Estimation of Interfacial Energies Based on the Shapes of Coherent Intragranular Precipitates

In a study of the precipitation and aging of Invar particles in Cu, we observed that the particles evolved from spherical to cuboidal as they grew in size. This behavior has been observed in other systems, and predicted by Voorhees et al. ; they showed that the precise shape of the particle is a balance between elastic anisotropy and surface energy. The correlation between our results and their predictions are very good. It is the purpose of this note to point out that simultaneous measurements of size, shape, and mismatch of a coherent particle can be used to estimate the interfacial energy under favorable conditions.Ternary alloys consisting of Cu - 12.8 wt% Ni -7.2 wt% Fe were arc-melted, held at 1030°C to develop extended regions of the Cu-rich solid solution, quenched, then aged at various times and temperatures to develop FCC precipitates near the Invar composition in the FCC Cu matrix.

K Absorption Edge Magnetic Circular-X-Ray Dichroism of Fe-Ni Alloys

We report Magnetic Circular X-ray Dichroism (MCXD) measurements in Fe-Ni alloys. We used an energy dispersive beamline in our measurements. A polychromator spectrum contains self reference both in intensity and energy since all energies are measured at the same time and remain stable during an energy scan since no movement of the X-ray optics is necessary. We measured the K absorption edges in Fe and Ni (s - p electronic states) in the à ferromagnetic alloys of Fe-Ni. We observe that the signal at the invar composition is of comparable strengh as other compositions in contrast to previous studies. We used cold rolled (disordered) foils instead of powders. The measurements reveal changes of the MCXD signal with composition and crystal structure.