Effet de l'environnement sur le comportement mécanique d'un alliage FeAl (40 at. % Al) renforcé

Abstract
Room temperature tensile tests at different humidity rates have shown that the FeAl40 Grade 3 alloy - a P/M alloy reinforced by 10 weight ppm of boron and by a fine Y₂O₃ dispersion - is susceptible to the environmental effect caused by the water vapour of the atmosphere. The relative elongation obtained in air corresponds to 35 % of the one obtained in dry argon (3 vol. ppm H₂O). The embrittlement remains superficial and is revealed by a lot of cracks (of irregular shape). They appear when the stress reaches the cleavage strength whose value depends on humidity and strain rate. However, in all conditions, the heart of the specimens breaks in a ductile manner at 1480 MPa. The formation of a thick oxide layer by a heat treatment in air could be an efficient mean of protection against the environmental effect, since it limits the reaction at the origin of the embrittlement and seems to have a high tensile strength.