Change in the short-range order in binary Al-Mn melts during partial substitution of manganese atoms by nickel or cobalt

Abstract

The structure of ternary melts Al80Mn14.7Ni5.3 (at 1233 K) and Al66.6Mn16.7Co16.7 (at 1393 K), the compositions of which correspond to ternary intermetallic compounds, is studied by X-ray diffraction. Structural models are constructed for the melts using experimental structure factor curves and the reverse Monte Carlo method. The structural models are analyzed by the Voronoi-Delaunay method of partitioning. Local atomic ordering is shown to change noticeably when passing from binary Al-Mn to the ternary melts. The causes of the appearance of a prepeak and the asymmetry of the second maximum in the experimental structure factor curves are discussed. Correlations between the short-range orders in the ternary melts and crystalline and pseudocrystalline phases are found.