A comparative analysis of the microstructure and mechanical properties of commercially pure copper and Cu-Al hybrid samples processed by the High Pressure Torsion Extrusion (HPTE), a novel technique of severe plastic deformation (SPD) had been performed. The new HPTE technique allows to achieve large strains (up to 30) during just one pass in large-scale rod specimens with the diameter of 10 mm and the length of 35 mm. Figure 1 schematically illustrates the HPTE process along the extrusion direction with composite Cu samples with embedded Al wires before and after one HPTE pass with translation velocity 3 mm/min and angle velocity 1 mm/min.
Room temperature mechanical tests, optical and scanning electron microscopy microstructure investigations of the as-processed samples were performed.
In pure copper a gradient structure of different types: coarse-grained, fine-grained and ultrafine-grained depending on HPTE regimes was detected. Applied HPTE regimes provided strong grain refinement in pure copper from 20 – 30 to the 0.3 – 0.4 micrometers.
In hybrid Cu-Al samples the variation of the shape of Al wires was monitored. It was found that Al wires got thinned as a result of HPTE processing, upon that wire thickness depends on its distance from the sample center. In the middle-radius areas initially 1 mm diameter wires were thinned to the tapes with the thickness of 20-30 micrometers, whereas in the edge areas their thickness was 2-3 micrometers, which reflects the strain gradient at HPTE. The influence of the HPTE regimes on the microstructure and mechanical properties of gradient and hybrid samples will be discussed.