Formation and crystallization of an amorphous Al80Fe10Ti5Ni3B2 alloy

In this study, we investigated the crystallization behavior of an Al₈₀Fe₁₀Ti₅Ni₃B₂ amorphous alloy (obtained by mechanical alloying) using X-ray diffraction (XRD), transition electron microscopy (TEM), and differential thermal analysis (DTA) techniques. The obtained results show that an amorphous phase formed during mechanical alloying (for 40 h) of the Al-10%Fe-5%Ti-3%Ni-2%B powder mixture. It was found that the Al₈₀Fe₁₀Ti₅Ni₃B₂ amorphous alloy exhibits one-stage crystallization when heated (amorphous to Al₁₃Fe₄, Al₅Fe₂ and AlFe intermetallic phases). The activation energy for the crystallization, evaluated from the Kissinger equation, was about 242 ± 5 kJ/mol. We also discuss kinetic parameters such as the Avarmi exponent and reaction order (n). The results show that only one three-dimensional diffusion-controlled growth mechanism was working during the amorphous-glass process of the investigated glass.     

Effect of nanoclay particles on mold‐filling performance in composites made via resin infusion process

This study investigates the effect of 3 and 5 wt% nanoclay (Cloisite 30B) addition on mold filling time and performance of continuous glass filament mat reinforced unsaturated polyester (UP) resin composites made by vacuum infusion process. X‐ray diffraction and transmission electron microscopy analysis as well as viscosity change in liquid state resin confirmed intercalation and exfoliation of the nanoclay in the resin system. The result shows mold filling time increase of 3 and 2.4 times for the samples containing 3 and 5 wt% nanoclay, respectively, compared with nanoclay‐free sample. This increase in mold filling time is directly attributed to the increase in resin viscosity. Filtration of nanoclay particles were observed in the resin flow direction. Result showed 8 and 14% filtration of nanoclay in flow direction for the samples with 3 and 5 wt% nanoclay content, respectively. Nanoclay containing specimens prepared from near resin entry port area showed relatively higher flexural and tensile modulus and as well as strength compared to specimens prepared from area close to vacuum port area. The result showed best performance for 3 wt% nanoclay containing specimen. However, impact strength decreased about 6.1 and 10.8% for 3 and 5% nanoclay, respectively. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Fabrication of Al-Zn/α-Al2O3 nanocomposite by mechanical alloying

In this study fabrication and characterization of alumina particles reinforced aluminum-based metal matrix nanocomposite by mechanical alloying were investigated. Aluminum and zinc oxide powders mixture milled by a planetary ball mill in order to produce Al-13.8 wt.% Zn/5 vol.% Al₂O₃ nanocomposite. The structural evaluation milled and annealed powders studied by X-ray diffraction, SEM observation and hardness measurement. The aluminum crystallite size estimated with broadening of XRD peaks by Williamson-Hall formula. The results showed that milling of aluminum and zinc oxide for 60 h led to displacement reaction of the zinc oxide and aluminum to produce Zn and Al₂O₃ phases. The milled powder had a microstructure consisting of nanosized Al₂O₃ particles in an Al-Zn solid solution with a nanoscale grain size of 40 nm. Microhardness of this nanocomposite was found to be about 190 HV.     

Synthesis and characterization of Zn/Al2O3 nanocomposite by mechanical alloying

In this study, fabrication and characterization of zinc-based metal matrix nanocomposite reinforced by Al₂O₃ particles was investigated. Aluminum and zinc oxide powder mixture was milled in a planetary ball mill in order to produce Zn/Al₂O₃ nanocomposite. The structural evaluation milled and annealed powders studied by X-ray diffraction, SEM observation and hardness measurement. The zinc crystallite size estimated with broadening of XRD peaks by Williamson-Hall formula. The zinc oxide was found to react with Al through a rapid self-sustaining combustion reaction process. As a result a zinc matrix composite reinforced by Al₂O₃ particulate was formed. The microhardness value of produced nanocomposite powder was about 350 HV which was 10–15 times higher than the microhardness of pure zinc (20–30 HV).     

Tribological Behavior of A356/Al2O3 Surface Nanocomposite Prepared by Friction Stir Processing

Surface A356 aluminum alloy matrix composites containing micro and nanosized Al₂O₃ are prepared by a new approach utilizing high-velocity oxy-fuel spraying and friction stir processing (FSP). Optical and scanning electron microscopy, microhardness, and wear tests were used to characterize the surface composites. Results indicated that, the presence of Al₂O₃ in matrix can improve the mechanical properties of specimens. The microhardness of surface composites containing micro and nanosized Al₂O₃ were 89.8 ± 2.6 HV and 109.7 ± 2.5 HV, respectively, which were higher than those for the as-received (79.6 ± 1.1 HV) and the FSPed A356-T6 with no alumina powder (66.8 ± 0.9 HV). Surface composites revealed low friction coefficients and wear rates, which were significantly lower than those obtained for substrate. The wear mass losses of the as-received, the FSPed, and surface micro and nanocomposite specimens after 500-m sliding distance were 50.5, 55.6, 31, and 17.2 mg, respectively. Scanning electron microscopy tests revealed different wear mechanisms on the surface of the wear test specimens.     

Multivariable optimization of thermal cracking severity

The changing market forces are driving olefin producers to operate their steam crackers at high operating rates and optimum production performances. These require the use of an optimizer for assessment of viable operational strategies. Most of the optimizers currently employed in this area make use of the coil outlet temperature to determine an improved severity. In rare cases only, a multivariable optimization is performed on the furnace operational conditions. This kind of optimization is implemented in PyroFur for optimizing both the furnace operation and the reaction severity using a set of first-principles mathematical models in which the coil outlet temperature, the total feed flow rate and the steam/hydrocarbon ratio are altered. The suggested procedure was applied as a case study for a typical liquid furnace. Typical improvements obtained from the optimizing control strategy proposed in this article include about 1.4% increased profitability per year per furnace. Effect of a change in the prices or the feed composition is also presented.