Influences of process parameters and microstructure on the fracture mechanisms of ODS steels

• Published in: Journal of nuclear materials Vol. 433; no. 1-3; pp. 108 - 115
• Main Authors: Rouffié, A.L., Wident, P., Ziolek, L., Delabrouille, F., Tanguy, B., Crépin, J., Pineau, A., Garat, V., Fournier, B.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.02.2013; Elsevier
• Subjects: Applied sciences; Controled nuclear fusion plants; Dispersion hardening alloys; Energy; Energy consumption; Energy. Thermal use of fuels; Engineering Sciences; Exact sciences and technology; Fission nuclear power plants; Fracture mechanics; Fracturing; Fuels; Grains; Installations for energy generation and conversion: thermal and electrical energy; Materials; Nuclear fuels; Steels; Surface layer; Texture; Grain size; Ductile brittle transition; Fracture; Steel; Microstructure; Texture; Nuclear reactor
• ISSN: 0022-3115; 1873-4820
• DOI: 10.1016/j.jnucmat.2012.08.050

The present work investigates the impact response of three ODS steels containing 9%Cr and 14%Cr. These steels were produced by hot extrusion in the shapes of a rod and a plate. The 9%Cr ODS steel has a quasi-isotropic microstructure and is given as a reference material. In comparison, the 14%Cr ODS steel has a strong morphological and crystallographic texture given by the process route. The impact behaviour is anisotropic and the fracture energies are higher when the material is tested in the longitudinal direction compared to the transverse direction. Moreover, the 14%Cr ODS steel has a better impact behaviour when it is extruded in the shape of a rod rather than in the shape of a plate. This work focuses on the fracture mechanisms involved in the ductile to brittle transition regime and in the brittle regime of these materials. In the case of the 14%Cr ODS steel, the cleavage facets observed at very low temperature are much larger than the actual size of the grains. Packets of grains with less than 15° of internal misorientation were defined as effective grains for cleavage. In the transition range, the texture enhances intergranular delamination on the 14%Cr rod material. The occurrence of delamination consumes a lot of energy and tends to enhance scattering in impact energies.