Effects of alloying elements on fracture toughness in the transition temperature region of base metals and simulated heat-affected zones of Mn-Mo-Ni low-alloy steels

This study is concerned with the effects of alloying elements on fracture toughness in the transition temperature region of base metals and heat-affected zones (HAZs) of Mn-Mo-Ni low-alloy steels. Three kinds of steels whose compositions were varied from the composition specification of SA 508 steel (grade 3) were fabricated by vacuum-induction melting and heat treatment, and their fracture toughness was examined using an ASTM E1921 standard test method. In the steels that have decreased C and increased Mo and Ni content, the number of fine M₂C carbides was greatly increased and the number of coarse M₃C carbides was decreased, thereby leading to the simultaneous improvement of tensile properties and fracture toughness. Brittle martensite-austenite (M-A) constituents were also formed in these steels during cooling, but did not deteriorate fracture toughness because they were decomposed to ferrite and fine carbides after tempering. Their simulated HAZs also had sufficient impact toughness after postweld heat treatment. These findings indicated that the reduction in C content to inhibit the formation of coarse cementite and to improve toughness and the increase in Mo and Ni to prevent the reduction in hardenability and to precipitate fine M₂C carbides were useful ways to improve simultaneously the tensile and fracture properties of the HAZs as well as the base metals.     

Effect of precipitation from tweed matrix on the mechanical properties in a metastable beta alloy of Ti-15-3

The effects of aging treatment on the microstructures and mechanical properties of a metastable beta titanium alloy Ti-15-3 (Ti−15V−3Al−3Sn-3Cr) have been investigated with hardness measurements, tensile test, and optical and electron microscopy. Precipitate-free beta structure with average grain size of about 56 μm was obtained after solution treatment at 800°C for 15 min followed by air cooling. Solution treated specimens were aged up to 800 h in the temperature range between 350 and 600°C. The morphology of the precipitates was varied significantly, depending on the aging temperature. The fine aggregates of α precipitates were dominant above 450°C. Peak hardness values were maintained up to 800 h at 500°C, which showed the superior thermal stability of α precipitates. Tensile strength increased up to 1600 MPa along with the decrease of elongation after aging at 350 and 400°C.     

Limit of ferrite grain refinement by severe plastic deformation of austenite

High-angle grain-boundary spacing in deformed austenite is analyzed using Ni-30Fe alloy to explain the change of ferrite grain size by severe plastic deformation (SPD) of austenite in low carbon steel. It is suggested that constant high-angle grain-boundary spacing in deformed austenite resulting from dynamic recrystallization (DRX) or geometric DRX is responsible for the limit of ferrite grain refinement over a certain level of plastic deformation of austenite.     

Effect of C Fraction on Corrosion Properties of High Interstitial Alloyed Stainless Steels

The effects of carbon fraction on various corrosion properties of Fe18Cr10MnNC alloys were investigated. The alloys contained 0.6?wt pct of nitrogen and carbon, and the carbon fraction varied from 0.03 to 0.47. With increasing the carbon fraction, corrosion potential raised, critical dissolution rate decreased, and pitting potential increased. The high carbon fraction was responsible for high resistance against intergranular corrosion of the alloys aged at 1123?K (850?°C) for 100?seconds. But after aging at 1123?K (850?°C) for 600?seconds, the intergranular corrosion accelerated with increasing the carbon fraction.     

Hydrophobicity and transparency of Al2O3-based poly-tetra-fluoro-ethylene composite thin films using aerosol deposition

Alumina and polytetrafluoroethylene (Al₂O₃-PTFE) composite films were fabricated by a simple aerosol deposition (AD) process, to confirm its applicability for various display screens requiring water resistant, anti-smudge and easy-to-clean properties. The surface morphologies, hydrophobic properties, and transparencies of the composite films with different PTFE contents, varying from 0.01 to 1?wt% were investigated. As a result, the composite films with over 0.3?wt% PTFE showed a sudden rise in surface roughness and low transmittance, despite having the highest contact angle of 128° at a PTFE content of 0.3?wt%. From the energy dispersive spectrometer analysis, the crash-cushioning effect of PTFE and agglomerated PTFE particles were determined to be major causes of surface roughness and opacity. In contrast, the transmittance showed a tendency to be enhanced, with an increasing PTFE content in the range of 0.01, 0.05, and 0.1?wt% PTFE, respectively. Especially, the film with 0.1?wt% of PTFE had contact angle of 111° and exhibited a high transmittance of over 75%, which was inferred to be an appropriate amount of PTFE, with a high elongation filling up the surface and the internal defects, leading to an enhancement of transparency. Consequently, these results implied that the AD-prepared Al₂O₃-PTFE composite coatings are promising candidates for various display applications.     

Red yeast barley reduces plasma glucose levels and activates AMPK phosphorylation in <Emphasis Type="Italic">db/db</Emphasis> mice

Red yeast (Monascus purpureus) fermented over rice has a limited hypoglycemic activity. To enhance its glucose-lowering effect, we fermented red yeast over waxy barley, a hypoglycemic grain with high levels of fibers and β-glucans, and investigated the metabolic effects of red yeast barley (RYB) in high-fat-fed hyperglycemic db/db mice for 6 weeks. The fasting glucose levels were significantly reduced in the RYB group at 6 weeks by 25% (p<0.05), as was the glucose tolerance (−27% of area under the curve in RYB vs. controls, p<0.05). Plasma insulin levels and the expression of PPAR-γ were unaltered, however, the phosphorylation activation of hepatic AMP-activated protein kinase (AMPK) was increased significantly in RYB group compared with controls suggesting that hypoglycemic effect of RYB may be achieved by AMPK-dependent mechanism. RYB may be used as a hypoglycemic functional food modulating cellular AMPK activity.     

A study on optimal scan conditions of Big Bore multi-slice computed tomography based on radiation dose and image noise

The newly introduced Big Bore computed tomography (CT) has a possibility to increase the tube current product scan time (mA s) for compensation of image degradation due to larger gentry opening without sound guideline. The objective of this paper is to derive optimal scan conditions for Big Bore CT scanner, mainly relating to the dose of diagnostic CT. The weighted CT dose index (CTDI(w)) was estimated at five typical protocols, such as head and neck, brain, paediatric, chest and abdomen. Noises were analysed in a circle of 1 or 2 cm of diameter in CT image slice. The results showed that measured CTDI(w) values generally follow the theoretical rule at all scanning conditions of every protocol. Although image noises decrease with increment of mA s, analysed image noises do follow the theoretical rule, but only in specific protocols. This phenomenon is presumed to result from the photon energy spectra arriving at the detection system of the Big Bore scanner.     

Effects of tomato ketchup and tomato paste extract on hepatic lipid accumulation and adipogenesis

Food Science and Biotechnology - Tomatoes include high levels of lycopene, which is a potent antioxidative, hypolipidemic, and antidiabetic phytochemical. The intake of lycopene is associated with...