Effect of external fields on ordering of FePd

When single crystals of equiatomic FePd in the disordered state are held at temperatures below the ordering temperature (923 K) but above 780 K, their transformation is markedly affected by application of either a compressive stress or a magnetic field. The distribution between orientational variants is affected, as expected, but also the volume fraction transformed and the rate of transformation change, each by as much as an order of magnitude. These effects are explained in terms of a change in nucleation rate brought about by the applied fields, and the associated development of an oriented internal stress field. The lower bound temperature of 780 K is identified with the spinodal ordering temperature for the transformation. A computer simulation based on the Ginzburg–Landau approach clearly supports these explanations.