Development and Microstructure of Cu–Zr Alloy Wire with Ultimate Tensile Strength of 2.2 GPa

Round, bar-shaped ingots of hypoeutectic Cu–4- and Cu–5 at%Zr alloys were cast using the copper-mold casting method. The ingots were drawn into wires with a drawing ratio (η) 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 Cu–5 at%Zr alloy wire drawn down to 40 µm in diameter with η = 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 Cu–4 at%Zr alloy, it could be wire-drawn down to 27 µm in diameter with η = 9.4.Both UTS and Young’s modulus increase linearly with η. A nanosized lamellar structure was noticed in the α-Cu and Cu9Zr2 intermetallic compound phases. Furthermore, it was observed that a nanosized amorphous phase was formed within the layers of the Cu9Zr2 intermetallic compound phase. The increase in the strength of the wire-drawn Cu–4- and Cu–5 at%Zr alloy is due to the synergistic effects resulting from the development of deformation twins in the α-Cu phase and the formation of the nanosized lamellar structure in the α-Cu and Cu9Zr2 intermetallic compound phases.High electrical conductivity of 16%IACS was obtained for the wire-drawn Cu–5 at%Zr alloy. This high value can be attributed to the low density of dislocations in the α-Cu phase.