Experiments at room temperature have established that the addition of 750ppm by weight (0.35at%) of boron to stoichiometric Ni3Al reduced the effectiveness with which grain boundaries strengthened the alloy. This effect led to boron-induced weakening of the most finely grained aggregates (< 10μm). The effect of boron was explained in terms of an increase in the mobility of grain boundary dislocations, and was related to boron-induced ductility

Grain Boundary Accommodation of Slip in Ni3Al Containing Boron. Schulson, E.M., Weihs, T.P., Baker, I., Frost, H.J., Horton, J.A.: Acta Metallurgica, 1986, 34[7], 1395-9