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An investigation has been conducted on AZ91 magnesium alloy processed in high-pressure torsion (HPT) at 296, 423 and 473 K for different numbers of turns. The microstructure has altered significantly after processing at all processing temperatures. Extensive grain refinement has been observed in the alloy processed at 296 K with apparent grain sizes reduced down to 35 nm. Segmentation of coarse grains by twinning has been observed in the alloy processed at 423 K and 473 K with average apparent grain sizes of 180 nm and 250 nm. Substantial homogeneity in microhardness has been observed in the alloy processed at 296 K compared to that found at 423 K and 473 K. The ultrafine-grained AZ91 alloy exhibited a significant dependence of the yield strength on grain size as shown by the microhardness measurements, and it obeys the expected Hall-Petch relationship. The alloying elements, fraction of nano-sized particles of b-phase, and the dominance of basal slip and pyramidal modes have additional effects on the strengthening of the alloy processed at 296 K.

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A composite material was prepared using epoxy as a matrix, and carbon fiber (20% volume fraction) together with nano titanium dioxide (TiO2) particles in varying weight fractions (0,2,4 and 6%) as hybrid reinforcement. Mechanical tests (impact strength and wear resistance) were carried out, in addition to the study of liquid uptake behavior during immersion in chemical solutions, and inspection with scanning electron microscope imaging to reveal the microscopic details. The results showed that the addition of TiO2 have improved the mechanical properties of the composites, as the specimen reinforced with 4% TiO2 showed the highest impact strength, in addition to improved wear resistance. The scanning electron images for the specimens showed finely dispersed carbon fibers surrounded by the ultrafine TiO2 nano powder, suggesting a uniform distribution of reinforcement throughout the whole matrix for all the prepared specimens. The liquid uptake results showed that the specimen reinforced with 20% carbon fibers and 6% nano TiO2 had the highest diffusion rate, especially when immersed in hydrochloric acid. The results show that the prepared composite could be a good alternative to traditional materials whenever good wear resistance is involved, together with impact and chemical resistance, such as in anti-skid flooring applications.

Flow patternHigh-pressure torsion Stainless steel a b s t r a c t Stainless steel was selected to study the flow patterns developed with anvil misalignments of 100, 200 and 300 m on the disc lower surfaces during processing by high-pressure torsion (HPT) through totals of up to 16 turns. A pair of anvils having a roughness of Ra ≈ 15 m was utilized to investigate the flow pattern development. Discs subjected to only compression in HPT exhibit similar characteristics to the as-received material in the phase domains and there were no overall curvatures of the austenitic (␥) and ferritic (␣) phases. Doubleswirl flow patterns were not observed in the 1 turn sample but they appeared on the disc lower surfaces after 5 and 16 turns with all three-anvil alignment conditions. There was no significant difference in the double-swirl configuration size for the 5 and 16 turns samples with different amounts of anvil misalignments. These results have important implications for processing metals by HPT.

Nano-crystalline SnO2 films were deposited on glass substrates using dip coating by sol–gel technique for gas sensor applications. These films have been annealed in air at 300, 350 400, and 450 °C for 60 min, and at 400 °C for 15, 30 min. The films have been analyzed through x-ray diffraction and optical absorption spectroscopy. The deposited films have shown tetragonal rutile structures. The average crystallite size increased as annealing temperature increased. The crystallite sizes of the annealed films were 8 nm at 300 °C, 10 nm at 350 °C, 14 nm at 400 °C, and 22 nm at 450 °C for 60 min. Whereas the crystallite sizes showed 16 and 15 nm at annealing temperature of 400 °C for 15 and 30 min, respectively. The energetic values of optical band gaps of the films showed increment with the elevation in annealing temperatures. The optical band gap energies were 2.86, 2.86, 3.14 and 3.35 eV at annealing temperatures of 300, 350, 400, and 450 °C, for 60 min, respectively, and 3.43 and 3.35 eV at annealing temperature of 400 °C for 15 and 30 min, respectively. Electrical D.C. conductivity were measured at temperatures ranging from 30 °C to 170 °C, and these measurements showed an exponential increment as the temperature and time increased. The films were studied in the matter of sensing capabilities for CO gas through evaluation at various times and temperatures. The optimum sensitivity was found at annealing temperature 400 °C. The outcomes revealed a high sensitivity of the deposited films for carbon monoxide at operation temperature of 200 °C.

Nanostructured Al-9%Si-3%Cu alloy was achieved by direct metal laser sintering (DMLS) and then processed using high-pressure torsion (HPT) processing, which resulted in considerable grain refinement down to 60 nm associated with a substantial dislocation density up 6.2 × 1014 m−2 and a significant reduction in the porosity. Hardness measurements across the horizontal and vertical cross sections showed an improvement in the strength homogeneity for processed samples after 10 turns of HPT processing. These results indicate that a controllable ultrafine-grained microstructure can be achieved by employing additive manufacturing, followed by effective severe plastic deformation processing.