The Experts below are selected from a list of 282 Experts worldwide ranked by ideXlab platform
Joseph T Mckeown - One of the best experts on this subject based on the ideXlab platform.
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Rapid Solidification growth mode transitions in al si alloys by dynamic transmission electron microscopy
Acta Materialia, 2017Co-Authors: John D Roehling, G H Campbell, D R Coughlin, John W Gibbs, Kevin J Baldwin, J C E Mertens, A J Clarke, Joseph T MckeownAbstract:Abstract In situ dynamic transmission electron microscope (DTEM) imaging of Al-Si thin-film alloys was performed to investigate Rapid Solidification behavior. Solidification of alloys with compositions from 1 to 15 atomic percent Si was imaged during pulsed laser melting and subsequent Solidification. Solely α-Al Solidification was observed in Al-1Si and Al-3Si alloys, and solely kinetically modified eutectic growth was observed in Al-6Si and Al-9Si alloys. A transition in the Solidification mode in eutectic and hypereutectic alloys (Al-12Si and Al-15Si) from nucleated α-Al dendrites at lower Solidification velocities to planar eutectic growth at higher Solidification velocities was observed, departing from trends previously seen in laser-track melting experiments. Comparisons of the growth modes and corresponding velocities are compared with previous Solidification models, and implications regarding the models are discussed.
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determination of crystal growth rates during Rapid Solidification of polycrystalline aluminum by nano scale spatio temporal resolution in situ transmission electron microscopy
Journal of Applied Physics, 2016Co-Authors: Kai Zweiacker, T Lagrange, Bryan W Reed, G H Campbell, Joseph T Mckeown, J M K WiezorekAbstract:In situ investigations of Rapid Solidification in polycrystalline Al thin films were conducted using nano-scale spatio-temporal resolution dynamic transmission electron microscopy. Differences in crystal growth rates and asymmetries in melt pool development were observed as the heat extraction geometry was varied by controlling the proximity of the laser-pulse irradiation and the associated induced melt pools to the edge of the transmission electron microscopy support grid, which acts as a large heat sink. Experimental parameters have been established to maximize the reproducibility of the material response to the laser-pulse-related heating and to ensure that observations of the dynamical behavior of the metal are free from artifacts, leading to accurate interpretations and quantifiable measurements with improved precision. Interface migration rate measurements revealed Solidification velocities that increased consistently from ∼1.3 m s−1 to ∼2.5 m s−1 during the Rapid Solidification process of the Al th...
Cijun Shuai - One of the best experts on this subject based on the ideXlab platform.
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a combined strategy to enhance the properties of zn by laser Rapid Solidification and laser alloying
Journal of The Mechanical Behavior of Biomedical Materials, 2018Co-Authors: Youwen Yang, Pei Feng, Fulai Yuan, Shiwei He, Cijun ShuaiAbstract:Abstract The orthopedic application of Zn is limited owing to the poor strength and low plasticity. In this study, a novel strategy by combining Rapid Solidification obtained by selective laser melting (SLM) and alloying with Mg was proposed to improve the mechanical properties of Zn. The microstructures, mechanical properties, as well as in vitro cytocompatibility of SLM processed Zn-xMg (x = 0–4 wt%) were studied systematically. Results shown that SLM processed Zn-xMg alloys consisted of fine equiaxed α-Zn grains with homogeneously precipitated Mg2Zn11 along grain boundaries. More importantly, the grains size of α-Zn was decreased from 104.4 ± 30.4 µm to 4.9 ± 1.4 µm with Mg increasing. And Mg mainly dissolved in α-Zn developing into supersaturated solid solution due to Rapid Solidification effect. As a consequence, the ultimate tensile strength and elongation were enhanced by 361% and 423%, respectively, with Mg containing up to 3 wt%. Meanwhile, alloying with Mg enhanced the corrosion resistance of Zn, with the degradation rate decreasing from 0.18 ± 0.03 mm year−1 to 0.10 ± 0.04 mm year−1. Furthermore, SLM processed Zn-xMg exhibited good biocompatibility. This research suggested that SLM processed Zn-3Mg alloy was a potential biomaterial for orthopedic applications.
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laser Rapid Solidification improves corrosion behavior of mg zn zr alloy
Journal of Alloys and Compounds, 2017Co-Authors: Cijun Shuai, Youwen Yang, Ping Wu, Yuanzhuo Zhou, Pei Feng, Shuping PengAbstract:Abstract Rapid Solidification process is an effective method to improve the corrosion behavior of Mg alloys. In the present study, laser melting, as a typical Rapid Solidification process, was used to fabricate Mg–5.6Zn–0.5Zr (ZK60). With the increase of laser energy density, the crystalline structures experienced successive changes: clustered finer dendrites→uniform equiaxed grains→coarsened equiaxed grains. Moreover, the fully divorced eutectic α-Mg + Mg7Zn3 homogeneously distributed along the boundaries of solid solution structure α-Mg. Meanwhile, at a laser energy density of 600 J/mm3, ZK60 was dense with an optimal hardness of 89.2 Hv and hydrogen evolution rate of 0.006 ml cm−2 h−1. The enhanced corrosion resistance was attributed to the refined grain, homogenized microstructure and extended solid solution caused by laser Rapid Solidification.
P K Galenko - One of the best experts on this subject based on the ideXlab platform.
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solute trapping in Rapid Solidification of a binary dilute system a phase field study
Physical Review E, 2011Co-Authors: P K Galenko, Ekaterina Abramova, Denis Danilov, V V Lebedev, D M HerlachAbstract:The phase-field model of Echebarria, Folch, Karma, and Plapp [Phys. Rev. E 70, 061604 (2004)] is extended to the case of Rapid Solidification in which local nonequilibrium phenomena occur in the bulk phases and within the diffuse solid-liquid interface. Such an extension leads to the fully hyperbolic system of equations given by the atomic diffusion equation and the phase-field equation of motion. This model is applied to the problem of solute trapping, which is accompanied by the entrapment of solute atoms beyond chemical equilibrium by a Rapidly moving interface. The model predicts the beginning of complete solute trapping and diffusionless Solidification at a finite Solidification velocity equal to the diffusion speed in bulk liquid.
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Rapid Solidification in situ diagnostics and theoretical modelling
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2007Co-Authors: D M Herlach, P K GalenkoAbstract:We report on progress in direct experimental investigations of non-equilibrium crystallization in undercooled melts. Containerless processing is applied for undercooling and is combined with diagnostic means. The results of such experiments are utilized to critically assess physical models for Rapid Solidification. Existing models of Rapid growth of solid into undercooled melts are reviewed. The sharp interface model is applied to quantitatively describe Rapid dendrite growth of metals and alloys. It is extended to include effects of fluid flow in liquids induced by forced convection in electromagnetically levitated drops. Morphological transitions resulting in grain refinement via instabilities of growing dendrites are analyzed and used to evaluate the effect of fluid flow on grain refinement. Theoretical predictions given by sharp-interface model are compared with results of phase-field modeling and with new data of crystal growth dynamics measured with high accuracy. Depending on the undercooling prior to Solidification the effects of solute diffusion, convective flow, solute trapping and microstructure evolution are demonstrated.
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linear morphological stability analysis of the solid liquid interface in Rapid Solidification of a binary system
Physical Review E, 2004Co-Authors: P K Galenko, D A DanilovAbstract:The interface stability against small perturbations of the planar solid-liquid interface is considered analytically in linear approximation. Following the analytical procedure of Trivedi and Kurz (Trivedi R, Kurz W. Acta Metall 1986;34:1663), which is advancing the original treatment of morphological stability by Mullins and Sekerka (Mullins WW, Sekerka RF. J Appl Phys 1964;35:444) to the case of Rapid Solidification, we extend the model by introducing the local nonequilibrium in the solute diffusion field around the interface. A solution to the heat- and masstransport problem around the perturbed interface is given in the presence of the local nonequilibrium solute diffusion. Using the developing local nonequilibrium model of Solidification, the self-consistent analysis of linear morphological stability is presented with the attribution to the marginal (neutral) and absolute morphological stability of a Rapidly moving interface. Special consideration of the interface stability for the cases of Solidification in negative and positive thermal gradients is given. A quantitative comparison of the model predictions for the absolute morphological stability is presented with regard to experimental results of Hoglund and Aziz (Hoglund DE, Aziz MJ. Mat Res Soc Symp Proc 1992;205:325) on critical solute concentration for the interface breakdown during Rapid Solidification of Si–Sn alloys. PACS: 05.70.Fh; 47.20.Ma; 81.10.Aj; 81.30.Fb
G H Campbell - One of the best experts on this subject based on the ideXlab platform.
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Rapid Solidification growth mode transitions in al si alloys by dynamic transmission electron microscopy
Acta Materialia, 2017Co-Authors: John D Roehling, G H Campbell, D R Coughlin, John W Gibbs, Kevin J Baldwin, J C E Mertens, A J Clarke, Joseph T MckeownAbstract:Abstract In situ dynamic transmission electron microscope (DTEM) imaging of Al-Si thin-film alloys was performed to investigate Rapid Solidification behavior. Solidification of alloys with compositions from 1 to 15 atomic percent Si was imaged during pulsed laser melting and subsequent Solidification. Solely α-Al Solidification was observed in Al-1Si and Al-3Si alloys, and solely kinetically modified eutectic growth was observed in Al-6Si and Al-9Si alloys. A transition in the Solidification mode in eutectic and hypereutectic alloys (Al-12Si and Al-15Si) from nucleated α-Al dendrites at lower Solidification velocities to planar eutectic growth at higher Solidification velocities was observed, departing from trends previously seen in laser-track melting experiments. Comparisons of the growth modes and corresponding velocities are compared with previous Solidification models, and implications regarding the models are discussed.
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determination of crystal growth rates during Rapid Solidification of polycrystalline aluminum by nano scale spatio temporal resolution in situ transmission electron microscopy
Journal of Applied Physics, 2016Co-Authors: Kai Zweiacker, T Lagrange, Bryan W Reed, G H Campbell, Joseph T Mckeown, J M K WiezorekAbstract:In situ investigations of Rapid Solidification in polycrystalline Al thin films were conducted using nano-scale spatio-temporal resolution dynamic transmission electron microscopy. Differences in crystal growth rates and asymmetries in melt pool development were observed as the heat extraction geometry was varied by controlling the proximity of the laser-pulse irradiation and the associated induced melt pools to the edge of the transmission electron microscopy support grid, which acts as a large heat sink. Experimental parameters have been established to maximize the reproducibility of the material response to the laser-pulse-related heating and to ensure that observations of the dynamical behavior of the metal are free from artifacts, leading to accurate interpretations and quantifiable measurements with improved precision. Interface migration rate measurements revealed Solidification velocities that increased consistently from ∼1.3 m s−1 to ∼2.5 m s−1 during the Rapid Solidification process of the Al th...
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revealing the transient states of Rapid Solidification in aluminum thin films using ultrafast in situ transmission electron microscopy
Philosophical Magazine Letters, 2011Co-Authors: A Kulovits, J M K Wiezorek, T Lagrange, Bryan W Reed, G H CampbellAbstract:Using high time resolution transmission electron microscopy, we have observed Rapid Solidification dynamics in 80 nm thick Al thin films after pulsed laser melting. The nanometer spatial and 15 nanosecond temporal resolution of the dynamic transmission electron microscope (DTEM) at Lawrence Livermore National Laboratory allowed us to study the morphology and dynamics of the transformation front moving at speed of 0.1–10 m/s during Rapid Solidification. Additionally, we used an automated orientation imaging system in the TEM for the post-mortem analysis of grain orientations of the solidified microstructure near the position of the solid liquid interface at the start of Solidification.
Marcello Baricco - One of the best experts on this subject based on the ideXlab platform.
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Rapid Solidification of alloys
International Journal of Materials & Product Technology, 2004Co-Authors: Marcello Baricco, E. Bosco, Elena Olivetti, Mauro Palumbo, Paola Rizzi, A. Stantero, Livio BattezzatiAbstract:This paper reviews some applications of Rapid Solidification processing of alloys. With reference to original work of the authors, the production and properties of amorphous alloys, mainly iron based, of nanocrystalline aluminium alloys and of granular materials are described. A section is devoted to the latest advancement of thermodynamic modelling of metastable systems using CALPHAD softwares.
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Rapid Solidification of cu fe ni alloys
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2004Co-Authors: Marcello Baricco, E. Bosco, Paola Rizzi, G Acconciaioco, M CoissonAbstract:Abstract Cu80−xNixFe20 (x=0, 5 and 20) alloys have been Rapidly solidified by planar flow casting. X-ray diffraction (XRD) analysis of as-quenched ribbons shows bcc-Fe precipitates embedded in an fcc phase (x=0), two co-existing fcc solid solutions (x=5) and a complete solid solution of the parent elements (x=20). Thermal treatments in the temperature range between 400 and 600 °C give precipitation and spinodal decomposition reactions. These phase transformations have been evidenced from a variation of lattice constants, from a broadening of diffraction peaks and from TEM observations. The role of Ni content on competition between precipitation and decomposition reactions during Rapid Solidification and annealing is discussed in terms of thermodynamic arguments. Recent CALPHAD assessment of thermodynamic properties for Cu–Fe–Ni system has been used for an estimation of composition and volume fraction of equilibrium phases.
