Microstructure Evolution and Mechanical Behaviour of Advance Structural Materials

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Material properties such as strength and ductility are strongly dependent on the internal structure (microstructure) of the material. The objective of the present work is to provide a better understanding of the processes which control the microstructure evolution during the processing and use of advanced steels. Ultimately, this would permit us to adjust the processing parameters (e.g. temperature and deformation) so as to produce a material with a favourable microstructure and consequently, favourable properties. The proposed work has three main thrusts. The first of these is the area of phase transformations in low carbon steels. It is well known that iron, Fe, exists in two forms; a high temperature form known as austenite and a low temperature form known as ferrite. The addition of alloying elements has been shown to have a strong effect on the kinetics of the transformation from austenite to ferrite on cooling. In spite of the great significance of this transformation, the mechanism by which the alloying elements affect the transformation is still poorly understood. The proposed work would involve highly controlled experiments which would permit us to better understand the effect of the alloying elements. Recent breakthroughs in the area of characterization at the atomic scale will be exploited in order to develop experimentally-validated phase-transformation models. The second area of interest is that of thermomechanical processing. The great interest in thermomechanical processes, such as hot-rolling, is due to the fact that these permit the refinement of the microstructure which, in turn, leads to improvements in strength and toughness. In the proposed work a series of experimental alloys will be investigated in order to determine key changes that occur within the microstructure during hot-rolling. Once these changes are understood, a physically-based model of multi-pass deformation will be developed and employed to optimize processing conditions. The third topic which will be investigated as part of this proposal is the engineering of microstructures at multiple length scales. In addition to the intrinsic scales within the microstructure, one can introduce new scales by introducing composition gradients (of the order of a millimetre) or by introducing architectured reinforcement (on the order of a centimeter). The proposed work will explore the potential of exploiting these length scales in order to produce materials with novel combinations of properties. In total, 10 highly qualified individuals will be trained in areas of great importance to the Canadian industry. The graduates will be qualified to work in the steel, automotive and manufacturing sectors.