Effects of solute content on grain refinement in an isothermal melt

This is the port-print version of the article. The official published version can be obtained from the link below - Copyright @ 2011 Acta Materialia Inc. Published by Elsevier LtdIt is well accepted in the literature that for effective grain refinement some solute is required in the melt to restrict the growth of the solid even if potent nucleating particles with a favourable physical nature are present. In this paper we investigate the effect of the solute on grain initiation in an isothermal melt, and an analytical model is developed to account for the effect of solute elements on grain size. This study revealed that the solute elements in the liquid ahead of the growing crystals reduce the growth velocity of the nucleated crystals and increase the maximum undercooling achievable before recalescence. This allows more particles to be active in nucleation and, consequently, increases the number density of active particles, giving rise to a finer grain size. The analytical model shows that the final grain size can be related to the maximum undercooling, average growth velocity and solid fraction at the moment of recalescence. Further analysis using the free growth model and experimental data in the literature revealed that for a given alloy system solidified under similar conditions the grain size can be empirically related to 1/Q (Q is the growth restriction factor) to a power of 1/3, which is considerably different from the empirical linear relationship in the literature. It is demonstrated that the 1/3 power law can describe the experimental data more accurately than a linear relationship.The EPSRC is gratefully acknowledged for providing financial support under Grant EP/H026177/1

Effects of lattice mismatch on interfacial structures of liquid and solidified Al in contact with hetero-phase substrates: MD simulations

Published under licence in IOP Conference Series: Material Science and Engineering by IOP Publishing Ltd. Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.In this study, the effects of the misfit on in-plane structures of liquid Al and interfacial structure of solidified Al in contact with the heterophase substrates have been investigated, using molecular dynamics (MD) simulations. The MD simulations were conducted for Al/fcc (111) substrates with varied misfits. The order parameter and atomic arrangement indicated that the in-plane ordering of the liquid at the interface decreases significantly with an increase of the misfit, i.e., solid-like for small misfit and liquid-like for large misfit. Further, our MD simulation results revealed that a perfect orientation relationship forms at the interface between the substrate and the solidified Al for a misfit of less than -3% and the boundary is coherent. With an increase in the misfit, Shockley partial and extended dislocations form at the interface, and the boundary becomes a semi-coherent or low-angle twist boundary.EPSR

China's Economic Diplomacy and Sino-EU Relations

La cooperación económica y las relaciones comerciales son la base en las relaciones UE-China. Desde hace varias décadas, su cooperación en la economía y en el comercio se desarrolló mucho más rápidamente que sus relaciones políticas. El diálogo a distintos niveles de una amplia gama de asuntos ayuda a institucionalizar las relaciones bilaterales, a regularizar el intercambio bilateral y a fortalecer la comunicación y el mutuo entendimiento. La UE se mantiene como primer socio comercial de China y a su vez China es el segundo de la UE. La diplomacia económica constituye una parte importante en las relaciones Sino-europeas. Sin embargo, en los últimos años, junto con el ascenso de China y la crisis del euro, hay nuevos retos para estas relaciones económicas bilaterales y comerciales. La diplomacia económica de China debe ser revisada para hacer frente a los cambios y a los desafíos. Este documento se compone de las siguientes partes: después de revisar las relaciones UE-China, se definirá la diplomacia económica de China y sus características y analizará cuatro casos de diplomacia económica de China en sus relaciones con la UE. En las conclusiones se analizarán los retos para esta colaboración.Economic cooperation and trade relations are the cornerstones in EU-China relations. For several decades, their cooperation in economy and trade developed much more rapidly than their political relations. Dialogue at different levels covering a broad range of issues help institutionalize bilateral ties, regularize bilateral exchange and strengthen communication and mutual understanding. The EU stays as China’s largest trading partner and China the EU’s second largest trading partner. Economic diplomacy serves as an important part in Sino-EU relations. Yet, in recent years, along with China’s rise and the euro crisis, there are new challenges to bilateral economic and trade relations. China’s economic diplomacy needs to be revised in order to deal with the changes and meet the challenges. This paper will be composed of the following parts: after a review of EU-China relations, it will define China’s economic diplomacy and its features and analyse four cases of China’s economic diplomacy in its relations with the EU. In the conclusion, it will examine the challenges for the partnership

Frequency spectra of the sources 3C 295 and 3C 380

Interferometric flux density measurements on stellar light source