## 3 Results  
### Characterization of the Samples and their Mechanical Properties  
A representative X-ray diffraction pattern corresponding to the sintered and polished Al\({}_{2}\)O\({}_{3}\)-TiC composites is shown in Figure 1. The pattern reveals that no contamination was detected, nor the presence of side reactions along the sintering of the powder.  
The polished and fractured microstructure of dense Al\({}_{2}\)O\({}_{3}\)-TiC composites was studied by SEM on 1 \(\upmu\)m polished surfaces, where the dark phases are for alumina grains, and the light ones are for titanium carbide grains (Figure 2).  
The microstructure analyses confirmed that the density of composites was the same as the theoretical value since no pores were observed.  
Figure 1: XRD pattern of the polished surface of Al\({}_{2}\)O\({}_{3}\)-TiC composites, where A is \(\alpha\)-alumina, and T is TiC.  
Figure 2: SEM micrographs of Al\({}_{2}\)O\({}_{3}\)-TiC composites: (**a**) polished surface of the sample with 30 vol.% TiC; (**b**) polished surface of the sample with 40 vol.% TiC; (**c**) fractured surface of the sample with 30 vol.%; (**d**) fractured surface of the sample with 40 vol.%. In the figure, alumina is dark, and TiC is light.  
Figure 3 shows energy-dispersive X-ray spectroscopy (EDX) maps of the polished surface of Al\({}_{2}\)O\({}_{3}\)-40 vol.% TiC composite, showing a homogeneous distribution of the elements throughout the sample and, consequently, indicating that the wet processing route was suitable for the fabrication of bulk materials. The main mechanical properties of sintered composites in comparison with a few properties of Al\({}_{2}\)O\({}_{3}\)-TiC (40 vol.%) cutting ceramic (K01, ISO) are shown in Table 1.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Material** & **Density 1** & **Flexural Strength 2** & **Hardness HV 2** & **Facture Toughness 2** \\  & [\%\(\varphi_{\text{ph}}\)] & \(\sigma_{f}\) [MPa] & [GPa] & \(K_{\text{{\tiny{L}}}}\) [MPa-m\({}^{1/2}\)] \\ \hline Al\({}_{2}\)O\({}_{3}\)-30 vol.\%TiC composite & 99 & 643 \(\pm\) 48 & 22.8 \(\pm\) 0.4 & 7.1 \(\pm\) 0.3 \\ Al\({}_{2}\)O\({}_{3}\)-40 vol.\%TiC composite & 99 & 687 \(\pm\) 39 & 23.3 \(\pm\) 0.3 & 7.8 \(\pm\) 0.4 \\ \hline Al\({}_{2}\)O\({}_{3}\)-40 vol.\%TiC 3 cutting & & & & \\ ceramic [51; 52; 53] & - & -637.0 & -13.5–14.0 & 3–5 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Mechanical properties of Al\({}_{2}\)O\({}_{3}\)-TiC composites with 30 and 40 vol.% TiC.  
Figure 3: The Al\({}_{2}\)O\({}_{3}\)-40 vol.% TiC composite: (**a**) polished surface of the sample; (**b**) combination map for phases in a composite; (**c**) distribution map of X-ray of individual element Ti K\(\alpha\); (**d**) distribution map of X-ray of individual element Al K\(\alpha\).  
The hardness of the composites increases as the TiC content increases because TiC is relatively harder than Al\({}_{2}\)O\({}_{3}\). The fracture toughness of the samples increases as the proportion of TiC additive increase in the samples. The inclusion of second phase particles in a matrix can hinder crack propagation and consequently increase toughness. Different toughening mechanisms, induced by interaction between the crack and microstructure, such as crack deflection and grain bridging by TiC grains, were observed and are presented in Figure 4, where the dotted red lines and solid yellow lines indicate the area where close-up was taken. The red and yellow arrows show the crack bridging and crack deflection by TiC. These mechanisms are effectively increasing the crack propagation resistance, resulting in an improvement in the fracture toughness.