A novel characterization technique for quantifying solute segregation and primary phase formation in rapidly solidified spray-atomized powders is presented. The method uses the twopoint correlation function to analyze solute concentration maps obtained by X-ray tomography analysis. The two-point correlation function analysis enables a statistical characterization of the scale of structure in solidified powders, yielding information about the in-plane primary phase size, spacing, and anisotropy as a function of depth through the sample. The technique is used to study the microstructure of Al-Fe powders solidified at different cooling rates. The change in spacing as a function of cooling conditions and depth through several samples is characterized.
Tin-rich, Sn-Au solder films were fabricated using electrodeposition, from a suspension composed of a Sn electrolyte with suspended Au particles. The Sn-rich eutectic alloy offers a potentially cheaper alternative to the Au-rich eutectic for optoelectronic and MEMS device packaging and may be applicable as a Pb-free solder for microelectronic packaging. Eutectic and near-eutectic deposits, with uniform thicknesses and compositions were fabricated. Gold content in the deposits increased with increasing Au particle loading in the electrolyte and increasing current density. Room temperature aging led to the formation of AuSn4 at the Au particle-Sn matrix interface. Reflow of deposits with near-eutectic compositions resulted in the formation of the two eutectic phases, Sn and AuSn4.
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