DISLOCATION-STRUCTURES AND THE CHARACTER OF SUPERDISLOCATIONS IN NI3AL ALLOYS

Lattice dislocations consisting of pairs of 1/3[112] superpartials bounding extended superlattice intrinsic stacking faults (SISFs) were observed by TEM. They were found to independently react to APE coupled 1/2[110] pairs in the commonly observed pure screw orientation. Boron was observed to have strong effects upon the population of boundary types, grain size, and grain growth. In addition, small amounts of B completely eliminate widely extended stacking faults. It is concluded that effects of B other than influencing boundary cohesion are important. Implications with regard to Kear-Wilsdorf type locking mechanisms and deformation behaviour are discussed.