LOCAL ARRANGEMENTS IN FE-31-PERCENT AT PD ABOVE M(S)

The diffuse x-ray scattering from an Fe -31 at. pet. Pd single crystal quenched from 1173 K was analyzed to obtain information about the loc al atomic environment around each atom including the local chemical or der and the average atomic displacements from the normal lattice posit ions. To better reveal the meaning of these average quantities, comput er simulations were employed to provide the structure using these valu es. The results indicate an interconnected distribution of ordered and clustered regions, no more than a few atoms in dimension, and only sl ightly more developed than for a random arrangement. The pattern of at omic displacements from the average lattice is revealed to be small em bryos of a displacement array similar to the FCT martensitic phase and aligned in <110> directions, which may be the premartensitic phase th at has been predicted by several authors.