Nucleation-Controlled Solidification Kinetics

Perepezko, J. H.; Uttormark, Michael J.

doi:10.1007/bf02648944

Cited by 46 publications

(23 citation statements)

References 40 publications

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“…[25] To address both effects, the nucleation kinetics model recently presented by Wu and Ando [21] is adopted. This model, which is based on the classical nucleation theory, is represented by:…”

Section: Models Nucleation Kinetics Modelmentioning

confidence: 99%

Nucleation Kinetics and Microstructure Evolution of Traveling ASTM F75 Droplets

Roy

Ando

2010

Adv Eng Mater

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ASTM F75 alloy, a cobalt-chromium-molybdenum alloy with high wear resistance, good strength, and excellent biocompatibility, is popularly used to manufacture artificial dental, hip, and knee replacements. [1] A novel method for using the alloy as a bioimplant involves fabricating a porous mating surface for the bone tissues to grow into for enhanced osseointegration (attachment of the bone to the implant). [2][3][4][5] This anchors the implant firmly to the bone, while making the implant's density and strength similar to those of the human bone. The osseointegration surface is fabricated by sintering balls of diameter 300-700 mm to obtain a porous surface. The present work explores the feasibility of producing F75 balls suitable for the bio-implant applications by the uniformdroplet spray (UDS) process, [6][7][8][9] with particular interest in developing a method to predict the solidification microstructure in relation to the process parameters.The UDS process is a droplet-based manufacturing process where mono-sized droplets are generated by the controlled breakup of a laminar jet of molten metal ejected through an orifice while applying a regulated perturbation. Figure 1(a) schematically illustrates the UDS droplet generator. Details of this process can be found elsewhere. [6][7][8][9] Droplets produced by the UDS process have high sphericity and nearly identical sizes (less than AE3% of target size) [7] and thermal history, which allows for precise control of droplet solidification microstructure. The thermal state of the traveling UDS droplets can be simulated using an in-flight solidification model [10,11] under Newtonian cooling conditions justified on the small Biot numbers that normally apply to UDS droplets. The process parameters of the UDS process, being decoupled, [6] allow for a systematic investigation of the solidification behavior of droplets as a function of experimental variables. The experimental variables are primarily represented by the droplet-cooling rate and volume of the droplet, which determine the amount of undercooling and the path of subsequent solidification, and hence the resultant solidification microstructure, of the droplet. In the UDS process, the droplet-cooling rate is controlled through the droplet size and the choice of cooling gas. The droplet volume, which affects not only the cooling rate but also the number of heterogenenous nucleation sites in a droplet, is controlled through the molten jet diameter, the mass flow rate and the frequency of the imposed perturbation, all of which can be varied independently from each other. This ability, unique to the UDS process, permits stringent control of solidification microstructure for virtually all the droplets in a UDS.In rapid solidification processing, high cooling rates are generally used to produce large prior supercoolings, which promote rapid solidification under a larger driving force, particularly during recalescence. In an alloy, the solid-liquid interface under such conditions normally takes a dendritic morphology, with...

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Section: Models Nucleation Kinetics Modelmentioning

confidence: 99%

Nucleation Kinetics and Microstructure Evolution of Traveling ASTM F75 Droplets

Roy

Ando

2010

Adv Eng Mater

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“…However, the undercooling of the metal droplet has a correlation with the droplet size [53]. For instance, the undercooling degrees of emulsified Sn droplets in diameter of 275 and 2 m reach 55 and 175 K, respectively [54]. Under the condition of the nonequilibrium solidification, the glass transition of the liquid Al-rich matrix may occur prior to the freezing of the liquid Pb-rich spheres.…”

Section: Microstructure Formationmentioning

confidence: 98%

Liquid phase separation and microstructure characterization in a designed Al-based amorphous matrix composite with spherical crystalline particles

Hai-quan

Yang

et al. 2010

Journal of Alloys and Compounds

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“…1. By using alloy emulsions that have been proven to exhibit a high undercooling before nucleation and equilibrating alloys in the liquid + a or liquid + b two-phase field, the catalytic effect of a or b on subsequent nucleation of the liquid can be examined without the possible interference from a foreign substrate [28]. An important preliminary step in the application of the DET to the study of heterogeneous nucleation is the evaluation of the possible catalytic potency of the droplet surface coating and other possible sites.…”

Section: Nucleation Catalysis By Primary Phasesmentioning

confidence: 99%

Melt undercooling and nucleation kinetics

Perepezko

Wilde

2016

Current Opinion in Solid State and Materials Science

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a b s t r a c tWhile melt undercooling is often observed during solidification the control of undercooling and nucleation is difficult due to the numerous possible heterogeneous sites present in even high purity melts. The identification of active nucleation sites has been a continuing challenge that requires developing well planned experimentation. In samples with well-defined and controlled undercooling, the identification can be established for a number of the active sites and mechanisms that can act to catalyze nucleation. The sites and mechanisms that have been identified involve primary phases developed during cooling of alloy melts, liquid-added particle interfaces being modified (e.g. by adsorption or reaction) creating a particle type independent nucleation potency, dissolved impurities precipitating out of the melt at high undercooling or acting to alter local atomic arrangements in the melt to catalyze nucleation and nucleation sites resulting from residual solid preserved in cavities in inclusions or surface coatings. Recent advances in clarifying the structure of liquids reveal local atomic arrangements such as short range order, medium range order and cluster structures, but the role of these local heterogeneities on the undercooling and crystallization behavior is incompletely understood at present.

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Nucleation-Controlled Solidification Kinetics

Cited by 46 publications

References 40 publications

Nucleation Kinetics and Microstructure Evolution of Traveling ASTM F75 Droplets

Nucleation Kinetics and Microstructure Evolution of Traveling ASTM F75 Droplets

Liquid phase separation and microstructure characterization in a designed Al-based amorphous matrix composite with spherical crystalline particles

Melt undercooling and nucleation kinetics

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