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Zhongyun Fan (BCAST, Brunel University London)18/06/2019, 10:30HighlightRecent Advances in Understanding the Early Stages of Solidification Z Fan BCAST, Brunel University London, Uxbridge, Middlesex, UB8 3PH, UK (zhongyun.fan@brunel.ac.uk) Solidification of single phase alloys occurs in a number of distinctive stages during the cooling process. For isothermal solidification these may include prenucleation (atomic ordering in the liquid adjacent to the...Go to contribution page
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Feng Wang (BCAST, Brunel University London)18/06/2019, 10:50Oral PresentationGrain refinement of aluminium alloys has always been desirable in foundries. It is a common practice to add grain refiners into the alloy melt to promote heterogeneous nucleation and hence achieve effective grain refinement. However, the efficiency of commercial grain refiners is extremely low as less than approximately 1% of the added particles initiate aluminium grains during solidification...Go to contribution page
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Yuanding Huang (MagIC Magnesium Innovation Centre, Helmholtz-Zentrum Geesthacht)18/06/2019, 11:10Oral PresentationA homogeneous microstructure of as-cast magnesium alloys is desired to improve the formability during their subsequent thermomechanical processing. Owing to its similar crystal structure to Mg, the part of Zr formed by peritectic reaction during solidification was considered to be the most effective nucleants for alpha-Mg. However, regarding the Al-containing magnesium alloys, up to now no...Go to contribution page
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Feng Gao (BCAST, Brunel Univerisity)18/06/2019, 11:30Oral PresentationEffective grain refinement strongly depends on the interplay between nucleation potency of nucleant particles (measured by nucleation undercooling), grain initiation behaviour (affected by size, size distribution, spatial distribution and number density of nucleant particles) and solidification conditions (specified by alloy concentrations and cooling rate). Recently, we have made good...Go to contribution page
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Alberto Fabrizi (University of Padova)18/06/2019, 11:50Oral PresentationRecent theories suggest the existence of an incubation time, over which a liquid alloy prepares for nucleation by decomposing into compositional fluctuations. Accordingly, in a recent work by the present authors, the solidification path of a Controlled Diffusion Solidification (CDS) mixture was calculated. The calculated CDS path begins at a higher liquidus temperature comparing to...Go to contribution page
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Michel Rappaz (รcole Polytechnique Fรฉdรฉrale de Lausanne)18/06/2019, 13:30KeynoteFrank in 1952 [1] already postulated that Icosahedral Short-Ranger Order (ISRO) in the liquid might explain the large undercoolings measured by Turnbull in fcc of hcp metals. ISRO was later confirmed by several observations such as the formation of quasicrystals or the atomic structure of their approximant intermetallic phases, neutron small angle scattering and atomistic simulations. In...Go to contribution page
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Julien Zollinger (Institut Jean Lamour)18/06/2019, 14:00Oral PresentationThe present contribution reviews the recent progress related to the influence of Icosahedral Short-Range Order (ISRO) and icosahedral Quasicrystals (i-QC) formation on the solidification of fcc alloys through minor solute element additions. From intensive crystallographic analysis of multi-twinned regions in as-cast Al-based and Au-based fcc alloys, Kurtuldu et al. have shown recently that a...Go to contribution page
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Yun Wang (BCAST, Brunel University London)18/06/2019, 14:20Oral PresentationInoculation with exogenous particles has been widely used in industry to grain refine various alloys during solidification. Among a series of Al-Ti-B based grain refiners developed for Al-alloys, the Al-5Ti-1B master alloy, which contains potent TiB2 particles for enhancing heterogeneous nucleation of ฮฑ-Al grains, has been most widely used for decades. However, it has been reported that, in...Go to contribution page
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Jincheng Wang (Northwestern Polytechnical University)18/06/2019, 14:40Oral PresentationNucleation of crystalline materials, the starting point for crystal formation from melts, has long been an important issue in condensed matter physics and materials science. Nucleation plays a key role in determining the microstructures and mechanical properties of crystalline materials; therefore, controlling nucleation is a very effective way for regulating the macrostructures of materials...Go to contribution page
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Changming Fang (BCAST Brunel University London)18/06/2019, 15:00Oral PresentationPrenucleation refers to the phenomenon of atomic ordering in the liquid adjacent to the liquid/substrate interface at temperatures above the nucleation temperature, which becomes the precursor for the subsequent heterogeneous nucleation process through structural templating. Understanding of prenucleation is therefore of both scientific and technological importance. Based on recent...Go to contribution page
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Hua Men (BCAST, Brunel University London)18/06/2019, 15:20Oral PresentationIt has been recently realized that atomic ordering in the liquid adjacent to the substrate (i.e., prenucleation) has a significant implication on the subsequent heterogeneous nucleation process. In this paper, we report an atomistic mechanism of heterogeneous nucleation through structural templating. Using molecular dynamics (MD) simulation, we investigated the process of heterogeneous...Go to contribution page
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Lars Arnberg (Department of Materials Science and Engineering, NTNUTNU), Yanjun Li (Department of Materials Science and Engineering, NTNUTNU)18/06/2019, 16:10HighlightAn in-situ study on the directional solidification of an inoculated Al-20 wt%Cu alloy under well controlled constant cooling rates and temperature gradients has been carried out using a microfocus X-radiography set-up. The influences of temperature gradient and cooling rate on the heterogeneous nucleation rate and growth kinetics of equiaxed grains have been studied quantitatively. It is shown...Go to contribution page
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David StJohn (The University of Queensland)18/06/2019, 16:30Oral PresentationThe Interdependence model [1] predicted that nucleation would occur in waves of events with regions of no nucleation in between each wave. The waves continue to form until nucleation covers the sample. The cause of this phenomenon was attributed to the formation of a nucleation-free zone which incorporates solute suppressed nucleation and inhibited nucleation zones. Recent real-time...Go to contribution page
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Mingxu Xia (Shanghai Jiao Tong University)18/06/2019, 16:50Oral PresentationFor liquid metal, heterogeneous nucleation is main channel towards the formation of solid crystal. Fine tuning of nucleation means an optimized solidification structure, and consequently promises tailored properties for application. There are a few extensively used industrial practices for nucleation tuning, as AlTiB catalyzed grain refining in Al alloys, silicon modification for AlSi alloys,...Go to contribution page
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Yijiang Xu (Department of Materials Science and Engineering)18/06/2019, 17:10Oral PresentationThe nucleation and Growth behaviors of primary Si particles in hypereutectic Al-Si-Cu alloys solidified under near-isothermal melt and constant cooling rate condition, have been studied by in-situ X-radiography. The influences of cooling rate and addition level of P on the nucleation temperature, maximum nucleation undercooling, nucleation rate, growth velocity and morphology development of...Go to contribution page
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Julien Zollinger (Institut Jean Lamour)18/06/2019, 17:30Oral PresentationIsomorphic inoculation has recently been introduced by the authors as a successful method to grain refine cast titanium aluminides [1]. Analyses of the cast grain size together with introduced particle size distributions revealed anomalously high grain refinement efficiency which was attributed to the particles breaking up during the holding stage prior to solidification [2]. In the...Go to contribution page
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