TiB 2 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 TiB 2 (0001) substrate (Ti or B) and the solid that forms on it (Al or Al 3 Ti). 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 TiB 2 is more stable than the B termination in the melt, and that the direct formation of Al off a Ti-terminated TiB 2 substrate is the most favourable mechanism for the nucleation of Al rather than the previously proposed formation of a Al 3 Ti interlayer. On the B termination of TiB 2 , Al formation is more stable for thick solid layers, but this is much more uncertain for thin solid layers where it is possible that Al 3 Ti formation is more stable.

In this work we use computer simulations to explain the variety of crystal orientations observed at interfaces between MgO and Mg when Mg single crystals are oxidized. Using first-principles density functional theory simulations we investigate the interfacial stability of MgO//Mg interfaces, and find that a combination of interfacial chemical bonding energy and epitaxial strain stored in the oxide layers can change the relative stability of competing MgO//Mg interfaces. We propose that a combination of the oxygen chemical potential at the interface plane and the epitaxial strain energy stored in the oxide layers is responsible for the differences in observed interfacial crystal orientations–a key insight for the design and development of Mg alloys reinforced by MgO particles

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The narrative of ‘reform’ in Saudi Arabia, recently recurring in British political discourse around the kingdom’s Crown Prince Mohammed Bin Salman, is situated within wider Orientalist themes, wherein a progressive and modern West is juxtaposed with an Arabian peninsula mired in backwardness. In this context, the purported Arab ‘reformer’ is presented as the ideal ally of the West, attempting to haul his society up to the West’s supposed standards, for example on women’s rights. This racialising narrative serves to legitimise British support for authoritarian Gulf regimes, thus helping to sustain the political economy of this set of international relations at the political level. It does this by obscuring the important role the United Kingdom plays in sustaining authoritarianism in the Arabian peninsula by externalising the explanatory focus onto the terrain of cultural difference. This article contributes to the literature on UK relations with the Arab Gulf monarchies by critically analysing the ways in which racialising discourses dovetail with material interests to reinforce and sustain these ties. In doing so, it also contributes to the emerging literatures on ‘racial capitalism’ and ‘race’ in international relations, through its exploration of the role of Orientalist discourse in this significant empirical case study.