The effect of cold working and solution heat treatment on microstructure and mechanical behavior of Ti35Nb2.5Sn alloy

Recently, β Ti alloys have been extensively studied, due to their advantageous properties. β titanium alloys can exhibit lower elastic modulus and may be produced by elements that do not exhibit cytotoxicity, such as niobium, molybdenum and zirconium. This study aims to evaluate the correlation between cold working and solution heat treatment regarding to the microstructure and hardness of the Ti35Nb2.5Sn alloy. The alloy was arc melted in inert atmosphere and the ingots were hot rolled with 40% reduction. Axial compression samples were then cold worked with 40%, 70%, 80% and 90%. After the cold working, the samples were then divided into two groups. In half of them, solution and quenching treatment was performed. Microstructural characterization was achieved by optical microscopy and X-ray diffraction. Vickers microhardness tests were also evaluated. The microstructural characterization confirmed the presence of β, α” and ω phases. Cold working above 70% reduction provides the increase of microhardness, which can be attributed to the grain refinement and others microstructural features, as the amount of strain induced α”, the amount of the ω phase when it is present, and also by the dislocation density.