KINETICS OF DEFECT RECOVERY AND LONG-RANGE ORDERING IN NI3AL-ROLLED MATERIAL(B .1. SIMULTANEOUS RECOVERY AND ORDERING IN COLD)

Defect recovery and long-range ordering (LRO) during isochronal anneal ing of cold-rolled Ni76Al24 + 0.19 at.% B (400 wt ppm) were studied by residual resistometry, transmission electron microscopy (TEM) and mic rohardness tests. The cold-rolling causes a decrease of the degree of LRO and an effective increase of the mobility of vacancies. The long-r ange ordering process during isochronal annealing proceeds, however, q ualitatively in a similar way both in as-rolled and in homogenised sam ples. TEM observations revealed two stages of the defect recovery. Fir stly, superlattice intrinsic stacking faults (SISF) of large density r ecovered almost completely in the temperature regime between 443 and 7 00 K showing that they are bounded by dislocations of opposite sign. S econdly, the recovery of antiphase-boundary (APB) dissociated superlat tice dislocations occurred by the annihilation of dipoles within the w hole temperature regime leading finally to a loss of all dislocations at 1273 K.