Ti-Al3Ti laminated composites have been fabricated through reactive sintering in vacuum using Ti and Al foils with differentinitial thicknesses. The aluminum layer is consumed by forming a titanium aluminide intermetallic compound. Thus, the final microstructureconsists of alternating layers of intermetallic compound and unreacted Ti metal. Microstructural characterization by scanningelectron microscopy (SEM), X-ray diffractometry (XRD) and energy dispersive spectroscopy (EDX) has shown that only theintermetallic Al3Ti is formed, which can be rationalized in terms of thermodynamics and kinetics of phase selection, as well as by thediffusion processes occurring in the presence of liquid Al.

The processing, microstructures and mechanical properties of intermetallic alloy based on AleMoeZreCo (AMZC) and its composites reinforcedwith micro-sized TiC, partially stabilized zirconia (PSZ)-ZrO2 or SiC particulates were investigated. The results showed that the alloysystem exhibits multi-phase microstructures, composed of several aluminides including ZrAl2, Al5Co2, Al9Co2, AlMo3, Al8Mo3 and Zr2Al. TheAMZC/SiC composite showed poor mechanical properties, due to the existence of residual porosity and weak interfacial bonding. In contrast,the other two composites exhibited superiority in both flexural strength and fracture toughness at room temperature than the AleMoeZreCobasedmulti-phase alloy. Homogeneous distribution of ceramic particles and perfect interfacial bonding accounted for the improvement ofstrength. The addition of TiC or ZrO2 particle into the matrix alloy produced remarkable toughening effect.

Mo-Si-Al-C-based multiphase compounds and their composites reinforced by micro-SiC and TiC particulates were manufactured by meansof reactive hot-pressed sintering method. Their microstructure and room temperature mechanical properties were studied. The results showedthat Al addition and the ratio of Si/Al exerted a remarkable effect on the reaction products in the Mo-Si-Al-C systems. For the stoichiometricMo5(Si,Al)3C mixed powders with a molar ratio of Mo∶Si∶Al∶C as 5∶1.5∶1.5∶1, the sintered body contained Mo3Si, Mo3Al2C, and Mo5Si3C as themajor reaction products whereas and the minor phases consisted of MoSi2, Mo2C, and Mo(Si,Al)2 compounds. When the starting powder mixturewas off-stoichiometric with a small amount of excess Si, only Mo2C accounted for the minor product. Moreover, the relative contents of the formerthree major phases were affected by the changed Si/Al ratio, where the amounts of Mo3Al2C and Mo5Si3C compounds decreased and increased,respectively with increasing Si/Al ratio. The two multiphase alloys showed poor mechanical properties, due to the existence of residual porosity.In contrast, the composites exhibited superiority in both flexural strength and fracture toughness at room temperature to the Mo-Si-Al-C-basedmultiphase compounds. MSAC1/20 wt.%SiC and MSAC1/20 wt.%TiC composites had a respective flexural strength and fracture toughness of 454and 438MPa, 4.93 and 4.85MPa√m.

Porous ceramic with a framework structure of aluminum borate (9Al2O3-2B2O3) whiskers was in situ synthesized by firing above 1150 8Ca green powder compact of a mixture of aluminum hydroxide, boric acid and an additive of nickel oxide. During sintering, the whiskers ofaluminum borate grew in situ in the compact, and were bonded together. The porous aluminum borate consisted solely of whiskers with aporosity of 54-58%. The average diameters of the whiskers increased from 0.2 to 2 mm with increasing sintering temperature from 1150 to1350 8C. However, the estimated whiskers aspect ratio decreased with increasing sintering temperature.

Fe3Al-based composites reinforced with micron-sized titanium carbide, tetragonal zirconia and nano-scaled alumina particles were hot-pressed, and the room temperature mechanical properties were investigated. Results show that nano-Al2O3 is not an efficient ceramic for the enhancementof mechanical properties of Fe3Al, primarily due to its inhomogeneous distribution and severe agglomeration within the matrix as well as the weakinterfacial bonding. By contrast, Fe3Al/5 wt.% ZrO2 composite had a strength as high as 1361 MPa and a fracture toughness of 19.0 MPa ffiffiffiffi mp. Theenhancing effect is attributed to the low thermal expansion mismatch between ZrO2 and Fe3Al matrix, and to the stress-induced transformation ofZrO2 particles. The flexural strength and fracture toughness for Fe3Al/10 wt.% TiC composite was 1086 and 20.0 MPa ffiffiffiffi mp, respectively. Themechanical properties of Fe3Al/TiC composites decreased with TiC content above 10 wt.% due to the suppression of plastic deformation, residualporosity and interfacial debonding.