Chemical Short Range Order in Molten MnCu and MnSn Alloys of the Null-Matrix Composition

Abstract

Neutron diffraction experiments have been made on molten alloys Mn_67.4Cu_32.6 and Mn_62.6Sn_37.4 which have the “null-matrix” composition. The scattered intensity distributions for these alloys have been corrected for paramagnetic neutron scattering and they then relate to composition fluctuations alone. They have been analysed to yield the Radial Concentration Function (RCF). The RCFs for both alloys give a clear indication of true short range order—a preference for unlike first neighbours. The curves are discussed in terms of expected first neighbour distances and the atomic correlations in the stable crystalline phases. Comparison is also made between the values of the chemical short range order parameter a, estimated from the RCFs and the measured values of the enthalpy of mixing AH.

Key Words:

• Null-matrix composition
• molten alloys
• radial concentration function.