Dislocation reactions at grain boundaries in Ll/sub 2/ ordered alloys

The characteristics of perfect grain boundary dislocations in ordered alloys are discussed, and consideration is given to the possible formation of perfect and imperfect grain boundary dislocations by the impingement of crystal lattice dislocations. It is shown that many dislocation reactions at grain boundaries in ordered alloys are made unfavorable if chemical co-ordination must be maintained in the structure of the grain boundary. This leads to a suggestion that the effect of boron in the grain boundaries of Ni/sub 3/Al is to reduce the importance of chemical ordering, and thus to promote deformation by allowing greater freedom for dislocation reactions to occur