Reaction of nanocrystalline Cu-Sn alloy with Ga-In-Sn eutectic

An extended solid solution of Cu-20wt%Sn with lattice parameter 0.3715 nm, was obtained by mechanical alloying. Depending on the milling conditions, solid solutions with crystalline grain sizes ranging from 30 to 7 nm were obtained. A DSC trace of mechanically alloyed Cu-20w%tSn showed an exothermic effect at 643 K. X-ray diffraction of the sample after annealing at 643 K revealed the crystalline grain growth and the formation of an equilibrium solid solution with a lattice parameter of 0.3654 nm. The reaction of Cu-20w%tSn with a Ga-In-Sn alloy was studied at room temperature by measuring peak intensities of CuGa2 as a function of time: the reaction rate increased significantly when D decreased to 7 nm. Nanocrystalline powders are highly reactive and the mechanical alloying process can be used to control the reactivity of nanocrystalline solid solutions, used as components in low temperature solder pastes.