Evolution of microstructure and impact-strength energy in thermally and thermomechanically aged 15-5 PH

Due to its outstanding mechanical resistance and resistance to corrosion, alloy 15-5 PH can be beneficially used for manufacturing aerospace structural parts. Following exposure to intermediate temperature, from300◦–400 ◦C, the alloy embrittles through the decomposition of the martensite into iron-rich and chromium-rich domains.Depending on the ageing time, these domains are either interconnected or unconnected with each other. The embrittlement results in a drastic drop of the impact strength-energy and an increase of the ductile-to-brittle transition temperature. The initial microstructure and mechanical properties can be recovered through a re-homogenization of the distribution of chromium and iron atoms in the material in the case where the decomposition of the matrix is not too pronounced. The application of a stress higher than 60 per cent of the yield strength further enhances the ageing kinetics in the case where the combined effect of temperature and time results in the spinodal decomposition of the martensite

Gilles Hayne, Biagio Marini et le duc de Neuburg

International audienceLe duc de Neuburg a été un mécène de choix durant la première moitié du XVIIe siècle. Dans son entourage ont évolué des musiciens de plus ou moins grande réputation. Une correspondance entre le duc et un de ces musiciens, Gilles Hayne révèle la face cachée de ce mécénat et met en scène un virtuose au talent incontestable et à la personnalité complexe : Biagio Marin