The progress and development of society can not be separated from the progress of materials. Materials as the pillar of contemporary civilization play a decisive role in various fields and have gradually become the material basis for human survival. Owing to its good stability in high temperature, high strain, corrosion, strong oxidation and other harsh conditions, ceramic materials are widely used to prepare various kinds of military and civilian materials, such as parts of automobile engines, protective appliances of armor and medical appliances [1–3]. However, owing to the interior bonding way of the ceramic material is high-energy covalent bond, which is difficult to break. Resulted in the lattice structure of ceramics are stable. The dislocation slip and deformation are hard to come into being when the ceramic material to be stressed, therefore, the ceramic materials will instantaneously rupture, it is the reason why ceramic materials are brittle [4–5]. Therefore, ceramics are mostly compounded with ductile fibers, ductile metal materials or polymer materials with excellent plasticity [6–9].
Alumina ceramics, which exhibit high hardness, high chemical stability, and suitable flexure strength, have attracted significant attention in recent years, and as a result, they have been commonly used in industry. However, their low fracture toughness limits their further development as a reliable ceramic material, therefore, the toughening and strengthening of Alumina ceramics is a research hotspot of ceramics [10–13]. The toughening of Al2O3 usually involves two ways: self-toughening and composite material toughening. The self-toughening means that in the process of sintering the seed of crystals is introduced within the matrix by phase transformation toughening of matrix. Composite toughening means that fiber, whisker, enhanced dispersion strengthening body, or good ductility of metal is introduced into the matrix to achieve the effect of toughening ceramic matrix. However, the above mentioned composite toughening materials still have some problems to be solved in system design and material combination.
With the development of the research, a new type of ceramic MAX phase has gradually appeared. MAX phases (M = early transition metal; A = main group element; X = C or N) , which were first reported by Jeitschko in the 1960s, have received considerable attention in recent years. To date, more than 150 types of MAX phases have been discovered, and their properties have been investigated [15, 16]. In the case of the 312 phase, Ti3SiC2, Ti3AlC2 and, Ti3GeC2 have been widely applied owing to their facile preparation and excellent stability. In this work, we continued the idea of complementing the advantages of composite materials, designed and prepared Ti3SiC2/Al2O3 ceramic composites with the main goal of improving the mechanical properties of the materials in the service environment. However, when employing an in-situ preparation at high temperature, highly pure Ti3SiC2/Al2O3 composites are challenging to obtain owing to the narrow phase area of Ti3SiC2, which results in the formation of TiC as an impurity.
Cai et al  fabricated Ti3SiC2/TiC-Al2O3 composites with different Al2O3 contents and believed the in-situ generated TiC to be the matrix phase. The composites showed high flexural strength. However, their fracture toughness was low. At the present stage, some researchers have realized the in-situ synthesis of Ti3SiC2 by adopting various methods such as thermal isostatic sintering, hot-pressed sintering, discharge plasma sintering, self-spreading sintering, and chemical vapor deposition synthesis [18–22]. Wang et al  used Al2O3, TiC, and Si as the raw materials and synthesized Ti3SiC2/Al2O3 composites via in-situ reaction using spark plasma sintering at 1300 °C. The resulting composites showed good mechanical properties, but contained a large amount of TiC impurities. Mishra et al  prepared Ti-Si-C series materials with high hardness (22.5 GPa) and elastoplastic deformation through self-propagating sintering with Ti, Si and C as raw materials. Zhang et al  used different mixing methods (vibrating sieve mixing for 24 h and mechanical alloying for 500 h) to fully mix the materials of Ti, Si and TiC with a ratio of 1:1:2, and used pulse discharge sintering at a lower temperature (1250 °C ~ 1300 °C) to prepare Ti3SiC2 materials. Although they have synthesized Ti3SiC2/Al2O3 composites with high purity, the composites has lower density, resulting in poor mechanical properties.
Therefore, the purpose of this study is to synthesize high density Ti3SiC2/Al2O3 composites at high temperature while ensuring the purity of Ti3SiC2/Al2O3 composites. In this study, Al was employed as a sintering additive for the synthesis of Ti3SiC2/Al2O3 composites. The optimum Al amount for improving the mechanical properties of the composites was determined. The effect of the Al content (mole percentage) on the microstructure and mechanical properties of the Ti3SiC2/Al2O3 composites was investigated. This study provides a basis for further investigate the anti-oxidation ability of Ti3SiC2/Al2O3 composites.