Equal channel angular pressing of Cu-Al bimetallic rods

Abstract

Coextrusion and corolling are the major processes to produce bimetallic rods, tubes and wires, the objective being to perform clad metals, bimetallic joints or seals. The aim of the present work is to produce bimetallic rods showing an ultra fine grained microstructure with enhanced properties. Bimetallic Cu-Al rods were deformed by equal channel angular pressing (ECAP) in order to study their microstructure. ECAP is an int eresting process for producing bulk materials with refined microstructure and, consequently, chan ges in physical, chemical and mechanical properties can be observed. Higher shear strength a nd dimensional stability are among the advantages of this process. A comparative experimen tal study of pure commercial copper with cylindrical inner aluminium rods of different diame ters processed by one-pass equal channel angular pressing has been carried out. The ECAP die used in this research was a 90º 2-channels intersecting angle. Electron backscattered (EBSD) a nd X-ray diffraction techniques were used for microstructure characterization (deformation, grain fragmentation and microstrain evaluation) at the interfaces and away from them. It was found that th e microstructure in the ECAP deformed Cu-Al bimetallic rods was influenced by the dimensions of the aluminium inner rod. In fact, the microstructure appeared to be much more elongated a nd refined in the samples containing smaller diameter aluminium rods.