Microstructure-dependent residual stresses in thick aluminium alloy components

The goal of the project is to better understand the stress build-up during quenching of heat treatable aluminium alloy components such as plates and forgings by taking into account the evolution of their microstructure and the influence of precipitation. Special attention is paid to thick products which experience different thermal paths during quenching going from the skin to the centre. The interactions during quench between cooling efficiency, solid state phase transformations, inferred mechanical hardening or softening and induced internal stresses are planned to be encompassed in a thermomechanical finite element model using a dedicated metallurgical model with internal variables. Microstructure observations are carried out using optical, scanning/transmission electron microscopy and small angle X-ray scattering. Gleeble thermomechanical testing’s during interrupted quench tests and in-situ X-ray and neutron diffraction tests are planned to assess the link between as-quenched microstructural features such as precipitates and stress-strain behaviour. A computational tool aimed at deriving dislocation densities and microstructural information from neutron diffraction peak will be developed. The computed results will be validated against residual stress and plastic strain measurements using neutron diffraction on thick industrial forgings and plates. Such a fundamental knowledge is required to optimise the fabrication route of thick aluminium components.

The research project is a collaboration between MSS and Dr. J-M. Drezet of the Computational Materials Laboratory LSMX at EPFL and is financed by the Competence Centre for Materials Science and Technology (link). Two PhD students and one postdoc research position are financed. The project is supported by Constellium and ABB Turbo Systems Ltd.