Elevated temperature tensile behaviour of a Cu-4.5Ti alloy

The high temperature tensile properties of a Cu-4.5Ti alloy have been investigated in the temperature range from room temperature (RT) to 550 °C in solution treated (ST) and peak-aged (PA) conditions. Yield strength (YS) and tensile strength (TS) in solution treated condition were found to be independent of test temperature up to 350 °C followed by a marginal increase at 450 °C and decreased, thereafter up to 550 °C. In situ age hardening during testing at 450 °C resulting in the precipitation of ordered, metastable and coherent Cu4Ti, β′ phase is attributed to the increase in strength. Coarsening of β′ precipitate particles at 450 °C and precipitation of equilibrium phase β at 550 °C decrease the strengths. In the peak-aged condition, the YS and TS were found to be constant up to 350 °C, beyond which they decreased with increasing test temperature. The decrease in strengths beyond 350 °C in the peak-aged alloy is attributed to the coarsening of β′ precipitate particles, as well as precipitation of equilibrium phase β at 550 °C. High temperature tensile properties of Cu-4.5Ti are superior to those of Cu-Be alloy (C17200). Transmission electron microscope (TEM) analysis of the alloy confirms the presence of metastable and coherent Cu4Ti, β′ precipitate when tested at 450 °C and both Cu4Ti, β′ and equilibrium precipitate Cu3Ti, β at the test temperature of 550 °C in solution treated as well as peak-aged conditions. Ductile mode of fracture was observed in both solution treated and peak-aged conditions of the alloy tested at RT as well as at elevated temperatures, i.e. 350, 450 and 550 °C.