X-ray Diffraction Study of Short-range Order and Long-range Ordered Structure in Cu-87.5 at.% Pt Alloy (Condensed Matter: Structure, Mechanical and Thermal Properties)

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X-ray diffraction study was performed for the atomic arrangements in Pt-rich (87.5 at.%) Cu-Pt alloy with the cubic structure both in the disordered and ordered states using single crystal samples. In the disordered state obtained by quenching from temperatures above 800℃, short-range order (SRO) diffuse scattering intensity maxima were observed at X-point (100, 110 and their equivalent positions) and at L-point (1/2 1/2 1/2 and its equivalent positions). The appearance of the two kinds of intensity maxima is as previously observed in alloys with less Pt concentration, but the intensity ratio of the two maxima is different. The Warren-Cowley SRO parameters, α_<lmn>, were determined from the observed SRO diffuse scattering intensities and a significant lower value has been found for α_<200> The short-range ordered structure is interpreted as being formed as a result of competition between the X-point ordering tendency and the L-point ordering tendency in the alloy. At temperatures lower than 430℃, an ordered structure forms with superlattice reflections both at the X- and L-points. Inspection of the intensities of the reflections shows that the structure is cubic and of the Tang's type [Acta Crystallogr. 4 (1951) 377], which is expressed as the ABC_6-type structure. This, together with our previous finding in Pt-rich Pt-Mn alloys [Takahashi et al.: J. Phys. Soc. Jpn. 71 (2002) 681], is the first experimental confirmation of the presence of long-range ordered state in the alloy with such a low solute concentration as 12.5 at.% and this ordering behavior is characteristic of Pt-based alloys.
社団法人日本物理学会の論文
2003-07-15

X-ray Diffraction Study of Short-range Order and Long-range Ordered Structure in Cu-87.5 at.% Pt Alloy (Condensed Matter: Structure, Mechanical and Thermal Properties)

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