Densification, microstructure, and nanomechanical evaluation of pulsed electric sintered zirconia-silicon nitride reinforced Ti-6Al-4 V alloy

In this study, the influence of silicon nitride (Si_3N_4) and zirconia (ZrO_2) ceramics was examined on the titanium alloy using the pulsed electric current sintering technique to investigate the microstructural behavior, densification, and nanomechanical properties of these composites. Si_3N_4 and ZrO_2 were dispersed in Ti-6Al-4 V at a functional pressure of 50 MPa, a sintering temperature of 1200 °C, a heating rate of 100 °C/min, and a holding time of 10 min. The ternary composite samples were prepared viz, Cs1 (Ti6Al4V- 3 vol.% Si_3N_4- 15 vol.% ZrO_2), Cs2 (Ti6Al4V- 3 vol.% Si_3N_4- 10 vol.% ZrO_2), and Cs3 (Ti6Al4V- 3 vol.% Si_3N_4- 5 vol.% ZrO_2). The bulk morphology of the composites was studied using scanning electron microscopy (SEM) equipped with EDS, and the phase contents were identified with an X-ray diffractometer (XRD). The relative density results for the tri-composites showed that the Cs1 sample recorded the highest at 99.94%, producing a fully dense sintered composite. However, there was a drop in the relative density of composites Cs2 and Cs3, recording 97.73% and 97.11%, respectively, comparable to the unreinforced Ti-6Al-4 V alloy with 98.65%. The nanoindentation examination conducted for the trio-composites showed linear mechanical responses/improvement, with Vickers hardness, from 589.31 to 865.70 MPa; nano hardness, from 6.466 to 9.441 GPa, and elastic modulus, from 113.52 to 185.95 GPa.