Local chemical and topological order in Al–Tb and its role in controlling nanocrystal formation

The role of amorphous precursor in phase selection hierarchy in marginal metallic glasses

“…There are strong pre-peak and side-peak reflections at wave momentum of approximately 13 and 34 nm -1 in ribbon specimens. The existence of such additional reflections with relatively robust intensities was previously associated to RE-Al interactions [14,17,18]. The strong atomic coupling between the RE and Al atom results in a selective accumulation of Al atoms around the Tb, which persists in molten state [19].…”

“…The strong atomic coupling between the RE and Al atom results in a selective accumulation of Al atoms around the Tb, which persists in molten state [19]. The average measured coordination number around Tb atoms was found to be 15 using ab-initio constrained RMC simulations, which approximately corresponds to 91% Al in the first shell neighborhood [14]. The presence of Tb atoms with such a high coordination of Al causes the amorphous matrix to be divided into Al-rich and Aldepleted regions.…”

“…It was reported that high number density of Al clusters in as-quenched states are inherited from the liquid state prior to quenching the melt, caused by Tb atoms attracting Al atoms in the first shell neighborhood, thus forming a continuous network. Upon rapid solidification, these chemically isolated regions are retained in the amorphous matrix with isolated regions of nearly pure Al, which act as nucleating sites for fcc-Al during devitrification [14]. In another recent study, the existence of such nanoscale amorphous regions, although larger in size, was also confirmed by atom probe tomography (APT) in Al-Y-Fe [15].…”

“…Several hypothesis, such as "quenched-in nuclei" [11,12], "phase separation in amorphous state" [13] have been previously proposed, however they do not explain the totality of the experimental observations. A more recent study on the short to medium-range ordering offers a different perspective by taking into account the topological ordering in the liquid state in Al-Tb system [14]. It was reported that high number density of Al clusters in as-quenched states are inherited from the liquid state prior to quenching the melt, caused by Tb atoms attracting Al atoms in the first shell neighborhood, thus forming a continuous network.…”

Monte Carlo simulation of thermophysical properties of binary Co–Gd liquid alloys

“…The enhancement of Gd content changes not only the liquid structure of the surface layer, but also the species and numbers of clusters in the bulk liquid, which can be tracked from the liquid viscosity and the diffusion coefficients. More and more research work found that many short-and mid-range orders, even some network topology exist in the liquid alloys which involved rare earth element [35][36][37][38][39][40]. It is due to that, with a complicated valence electron structure, the rare earth atoms intensify the s-f exchange interaction in the liquid alloy.…”