In brittle composites, spontaneous microcracking might occur due to the presence of residual stresses. As microcracking has a significant influence on the properties of composite ceramic materials, it is important to understand the mechanism of microcrack formation in order to introduce a controlled amount of microcracking. However, there are fairly few materials where toughening by microcracking has been rigorously verified. Fully validated examples of microcracking toughening are restricted to the composite materials such as zirconia toughened alumina (ZTA) [1], SiC/TiB2 [2] and some of the liquid-phase sintered SiC ceramics [3]. The appropriate addition of additives plays an important role in improving physical and mechanical properties of ceramic composites [4, 5]. Various additives such as the rare earth, the oxide of alkaline metals, metallic elements and carbon, and so on, have got wide applications in both structural and functional ceramics. Specifically, the addition of carbon is beneficial for sintering and improvement of the properties of SiC/TiB2/TiC ceramic composite [6]. Moreover, it was reported by Sigl et al. [7] that the fracture toughness of B4C/TiB2 ceramic was notably increased because of the addition of a certain amount of free carbon. On the other hand, Al2O3/TiC composite is one of the popularly used structural ceramic materials. Since the 1970s, a great deal of research work has been done focusing on the microstructure, mechanical property and engineering performance of Al2O3/TiC composite [5, 8–10]. Sintering aids like MgO, TiO2, Y2O3, TiH2, Ni and Mo, etc. has been adopted in the fabrication of Al2O3/TiC composite for high density and properties [10–14]. In the present study, a certain amount of free carbon is purposely incorporated into Al2O3/TiC ceramic composite. Attempts have been made to investigate its influence on the microstructure and fracture toughness of the material. High purity Al2O3 and TiC powders were used as the starting materials with average sizes of 0.5 and 0.8 μm, respectively. Al2O3 was blended with TiC (30 vol.%) and doped with different amounts of phenolic resins to yield samples with varying amounts of free carbon additives in the as-sintered bodies. The mixtures were subsequently homogenized with alcohol media in a ball