Papers by Author: Laure Bourgeois

Abstract: The microstructural evolution and associated strengthening during isothermal ageing of an Al-3Cu-0.05Sn reinforced by non-spherical θ' (Al2Cu) precipitates is studied. Emphasis is placed on the plate shape of the θ'. It is found that the microstructure parameters governing the magnitude of the precipitation strengthening effect are completely different from the classical case of spherical precipitates. New possibilities for microstructure design are discussed.

Abstract: The work hardening behavior of an Al-3Cu-0.05Sn (wt %) alloy was studied using tensile tests and Bauschinger tests. Emphasis is placed on the influence of the precipitation state (number density, size distribution and volume fraction) and separating the isotropic and kinematic components of the work hardening.

Abstract: The interaction between vacancies and Sn and Cu solute atoms in an Al-1.7at.%Cu- 0.01at.%Sn alloy was investigated by exploring the effect of incorporating natural ageing into conventional age hardening treatment. It was found that provided the artificial ageing temperature does not exceed a critical value between 160°C and 200°C, a narrow window of natural ageing (3-100 h) will result in a significant acceleration of the age hardening response and no decrease in peak hardness. Transmission electron microscopy showed that this effect reflects a large and rapid increase in number density of Cu GP(I) zones, and, to a lesser extent, of θ". The distribution and number density of θ' are essentially unaffected. Three-dimensional atom probe provided strong evidence that refinement of GP(I) zone distribution is not due to clustering of Cu atoms onto pre-existing Sn clusters. Instead it appears to be caused by a subtle interaction between vacancies, Sn and Cu atoms.