Structural evolution of medium range and short-range order with temperature in Cu-25 wt.% Sn

The structure of Cu-25 wt.% Sn in the liquid state with different temperatures has been determined by using X-ray diffraction studies. It has been found that there exists not only short-range order (SRO) but also medium-range order (MRO) in the melt of Cu-25 wt.% Sn alloy. Distinct pre-peaks have been found in front of the main peak of the total structure factor. Pre-peak positions shift to the large-Q side with increasing temperatures. Structural unit sizes corresponding to the pre-peak are not unchanged and thus, MRO in the Cu-25 wt.% Sn is unstable. The nearest neighbor distance, the coordination number and the atomic density present a identical variation trend in the range of 1000–1200 °C, which shows that structural variation of SRO occurs at 1000 °C.