The Si-coated SiC (Si-SiC) composite nanoparticle was prepared by non-transferred arc thermal plasma processing of solid-state synthesized SiC powder and was used as a sintering additive for SiC ceramic formation. Sintered SiC pellet was prepared by spark plasma sintering (SPS) process, and the effect of nano-sized Si-SiC composite particles on the sintering behavior of micron-sized SiC powder was investigated. The mixing ratio of Si-SiC composite nanoparticle to micron-sized SiC was optimized to 10 wt%. Vicker’s hardness and relative density was increased with increasing sintering temperature and holding time. The relative density and Vicker’s hardness was further increased by reaction bonding using additional activated carbon to the mixture of micron-sized SiC and nano-sized Si-SiC. The maximum relative density (97.1%) and Vicker’s hardness (31.4 GPa) were recorded at 1800 °C sintering temperature for 1 min holding time, when 0.2 wt% additional activated carbon was added to the mixture of SiC/Si-SiC.

In this study, analysis was performed on the microstructural change in the friction stir welding (FSW) region of AA5052-H32 thin sheets. The micro texture and microstructure in the stir zone (SZ) and base metal were characterized using the electron back-scattered diffraction (EBSD) technique and transmission electron microscopy (TEM) observation. The grain size and misorientation angle distribution were also investigated. The hardness profile of the FSW region with the microstructure in each area was discussed. The grains in the stir zone were more refined than those of the base metal. The base metal has {001}< 100> textures, while the stir zone takes a {112}<110> textures attributed to the severe shear deformation during FSW. The TEM observation results suggest that recrystallization during the friction stir welding process diminishes the density of dislocation in the SZ. It is also considered that the drop of hardness in the SZ is caused by the decrease of dislocation density, even though the grains were refined.

The influence of iron on the the microstructure and properties of B2 NiAl has been investigated using electrical resistivity, magnetic susceptibility, microhardness and transmission electron microscopy. The resistivity data suggest that quenched-in vacancies (1) enhance iron rearrangement at low temperatures (600–800 K) and (2) annihilate above 800 K. These effects depend strongly on Ni/Al ratio and are greatest for Ni/Al=1. It is also shown that these data correlate directly with the results obtained using the other experimental techniques.

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