Microstructure Evolution in Cu-0.5 wt% Zr Alloy Processed by a Novel Severe Plastic Deformation Technique of Rotational Constrained Bending

Abstract

In the present study, a coarse-grained Cu-0.5 wt% Zr alloy was repeatedly processed by a novel technique of rotational constrained bending (RCB). In this technique, the workpiece was deformed by bending in a channel with an angle of 90 degrees, using a rotating roller. The influence of the number of passes (N) of RCB on strain distribution, microstructure evolution and mechanical properties of the alloy was investigated. The heterogeneous distribution of the microhardness in the billet cross-section after the first pass was transformed into a homogeneous one after twelve passes, due to the rotation of the sample by 90 degrees clockwise between individual passes. In addition, the gradual refinement/homogenization of the microstructure and formation of strong (110) crystallographic texture were found with increasing N. The initial grain size of 180 mu m decreased down to 3.4 mu m after twelve passes. The dislocation density increased by two orders of magnitude after RCB processing. In accordance with the grain-size refinement and the strong increase of the dislocation density, RCB processing significantly enhanced the strength of the alloy, while the ductility considerably decreased. The yield stress increased from 63 to 524 MPa, while the elongation to failure decreased below 10% after twelve passes.