In friction stir welding (FSW), a rotating threaded pin tool is inserted into a weld seam and literally stirs the edges of the seam together. The dynamically recrystallized zone (DXZ) of a polished and etched FSW cross section exhibits contrasting bands (the "onion-ring" structure), the origins of which are unclear. An orientation image mapping (OIM) study suggests that the bands may correspond, respectively, to a "straight-through" current of metal bypassing the pin tool in a single rotation or less and a "maelstrom" current rotating a number of times around the pin tool.

The more-stringent requirements for densification of new out-of-equilibrium powders have created a growing demand for nonconventional rapid sintering processes. Among those, field-assisted sintering techniques (FASTs) have seen a recent renewed interest motivated by their ability to consolidate a large variety of powder materials into high densities in short times. Characterization of a range of FAST-consolidated materials displayed relevant associated surface effects, such as grain boundary cleaning with direct grain-to-grain contact and advanced densification without sintering aids. These effects may be attributed to phenomena ranging from dielectric breakdown to a possible nonconventional plasma generation. Such surface effects provided a better intergranular bonding of powder particles during subsequent sintering.

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Key aspects of nanofiber morphology in vapor-grown carbon nanofiber (VGCNF)/vinyl ester nanocomposites were characterized using transmission electron microscopy (TEM) images. Three-parameter Weibull probability density functions were generated to describe the statistical variation in nanofiber outer diameters, wall thicknesses, relative wall thicknesses, visible aspect ratios, and visible waviness ratios. Based upon a linear regression of experimental data, the relative nanofiber wall thicknesses were reasonably constant over a range of nanofiber radii. Such information could be used to establish more realistic nanofiber moduli and strengths obtained from nanofiber tensile tests, as well as to develop physically motivated computational models for predicting nanocomposite behavior. While the nanofiber aspect ratios and fiber waviness measurements were restricted to the visible portions of nanofibers lying in the plane of the TEM images, such data can be used to predict bounds on the effective nanocomposite elastic properties. This study represents one of the first attempts to experimentally characterize the distribution of VGCNF features in real thermoset nanocomposites.