Phase transformations and recrystallization in Ni-33at.%Cr alloy

Abstract

The phase transformations were investigated in Ni-33at.%Cr alloy with two initial structures: recrystallized at 1100 °C and cold worked. Transformation of the cold-worked structure was evaluated quantitatively and Ni-20at.%Cr alloy was used for comparison. Annealing temperatures (450–530 °C) were chosen from the Ni 2Cr superstructure phase field. The interaction of three processes, namely long-range ordering, Cr-rich α phase precipitation and recrystallization, was followed. This interaction depend on the annealing temperature and initial structure. Common features are as follows. Ordering takes place in both structures although its extent and time necessary for its formation are different in both structures. Cr-rich precipitates form in cold-worked specimens only and give rise to concentration changes in the matrix. The recrystallization is, in the same time, hindered by the formation of large-range order (LRO) in the deformed structure. Both initial structures exhibit ordering to some extent although the final structures are different. The results lead to the conclusion that the difference between the free energies of the ordered Ni 2Cr phase and of the mixture containing Cr-rich particles and hypostoichiometric LRO is small.