Machinability Research and Workpiece Microstructure Characterization in Turning of Ultrafine Grained Copper

Abstract

Various methods for production of bulk ultrafine grained/nanostructured materials have been developed. They can be classified into two categories based on their approaches: the bottom-up and top-down approaches. Recently, a top-down approach named equal channel angular extrusion (ECAE), a form of severe plastic deformation (SPD), has been gaining more and more attention in making bulk ultrafine grained/nanostructured materials. Such bulk materials are favored for there high strength, wear resistance, ductility, and high strain-rate superplasticity, which makes them suitable for light weight engineering and medical applications. Further precision machining work is normally indispensable for structural applications after bulk ultrafine grained/nanostructured materials are manufactured from any SPD processes. While researchers are increasingly interested in commercially producing SPD-processed bulk ultrafine grained/nanostructured materials and characterizing their chemical and physical properties, the machinability and microstructure stability issues in precision machining such materials are frequently ignored. Using an ECAE processed bulk ultrafine grained copper bar as an example, this study investigates the machinability as well as machining-induced workpiece microstructure variation of such ECAE processed materials in precision turning. Tool cutting performance in turning the ultrafine grained copper bar is also compared with that of the regular copper bar.