Modeling the texture evolution of Cu/Nb layered composites during rolling

Metallic based multi-layered nano-composites are recognized for their increased plastic flow strength and indentation hardness, increased ductility, improved radiation damage resistance, improved electrical and magnetic properties, and enhanced fatigue failure resistance compared to conventional metallic materials. One of the ways in which these classes of materials are manufactured is through accumulated roll bonding where the material is produced by several rolling and heat treatment steps during which the layer thickness is reduced through severe plastic deformation. In this article, a single rolling pass of the accumulated roll bonding process in which a Cu/Nb layered composite with an initial average layer thickness of 24 μm subjected to a 50% height reduction is examined. Experimental morphological and crystallographic texture data is presented and used to initialize numerical models for these layered material systems. This study focuses on the Cu/Nb combination of fcc/bcc materials for incoherent material interfaces. A single crystal model based upon thermally activated dislocation motion is used and the evaluation of material parameters is presented. Since the initial state of the composite is not in a fully annealed condition, nano hardness tests for both the Cu and Nb layers are used to initialize the model for each of the two materials. EBSD data of the heat treated material is used to characterize the initial state of the composite and used to produce 40 combined morphological and crystallographic numerical model realizations of the material. Each of the models is then imposed to a plane strain compression deformation height reduction of 50%. Numerical data from the 40 simulations was then combined to arrive at the statistically comparable crystallographic texture for each of the Cu and Nb materials. This data was compared with the experimental data and the results suggest very good agreement between the predicted and experimental textures for both the materials. Selected stress profile predictions for two realizations are presented and demonstrate a strong difference in stress state between the Cu and Nb layers.