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Which wets TiB2 inoculant particles: Al or Al3Ti?

Wearing, D; Horsfield, AP; Xu, W; Lee, PD; (2016) Which wets TiB2 inoculant particles: Al or Al3Ti? Journal of Alloys and Compounds , 664 pp. 460-468. 10.1016/j.jallcom.2015.12.203. Green open access

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TiB2 particles are proven effective nucleants of commercial purity aluminium, resulting in smaller grains and hence greater desired mechanical properties; however, there is uncertainty as to the mechanism by which it operates. Here we clarify what happens in the initial stages by computing the total Gibbs energy change associated with four possible nucleation mechanisms, each characterised by the termination of the TiB2(0001) substrate (Ti or B) and the solid that forms on it (Al or Al3Ti). The appropriate solid//solid interfacial energies are derived from Density Functional Theory (DFT) calculations, while the bulk energies are derived from thermodynamic data, supplemented with strain energies calculated from DFT. Solid//liquid interfacial energies are estimated using simple models with parameters based on the literature and DFT calculations. The results suggest that the Ti termination of TiB2 is more stable than the B termination in the melt, and that the direct formation of Al off a Ti-terminated TiB2 substrate is the most favourable mechanism for the nucleation of Al rather than the previously proposed formation of a Al3Ti interlayer. On the B termination of TiB2, Al formation is more stable for thick solid layers, but this is much more uncertain for thin solid layers where it is possible that Al3Ti formation is more stable.

Type: Article
Title: Which wets TiB2 inoculant particles: Al or Al3Ti?
Open access status: An open access version is available from UCL Discovery
DOI: 10.1016/j.jallcom.2015.12.203
Publisher version: https://doi.org/10.1016/j.jallcom.2015.12.203
Language: English
Additional information: This version is the author accepted manuscript. For information on re-use, please refer to the publisher’s terms and conditions.
Keywords: Science & Technology, Physical Sciences, Technology, Chemistry, Physical, Materials Science, Multidisciplinary, Metallurgy & Metallurgical Engineering, Chemistry, Materials Science, Interfacial energy, Density functional theory, Nucleation, Aluminium, Al3Ti, TiB2, RADIAL-DISTRIBUTION FUNCTION, GRAIN-REFINEMENT, ALUMINUM-ALLOYS, AB-INITIO, HETEROGENEOUS NUCLEATION, THERMODYNAMIC STABILITY, SURFACE-TENSION, FREE-ENERGY, INTERFACE, MECHANISM
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Mechanical Engineering
URI: https://discovery.ucl.ac.uk/id/eprint/10049205
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