Grain refinement and mechanical properties of metals processed by constrained groove pressing

Abstract

Constrained groove pressing (CGP), as a new severe plastic deformation technique, can be used for fabricat ing high performance sheet materials. Because of its potential for largescale industrial production, CGP is prospective for application in aviation, aerospace, transportation and many other fields. In this work, Cu-Zr and titanium (CP-Ti) sheets were processed by CGP. Microstructures of these two kinds of sheets before and after CGP were analyzed and the grain sizes were moderately refined after two-pass CGP processing. Mechanical testing results show that Vickers hardness, yield stress and ultimate strength of Cu-Zr alloy after two-pass CGP increased by 70%, 273% and 64% respectively, while those of CP-Ti increased by 26%, 66% and 48% respectively comparing with the unprocessed material. These two kinds of materials exhibit pronounced positive st rain rate sensitivity (SRS) and the SRS of Cu-Zr alloy increases with increasing pass number of CGP, while the SRS of CP-Ti is not so sensitive. The strengthening mechanism analysis indicates that the stress elevation after CGP is mainly due to dislocation accumulation and interaction, while grain boundary strengthening is not significant. The grain refinement efficiency of CGP is comparatively studied with respect to other SPD methods.