Evolutions in precipitates, microstructure and properties of cold-worked CuNiCoSi alloy during short-time solid solution

Abstract

The CuNiCoSi alloy is a promising precipitation strengthening Cu alloy, while the high content of alloy elements in it increases the difficulty of solid solution, thus it is essential to understand the evolutions of the alloy during solid solution. In this study, the cold-rolled CuNiCoSi alloy were precisely solid solution treated for 15–120 s and then partially aged, and the influences of solution time (ST) on the precipitates, microstructure and properties of the alloy were investigated. High density (Ni,Co)xSi precipitates, dislocations and deformation texture were found in the cold-rolled CuNiCoSi plate. Decomposition of the precipitates, elimination of the dislocations and grain recrystallization occur during the period between 15 and 30 s. Then, the grain size grows with increasing ST but the residual precipitates change little. The strength of the solution treated specimens decreases with increasing ST, while that of the solution+aging treated specimens increases with increase of the previous ST, and both become almost stable after solution for over 30 s. It is demonstrated that recrystallization and precipitates decomposition of the cold-worked CuNiCoSi alloy occur within a short time at a high solid solution temperature, and sufficient decomposition of the precipitates with little grain coarsening can be achieved through reduce and precise control the ST, while prolonging the ST is negative to the strength and ductility of the alloy.