Load partition and microstructural evolution during hot tensile tests of unreinforced and TiC particle reinforced in Ti-6Al-6V-2Sn

Load partition in multiphase materials can be studied by means of in-situ high energy synchrotron diffraction (HEXD). An example of the capabilities of this technique was applied to an unreinforced and two particle reinforced Ti-6Al-6V-2Sn alloys with 12 vol.% and 20 vol.% of TiC particles, with higher E and better wear resistance than the matrix. This matrix contains larger amount of beta phase than Ti-6Al-4V and its service temperature is raised up to 315°C due to the addition of Sn. The alloys, produced by a powder metallurgy route, exhibit lamellar microstructure of the alpha phase with inhomogeneous distribution of the TiC particles for the composites. In-situ HEXD experiments were carried out during tensile tests at 750°C to determine the load partition between alpha, beta and TiC and their plastic deformation mechanisms. The reinforced alloys show higher ultimate strength than the matrix owing to the smaller size of the alpha lamellae. Nevertheless, the subsequent softening is more noticeable for the composites. The in-situ method allows following the rotation of the alpha phase and the increment of the misorientation in the beta phase within individual grains during the deformation. The small gauge volume of the synchrotron beam compared to the grain size allows studying regions with high particle concentration which are capable of bearing load, although in average the reinforcement is not efficient for strengthening owing to its non-homogeneous distribution. The stress concentration between particle clusters and debonding between matrix and particles during deformation are also studied.