Bending Properties of AA7055 Aluminum Alloy Reinforced with In Situ TiB2 Particles

In-situ TiB2 particles reinforced AA7055 composites were fabricated through mixed-salts route and their bending properties were studied. The composites reinforced with 5 wt % and 10 wt% TiB2 exhibit higher bending strength than the unreinforced matrix alloy. The improvement in bending strength may be attributed to dislocation strengthening, Orowan strengthening, and grain strengthening. The good bonding between the reinforcements and the matrix also plays an important role.

Interfacial characteristics and mechanical properties of a modified Nb-containing Zr-based bulk metallic glass composite reinforced with W fiber

Tungsten (W) fiber reinforced Zr47Ti13Cu11Ni10Be16Nb3 bulk metallic glass composite has been prepared by melt infiltration casting. Interfacial characteristics of the composite were analyzed by sessile drop technique, x-ray diffraction (XRD), scanning electron microscopy (SEM), electron probe x-ray microanalysis (EPMA), and nanoindenter. Results indicate that Zr47Ti13Cu11Ni10Be16Nb3 melt wets the W substrate, and the interfacial bond composed of a diffusion–dissolution layer between Zr47Ti13Cu11Ni10Be16Nb3 matrix and W fiber is in good condition. Due to these excellent interfacial characteristics, the mechanical properties of the composite are considerably enhanced with increasing volume fraction of W fiber. It was found that the compressive strength of 70% volume fraction of W fiber composite is 2.6 GPa, which is 58% higher than the value exhibited by the unreinforced matrix. At the same time, the reinforced matrix exhibits 13% plastic deformation when tested under quasi-static compression conditions. Instead of shear mode seen for the unreinforced matrix, the failure mode of the 70% volume fraction W fiber composite is mainly caused by fiber splitting and buckling. Also, the W fiber hinders localized shear bands from propagating and gives rise to multiple shear bands, which results in the enhancement of the compressive strength and plastic deformation.

Wear-Resistant Property of SiCp/Al Composites

Al alloy reinforced with SiCp (size: 70-220μm) was fabricated by pressureless-infiltration. Its wear resistant property was investigated under different heat-treatment conditions, and morphology of worn surface was examined. The results showed that the composite was integrated, uniform and compact, and its wear resistant property was better than that of the unreinforced matrix alloy. It was indicated that some rigid SiCp in the abraded surface of the composite could support part of loads and replace matrix to wear-tear, which improved the wear resistant property. Compared to annealing, solution aging strengthens Al alloy matrix and cohesion with SiCp, and the wear resistant property of composites was better. Combining interface is also an important factor which influences on wear resistant property. During the wear test, the smaller SiCp size, the more interfaces, there are more SiCp falling off because of loosening combining interface, which results in more wear-tearing value. The wear rate of composite increases with decreasing SiCp size, thus, the composite with larger SiCp has better wear-resistant property than that with smaller SiCp. At last, the wear mechanism of the composite was also studied, and it showed that abrasive wear dominated in the abrasion process.

Plasma Deposited Ni-Al-Mo Metal-Metal Composites

ABSTRACTSix different composite microstructures were produced by low pressure plasma deposition of γ/γ'-α Ni-Al-Mo materials. Interlaminate spacing, volume fraction of α Mo, and continuity of the laminate structure were varied. Thermal expansion behavior (25–1250°C), density, and room temperature elastic modulus were correlated with volume fraction of α Mo. Tensile ductility (25–960°C) was correlated with both volume fraction and distribution of the α Mo phase, while yield strength was nearly insensitive to composite structure. Composite strengths were greater than were the unreinforced matrix strengths.