Unified Interpretation of the Short- and Long-Range Ordered States in Cu-Pt Alloys(Condensed Matter : Structure, Mechanical and Thermal Properties)

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This paper describes a unified interpretation of unusual short-range order diffuse scattering intensity distribution, the appearance of intensity maxima simultaneously at the special points L and X of the reciprocal space, and of the formation of a variety of long-range ordered structures, including less common structures, in the face-centered cubic Cu-Pt alloys. Reassessment is first made of the ordered structures on the Pt-rich composition side and then it is shown that all the structures in the alloys are systematically described adopting the static concentration wave model, originally developed by Khachaturyan, with the two kinds of waves, L1_1 wave and L1_2 wave, and their combination. These waves are assumed to be still alive at temperatures above the order-disorder transition point with appreciably decreased amplitude and coherency length and lead to the appearance of the two types of diffuse intensity maxima. Comparison is made with the ordering behaviors in the well-known Cu-Au alloys, in which ordered structures forming are described simply by the L1_2 waves and diffuse intensity maxima appear only at the X point and its equivalent positions. Discussion is made on the difference between the Cu-Au and Cu-Pt alloys taking into account of the uniqueness of Pt as an alloying element.
社団法人日本物理学会の論文
2005-09-15