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

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 heattreated, 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 beta titanium alloy. When deformation in beta region, the deformation mechanism was associated with cDRX by lattice rotation and dynamic recovery; when deformation in (alpha + beta) 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 (alpha + beta) region and 181.8 kJ/mol in the beta region. According to the processing map, the optimum deformation windows are 770-800 degrees C and 850-880 degrees C, 0.001 s-1. In addition, the microstructure of 770R + SAT is characteristic of duplex microstructure with a certain amount of alpha p, considerable precipitation of fine acicular alpha s and continuous alpha 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).