Two complementary methods were used to analyse the deformation mechanisms involved in the plasticity of commercially pure titanium during compressive loading: neutron diffraction and the ...self-consistent model. The strain response of 15 crystallographic planes was tracked during the measurement, in directions both parallel and transverse to the straining direction, providing new insight into the mechanical behaviour of the polycrystal. The neutron diffraction results show evidence of tensile twins in the titanium alloy studied. The twin volume fraction was determined from the change in crystallographic texture. The influence and the role of plastic anisotropy were also studied and explained in this work. Good agreement was found between the experimental and predicted results.
Additive manufacturing processes and especially the family of laser powder bed fusion technologies have a great industrial potential since it enables, from metal powder beds, to produce full density ...complex monolithic parts. The high-temperature gradient resulting from the locally concentrated energy input leads to strong temperature fields driving non-negligible residual stress gradients, part deformations and crack formation. Resulting stress and texture gradients arise from the interdependent physical phenomena (metallurgical, thermal, mechanical and fluid mechanics) occurring during the process. Present work focuses on the residual stress being built in an austenitic stainless steel cubical shaped part of 1 cm side, prepared by a laser powder bed fusion process from a gas-atomized metallic powder (from martensitic X40CrMoVN16-2 stainless steel), through a full residual stress tensor mapping achieved thanks to neutron diffraction. Stress analyses incorporate morphological and crystallographic textures, as well as elastic anisotropy. Components of the principal stress tensor display compressive values close to the baseplate that develop into low compression, and a tensile stress state at the subsurface (surrounding thermal history effects). Results also underline the strong impact of matter environment (and thus thermal environment) onto stress gradient magnitude and the complex loading origins of the residual stress.
During hot forming process, tools are exposed to severe and complex loads. As result, damages by oxidation and thermal and mechanical fatigue are generated which cause tool failure. The aim of this ...work is a multi-scale analysis of damaged hot forging tools. An expertise of main failures on industrial hot-forging die, made of hot-working die steel X40CrMoV5-1 is presented. Die was previously sectioned and examined after its service life. The measurements of micro-hardness depth profiles, SEM and optical observations of oxidized surfaces were achieved on the most loaded sections of the die. An analysis of residual stresses in damaged die was also performed in order to estimate and then predict the most solicited zones on the die, a simplified numerical approach was investigated. The cracks on the observed areas are caused by local elasto-plastic stress due to mechanical load. A good correlation between expertise and numerical results was established.
•A failure analysis of used hot forming die is presented.•Different damage phenomena characterizations, occurred in failed die are discussed.•As the complexity damage modes, analysis of residual stresses is also performed.•Local stress is determined by numerical approach based on multilinear hardening model.•A thermal superficial softening of failed die is investigated during forging process.
We present 0.̋5 resolution ALMA detections of the observed 246 GHz continuum, CI 3P2→3P1 fine structure line (CI2–1), CO(7–6), and H2O lines in the z = 2.161 radio galaxy MRC1138-262, the so-called ...Spiderweb galaxy. We detect strong CI2–1 emission both at the position of the radio core, and in a second component ~4 kpc away from it. The 1100 km s-1 broad CI2–1 line in this latter component, combined with its H2 mass of 1.6 × 1010 M⊙, implies that this emission must come from a compact region <60 pc, possibly containing a second active galactic nucleus (AGN). The combined H2 mass derived for both objects, using the CI2–1 emission, is 3.3 × 1010 M⊙. The total CO(7–6)/CI2–1 line flux ratio of 0.2 suggests a low excitation molecular gas reservoir and/or enhanced atomic carbon in cosmic ray dominated regions. We detect spatially-resolved H2O 211−202 emission – for the first time in a high-z unlensed galaxy – near the outer radio lobe to the east, and near the bend of the radio jet to the west of the radio galaxy. No underlying 246 GHz continuum emission is seen at either position. We suggest that the H2O emission is excited in the cooling region behind slow (10–40 km s-1) shocks in dense molecular gas (103−5 cm-3). The extended water emission is likely evidence of the radio jet’s impact on cooling and forming molecules in the post-shocked gas in the halo and inter-cluster gas, similar to what is seen in low-z clusters and other high-z radio galaxies. These observations imply that the passage of the radio jet in the interstellar and inter-cluster medium not only heats gas to high temperatures, as is commonly assumed or found in simulations, but also induces cooling and dissipation, which can lead to substantial amounts of cold dense molecular gas. The formation of molecules and strong dissipation in the halo gas of MRC1138-262 may explain both the extended diffuse molecular gas and the young stars observed around MRC1138-262.
A round-robin test of X-ray residual stress determination was performed by the Groupement Francais d'Analyse des Contraintes and involved 16 laboratories. The standard deviation of the measurements ...was about 36 MPa, but a posttreatment of the raw data with the same software reduced the dispersion to 19 MPa. Analysis of the uncertainty sources (goniometer alignment, operator, counting statistics, nonlinearity of the material, etc.) revealed that the main sources come from the data treatment and the operator.
Partial dislocation nucleation and multiplication in III–V semiconductor compounds are usually ascribed to the difference in mobility between α and β partials. These differences in mobility increase ...when the temperature decreases, so that the contribution of twinning to the deformation mechanisms becomes important for high stresses and low temperatures. Starting from transmission electron microscopic observations of plastically deformed InSb under high stresses and hydrostatic pressure at room temperature, showing the multiplication of α as well as β partial dislocations, a model for the partial dislocation multiplication is proposed. This model does not rely on the difference in α and β partial dislocation mobilities but on the formation of Lomer‐Cottrell sessile dislocations issued from dislocation dipoles.
Les phénomènes de nucléation et de multiplication de dislocations partielles dans les semi‐conducteurs III–V sont habituellement attribués à la différence de mobilité entre les partielles α et β. Cette différence de mobilité augmente lorsque la température diminue, de sorte que la contribution du maclage dans les mécanismes de déformation devient importante pour les fortes contraintes et les basses températures. A partir d'observations en microscopie électronique en transmission de InSb déformé à température ambiante sous fortes contraintes et sous pression hydrostatique, mettant en évidence la multiplication de dislocations partielles α et β, nous proposons un modèle de multiplication des dislocations partielles. Ce modèle ne fait pas appel à la différence de mobilité entre les dislocations partielles α et β, mais il fait intervenir la formation de dislocations sessiles de Lomer‐Cottrell à partir de dipoles de dislocations.
This paper considers the plasticity of InSb under high stress, at low temperatures. The studies cover the plasticity of InSb in the temperature range between 20 and 200 °C and under stress, which is ...applied by superimposing uniaxial pressure on a confining hydrostatic pressure. The analysis of the deformed substructures by transmission electron microscopy revealed the existence of different deformation mechanisms at different temperatures, and consequently, stress regimes. At temperatures T ≥ 50 °C the dominant deformation mechanism is the glide of perfect dislocations, while at room temperature the deformation can be attributed to partial dislocations. At lower temperatures, screw dislocations become dominant, a fact that demonstrates the small mobility of these dislocations. Extended stacking faults introduced by the dissociation of 60° β‐type segments demonstrate the higher mobility of the 90° β partial dislocations compared to the mobility of the 30° β ones. In contrast, the absence of an extended dissociation for the 60° α‐type dislocations suggests that the 90° α and the 30° α partial dislocations have the same mobility. An additional interesting issue arises from the observations showing a small difference in mobility between the 30° α and the 30° β partial dislocations. The significance of these observations is discussed and the results are correlated to similar observations in other III–V compounds.
La plasticité sous forte contrainte de l'antimoniure d'indium a été étudiée dans le domaine de température de 20 à 200 °C au moyen d'un appareillage de déformation sous pression de confinement solide. L'analyse des sous‐structures de dislocations par microscopie électronique en transmission nous a permis de mettre en évidence qu'un abaissement de la température, et l'augmentation de la contrainte qui en résulte, modifient le mécanisme de déformation. Pour T ≥ 50 °C, la déformation procède par glissement de dislocations parfaites. A température ambiante, les sous‐structures de déformation sont principalement constituées de dislocations partielles. Le caractère vis des dislocations parfaites est de plus en plus marqué à mesure que la température diminue, ce qui témoigne de la faible mobilité de ces segments. Des fautes d'empilement étendues sur des fronts à 60° β montrent la plus grande mobilité des dislocations partielles à 90° β par rapport aux dislocations partielles à 30° β. Aucun événement semblable n'a été observé sur des fronts à 60° α. Ceci suggère une mobilité identique des dislocations partielles à 90° α et à 30° α. De plus les observations montrent que les dislocations partielles 30° α et 30° β ont une faible différence de mobilité. Les résultats sont discutés et comparés aux autres composés III–V.
The single‐step, fast spray‐drying process may represent a valuable alternative to the multistep, time‐consuming freeze‐drying process in the area of formulation and processing of ...biopharmaceu‐ticals. In this study, we tested the use of sucrose and hydroxypropyl‐β‐cyclodextrin (HP‐β‐CD) as stabilizing excipients in the spray‐drying of a model protein, β‐galactosidase. The solutions were processed using a Bu?chi 190 cocurrent Mini Spray Dryer at an outlet temperature of 61 ± 2 °C. The powders were redissolved and analyzed for catalytic activity, aggregation, chemical decomposition, and thermal susceptibility as observed by high‐resolution calorimetry. Spray‐drying significantly inactivated β‐galactosidase. Spray‐drying β‐galactosidase in the presence of sucrose did not prevent inactivation. However, after spray‐drying β‐galactosidase in the presence of HP‐β‐CD, or HP‐β‐CD and sucrose, full catalytic activity was exhibited on reconstitution. Furthermore, the reconstituted product was unchanged in terms of molecular weight, charge, and thermal stability. These findings are consistent with a hypothesis that the change responsible for inactivation of β‐galactosidase was mainly a monomolecular, noncovalent change, i.e., the formation of incorrect structures, that arose from surface denaturation. This study clearly demonstrates that cyclodextrins can be useful stabilizing excipients in the preparation of spray‐dried protein pharmaceuticals.
Nanostructured SiC has been elaborated from coarse grained SiC by mechanical attrition. Milling time ranged from 1 h to 14 h. Crystallites sizes and microstrains have been determined from X-ray ...diffraction peak profile analysis using a “one peak method”. According to this method, the average crystallite size calculated from the (11.0) and (10.4) 6H-SiC reflections is less than 50 nm with a milling time of one hour. Up to 6 h milling time, crystallite sizes determined from these two peaks are very close, indicating that crystallite size evolution versus milling time is nearly identical for these two crystallographic directions. We observe a strong decrease of the crystallite size up to 3 h milling time. A saturation value is reached after 6 h milling time, associated with a strong increase of microstrains.
From density-pressure measurements performed in uniaxial compression, the powder's compressibility behavior appears to be strongly related to changes in powder morphology and granularity during ball milling. The evolution of the powder morphology was followed by scanning electron microscopy. The iron contamination level by the steel vial and balls was controlled by X-ray microanalysis.
We present 0."5 resolution ALMA detections of the observed 246GHz continuum, CI^3P_2-^3P_1 fine structure line (CI2-1), CO(7-6) and H2O lines in the z=2.161 radio galaxy MRC1138-262, the 'Spiderweb ...Galaxy'. We detect strong CI2-1 emission both at the position of the radio core, and in a second component ~4kpc away from it. The 1100km/s broad CI2-1 line in this latter component, combined with its H2 mass of 1.6x10^10Msun implies this emission must come from a compact region <60pc, possibly containing a second AGN. The combined H2 mass derived for both objects using the CI2-1 emission is 3.3x10^10Msun. The total CO(7-6)/CI2-1 line flux ratio of 0.2 suggests a low excitation molecular gas reservoir and/or enhanced atomic carbon in cosmic-ray dominated regions. We detect spatially-resolved H2O 2_{11}-2_{02} emission - for the first time in a high-z un-lensed galaxy - near the outer radio lobe to the east, and near the bend of the radio jet to the west of the radio galaxy. No underlying 246GHz continuum emission is seen at either position. We suggest that the H2O emission is excited in the cooling region behind slow (10-40km/s) shocks in dense molecular gas (10^{3-5} cm^-3). The extended water emission is likely evidence of the radio jet's impact in cooling and forming molecules in the post-shocked gas in the halo and inter-cluster gas similar to what is seen in low-z clusters and other high-z radio galaxies. These observations imply that the passage of the radio jet in the interstellar and inter-cluster medium not only heats gas to high temperatures as is commonly assumed or found in simulations, but also induces cooling and dissipation which can lead to substantial amounts of cold dense molecular gas. The formation of molecules and strong dissipation in the halo gas of MRC1138-262 may explain both the extended diffuse molecular gas and young stars observed around MRC1138-262.
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