Microstructural characterizations of Ni activated sintered W-2 wt% TiC composites produced via mechanical alloying

Blended W-2 wt% TiC powders were mechanically alloyed (MA'd) for 3 h, 6 h, 12 h and 24 h in a Spex Mixer/mill at room temperature. 1 wt% Ni was added as sintering aid after mechanical alloying to investigate the coupled effects of MA and activated sintering. MA'd powders were sintered at 1400 °C for 1 h under Ar, H₂ gas flowing conditions. Microstructural and phase characterizations of MA'd powders and sintered samples were carried out via SEM, TEM and XRD analyses. Whereas XRD investigations on MA'd powders revealed stable W and WC phases, those on sintered samples showed the presence of Ni in addition to the matrix W phase. TEM investigations on MA'd and sintered samples revealed the presence of the matrix W, TiC_0.62, Ni₄W and W₂C particles. Relative density values were about 94.2% for all sintered composites which did not change with MA, indicating that distribution of Ni is the dominant factor on densification. Microhardness values of the sintered composites varied between 5.4 GPa and 6.0 GPa which increased with increasing MA duration.