COMPOSITION DEPENDENCE OF TOPOLOGICAL AND CHEMICAL ORDERS IN LIQUID AL1-X(MNY(FECR)1-Y)X ALLOYS BY NEUTRON-DIFFRACTION

The composition dependence of the topological order in liquid Al(1-x)M(x) (M = Mn or FeCr) alloys was studied by measuring the neutron structure factors of alloys Al1-x(Mn0.304(FeCr)0.696)x (x = 0.14, 0.2, 0.267 and 0.4). The composition of the 3d metal mixture was chosen in such a way that its average coherent scattering length was equal to that of Al atoms, so that the S(NN) function was directly available from experiment. Important clues indicating a local icosahedral order have been found in the four liquid alloys. Three other neutron diffraction measurements have been performed with the 40 at. % Al liquid alloy with different Mn to sigma-FeCr atomic ratios, yielding an accurate determination of the three partial pair-correlation functions. The comparison between the local structures of Al80M20 and Al60M40 has shown that the strength of heteroatomic interactions is similar in both alloys, while the first MM and AlAl distances are significantly shorter in Al60M40.