In terms of mechanical properties, EHA samples exhibited the highest Vickers hardness of 4.96 GPa at a sintering temperature of 1250 °C. The Vickers hardness of EHA was observed to be governed by relative density and the reverse Hall–Petch relationship below a critical grain size (Dc) of 1.72 µm whereas beyond this particular point, hardness was governed by grain growth. On the other hand, the fracture toughness reached an optimum value of 1.14 MPa m1/2 at 1000 °C attributed mainly to the small grain size of 0.33 µm achieved at this sintering temperature.