Kinetics of defect recovery and long-range ordering in Ni3Al+B .1. Simultaneous recovery and ordering in cold-rolled material

Defect recovery and long-range ordering (LRO) during isochronal annealing of cold-rolled Ni76Al24 + 0.19 at.% B (400 wt ppm) were studied by residual resistometry, transmission electron microscopy (TEM) and microhardness tests. The cold-rolling causes a decrease of the degree of LRO and an effective increase of the mobility of vacancies. The long-range ordering process during isochronal annealing proceeds, however, qualitatively in a similar way both in as-rolled and in homogenised samples. TEM observations revealed two stages of the defect recovery. Firstly, superlattice intrinsic stacking faults (SISF) of large density recovered almost completely in the temperature regime between 443 and 700 K showing that they are bounded by dislocations of opposite sign. Secondly, the recovery of antiphase-boundary (APB) dissociated superlattice dislocations occurred by the annihilation of dipoles within the whole temperature regime leading finally to a loss of all dislocations at 1273 K.