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In this paper, high-density (60−x)Fe−Cr−Co−xCu (x: 0–6 wt.%) permanent magnet alloys were fabricated by laser powder bed fusion (LPBF) in-situ alloying technique, and the effects of Cu content on the microstructure, magnetic, and mechanical properties of the alloy were systematically investigated. The addition of 2 wt.% Cu enhanced the coercivity H c and the energy product (B H) max of the alloy in the isotropic state by 19.4 and 27.9%, respectively, compared to the alloy without Cu. The impacts of Cu content on the magnetic properties were investigated by combining experimental results and first-principles calculations. Furthermore, the addition of Cu improved the yield strength of the alloy, and the strengthening mechanism was analyzed in detail. The yield strength of the alloy with 2 wt.% Cu reached 908 MPa, representing a notable 7% increase relative to the Cu-free alloy. [ABSTRACT FROM AUTHOR]

The paper focuses on thermal and electrical properties of copper-graphite composites. Copper-graphite composites in the range of 0-50 vol% of graphite were prepared from the mixture of copper and graphite powder by the powder metallurgy method. Such composites combine high thermal and electrical conductivities provided by copper matrix and low thermal expansion coefficient and lubricating properties due to the graphite phase. We model thermal and electrical conductivities and thermal expansion coefficient using methods of micromechanics in connection with the material microstructure and measure these quantities experimentally to compare with the results of modeling. Cross-property connections between thermal and electrical properties of the composites are established and experimentally verified. [ABSTRACT FROM AUTHOR]

The φ16 mm single-crystal copper rod billet was prepared by the heated mold horizontal continuous casting process. After cold drawing + 600 °C× 5 s annealing to φ1 mm, the annealed φ1 mm single-crystal copper processing wire was cold drawn to φ0.2 mm (φ1 mm → φ0.2 mm), and the electrical conductivity, tensile strength and microstructure evolution of single-crystal copper wire were compared and analyzed. The research shows that the conductivity of the as-cast single-crystal copper rod is 102.1% IACS, the tensile strength is 141 MPa, the conductivity is as high as 97.26% IACS, after cold drawing to φ0.2 mm, and the tensile strength is greatly increased to 506 MPa. Compared with the as-cast properties, the electrical conductivity of the as-drawn wire is only reduced by 4.7%, while the tensile strength is increased by 258.9%. The as-cast rod exhibits typical characteristics of single-crystal copper; with the increasing amount of deformation, the microstructure evolves in the following form: dislocations generated by slip entanglement into dislocation cells → microstrip structure → layered structure → twin structure. A prediction model for the strength and electrical conductivity of single-crystal copper wire was constructed. The results show that grain refinement strengthening and dislocation strengthening are the key factors affecting the strength and conductivity of single-crystal copper wire, when deformed to φ0.2 mm, and twinning strengthening is superimposed in the above strengthening mechanism. [ABSTRACT FROM AUTHOR]

In this study, graphite/copper composites were prepared by microwave sintering. The microstructure and properties of the composites were characterized. The effects of different sintering temperatures on the properties of the composites were studied, and the differences between microwave sintering and conventional sintering composites were compared. The results show that after microwave sintering, the grain size of the copper matrix is refined and the graphite/copper interface is improved, and the distribution of graphite over the matrix becomes more uniform. Compared with conventional sintering, the properties of microwave-sintered samples have been further improved. Besides, with the increase in sintering temperature, the density, hardness, electrical conductivity and thermal conductivity of the composite have been improved, and some properties have become anisotropic obviously. Thus, the electrical conductivity and thermal conductivity along the direction of graphite sheet are higher than those perpendicular to the sheet. [ABSTRACT FROM AUTHOR]

Pure Cu and an Al-3 %Mg-0.2 %Sc alloy are processed by high-pressure torsion with ring-shape samples having an initial thickness of 4 mm. Microstructural observation across the thickness is carried out using optical microscopy and transmission electron microscopy to correlate with hardness variation. It is shown that the strain is introduced more intensely in the center of thickness on the cross sections for both pure Cu and the Al alloy. This area expands with an increasing number of revolutions but the expansion saturates before covering the entire cross section. Softening occurs with straining in pure Cu but saturation reaches without softening in the Al alloy. It is suggested that imposed strain is estimated using the thickness of severely deformed region. [ABSTRACT FROM AUTHOR]