Scaling up Segal's principle of Equal-Channel Angular Pressing

This paper focuses on scaling of Equal-Channel Angular Pressing (ECAP) from conventional, laboratory scale (billet cross section 15 x 15 mm(2)) to large scale (50 x 50 mm(2)). We study pure copper billets produced by ECAP in two identical ECAP-dies (but with different cross-sections) that have been optimized to provide reduced contact friction. In order to characterize processing parameters and the resulting properties, the billets are processed by 4 and 8 passes on both scales. Mechanical and microstructural characterization is performed by hardness testing and EBSD measurements. The materials produced in the different scales show very similar properties. A slight top to bottomhardness gradient (<6 %) is detected in the billets on both scales. After 4 passes, this gradient is also reflected in grain size distributions. The higher cumulated strain after 8 passes leads to a more homogenized microstructure, again with similar grain sizes for both scales. Our results show that there are no scaling effects regarding the mechanical properties and the microstructures when comparing laboratory and large scale ECAP. This study clearly highlights the potential for scaling ECAP (using a suitable die-design) for a commercial implementation of ultrafine-grained materials. (C) 2016 Elsevier Ltd. All rights reserved.