Impact of medium-range order on the glass transition in liquid Ni-Si alloys

Abstract

We study the thermophysical properties and structure of liquid Ni-Si alloys using molecular dynamics simulations. The liquid Ni-5% and 10%Si alloys crystallize to form face-centered cubic (Ni) at 900 and 850 K respectively, and the glass transitions take place in Ni-20% and 25%Si alloys at about 700 K. The temperature dependent self-diffusion coefficients and viscosities exhibit more pronounced non-Arrhenius behavior with the increase of Si content before phase transitions, indicating the enhanced glass-forming ability. These appearances of thermodynamic properties and phase transitions are found to closely relate to the medium-range order clusters with the defective face-centered cubic structure characterized by both local translational and orientational order. This local order structure tends to be destroyed by the addition of more Si atoms, resulting in a delay of nucleation and even glass transition instead.

Bond orientational order in liquids: Towards a unified description of water-like anomalies, liquid-liquid transition, glass transition, and crystallization

“…The similar conclusion was drawn by Wu et al [452]. Lü and Entel also found by numerical simulations that a Ni-Si system has fcc-like MRCO, which is perturbed by the addition of Si atoms [453]. Liu et al found that glass transition can be seen as a process of increasing MRCO [454].…”

Hydrogen-induced dynamic slowdown of metallic glass-forming liquids*

“…9. [36] Table 5. Ratios of the second, third, and fourth peak positions in RDF to the nearest neighboring distance for Cu-H and Zr-H pairs.…”

Non-Arrhenius behaviour of nickel self-diffusion in liquid Ni77Si23

“…influenced by the composition and by process parameters like cooling rate and melt undercooling [5,6]. MD-simulations showed that the molar volume of a NiSi melt decreases at first with rising Si concentration hinting to strong interactions between the particles [7]. A consequence of this mixing effect might be the tendency for an increased glass forming ability with increasing Si content [7].…”

“…MD-simulations showed that the molar volume of a NiSi melt decreases at first with rising Si concentration hinting to strong interactions between the particles [7]. A consequence of this mixing effect might be the tendency for an increased glass forming ability with increasing Si content [7]. For example, the eutectic composition Ni 78.6 Si 21.4 can be undercooled several hundreds K [8].…”