Relationship between microstructure and mechanical properties of a spinodally decomposing Cu-15Ni-8Sn alloy prepared by spray deposition

A spinodally decomposing alloy of composition Cu-15 wt pct Ni-8 wt pct Sn processed by Osprey spray deposition was examined and the principal factors determining strength and ductility studied. Strengthening contributions are shown to arise from grain-size reduction by controlled recrystallization, and from the internal stress fields created by spinodal decomposition. Discontinuous precipitation takes place after the completion of spinodal decomposition and is partly responsible for the decrease of yield stress after such prolonged aging. At the same time, there is some loss of ductility, but the discontinuous precipitation is not believed to be the main cause. Instead, it is the appearance of additional phases, such as Ni3Sn, in the matrix that is considered to be the main cause of the brittleness.

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