The kinetics and mechanisms of interface reactions in a unidirectional continuous SiC fiber-reinforced Ti-17 matrix composite were investigated using transmission electron microscopy and scanning electron microscopy. It was found that a reaction zone (RZ) consisting of two-layered TiC-type carbide forms at the fiber/matrix interface during fabrication of the composite. After isothermal exposure at elevated temperatures, the two-layered TiC-type carbide is inherited, and a new TiC-type carbide layer forms within the RZ after exposure at temperatures lower than 900°C, while a new Ti3C2-type carbide layer forms after exposure at 900°C. It was also observed that the growth of RZ is a diffusion-controlled and temperature-dependent process, obeying the Fick's law-based parabolic relationship and the Arrhenius equation. Two material constants, the temperature-independent rate constant k0 and activation energy Q, are determined as 31.5 × 10−4µm/s1/2 and 49.9 kJ/mol, respectively.

TiB2 particulates were formed in situ in an aluminum matrix via chemical reactions between an aluminum melt and the mixture of K2TiF6 and KBF4 salts. Different effects of Sc addition on the formation of the TiB2 particulates were revealed depending on the participation of Sc at different stages of the formation of the particulates. The metal–salt reactions resulted in boride layers along the α-Al grain boundaries in the presence of Sc, while the addition of Sc after the metal–salt reactions broke up the boride layers improving the dispersion of the TiB2 particulates to a limited degree. Sc promoted the growth of the TiB2 particulates, resulting in the coarsening of TiB2 particulates. The participation of Sc in the formation of TiB2 particulates altered the coarsening of the TiB2 particulates, resulting in different morphologies of the TiB2 particulates depending on the participation of Sc in the formation of the TiB2 particulates at different stages.

Laser metal deposition (LMD) additive manufacturing was used to deposit Inconel 625 matrix composites reinforced with nano-TiC particles. The effects of laser energy input per unit length (E) on the densification level, microstructural features, mircohardness, and wear property were investigated. The relatively low E induced insufficient liquid with higher viscosity, thus inhibiting the melted liquid from spreading out smoothly. As a result, a large number of micropores and reduced densification level of LMD-processed parts were obtained. When the E of 100 kJ/m was properly settled, the obtainable densification level generally approached 98.8%. The TiC reinforcements experienced successive microstructural changes from agglomeration to uniform distribution with coarsening grain, as the applied E increased. The nearly fully dense parts using optimal experimental parameters achieved an increased average microhardness of 330 HV0.2, resultant considerably low coefficient of friction of 0.41 and reduced wear rate of 5.4 × 10−4 mm3/(N m) in dry sliding wear tests.

We have investigated the microstructure, the quasistatic and high-rate mechanical properties of magnesium (Mg)-based metal-matrix composites (MMCs) reinforced with nanoparticles, also termed as metal-matrix nanocomposites (MMNCs), in this case reinforced with nanoparticles of β-phase silicon carbide (β-SiC) the volume fraction ranging from 5 to 15 vol%. The yield and the ultimate strength increase with reinforcement volume fraction up to 10 vol% nanoparticles. MMCs with micrometer-sized SiC particles have higher yield strength than their MMNC counterparts, whereas the ultimate strength shows the opposing trend, suggesting greater strain hardening in the MMNCs. Transmission electron microscopy shows that the average interparticle distance decreases with increasing SiC vol%. Recrystallization was reported as completed during sintering at 575 °C [R.D. Doherty et al., Mater. Sci. Eng. A, 238, 219 (1997)], but dislocations might be generated due to thermal expansion mismatch of Mg/SiC during cooling. The majority of Mg-grains below 20 nm remain around the nanoparticles. As such a reverse volume fraction effect takes place in 15 vol% nanoparticle-reinforced MMNCs, which off sets the strengthening advantage induced by the nanoparticles.