Characterization of Cu-5Fe (wt.%) fabricated by powder consolidation using high-pressure torsion

Abstract

Bulk pure Cu and Cu-5Fe (wt%) materials were successfully fabricated at room temperature by powder consolidation using high-pressure torsion (HPT) processing through 30 turns under a pressure of 6 GPa. The microstructure, texture and mechanical properties of the fabricated bulk discs were systematically characterized across their diameters using electron backscatter diffraction, scanning electron microscopy, transmission electron microscopy, X-ray diffraction and Vickers microhardness. Additionally, their thermal stability was evaluated after annealing treatment at 500 °C for 6 h. The results show that two grain refinement stages occurred in the Cu disc accompanied by the formation of partial A-fibre (\({A}_{1}^{*}\)/\({A}_{2}^{*}\) and A components). The dynamic recrystallization was delayed in the Cu-5Fe disc owing to the pinning effect of Fe content. Consequently, the grain refinement was more effective, and the texture gradually developed the B, A and \({A}_{1}^{*}\) components. The Cu-5Fe disc was harder than the Cu disc, and the microhardness increased across the disc diameter. Rapid grain growth with a high amount of Cu₂O oxide and retained texture were the main characteristics of the annealed Cu disc. The precipitation of Fe phase during annealing led to the development of a duplex microstructure at the centre and mid-radius positions and a stable microstructure at the edge of the Cu-5Fe disc. Eventually, the annealing texture was transformed into a complete A-fibre (\({A}_{1}^{*}\)/\({A}_{2}^{*}\) and A/\(\overline{A }\) components) which was quite similar to the Cu disc. The microhardness decreased after annealing but it was more homogeneously distributed across the disc diameter than the HPT-processed disc. The results were discussed based on the different grain refinement mechanisms, static recrystallization mechanisms, solute elements, dislocations and annealing twins.