EFFECT OF ENVIRONMENT ON MECHANICAL-BEHAV IOR OF A REINFORCED FEAL ALLOY (40 AT.PERCENT AL)

Room temperature tensile tests at different humidity rates have shown that the FeAl40 Grade 3 alloy - a P/M alloy reinforced by 10 weight pp m of boron and by a fine Y2O3 dispersion - is susceptible to the envir onmental effect caused by the water vapour of the atmosphere. The rela tive elongation obtained in air corresponds to 35 % of the one obtaine d 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 h umidity aid strain rate. However, in all conditions, the heart of the specimens breaks hi a ductile manner at 1480 MPa. ?he formation of a t hick oxide layer by a heat treatment in air could be an efficient mean of protection against the environmental effect, since it limits the r eaction at the origin of the embrittlement aad seems to have a high te nsile strength.