The type of order in Cu-10 at.% Au - Evidence from the diffuse scattering of X-rays

In a recent publication, Kuhlmann ct ai. (Acta mater., 1997, 45, 3319) clai med Cu-10 at.% Au to be long-range ordered at temperatures above 473 K and as high as 723 K. This is in contrast to the generally accepted phase diagr am where this region is attributed to the range of solid solutions. To clar ify this problem, a three-dimensional diffuse X-ray scattering experiment w as performed at room temperature on a Cu-10 at.% Au single crystal aged at 573 K. The Warren-Cowley short-range order parameters derived from this exp eriment show conclusively that only short-range order is present. Effective pair interaction parameters determined by the inverse Monte-Carlo method a re somewhat different from those obtained for Cu-25 at.% Au in the short-ra nge ordered state. (C) 1999 Acta Metallurgica Inc. Published by Elsevier Sc ience Ltd. All rights reserved.