Diffusion-controlled crystal growth in deeply undercooled melt on approaching the glass transition

Abstract

Crystal-growth velocity in metallic melts has been reported by others to increase monotonically with undercooling. Nevertheless, such an observation is not predicted by conventional growth theory. In this work, the metallic melt of Zr 50 Cu 50 is studied to address the problem by measuring the growth velocity over a wide range of undercooling up to 325 K. A maximum growth velocity is observed at an undercooling of 200 K instead of the monotonic increase reported in the literature. We find that the planar or dendrite growth theories can explain the value of the maximum growth velocity, but the predicted location of the maximum in undercooling is far less than that seen by experiment. With the assistance of current results, a general pattern of crystal growth is established for melts of a variety of substances, where all sluggish crystal-growth kinetics is explained by the diffusion-controlled mechanism at deep undercooling.

Non-Equilibrium Solidification of Undercooled Metallic Melts

“…It is interesting to see that the evolution of V 0 with T i follows the Arrhenius law except for the last three experimental points at high ∆T. This means that crystallization of Cu 50 It is interesting to note that using the temperature dependent viscosity does not lead to a matching of the experiments and the modelling [32], in contrast to the present work where the temperature dependent diffusion coefficient is used to take into account the mobility of the solid-liquid interface. This may be understood by the fact that the Einstein-Stokes relation does not hold for Zr-based glass forming alloys [78].…”

“…This was experimentally observed in a great variety of non-metallic glass-forming systems, such as o-terphenyl [66], tri-α-naphthylbenzene [67], Li 2 O-2SiO 2 [68], and MgO-CaO-2SiO 2 [69]. However, thus far, there is only one work that reports a maximum in the V-∆T relation measured for the Cu 50 Zr 50 glass-forming alloy [32].…”

“…The kinetic undercooling is controlled by the atomic attachment kinetics at the solid-liquid interface that can differ essentially for specific atomic bonding conditions and structural peculiarities. Investigations of the growth kinetics in an undercooled melt of the intermetallic compound Cu 50 Zr 50 that melts congruently, and is a glass forming alloy with highly reduced glass temperature, gives evidence of dendrite growth to be controlled by atomic diffusion in the temperature range above the glass temperature [32].…”

Dendrite Growth Kinetics in Undercooled Melts of Intermetallic Compounds

“…This was experimentally observed in a great variety of non-metallic glass-forming systems, such as o-terphenyl [52], tri-α-naphthylbenzene [53], Li2O-2SiO2 [54], and MgO-CaO-2SiO2 [55]. However, so far, there is only one work that reports a maximum in the V-∆T relation measured for the Cu50Zr50 glass-forming alloy [56].…”

Atomic packing and short-to-medium range order evolution of Zr-Pd metallic glass

“…Based on the hypothesis that linking icosahedra can form the quasicrystalline phase, there has been considerable interest in the icosahedral medium range ordering (IMRO) of MGs's [8][9][10][11][12][13], which probably affects the glass formability as well as the mechanical properties, including Young's modulus and shear banding resistance [14]. Recently, some models for IMRO in MGs have been suggested by experimental and computational studies [15][16][17][18][19][20][21][22].…”