Behaviors of the interface and matrix for the Ag/Cu bimetallic laminates prepared by roll bonding and diffusion annealing

The Ag/Cu bimetallic laminates were prepared by roll bonding at different temperatures and annealing for different times at 673 and 1023 K. Their microstructure, composition and hardness were investigated in the matrix or diffusion zone of the laminates. Dynamic recrystallization induced in rolling process produces the mixture microstructure containing deformed and equiaxial grains. There exists an incomplete recrystallized structure for the laminates annealed at 673 K and a polygonal grain structure for the laminates annealed at 1023 K. The grain size in the strip matrixes increases with increasing rolling or annealing temperature. Recrystallization process during rolling or annealing causes the hardness reduction. The reduction is more significant in the Cu side of the laminates rolled at 873 K and in the strip matrixes annealed for 0.5 h. Faster velocity of Cu atom moving into the Ag side than Ag atom into the Cu side results in a position shifting of Cu concentration curve in the Ag side. The shifting becomes more significant with prolonging annealing time. In the Ag side of the laminates annealed at 1023 K, there is a region of fine equiaxial grains along original interface and its width increases with prolonging annealing time. Some Cu-rich particles precipitate along grain boundaries in the fine grain region and can slightly harden the Ag strip component.