Effects of composition and heat treatment on the mechanical behavior of Ti–Cu alloys

Ti alloys are applied extensively in several fields, particularly in the aerospace, chemical, dental and medical industries, due to their outstanding properties. The mechanical behavior of Ti alloys depends on microstructural characteristics that are dictated by the amount and type of alloying elements and the processing routes employed. The aim of this work is to evaluate the effect of the cooling rate, composition and heat treatment on the microstructure and mechanical behavior of Ti–Cu hypo-, hyper- and eutectoid alloys. To this end, samples of different compositions were prepared in an arc furnace with non-consumable tungsten electrode and a water-cooled copper crucible in a high purity argon atmosphere. The samples were then cast in an arc-melting centrifugal casting machine in an argon atmosphere and copper molds. To obtain a room-temperature microstructure with stable phases, some of the cast samples were then β solution-treated at 900 °C for 2 h and furnace cooled. Microstructural and mechanical characterizations were performed by X-ray diffraction, Vickers hardness measurements, scanning electron microscopy, transmission electron microscopy, tensile test, differential scanning calorimetry and ultrasonic methods for the determination of Young’s modulus. The microstructure of cast samples displays a martensitic structure and heat-treated samples a microstructure composed of α/α′ and Ti2Cu intermetallic phases formed during eutectoid transformation. The mechanical characterization of the cast samples show low ductility and high mechanical strength while the heat-treated samples display slightly higher ductility and low mechanical strength.