Studies of intergranular and intragranular stresses in cold-rolled CuNiSi alloys

Applying cold rolling after solution treatment and before aging has been approved to be effective in increasing the strength and electrical conductivity in the Cu–Ni–Si alloys. The present work aims at identifying the evolution of the microstructures and stress states in the aging process of the cold-rolled Cu-2.29 wt%Ni-0.49 wt%Si (Cu-2.29Ni-0.49Si) by means of advanced electron microscopy analysis techniques (SEM-EBSD and TEM) and synchrotron-based high-energy x-ray diffraction techniques (ex-situ and in-situ tension test). Deep attention is paid on the evolution of intergranular and intragranular stresses during aging. A large grain-orientation-dependent intergranular stress is observed in the cold-rolled alloys, which is reduced as extending the aging time. Meanwhile, the intragranular stress is also detected, which keeps stable in the aging process. At last, the individual contributions to the overall electrical resistivity in the aging process are discussed.