Influence of Structure Development on Performance of Copper Composites Processed via Intensive Plastic Deformation

Abstract

Designing a composite, possibly strengthened by a dispersion of (fine) oxides, is a favorable way to improve the mechanical characteristics of Cu while maintaining its advantageous electric conductivity. The aim of this study was to perform mechanical alloying of a Cu powder with a powder of Al2O3 oxide, seal the powder mixture into evacuated Cu tubular containers, i.e., cans, and apply gradual direct consolidation via rotary swaging at elevated temperatures, as well as at room temperature (final passes) to find the most convenient way to produce the designed Al2O3 particle-strengthened Cu composite. The composites swaged with the total swaging degree of 1.83 to consolidated rods with a diameter of 10 mm were subjected to measurements of electroconductivity, investigations of mechanical behavior via compression testing, and detailed microstructure observations. The results revealed that the applied swaging degree was sufficient to fully consolidate the canned powders, even at moderate and ambient temperatures. In other words, the final structures, featuring ultra-fine grains, did not exhibit voids or remnants of unconsolidated powder particles. The swaged composites featured favorable plasticity regardless of the selected processing route. The flow stress curves exhibited the establishment of steady states with increasing strain, regardless of the applied strain rate. The electroconductivity of the composite swaged at elevated temperatures, featuring homogeneous distribution of strengthening oxide particles and the average grain size of 1.8 µm2, reaching 80% IACS (International Annealed Copper Standard).

Structural Phenomena Introduced by Rotary Swaging: A Review

“…Therefore, IPD and SPD methods are also highly advantageous for processing materials with challenging formability [52,53], multiphase materials [54][55][56], shape memory alloys [57,58], or various composites [59,60]. Moreover, the generally advantageous combination of compressive stress state and high shear strain is also favorable for the direct consolidation of powders [61,62].…”

“…Moreover, by varying the processing conditions, the optimization of the properties of mutual Al-Cu interfaces can be achieved [94,100,101], see also Figure 4a Cu has also advantageously been combined with other metals to prepare various composites, for example Tian et al [102] combined Cu with Mg to fabricate a laminated wire via cold RS; by applying a reduction of up to 71%, they achieved wires with the UTS reaching 290 MPa and an electric conductivity of up to 81.1% IACS. Yu et al [103] used RS at 950 °C to manufacture a W-Cu composite from original powders, the deformation processing not only provided favorable strength but also ensured the density exceeding 99%, whereas Kocich et al [62] used RS at both room and elevated (400 °C and 600 °C) temperatures to fabricate Cu composites reinforced with Al2O3 particles featuring UFG microstructures (average grain size refined down to 1.2 µm 2 for the composite swaged at room temperature). An UFG composite combining Al2O3 particles and an Al matrix was prepared at room temperature RS by Kunčická et al [60].…”