The ternary carbide Ti3AlC2 was reactively synthesized from the elemental powder mixtures of Ti, Al and activated carbon. Cu/Ti3AlC2 composites were fabricated by hot-pressing method. Their microstructures and properties were investigated. The resultsdemonstrated that Ti3AlC2 is a promising reinforcement for copper and the Cu/Ti3AlC2 composites exhibited lower electrical conductivityand much superior flexural strength to pure copper matrix without remarkable loss of fracture toughness.

NiAl-based alloys and their composites reinforced with in situ formed TiC and externally added ceramic particles are fabricated by hot-pressing.Their microstructures and mechanical properties are evaluated. Comparatively, the Ti-and/or C-alloyed NiAl and the ceramic particulate reinforcedcomposites possess a significant improvement in both flexural strength fracture toughness at room temperature. Nevertheless, the NiAl-TiC-nano-Al2O3 composite has low strength, mainly due to the existence of residual porosity, inhomogeneous distribution and severe agglomeration ofnano-scaled Al2O3 particle within the NiAl matrix.

Microstructures of Al45-Mo25-Zr25-Ge5 (in at.%, AMZG) alloy, produced by reaction hot pressing of elemental powder mixtures,have shown co-existence of AlMo3, Al3Mo8, ZrAl2, Zr2Al, MoGe2 and ZrGe2. In addition, its composites were fabricated through additionof micro-sized TiC, partially stabilized zirconia (PSZ-ZrO2) or SiC particulates into the pulverized multi-phase aluminide powders.The presence of SiC particulates showed a much less significant contribution to the strength/toughness enhancement of AMZG alloy,due to the existence of residual porosity and weak interfacial bonding. In contrast, the other two composites were superior in both flexuralstrength and fracture toughness to the AMZG multi-phase alloy, which is derived from the contribution of uniformly distributedand well-embedded harder particulates and the constrained plastic deformation of the matrix. The addition of hard ceramic particlessimultaneously yielded higher bulk Vickers hardness. The toughness enhancement in the composites was attributed to the increased tortuousityby crack deflection, branching and bridging. Moreover, the transformation of tetragonal zirconia particles into the monoclinicform might also partially contribute to the toughness enhancement in the AMZG/ZrO2 composite.

Ti–Al3Ti laminated composites have been fabricated through reactive sintering in vacuum usingTi and Al foils with different initial thickness.The aluminum layer was completely consumed resulting in microstructures of well-bonded metal–intermetallic layered composites with Tiresidual metal layers alternating with the aluminide intermetallic layers. The MIL composites exhibit a very high degree of microstructuraldesign and control. Microstructure characterization by scanning electron microscopy (SEM), X-ray diffractometry (XRD) and energy dispersivespectroscopy (EDX) has shown that Al3Ti is the only titanium aluminide phase due to the thermodynamics and phase selection of the reactionbetween Ti and Al through mass diffusion in the presence of liquid Al. The mechanical properties and fracture behavior of the fabricatedlaminated composites were examined through three-point bending test. The results indicated that the composites exhibited anisotropic features.When the load perpendicular to the laminates was applied, they displayed a step-like or saw-tooth load-displacement response and superiorflexural strength as well as fracture toughness, which is also dependent on the number and thickness of individual layers. A non-catastropicfracture was observed in the laminated composites due to the deflection of cracks along the Ti/Al3Ti interface. The Ti layer failed by cleavagemode, showing extensive plastic deformation during the bending process.

High-volume-fraction Si3N4-Al-based composites have been fabricated by high-pressure casting method. The effects of chemical compositionof infiltrated Al alloys, microstructures of Si3N4 preforms, and test temperature on the mechanical properties were investigated.The maximum four-point bending strength and fracture toughness of the composites reached 924 and 8.2MPa(√m), respectively. Increasingsintering temperature above 1650℃ for Si3N4 preforms resulted in an enhancement of fracture toughness at the expense of degradation inflexural strength. However, an increase in sintering time for Si3N4 preforms at moderately sintering temperature yielded an improvement inboth flexural strength and fracture toughness of the corresponding composites. Both flexural strength and fracture toughness decreased withincreasing temperature and CIP pressure due to inhomogeneous distribution of Al phase and some defects introduced into the preforms duringthe casting process. The Si3N4–6061 Al composite exhibited the lowest strength, which may be attributed to the presence of porosities andinterfacial reactions.