X-Ray Measurement of Order in the Alloy Cu3Au

Abstract

X‐ray diffraction theory is developed for the evaluation of long range order and short range order in the alloy Cu₃Au, and experiments are described whereby each type of order was measured. Values of the long range order parameter S were found to be 0.86 for 250°C, 0.81 for 370°C, and 0.79 for 380°C, the samples being held at elevated temperatures during the x‐ray exposures. At the critical temperature T_c=388°C, S suddenly dropped to zero. Above T_c short range order was found to exist, the amount present being specified by a set of parameters σ_i which are associated with the interatomic distances r_i. The dominant short range order parameter σ₁, referring to nearest neighbors, was evaluated as 0.50 for 540°C and 0.25 for 750°C.