Severe plastic deformation at subzero temperatures: processing technology and effects on microstructure and mechanical strength of aluminum and copper alloys

Abstract

The subject of this proposal is the achievement of ultrafine grained materials by the application of severe plastic deformation (SPD). There are several techniques for applying high levels of deformation in order to reduce drastically the grain size of metals, below 1 micron, and thus improve the mechanical strength. Among these techniques, the most commonly employed are Equal-channel angular pressing (ECAP) and High-pressure torsion; SPD techniques can also be combined with other conventional processing techniques, seeking to optimize the strength-ductility pair. In this context, the processing temperature exerts an important role: in the recent literature, there are some evidences that SPD at very low temperatures can be an effective strategy to increase the accumulation of crystalline defects by suppressing dynamic recovery during deformation. This proposal aims to develop SPD techniques for low temperatures, close to that of liquid nitrogen, building on the experience of this group in applying such techniques at room and moderate temperatures, up to 400 ° C. The goal is to increase the ductility of the product, since this property is notably deficient in materials processed by SPD. The materials here employed are commercially pure Al and Cu and a 6xxx series aluminum alloy. The deformation processes are ECAP, conventional rolling and closed die cyclic forging (CDCF). This project proposes to develop SPD techniques performed at cryogenic temperatures and evaluate their effects on the resulting products, in terms of microstructure and mechanical properties (AU)