Effect of Composition on the Strength and Electrical Conductivity of Cu-Ti Binary Alloy Wires Fabricated by Aging and Intense Drawing

The strength and electrical conductivity of Cu-Ti alloy wires fabricated by over-aging and intense drawing were investigated as a function of Ti content (2.7 to 4.3 at. pct). The microstructure of all over-aged Cu-Ti alloys before drawing showed mainly coarse cellular components laminating the plates of a terminal Cu solid solution and a β-Cu₄Ti intermetallic compound precipitated discontinuously by grain boundary reactions. The volume fraction of β-Cu₄Ti plates increased with Ti content, although the compositions of the two phases remained unchanged. When the over-aged alloys were drawn to the same deformation strain, the hardness and tensile strength of the wires increased monotonically with Ti content due to strain-induced strengthening; a high volume fraction of hard β-Cu₄Ti fibers formed from laminating plates during drawing promoted a high dislocation density in the matrix. The electrical conductivity of the wires decreased gradually with Ti content due to the higher volume fraction of β-Cu₄Ti fibers and due decomposition of the fibers during drawing. The overall performance of the Cu-Ti alloy wires improved as the Ti content increased and was superior to that of conventional Cu-Ti alloy wires fabricated by peak-aging and drawing, and to that of commercial Cu-Be alloy wires.