Analysis of orientational short-range order reveals existence in the supercooled liquid Fe-centered icosahedral clusters which are discussed in the literature as structural motifs of the quasicrystal phase. In the concentration region corresponding to the composition of the icosahedral phase, minima on the viscosity and undercoolability isotherms are observed which affect noticeably the initial stage of solidification. Thus, we argue that SRO and structural-sensitive properties of a melt may serve as useful indicators of solid phase formation.