Long-range ordering in B2 FeAl: a resistometric study

Changes in the degree of order have been studied by residual electrical resistivity measurement (REST) in B2 long-range ordered Fe–44.8 at.% Al during isochronal and isothermal step-annealing temperature treatment. Restricted atomic mobility starts already below about 500 K. Assuming the vacancy concentration to remain constant over an extended temperature range, as known from the literature, the complicated variations of resistivity with temperature can be explained by two regimes of ordering: a fast local ordering due to the restricted motion of the vacancies at low temperatures and a very slow global adjustment of long-range order (LRO) within the total sample volume. Kinetic parameters are determined from the detailed process analysis of the ordering kinetics during isothermal small-step annealing. Using these parameters, the results of isochronal annealing treatment can be calculated with a very good correspondence to experiment.