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

Emilie Herny (1, 2) , Philippe Lours (1) , Eric Andrieu (2) , Jean-Marc Cloué (3) , Philippe Lagain (4)

1 CROMeP - Centre de Recherche Outillages, Matériaux et Procédés
2 CIRIMAT - Centre interuniversitaire de recherche et d'ingenierie des matériaux
3 AREVA NP Lyon
4 Airbus [France]

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.

Mots clés: PH steel; ductile-to-brittle transition; ageing; spinodal decomposition; martensite

Domaines: Matériaux

Emilie Herny, Philippe Lours, Eric Andrieu, Jean-Marc Cloué, Philippe Lagain. Evolution of microstructure and impact-strength energy in thermally and thermomechanically aged 15-5 PH. Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications, 2008, vol. 222 (n° 4), pp.299-304. ⟨hal-01688569⟩