The Partition Coefficients of Components in Cu-Ni-Mn Alloys

Dendritic microsegregation was calculated using a Scheil-based solidification model for three alloys: 50.1 pct Cu-25.8 pct Ni-24.1 pct Mn; 42.4 pct Cu-25.4 pct Ni-32.2 pct Mn; 34.3 pct Cu-26.2 pct Ni-39.5 pct Mn. The dendritic microsegregation in these alloys was investigated using energy-dispersive X-ray analysis. It was shown by calculation and experimental methods that in all three alloys, the partition coefficient (k) of manganese passes through the value k Mn = 1. This is shown by the presence of two maxima on the manganese concentration profile in the dendritic cell. It was calculated that the copper partition coefficient in these alloys should also pass through the value k Cu = 1; however, this has not been confirmed experimentally. The possible reason for this may be because of the inaccuracies in the phase diagram of the Cu-Ni-Mn system that was used and also in the difference of the copper and manganese diffusion coefficients in the alloy.