Development of fluctuations into domains during ordering inFe3Al

The early-stage kinetics of a second-order phase transition with a nonconserved order parameter (the B2-${\mathit{DO}}_3$ transition in ${\mathrm{Fe}}_3$Al) has been investigated using in situ synchrotron x-ray scattering. A line-shape analysis allows the short- and long-range-order components to be determined separately as a function of time during the ordering process. At all temperatures investigated, the correlation length of short-range-order fluctuations ξ(t) grows to a maximum and then decreases, while the long-range-order domain size L(t) increases monotonically from an initial value 1 order of magnitude larger than ξ.