Microstructure, hardness and corrosion behaviour of friction-stir processed AA5083

Purpose The purpose of this study is to refine the microstructure and improve the corrosion behaviour of aluminium alloy AA5083 by subjecting it to friction stir processing (FSP). Design/methodology/approach FSP trials are conducted as per central composite design, by varying tool rotation speed, tool traverse speed and shoulder diameter at three levels. The microstructure is examined and the hardness is measured for both the base material and the processed workpieces. The corrosion behaviour of the base material and processed workpieces is studied using potentiodynamic polarization technique for three different testing temperatures, and the corrosion current and corrosion rate are calculated. Findings The results reveal that FSP refined the grains, dispersed secondary phases, increased the hardness and improved the corrosion resistance of most of the friction stir processed specimens than the base material at all the three testing temperatures. Grain refinement and fine dispersion of ß phase improves the hardness and corrosion resistance of most of the FSPed specimens. However partial dissolution of ß phase decreases the hardness in some of the specimens. Most of the FSPed specimens displayed more positive potential than the base material at all the testing temperatures representing a higher nobility than the base material, as a result of fine dispersion of secondary phase particles in the matrix. Large pits formed on the surface of the base specimen indicating a higher corrosion rate at all three testing temperatures. The SEM image of FSPed specimens reveals the occurrence of very few pits and minimal corrosion products on the surface, which indicates lower corrosion rate. Originality/value The corrosion mechanism of the friction stir-processed AA5083 specimens is found to be a combination of activation and concentration polarization.

Research of Modified Atomizers and Their Application for Moistening of Air-Cleaning Device Charges

The size of sprayed droplets is a very important parameter that influences the operational efficiency of air-cleaning device charges. It is desirable for atomizers to spray droplets that are dispersed as much as technically and economically reasonable and possible. Fine dispersion spraying ensures effective moistening of the air-cleaning device charges, as well as an optimal consumption of water or other liquids. Three modifications of special atomizers were used for experimental analysis. The atomization of liquid and spraying in the special atomizer occurs when two frontal streams confront each other. Frontal streams are formed by an inner shield located in the special atomizer. The experiment was conducted using different spraying pressures, namely: 6 bar, 4 bar, 2 bar. The evaluation (performed using a microscope) of the size of sprayed droplets shows that the best (finest) spraying was by the special atomizer of modification 3. The depth of the channel of the inner shield is the parameter that has the biggest influence on the size of sprayed droplets. The special atomizer of modification 3 produces droplets with the following size distribution and rates: ≤0.05 mm—63.2 vol%; 0.2–0.6 mm—28.3 vol%; 0.6–1.0 mm—8.1 vol%; ≥1.0 mm—0.4 vol%.

Aerosol Systems of Supply Ventilation, as Means of Air Quality Improvement of Working Zones

Article is devoted to a research of aerosol systems of supply ventilation. Expediency of creation and use of water and aerosol systems for decrease in concentration of fine-dispersion dust in working zones, and as a result, decrease in negative impact on operators of various productions is proved. The design of a centrifugal mechanical one-slot-hole nozzle is proposed. Problems of dust content in air of a working zone and impact of particles of PM10 and PM2,5 on an organism of workers are considered.

Fine dispersion morphology of polystyrene/poly(ethylene terephthalate glycol) blending generation for controlled foaming behavior

Polystyrene/poly(ethylene terephthalate glycol) (PS/PETG) blends with different PETG contents were prepared using a Haake internal mixer at 190 °C.