Microstructure evolution, mechanical properties and high temperature deformation of (TiB + TiC)/Ti–3.5Al–5Mo–6V–3Cr–2Sn–0.5Fe titanium alloy

Abstract

The addition of trace (TiB + TiC) reinforcements could minimize the deformation steps and decreases its costs according to recent study. In present work, the hot deformation behavior and microstructure evolution were studied via the isothermal hot compression at different temperature and strain rate. Based on the DMM model, the activation energy Q and processing map were obtained. Subsequently, two billets were hot-rolled and heat-treated, to study the microstructure and tensile properties of the alloy. Results revealed that the flow behavior of the (TiB + TiC)/Ti–3.5Al–5Mo–6V–3Cr–2Sn–0.5Fe alloy was similar with other near β titanium alloy. When deformation in β region, the deformation mechanism was associated with cDRX by lattice rotation and dynamic recovery; when deformation in (α + β) region, the deformation mechanism was associated with substructure evolution, such as DRX and dynamic recovery. The lower strain rate guarantees abundant time for microstructure transformation, while the higher strain rate leads local flow instability and cracks. The activation energies Q is 264.1 kJ/mol in (α + β) region and 181.8 kJ/mol in the β region. According to the processing map, the optimum deformation windows are 770–800°C and 850–880°C, 0.001 s −1 . In addition, the microstructure of 770R + SAT is characteristic of duplex microstructure with a certain amount of α p , considerable precipitation of fine acicular α s and continuous α GB , which is achieved a UTS of 1414 MPa with a poor ductility. Therefore, the (TiB + TiC)/Ti–3.5Al–5Mo–6V–3Cr–2Sn–0.5Fe alloy shows excellent deformability and higher strength, which is possible to achieve both high economy (less deformation step) and advancement (high mechanical properties due (TiB + TiC) reinforcements). • The deformation behavior of was associated with grain boundary sliding, dynamic recovery and dynamic recrystallization. • The UTS of 770R + SAT achieved 1414 MPa, which was slight higher than other Ti55531 or Ti1023 titanium alloy. • The fine acicular αs achieved high strength while the continuous αGB decrease the ductility. • The (TiB + TiC)/Ti–3.5Al–5Mo–6V–3Cr–2Sn–0.5Fe alloy was possible to achieve both high economy and advancement.