Scientific Events

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The austenite-ferrite transformations are a key metallurgical tool to tailor properties of advanced low-carbon steels. Even though significant progress has been made to develop knowledge-based process models for the steel industry it remains critical to improve the predictive capabilities of these models by developing next generation modelling approaches with a minimum of empirical parameters. Computational materials science now offers tremendous opportunities to formulate microstructure evolution models containing fundamental information on the underlying atomistic mechanisms that can be implemented across different length and time scales. The phase transformation kinetics depends critically on interface migration rates which are significantly affected by the presence of alloying elements, e.g. Mn, Mo and Nb in steels. Here, an approach is illustrated that links atomistic scale models for the solute-interface interaction with phase field modelling and conventional diffusion models. The overall status of this multi-scale phase transformation model approach will be analyzed for intercritical annealing of dual-phase steels and the rapid heat treatment cycles in the heat affected zone of linepipe steels. [more]

The processing regime relevant to superplasticity in the Ti-6Al-4V alloy is identifed. The effect is found to be potent in the range 850 to 900 deg ?C at strain rates between 0.001/s and 0.0001/s. Within this regime, mechanical behaviour is characterised by steady-state grain size and negligible cavity formation; electron backscatter diffraction studies confirm a random texture, leaving grain boundary sliding as the overarching deformation mechanism. Outside of the superplastic regime, grain size refinement involving recrystallisation and the formation of voids and cavities cause macroscopic softening; low ductility results. Stress hardening is correlated to grain growth and accumulation of dislocations. The findings are used to construct a processing map, on which the dominant deformation mechanisms are identified. Physically-based constitutive equations are presented which are faithful to the observed deformation mechanisms. Internal state variables are used to represent the evolution of grain size, dislocation density and void fraction. Material constants are determined using genetic-algorithm optimisation techniques. Finally, the deformation behaviour of this material in an industrially relevant problem is simulated: the deformation of diffusion-bonded material for the manufacture of hollow, lightweight structures, e.g. those used for fan blades of aeroengines. [more]

In this talk, I will give an overview of our attempts to design various solid catalysts for industrially important chemical conversions. These reactions include conversion of biomass derived platform chemicals to other value-added chemicals, lower alkane activation and CO2 activation. We try to understand how the structural aspects of catalysts affect the reactivity, which is crucial in developing better catalysts. For this purpose, we try to make use of various characterization techniques. Recent results from our work in this direction will be described, taking a few examples. [more]