The project is based on recently published work that has shown it is possible to obtain extremely high strengths in cheap, low strength Al-Mg-Si automotive alloys, with a new processing route that involves heavily cold rolling of a pre-underaged material and then re-aging (UA-CR-RA). The aim of the project is to develop a fundamental metallurgical understanding of how this novel processing route achieves such a dramatic improvement in properties of Al-alloys. The work involves:
Quantifying the microstructure development and contribution of strengthening terms, during the UA-CR-RA process, using advanced analytical techniques and in-situ, time-resolved simulations
Developing physical-based models to capture the microstructure evolution and properties of materials processed using sequential precipitation and deformation steps, to aid process optimisation
In preliminary work I have repeated a previous study and confirmed that by hybrid processing the yield strength can be increased to the unprecedented level, in AA6013, of >450 MPa, while maintaining sufficient tensile elongation for practical application.
It has not currently been explained why the UA-CR-RA processing route is capable of obtaining such high strengths while achieving comparable ductility to alloys of similar high strength, but it is likely that it benefits from synergistic effects of pre-ageing increasing dislocation storage during cold work and then nucleation occurring on dislocations in the re-aging treatment that locks-up the dislocation networks.
Transmission Electron Microscopy (TEM) will be used to characterise the precipitate particles as well as the dislocation lines behaviour. X-ray Diffraction (XRD), Electron Backscatter Diffraction (EBSD) will be adapted to analyse the dislocation density and texture evolution during thermo-mechanical process.
Digital Image Correlation (DIC) and Differential Scanning Calorimetry (DSC) will be used to characterise the influence of different ageing steps on mechanical properties and precipitation behaviour.