A model was developed to explain the experimental observation that small additions of boron to Ni3Al reduced the effectiveness with which grain boundaries strengthened the alloy, following the proposal of Schulson et al. (1985, 1986). This model was based upon the effect of ordering upon the mobility of grain boundary dislocations. If the addition of boron lowered the difference in energy between different ordering configurations at the boundary, then it should promote accommodation of stress concentrations by the motion of grain boundary dislocations.Grain Boundary Structure and the Effect of Boron in Ni3Al. Frost, H.J.: Acta Metallurgica, 1988, 36[8], 2199-211