Deformation and annealing behaviour of a low carbon high Mn TWIP steel microalloyed with Ti

ABSTRACT

A low carbon high Mn, Ti microalloyed dual phase TWIP steel has been processed through cold rolling and annealing. X-ray diffraction reveals the maximum austenite (≈92%) in HRACST sample whereas, the 50CD sample shows 29% ferrite. The microstructure of HRAC and HRACST samples reveal austenite grains with annealing twins and deformation induced ferrite (DIF). The higher amount of DIF along with deformation twins form during cold deformation. Annealing at 500°C shows recovery, whereas at 700°C shows partial recrystallisation and at 900°C reveals almost full recrystallisation. TEM microstructures of the 900°C for 30?min samples reveal annealing twins with TiC particle. Strong Brass {110}<112> and Goss{110}<001> texture components are observed in HRAC, HRACST and 50CD samples. Goss Twin (GT) {113}<332> and Copper Twin (Cu-T) {552}<115> components are observed in 50CD sample. Addition of Ti results in an average grain size of 20?μm. Maximum YS (1176?MPa) and UTS (1283?MPa) values with the lowest ductility of 11% have been obtained for the 50CD sample which is related to the formation of extensive deformation twin and a higher fraction of DIF. 700°C-30?min and 700°C-60?min samples show an increase in ductility (23% and 34%, respectively) with a marginal decrease in tensile strength (1054?MPa). Annealing at 900°C shows ductility restoration up to 60% with higher tensile strength compared to HRACST sample. Ductile fracture of HRAC and HRACST samples transform to brittle fracture in the 50CD sample. Annealing at 900°C for 30?min shows ductile fracture with some (Fe, Mn)S and TiC particles.     

Gamma-ray,X-ray and ultraviolet light induced low temperature thermoluminescencez of KN3 and NaN3

Abstract

On évalue, pour une chaine atomique linéaire, la variation du coefficient de dilatation thermique Δ α lorsque la chaine est sous contrainte. On en déduit la variation du module de Young avec la température. L'accord raisonnable, sur ce second point, avec les résultats expérimentaux montre que le sens de variation trouvé pour Δ α demeure, au moins qualitativement, pour un cristal à 3 dimensions.

On montre alors que, pour un cristal irradié sous contrainte par des particules de grande énergie, cette variation Δ α peut entrainer une contribution négative au fluage.

THERMAL EXPANSION OF A LINEAR CHAIN UNDER STRESS APPLICATION TO CREEP UNDER IRRADIATION

Variations of thermal expansion coefficient Δ α of a linear atomic row under stress, are evaluated. Variations of Young's modulus with temperature are deduced. A reasonable agreement, on this point, with experimental measurements indicates that at least the sign obtained for Δ α subsists qualitatively for a 3-dimensional crystal.

It is then shown that, for a crystal irradiated under stress with high energy particles, this variation Δ α may lead to a negative contribution to creep.     

Effect of High-pressure Treatment on Polyphenoloxidase Activity of the Agaricus Bisporus Mushroom

High pressure treatments (100-500 Mpa/4 °C/10 min) were carried out on freshly sliced mushrooms ( Agaricus bisporus ) and on liquid extract. Pressure above 200 MPa led to respiratory activity loss, significant enzymatic browning and polyphenoloxidase (PPO) activation in treated mushrooms. Increasing pressure from 200 to 500 MPa enhanced the PPO activation (in whole tissue and in liquid extract). Stabilization of mushroom by high-pressure (HP) alone cannot be considered. A combination of HP with thermal or chemical treatments is found necessary.     

Design of angle-dispersive spectrometer for xanes under high pressure

Abstract

The angle-dispersive spectrometer with elliptically curved crystal for XANES is proposed. The design is suited to high pressure research with a diamond-anvil cell.

Un spectromètre de dispersion angulaire au cristal elliptiquement courbé pour XANES est proposé. Sa construction est spécialement convenable à la recherche dans le domaine des hautes pressions avec chambre à l'enclume de diamant.     

Controle de l'enrichissement de l'uranium metallique a l'aide du nitrate de cellulose

Abstract

Le nitrate de cellulose permet d'enregistrer le passage de particules α done de mesurer l'activité spécifique d'une source radioactive épaisse. Nous utilisons cette propriété pour mesurer le taux d'eorichissement en uranium 235 d'un éhantillon d'uranium métallique. Afin de faciliter la mesure et de s'affranchir de la lecture du nombre de traces au microscope optique, les échantillons sont révélés dans un bain spécial et le nombre de traces α par unité de surface est évalué en fonction du pouvoir réflecteur de l'échantillon.

Les moyens et le temps nécessaires pour une mesure sont, ainsi que le prix de revient, très réduits.

Cellulose nitrate can be used for the registration of α-tracks and therefore for the measurement of the specific activity of thick radioactive sources. This characteristic is applied to the determination of ²³⁵U enrichment rate of metallic uranium samples. For the measurement of track density a method is developed which replaces the counting procedure under a microscope. The samples are etched in special solutions and track density is evaluated from the diffuse reflecting power of the samples.

The main advantages of this method are its rapidity, easiness and low cost.     

Effect of plating and incubation conditions on the detection of lactic acid bacteria after high hydrostatic pressure treatment

ABSTRACT

Lactic acid bacteria (Leuconostoc mesenteroides, Enterococcus faecalis, and Lactobacillus fermentum) were subjected to high hydrostatic pressures (HHPs) of 400 and 600?MPa at 25°C for 10?min in phosphate-buffered saline. Differential plating methods were applied to evaluate HHP-treated cell populations, assuming that healthy and injured cells during plate incubation survived maximum and minimal stress, respectively. The stress was altered by using several selective media in combination with aerobic or anaerobic incubation at 25°C or 30°C. E. faecalis was detectable after 600?MPa treatment while L. mesenteroides and L. fermentum were nondetectable. Specific combinations of incubation conditions were suggested to determine maximum and minimum viable counts of L. mesenteroides and E. faecalis. The difference between the maximum and minimum counts can be used to evaluate HHP-injured population with reduced risks to overestimate healthy and/or underestimate HHP-injured cells.     

Equation of state of 7LiD up to 6 GPa from neutron powder diffraction experiments

Abstract

The equation of state of ⁷LiD has been measured at 300 K up to 6GPa by 90° time-of-flight neutron scattering methods, in a novel cell with toroidal anvils. The increased precision over previous data allows to check theoretical calculations on lithium hydrides.

L'équation d'état de ⁷LiD a été établie à 300 K jusqu'à 6 GPa par des mesures de durée de vol de neutrons diffractés à 90°, dans une cellule à enclumes toroidales de conception originale. La prkision de ces mesures permet un test significatif des calculs théoriques sur les hydrures de lithium.     

Beneficial effects of an ultra-fine α-SiC incorporation on the sinterability and mechanical properties of ZrB2

A fully dense ZrB₂ ceramic containing 10 vol. % ultra-fine α-SiC particulate was successfully hot pressed at 1900 °C for 20 min and 40–50 MPa of applied pressure. Faceted ZrB₂ grains (average size ≈3 μm) and SiC particles dispersed regularly characterized the base material. No extra secondary phases were found. The introduction of the ultra-fine α-SiC particulate was recognized as the key factor that enabled both the control of the diboride grain growth and the achievement of full density. The mechanical properties offered an interesting combination of data: 4.8±0.2 MPafracture toughness, 507±4 GPa Young’s modulus, 0.12 Poisson’sratio, and 835±35 MPa flexural strength at room temperature. The flexural strength measured at 1500 °C (in air) provided values of 300±35 MPa. The incorporated ultra-fine α-SiC particulate was fundamental, sinterability apart, to enhancing the strength and oxidation resistance of ZrB₂. The latter property was tested at 1450 °C for 20 h in flowing dry air. In such oxidizing conditions, the formation of a thin external borosilicate glassy coating supplied partial protection for the faces of the material exposed to the hot environment. The oxidation attack penetrated into the material’s bulk and created a 200-μm-thick zirconia scale. The SiC particulate included in the oxide scale, lost by active oxidation, left carbon-based inclusions in the formerly occupied sites. PACS 81.05.Je; 81.20.Ev; 81.70.Bt     

Evaluation of the importance of germinative cycles for destruction of bacillus cereus spores in miniature cheeses

Our objective was to determine the effect of high pressure on inactivation of spores of Bacillus cereus ATCC 9139 inoculated into cheese made of raw cow's milk. Inoculated miniature cheeses were manufactured under controlled bacteriological conditions, vacuum packed and kept at 8 °C for 15 days after pressure treatment. Cheeses were submitted to pressures of 300, 400 or 500 MPa at 30 °C, during 15 min. Some of them were treated with a germination cycle of 60 MPa at 30 °C for 210 min. Lethality was calculated comparing surviving sample counts to control ones. Adding the germinative cycle resulted in higher efficiency, and when applied with 500 MPa, lethality reached 2.0 log cfu/mL. We saw that with both cycles initial counts of spores diminish, but all of them were not inactivated. However, considering that in raw milk mesophilic spore counts are 2.6-2.9 log cfu/mL, this treatment may be useful.     

Etude des mouvements moléculaires du furanne en phases plastique et liquide par relaxation magnétique nucléaire

Les temps de relaxation spin-réseau du proton ont été mesurés dans les phases liquide et plastique du furanne pur et en solution dans le furanne perdeutéré, les relaxations nucléaires d'origine intra et inter-moléculaire ont été ainsi séparées. Des temps de corrélation pour le second harmonique sphérique τ₂ ont été déduits de ces mesures et comparés aux temps de corrélation du premier harmonique sphérique τ₁ obtenus par des mesures antérieures d'absorption micro-onde ; les valeurs du coefficient de diffusion translationnelle sont estimées en phase liquide.

Sur la base de ces résultats et en utilisant, pour la phase plastique, les donnés cristallographiques, un modèle est proposé pour dépeindre les mouvements réorientationnels des molécules dans chacune des deux phases condensées.

Dans le liquide, près du point triple, un modèle de type Ivanov s'applique avec des angles moyens de saut voisins de 50° et des durées de piegeage orientationnel de l'ordre de 1,3 ps. En augmentant la température, les temps de résidence tendent à devenir comparables aux durées de saut ou même inférieurs.

Dans la phase plastique, les sauts réorientationnels ont lieu de façon concertée (simultanée) entre les quatre orientations permises. Un modèle analytique décrivant les mouvements d'un ensemble de rotateurs dans un potentiel de symétrie rectangulaire permet d'expliquer les résultats expérimentaux en supposant que les sauts ont lieu de façon privilégiée entre puits de potentiel non adjacents. Un calcul numérique confirme l'existence de quatre puits de potentiel séparés par de faibles barrières et montre que les corrélations d'orientation ont principalement pour origine des intéractions de type Van der Waals entre atomes d'hydrogène de molécules voisines.     

Réaction de substitution d'un complexe paramagnétique du nickel (II): Etude du solvate Ni(HMPT)4 2+ par RMN pulsée du phosphore-31

Un complexe tétraédrique du nickel (II) est étudié cinétiquement pour la première fois. Le solvate Ni(HMPT)₄ ²⁺, 2ClO₄ ^- est préparé au sein du HMPT anhydre, et les temps de relaxation de ³¹P mesurés à deux fréquences (8 et 14 MHz), six températures (8–66°C) et plusieurs concentrations (10^-3-10^-2 M). On détermine ainsi: le déplacement de contact: Δ_ωm = 41800 Hz (25°C et 14 MHz); la constante de couplage hyperfin A = 11,9 MHz; les temps de relaxation électronique, T _1e et T _2e = 1,32 et 0,69 × 10^-12 s; la trace du carré du tenseur de couplage spin-spin à champ nul Δ = 3,31 cm^-1 et le temps de corrélation afférent τ_v = 5,6 × 10^-12 s (à 25°C); les paramètres cinétiques de l'échange: libre: k _M (25°C) = (9,6 ± 0,60) × 10⁵ s^-1; ΔH ^? = 3,6 ± 2,1 kJ mol^-1; ΔS ^? = -117 ± 8 J deg^-1 mol^-1. Le mécanisme de cet échange est associatif, et l'enthalpie d'activation associée extrêmement faible, conformément aux prévisions qualitatives de la théorie du champ cristallin.     

Hydrostatic high pressure applied to food sterilization III: Application to spices and spice mixtures

Abstract

The response of suspensions of spices and spice mixtures in water to high pressure treatment was investigated. Inactivation of the microbial load–mainly aerobic and unaerobic spore formers–was strongly dependent on water activity and temperature. Samples were completely decontaminated after three pressure cycles (30 min at 80 MPa followed by 30 min at 350 MPa) at 70 °C at a minimum water activity of 0.91. Pressure treated samples were examined for sensory and chemical changes. No significant changes in odour and appearance were recognized by a trained sensory panel, nor were changes in the volatile compounds of the samples detected by static headspace gaschromatography.     

Measurements of the complex shear modulus of polymers under hydrostatic pressure usina the quartz resonator method

Abstract

The quartz resonator method measures the complex shear modulus or compliance of viscoelastic materials in the frequency range from 50 kHz to 140 MHz at temperatures between ?150°C and 300°C and pressures up to 1 GPa. This method can be applied to viscous fluids or polymer melts -even in their glassy or seminystalline regime.

The phase diagram of poly(diethylsiloxane) PDES (a mesophase polymer) was determined for two samples with different molecular weight at pressures up to 400 MPa and temperatures between 20°C and 100°C. Phase transitions are indicated by a sharp bend in the shear compliance although the volume effect of the mesophase-isotropic transition vanishes around 80 MPa.

The pressure dependence of the glass relaxation process (in PVAc), was studied by measuring the change of the complex shear modulus with pressure at constant temperatures between 95°C and 145°C and pressures up to 600 MPa. Additionally to the relaxation process, also the pressure dependence of the real part of the shear modulus in the glassy region can be determined for testing the dislocation concept in the meandermodell by W. Pechhold.     

Effect of high pressure treatment on the characteristics of a model emulsion

The aim of this study was to investigate the use of HP (high pressure) technology as a possible alternative method for decontamination of non-food medium. HP (500?MPa) did not modify significantly the physicochemical characteristics of a model non-food emulsion. A 10?min HP treatment inactivated totally Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Aspergillus niger and Candida albicans even if all the five microorganisms were inoculated together, regardless of the initial load. No recovery was observed until six months of storage at 25°C.     

Properties of Al-Si alloys prepared by rapid quenching from the melt under high pressure

Abstract

The substantial improvement of the mechanical properties and increase of superconductivity temperature of Al-Si alloys is achieved by rapid quenching from the melt under high pressure. The preparation procedure and the main properties of these alloys are presented.

L'amélioration notable de propriétés mècaniques et un accroissement de la températur critique de supra-conductivitě des alliages Al-Si sont obtenus par trempe rapide depuis la fusion, sous HP. La procédure de prkparation et la propriétés principales de ces alliages sont présentěs.     

Electron microscopy studies of void swelling and annealing of voids in aluminium irradiated with aluminium ions

Abstract

MgO single crystals implanted with Au⁺ ions (180 keV, 6 10¹⁶-10¹⁷ ions cm^?2) and annealed at temperatures between 25°C and 1100°C, have been analysed—by optical spectrophotometry—by Rutherford back-scattering (to confirm the effective presence and to study the distribution profile of Au atoms), and by TEM and X-ray diffraction (to identify the phases precipitated by thermal treatment).

Thermal annealing between 550°C and 1100°C produced an optical absorption band located between 565 nm and 600 nm. This band can be attributed to a fee Au precipitate with diameter varying from 50 to 200 Å. Larger metallic colloids 1000 Å are in simple orientation with the matrix.

Annealing at temperatures higher than 500°C produces a supplementary optical absorption located at 425 nm. This band can be attributed to Au plasma resonance.

After annealing for 15 min at 1100°C, a new phase is detected by X-ray diffraction and TEM and identified as Au₃Mg alloy with hexagonal structure.     

The role of electron shells in kinetic electron emission and luminescence under ion bombardment

Abstract

PRODUCTION ET RESTAURATION DES DEFAUTS PRODUITS PAR DES ELECTRONS A BASSE TEMPERATURE DANS LE CADMIUM On a irradié du cadmium par des électrons de 3 MeV à 20°K et étudié la restauration des défauts cristallins par des mesures de résistivité électrique. On compare nos résultats à ceux obtenus auparavant par R. R. Coltman concernant du cadmium irradié par des neutrons thermiques. Les différentes hypothèses pour expliquer ?important stade III sont discutées à la lumière des résultats connus sur les défauts ?irradiation et les défauts de trempe dans le cadmium.

Cadmium samples were irradiated with 3 MeV electrons at 20°K. The defect production and subsequent recovery up to 20°K were studied by means of electrical resistivity measurements. Our results are compared with those obtained earlier by R. R. Coltman relating to irradiated cadmium with thermal neutrons. The different hypotheses, in order to explain the important stage III, are discussed in the light of the existing experimental data on irradiation defects and quenched defects in cadmium.     

Effect of high hydrostatic pressure and reducing sodium chloride and phosphate on physicochemical properties of beef gels

ABSTRACT

The effect of high hydrostatic pressure (HHP) treatment (100–200?MPa, 10?min, 20°C) combined with sodium chloride and sodium phosphate on the physicochemical properties of beef gels was investigated. The water content, cooking losses, color, protein composition by SDS-PAGE analysis and texture parameters of beef gels were determined. The beef gels treated with high pressure at 150?MPa showed a synergistic effect in the increased water content and the decreased cooking losses compared with the unpressurized gels. The L*, a* and b* color values of beef gels were slightly decreased under HHP treatment at 100–200?MPa. In the SDS-PAGE analysis, the staining intensity of the α-actinin protein band was decreased in pressurized samples. The cohesiveness, adhesiveness, gel strength and modulus of elasticity were improved after HHP treatment. Application of high pressure treatment (150–200?MPa) before heat treatment would be beneficial for the manufacturing of low salt and/or low phosphate meat products for a healthy diet.     

Listeria monocytogenes cells injured by high hydrostatic pressure and their recovery in nutrient-rich or -free medium during cold storage

ABSTRACT

Cells of Listeria monocytogenes suspended in phosphate-buffered saline (PBS) were treated by high hydrostatic pressure (HHP; 500?MPa, 25°C, 10?min), diluted by ten folds using trypticase soy broth (TSB) or PBS, and stored at cold temperatures of 0–15°C. Viable cell count in TSB increased logarithmically close to the initial count at each storage temperature, while that in PBS increased temporarily and subsequently decreased to almost nondetectable level except the case at 15°C, where it showed logarithmic increase thereafter. Based on proliferation experiments where their healthy cells were inoculated to TSB or to PBS containing their heat-killed dead cells, it was suggested that increase in the viable count of HHP-treated cells in TSB and PBS could be ascribed to the recovery of colony forming ability and/or proliferation depending on the cold storage temperature.     

High Pressure/Thermal Treatments Effects on Functionality of Comminuted Muscle from Different Meat Species

This paper analyses the response of comminuted meat from different species (pork, chicken, turkey and ostrich) to heating (45 and 70 °C/30 min) under pressure (400 MPa) condition. The results (protein solubility, thermal analysis and rheological properties) indicate that the effect of temperature on protein denaturation is reduced if heating takes place at high pressure; then, the pressurization process partially preserves the protein from thermal denaturation. They also show that it is the processing conditions rather than the species that modulate protein thermal stability.