Particle‐Based Computer Simulation of Crystal Nucleation and Growth Kinetics in Undercooled Melts

Rozas, Roberto; Kühn, Philipp; Horbach, Jürgen

doi:10.1002/9783527647903.ch18

Cited by 2 publications

(1 citation statement)

References 63 publications

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“…Assuming diffusion controlled attachment kinetics in pure Ni, a kinetic growth coefficient of µ = 0.0069 m/s/K is estimated. For comparison, atomic simulation of kinetic growth coefficients give for growth in 100 direction µ 100 = 0.36 m/s/K for pure Ni and µ 100 = 0.015 m/s/K for the equiatomic intermetallic compound AlNi, respectively [48]. These values are not directly comparable with the figures given above, but reveal, qualitatively, the decrease of the kinetic growth coefficient for collision-limited growth of pure Ni and diffusion-controlled growth for the intermetallic compound AlNi.…”

Section: Deviations From Local Equilibrium During Rapid Dendrite Growmentioning

confidence: 99%

Non-Equilibrium Solidification of Undercooled Metallic Melts

Herlach

2014

Metals

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Abstract:If a liquid is undercooled below its equilibrium melting temperature an excess Gibbs free energy is created. This gives access to solidification of metastable solids under non-equilibrium conditions. In the present work, techniques of containerless processing are applied. Electromagnetic and electrostatic levitation enable to freely suspend a liquid drop of a few millimeters in diameter. Heterogeneous nucleation on container walls is completely avoided leading to large undercoolings. The freely suspended drop is accessible for direct observation of rapid solidification under conditions far away from equilibrium by applying proper diagnostic means. Nucleation of metastable crystalline phases is monitored by X-ray diffraction using synchrotron radiation during non-equilibrium solidification. While nucleation preselects the crystallographic phase, subsequent crystal growth controls the microstructure evolution. Metastable microstructures are obtained from deeply undercooled melts as supersaturated solid solutions, disordered superlattice structures of intermetallics. Nucleation and crystal growth take place by heat and mass transport. Comparative experiments in reduced gravity allow for investigations on how forced convection can be used to alter the transport processes and design materials by using undercooling and convection as process parameters.

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Section: Deviations From Local Equilibrium During Rapid Dendrite Growmentioning

confidence: 99%

Non-Equilibrium Solidification of Undercooled Metallic Melts

Herlach

2014

Metals

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Containerless Undercooled Melts: Ordering, Nucleation, and Dendrite Growth

Herlach

Binder

Galenko

et al. 2015

Metall Mater Trans A

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Electromagnetic and electrostatic levitation are applied to containerless undercool and solidify metallic melts. A large undercooling range becomes accessible with the extra benefit that the freely suspended drop is accessible directly for in situ observation. The short-range order in undercooled melts is investigated by combining levitation with elastic neutron scattering and X-ray scattering using synchrotron radiation. Muon Spin Rotation (lSR) experiments show magnetic ordering in deeply undercooled Co 80 Pd 20 alloys. The onset of magnetic ordering stimulates nucleation. Results on nucleation undercooling of zirconium are presented showing the limit of maximum undercoolability set by the onset of homogeneous nucleation. Metastable phase diagrams are determined by applying energy-dispersive X-ray diffraction of Ni-V alloys with varying concentration. Nucleation is followed by crystal growth. Rapid dendrite growth velocity is measured on levitation-processed samples as a function of undercooling DT by using high-speed video camera technique. Solute trapping in dilute solid solutions and disorder trapping in intermetallic compounds are experimentally verified. Measurements of glass-forming Cu-Zr alloy show a maximum in the V(DT) relation that is indicative for diffusion-controlled growth. The influence of convection on dendrite growth of Al 50 Ni 50 is shown by comparative measurements of dendrite growth velocity on Earth and in reduced gravity. Eventually, faceting of a rough interface by convection is presented as observed on Ni 2 B alloys.

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Particle‐Based Computer Simulation of Crystal Nucleation and Growth Kinetics in Undercooled Melts

Cited by 2 publications

References 63 publications

Non-Equilibrium Solidification of Undercooled Metallic Melts

Non-Equilibrium Solidification of Undercooled Metallic Melts

Containerless Undercooled Melts: Ordering, Nucleation, and Dendrite Growth

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