Loss in coherency and coarsening behavior of Cr precipitates in Cu-Ag-Cr alloy

The coarsening behavior of Cr precipitates in Cu-0. 1Ag-0. 5Cr alloy was investigated, and the effects of aging processes on the microstructure and properties were discussed. The results show that the radius for coherent/semi-coherent transition of the Cr precipitates is determined from TEM micrographs as 15-45 nm. The calculated value of critical radius for a particle begining to lose coherency is about 12.5 nm. The coherent (r < 15 nm) precipitates are found to coarsen and become semi-coherent during the passage of low-angle boundaries during recovery. The passage of high-angle boundaries through semi-coherent precipitates during recrystallization occurs by migration of the particle, resulting in the precipitates maintaining semi-coherent with the new grain.