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Ultrafine WC–Co–VC cemented carbides are used extensively in a variety of industrial environments due to their excellent mechanical properties and outstanding wear resistance. Co content affects the service performance of the cemented carbides. In the present study, the influences of Co content on microstructure, physical, and mechanical properties were investigated systematically. Ultrafine WC–Co–VC cemented carbides with Co content varying from 4 wt% and 7 wt% and assistance of VC (0.35 wt%) as inhibitor of WC grain growth were prepared. The physical and mechanical properties were tested and the microstructure characteristics were observed by optical microscope (OM) and scanning electron microscopy (SEM). From the results, it is found that with Co content increasing, both the cobalt magnetism and bending strength increase, while the coercive force, Rockwell hardness, density, and abrasive wear resistance decrease. In addition, the OM and SEM results show that the increase of Co content in WC–Co–VC cemented carbides tends to reduce the quantity and size of micro-pores, and make the fracture mode change from brittle fracture to ductile fracture. [ABSTRACT FROM AUTHOR]

A kind of nickel–aluminum bronze (Cu–10Al–4Fe–4Ni) prepared by centrifugal casting (CC) and gravity casting (GC), respectively, were investigated. The results indicate that CC alloy, which is totally different from GC alloy, consists of α, κI, κII, κIII, κIV, and β′ phases and the microstructures of CC alloy shows nonuniformities from external to internal layer mainly because the distribution of iron and nickel are influenced by centrifugal force. Besides, it is noted that comprehensive mechanical properties of CC alloy are superior to those of GC alloy. Additionally, heat treatments were performed on CC alloy. The results demonstrate the optimal heat treatment is aging at 450 °C/1 h by air cooling after solution treated at 890 °C/1 h by water quench. The ultimate tensile strength and hardness are increased by about 10% and 56%, respectively, and wear resistance is also greatly improved. However, the elongation is decreased by 53%. [ABSTRACT FROM AUTHOR]

Diamond-Cu composites have been considered to be the next generation of electronic packing materials. One of the key stumbles for such an application is the joining problem between diamond-Cu composites and other materials due to the poor wettability of the diamond particles in the composites. In order to overcome this hurdle, pure Cu powder was thermally sprayed onto diamond-Cu substrate by low-temperature high-velocity oxygen fuel spraying process. Microstructure and some fundamental properties of the coating obtained were systematically investigated, and morphologies of the single splat deposited on the diamond-Cu substrate were also observed. The splats obtained have good adhesion with the substrate as fine particles flattened sufficiently, while the coarse particles were significantly deformed. The coating was quite dense with porosity lower than 1%, oxygen content under 0.5% and thermal conductivity about 266 Wm K and still remained on the diamond-Cu substrate after 50 thermal shock cycles between 300 °C and water bath at room temperature. Meanwhile, the solderability of the coating was significantly improved. Therefore, Cu coating deposited on diamond-Cu substrate by low-temperature high-velocity oxygen fuel spraying process can be beneficial in electronic industry assisting with soldering and improved wettability for joining of other materials. [ABSTRACT FROM AUTHOR]

The initial WC grain-size distribution, as one of the most important factors influencing the properties of alloys, has been focused on for a long time in some fields other than cemented carbides. In the present work, five groups of WC-6Ni cemented carbides were prepared and the effect of initial WC grain-size distribution on the microstructure and properties of the hard alloys was studied. The results indicate that initial WC grain-size distribution has significant influence on the microstructure and properties of WC-6Ni cemented carbides, except density. When the mass ratio of coarse-WC and fine-WC is 7:3, WC-6Ni cemented carbide samples with initial WC grain-size distribution of WC-1(4.8 μm) and WC-4(0.7 μm) show a relatively good combination properties, while the cemented carbide samples with WC-5(0.4 μm) as the fine-WC component exhibit higher values on some properties, mainly hardness and immersion corrosion resistance in acid and alkali. [ABSTRACT FROM AUTHOR]

The solid state interdiffusion between NiFeO and NiO in nitrogen atmosphere was studied by means of diffusion couple technique. NiFeO/NiO diffusion couple with plane interfaces was made by clamping method and sintering at 1 300 °C for 10 h. Scanning electronic microscopy (SEM) and energy-dispersive X-ray spectrometry (EDS) were used to analyze the microstructure and phase composition of the diffusion couples. The results indicate that a porous layer of uniform thickness forms along the NiFeO/NiO bonding interface and exhibits a deep penetration in the NiFeO due to the Kirkendall effect. Furthermore, SEM observations reveal that the needle-like nickel ferrite precipitates form in NiO near the interface and the formation mechanism of them are inferred to be diffusion type solid-state phase changes. [ABSTRACT FROM AUTHOR]

A TiAl base alloy ingot with a height-to-diameter ratio of 2.2 was broken down by multiple step canned forging. The microstructures after every deformation and subsequent recrystallization were observed by optical microscopy. Results show that at the first step the reduction should be carefully controlled in case of double-bulge and crack of the ingot. After the first annealing, recrystallization occurred at the deformed grain boundaries and inside the grain. The recrystallized microstructure is favorable for further deformation. After the second deformation and annealing, coarsening of the lamellae occurred and the microstructure became equiaxed. By the final deformation and subsequent recrystallization, the coarse lamellar colony can be refined to about 20 µm, and homogeneous microstructure was obtained from the ingot with a large initial height-to-diameter ratio. [ABSTRACT FROM AUTHOR]

Blended elemental Ti-34% Al powders (mass fraction), containing 1.5% TiC, were hot isostatic pressed to prepare TiAl alloys. The effects of HIPing pressure on the sintered density, microstructure, constitutions phase were studied in details. The results show that the density of TiAl alloy increases repaidly with the increase of the HIPing pressure. At the same time, with the increase of pressure, the Ti3Al phase in matrix disappears. TiC reacts with other substance, forming Ti2AlC phase, which precipitates at grain boundaries. With the increase of hot isostatic pressing (HIPing) pressure, the shrinkage of the alloys increases, the fine spherical Ti2AlC phase can meet together and forms a needle-shape Ti2AlC, and the amount of needle-shaped Ti2AlC phase increases. The composite material of TiAl containing C can be made easily by HIPing technology. [ABSTRACT FROM AUTHOR]