The room temperature strengthening effect of boron as a function of aluminum concentration in FeAl

Measurements of the effects of boron on the yield strength, lattice parameter, vacancy concentration and anti-site atom concentration of FeAl as a function of aluminum concentration have been performed and the results compared with data for similar but undoped FeAl. It has been shown that boron does not affect the degree of order, vacancy concentration or anti-site atom concentration in FeAl. Boron produces an increase in lattice parameter in FeAl but both this increase and the lattice strain per atomic percent boron decrease with increasing aluminum concentration. The effect of boron on the strength of FeAl depends on whether vacancies are present. For FeAl containing few vacancies (less than or equal to 45 at %Al) the strength increase per atomic percent boron increases with increasing aluminum concentration; when vacancies are present (greater than or equal to 48 at %Al), boron strengthening shows little change with aluminum concentration, suggesting that the vacancies affect the boron strengthening mechanism. The strength increase per unit increase in lattice parameter depends on the aluminum concentration and is 0.23-0.80 G, where G is the shear modulus. (C) 1997 Elsevier Science Limited.