Abstract
Small additions of boron (few hundreds at ppm) are known to be able to suppress the intergranular weakness of grain boundaries of intermetallic alloys, like FeAl (B2-ordered). It is now currently admitted that this ductilising effect of boron is due to its intergranular segregation; the elementary mechanism of the action of boron being an increase of the GB cohesion, or a modification of the GB slip transmission. In this work, an extended study of both intergranular and bulk effect of boron doping of FeAl alloys is given. The intergranular segregation of boron is confirmed and characterized; both the equilibrium and non-equilibrium (due to a solute atom/thermal vacancy interaction) segregation mechanisms are identified. Thanks to a study by atom probe FIM, a strong tendency of boron to segregate on other kinds of crystal defects, like dislocations, could also be shown. A surprisingly strong effect of boron on the temperature dependence of mechanical properties of the FeAl alloys was also observed and characterized. These observations suggest that the boron effect in FeAl can not be limited to only intergranular phenomena; in fact, its presence seems to influence the elementary mechanisms of plastic deformation of the material.
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