The interest of materials with high specific properties and good tribological behaviour raises the needs in terms of improving the properties of materials like titanium and its alloys. In the fields of aerospace, military industry and biomedicine, the use of these materials is very popular [1
]; however, nowadays, there are limitations regarding their mechanical and poor tribological properties. Therefore, titanium matrix composites (TMCs) are valuated as materials that combine low density with mechanical properties [5
]. Presently, there is a great variety of reinforcements employed in these composites. The most popular ones showed in diverse research works tend to increase the hardness, Young’s modulus and the tribological behaviour without incrementing the density. As examples, it may include TiB2
, TiB, TiC, B, B4
C, carbon nanotubes, graphite and nanodiamonds [9
]. Among these materials, B4
C ceramic particles have been presented in investigations as an optimal form to obtain B and C sources to origin in situ TiB and TiC [13
]. In this regard, these secondary phases play a key role in the strengthening of the titanium matrices [17
]. The main advantage of these in situ phases resides in the existence of a good interfacial bonding of the reinforcement-matrix. Moreover, the ceramic reinforcements formed during in -situ processing are finer, more thermodynamically stable and uniform in size distribution in the metal matrix [18
]. Therefore, the study of the reaction layer between the matrix and the particles is important in order to achieve a better understanding of the cause that could promote or not these reactions and their products. While there is considerable literature on the grounds of strengthening and the reaction mechanisms [20
], there are only a few studies where the reaction layer is analysed. It is also investigated how the presence of Tix
as intermetallic in the titanium matrices could affect the final appearance of these secondary phases (TiB and TiC) [22
]; however, the reaction layer in the presence of intermetallic, as well as its decomposition, has been little studied [25
]. Hence, here lies the importance for understanding and determining the evolution of the reaction layer with B4
C particles and intermetallics Tix
and how these layers and the final properties of the consolidated composites could be affected by the combination of the starting materials. Therefore, this research aims not only to study the reaction layer but also to investigate and characterise TMCs from five different blends. These blends were designed and processed considering interesting combinations of starting powders, in order to observe the regarding properties and the above-mentioned reaction layer phenomenon. Through the selection of the diverse intermetallic starting powders, variations in the behaviour of the TMCs may be expected.
In several investigations concerning the manufacture of titanium composites via powder metallurgy (PM) [27
], inductive hot pressing (iHP) is considered as a suitable fabrication option due to its flexibility and short cycles. For that reason, and thanks to the experience of the authors on TMCs manufacturing, the fabrication route of the specimens was through iHP. In preliminary studies [29
], an inflexion temperature, at which secondary phases were formed in situ, was observed. The analysis of the reaction layer has been carried out in specimens produced at this inflexion temperature (1100 °C) in vacuum conditions.
Hence, the five specimens were in detail characterised through scanning and scanning-transmission electron microscopies (SEM and (S)TEM) and by X-ray diffraction analysis (XRD). Furthermore, their tribological and physical properties were measured and evaluated. In this regard, the relation between the starting materials and the final properties was thoroughly investigated.