The cold drawing of cast Cu 100Àx Zr x (x ¼ 3, 4 and 5 at%) alloys to the reduction ratio of 99.7% was found to cause simultaneous achievement of ultrahigh tensile strength of 1350 to 1800 MPa and high electrical conductivity of 30 to 45%IACS (International Annealed Copper Standard). The cold-drawn Cu 95 Zr 5 alloy wire has a well-developed fibrous structure of fcc-Cu and tetragonal Cu 9 Zr 2 phases. The volume ratio of the fcc-Cu phase was evaluated to be about 76%. A very high density of internal defects was observed inside the Cu 9 Zr 2 phase in the cold-drawn Cu 95 Zr 5 alloy. The microstructure data suggest that the Cu fibrous phase with high aspect ratios is the origin for the achievement of high electrical conductivity and the well-developed fibrous structure contributes to the high tensile strength. The success of synthesizing the Cu-Zr alloy wire with simultaneously high tensile strength and high electrical conductivity exceeding the best combination of all Cu-based alloys reported up to data is expected to be used as a new type of high-strength and high conductivity material because of some advantages of energy saving, low materials cost and simple production process.

Hypoeutectic CuZr binary alloys have originally been studied in order to develop wires with both high strengths and high electrical conductivities. This study aimed to improve the electrical conductivities of Cu0.5, Cu1 and Cu2 at% Zr alloys, which have Zr contents lower than those of high-strength Cu3, Cu4 and Cu5 at% Zr alloys. Cast rod samples, whose lengths and diameters were 180 and 12 mm, respectively, were prepared by copper-mold casting and wire-drawn to diameters in the range of 10.031 mm (drawing ratio, © = 4.811.1). The microstructures and mechanical properties of the obtained wires were investigated and compared to those of Cu3, Cu4 and Cu5 at%Zr alloy wires that had been investigated in a previous study.The eutectic phases found in the cast rods consisted of ¡-Cu primary phases and phases of the intermetallic compound Cu 5 Zr. The eutectic phases became isolated, like small islands, in the matrices, and their volume fractions decreased with a decrease in the Zr content. The orientations of the ¡-Cu and Cu 5 Zr phases around the boundaries of these eutectic phases were similar. After the wiredrawing process, the intermetallic compound in the eutectic phases transformed into Cu 9 Zr 2 in the case of the Cu0.5 at%Zr alloy and into Cu 8 Zr 3 in the case of the Cu1 at%Zr alloy. The electrical conductivity (EC) and ultimate tensile strength (UTS) values of the alloys depended on the volume fractions of their eutectic phases. However, the changes in these properties with the change in the drawing ratio were smaller than those in the case of the high-strength Cu3, Cu4 and Cu5 at%Zr alloy wires. The EC and UTS values of the Cu0.5, Cu1 and Cu2 at%Zr alloy wires drawn at values of © greater than 8.0 were 6183% IACS (International Annealed Copper Standard) and 6901010 MPa, respectively. When combined together, wires of the resulting hypoeutectic CuZr binary alloy exhibited EC and UTS values of 1683% IACS and 6902234 MPa, respectively. These results showed that instead of there being a tradeoff between these properties, the values of both these properties increased at the same time.

Round, bar-shaped ingots of hypoeutectic Cu4-and Cu5 at%Zr alloys were cast using the copper-mold casting method. The ingots were drawn into wires with a drawing ratio (©) of 5.9 or more. The relationship between the mechanical and electrical properties of these wires as well as their microstructure was investigated. It was found that the Cu5 at%Zr alloy wire drawn down to 40 µm in diameter with © = 8.6 exhibited an ultimate tensile strength (UTS) of 2234 MPa, 0.2% proof stress of 1873 MPa, total strain to fracture of 4.2%, Young's modulus of 126 GPa, and electrical conductivity of 16%IACS. As for the Cu4 at%Zr alloy, it could be wire-drawn down to 27 µm in diameter with © = 9.4.Both UTS and Young's modulus increase linearly with ©. A nanosized lamellar structure was noticed in the ¡-Cu and Cu 9 Zr 2 intermetallic compound phases. Furthermore, it was observed that a nanosized amorphous phase was formed within the layers of the Cu 9 Zr 2 intermetallic compound phase. The increase in the strength of the wire-drawn Cu4-and Cu5 at%Zr alloy is due to the synergistic effects resulting from the development of deformation twins in the ¡-Cu phase and the formation of the nanosized lamellar structure in the ¡-Cu and Cu 9 Zr 2 intermetallic compound phases.High electrical conductivity of 16%IACS was obtained for the wire-drawn Cu5 at%Zr alloy. This high value can be attributed to the low density of dislocations in the ¡-Cu phase. [

Microstructures and mechanical properties of CuBeCo alloys having four different Be contents prepared by simply heavy cold rolling (CR) were systematically investigated. The cold-rolled alloys exhibited excellent mechanical properties due to development of heterogeneous nano-structure (HN), which consisted of "eye"-shape deformation twin domains surrounded by shear bands, and they were further embedded in conventional low-angle lamellae. The strength of each alloy increased with increasing Be content. The volume fraction of the twin domains quantitatively evaluated by the texture analyses that increased with increasing Be content rapidly from 0.40 mass% to 1.27 mass% and gradually from 1.27 mass% up to 2.14 mass%. The latter stagnation was attributed to the formation of coarse intermetallic particles, which impeded the formation of the HN structure. It revealed that the strength was correlated closely with the volume fraction of twin domains.