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

• We scale up Equal-Channel Angular Pressing from laboratory scale to large-scale.
• We present an up-scaled die-design which significantly reduces contact friction.
• Hardness distributions as well as microstructures are very similar for both scales.
• We found no scaling effects when comparing laboratory and large-scale ECAP.
• Our study highlights the potential for scaling ECAP with a suitable die-design.

This paper focuses on scaling of Equal-Channel Angular Pressing (ECAP) from conventional, laboratory scale (billet cross section 15 × 15 mm2) to large scale (50 × 50 mm2). 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 bottom hardness 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.

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