The effect of boron on the reordering of Ni 3Al powders produced by filing

Abstract

Changes in the degree of long-range order (LRO) and the evolution of the microstructure of pure and boron-doped (0.1 and 0.2wt%) Ni 3Al powders have been investigated using XRD and DSC. The powders obtained by filing were completely disordered, with a crystallite size of 100 to 120 Å and an equivalent strain of 0.5 to 1.1%. From the comparison between the experimental heat-flows recorded in DSC and the estimated ordering energy, it was deduced that reordering process is the result of nucleation and growth of ordered domains. The influence of boron on the thermal evolution was investigated. During isochronal anneals, the recovery of the microstructure and of the long-range order takes place at higher temperatures in boron-doped alloys. A comparison of the present results with those of previous irradiation experiments revealed that the effect of boron in slowing-down the reordering processes is the same with and without irradiation, indicating a possible similarity between the operating mechanism of reordering.