The orientation dependence of the austenite‐to‐martensite transformation during uniaxial tensile testing was modelled using the phenomenological theory of martensite crystallography and the ...mechanical driving force. It was validated experimentally by means of electron backscatter diffraction measurements on a pre‐defined zone of a quenched and partitioned steel during interrupted tensile tests. A close match is obtained between the predictions of the model and the experimental observations.
In the first part of this two-part paper, the effect of increasing Ce in solid solution on the recrystallization and texture evolution of four Mg–Zn–Ce sheets was investigated in the as-deformed and ...annealed state. In this second part, the effect of rolling speed on the microstructure and texture development of these alloys is evaluated. The effect of rolling speed on the recrystallization and texture evolution of four Mg–Zn–Ce sheets was investigated at as-deformed and different stages of annealing. The deformation microstructure was obtained through two stages that can be characterised as rough rolling and finish rolling. To study the effect of finish rolling temperature, one rolling pass with a 65 % reduction in thickness was performed at 300 and 450 °C and at rolling speeds of 15 and 1000 m/min. The results showed that by increasing the rolling speed, more secondary and compression twins were activated, which leads to the formation of more numerous local shear bands and a more uniform microstructure. Annealing secondary twins (S-twins) and their vicinity were observed to be the preferential sites for nucleation, and it seems that recrystallization on S-twins contributes to basal texture weakening. Therefore, an increasing number of such twins increase the texture weakening. In this way, the combination of these RE additions and HSR resulted in a weaker deformed and annealed texture.
Context. The Very Large Telescope Interferometer (VLTI) has been providing breakthrough images of the dust in the central parsecs of active galactic nuclei (AGNs), which is thought to be a key ...component of the AGN unification scheme and AGN host galaxy interaction. In single infrared bands, these images can enjoin multiple interpretations, some of which could challenge the unification scheme. This is the case for the archetypal type 2 AGN of NGC 1068, whereby the degeneracy is reduced by multi-band temperature maps that are hindered by an ambiguity in the alignment between different single-band images. Aims. We aim to solve this problem by creating a chromatic model capable of simultaneously explaining the VLTI GRAVITY+MATISSE 2 μm–13 μm observations of AGNs hosted by NGC 1068. Methods. We employed a simple disk and wind geometry populated by spherical black-body emitters and dust obscuration to create a versatile multi-wavelength modelling method for chromatic IR interferometric data of dusty objects. Results. This simple geometry is capable of reproducing the spectro-interferometric data of NGC 1068 from the K through N bands. It explains the complex single band images with obscuration and inclination effects, and it solves the alignment problem between bands. We find that the resulting model disk and wind geometry is consistent with previous studies of comparable and larger scales. For example, compared to molecular gas emission, our model wind position angle (PA) of 23 2 2° is close to the mas-scale outflowing CO(6–5) PA of ∼33° seen with ALMA. The equivalent 90° offset model disk PA is also consistent with the CO(6–5) disk axis of 112° as well as the mas-scale disk axis from CO(2–1), CO(3–2), and HCO + (4–3) of 115 ± 5°. Furthermore, the resulting model images visually resemble the multiple achromatic image reconstructions of the same data when evaluated at the same wavelengths. We conclude that the IR emitting structure surrounding the AGN within NGC 1068 can indeed be explained by the clumpy disk+wind iteration of the AGN unification scheme. Within the scheme, we find that it is best explained as a type 2 AGN and the obscuring dust chemistry can be explained by a mix of olivine silicates and 16 ± 1% amorphous carbon.
Two AHSS steels (0.2C-2.4Mn-1.5Si with/without Nb+Cr addition) were subjected to pilot reversing mill hot rolling in 5 passes varying the finish rolling and coiling temperature. After coiling ...simulation, the final microstructures were characterised by the EBSD technique measurements. One sample was analysed to determine the presence and the level of Nb precipitated by TEM and chemical extraction. The austenite evolution was inferred from the measured transformation textures and reconstructed final austenite texture and microstructure. Further insights were obtained by comparing the results to a semi-empirical austenite evolution model, which predicted recrystallization behaviour and level of Nb precipitation. From the combined experimental and modelling work it was shown that Nb addition led to recrystallization inhibition via partial strain induced precipitation for this high Mn and high Si steel. Applying the austenite evolution model to a more realistic industrial hot strip rolling schedule revealed earlier Nb precipitation during hot rolling and higher strain accumulation with a finer grain size. The final Nb level in solution was lower for the industrial schedule, although a significant amount was not precipitated (two thirds of the total).
The reactivity of the diaminoacetylene Pip‐C≡C‐Pip (Pip=piperidyl=NC5H10) towards phenyldichloro‐ and triphenylborane is presented. In the case of the less Lewis acidic PhBCl2, the first example of a ...double Lewis adduct of a vicinal dicarbenoid is reported. For the more Lewis acidic triphenylborane, coordination to the bifunctional carbene leads to a mild B−C bond activation, resulting in a syn‐1,2‐carboboration. Ensuing cis/trans isomerization yields a novel ethylene‐bridged frustrated Lewis pair (FLP). The compounds were characterized using multinuclear NMR spectroscopy, structural analysis, and mass spectrometry. Reactivity studies of both isomers with the N‐heterocyclic carbene 1,3‐dimethylimidazol‐2‐ylidene (IMe) aided in elucidating the proposed isomerization pathway. DFT calculations were carried out to elucidate the reaction mechanism. The rather low free energy of activation is consistent with the observation that the reaction proceeds smoothly at room temperature.
More than the sum of its parts: The reactivity of a vicinal dicarbenoid towards organoboron reagents has been investigated. Depending on the Lewis acidity of the borane, double adduct formation or B−C bond activation in a formal syn‐1,2‐carboboration is observed. The obtained activation product undergoes cis/trans isomerization to an internal Lewis pair.
Aims. We present aperture-synthesis imaging of the red supergiant Antares (α Sco) in the CO first overtone lines. Our goal is to probe the structure and dynamics of the outer atmosphere. Methods. ...Antares was observed between 2.28 μm and 2.31 μm with VLTI/AMBER with spectral resolutions of up to 12 000 and angular resolutions as high as 7.2 mas at two epochs with a time interval of one year. Results. The reconstructed images in individual CO lines reveal that the star appears differently in the blue wing, line center, and red wing. In 2009, the images in the line center and red wing show an asymmetrically extended component, while the image in the blue wing shows little trace of it. In 2010, however, the extended component appears in the line center and blue wing, and the image in the red wing shows only a weak signature of the extended component. Our modeling of these AMBER data suggests that there is an outer atmosphere (MOLsphere) extending to 1.2–1.4 R⋆ with CO column densities of (0.5–1) × 1020 cm-2 and a temperature of ~2000 K. The CO line images observed in 2009 can be explained by a model in which a large patch or clump of CO gas is infalling at only 0–5 km s-1, while the CO gas in the remaining region is moving outward much faster at 20–30 km s-1. The images observed in 2010 suggest that a large clump of CO gas is moving outward at 0–5 km s-1, while the CO gas in the remaining region is infalling much faster at 20–30 km s-1. In contrast to the images in the CO lines, the AMBER data in the continuum show only a slight deviation from limb-darkened disks and only marginal time variations. We derive a limb-darkened disk diameter of 37.38 ± 0.06 mas and a power-law-type limb-darkening parameter of (8.7 ± 1.6) × 10-2 (2009) and 37.31 ± 0.09 mas and (1.5 ± 0.2) × 10-1 (2010). We also obtain an effective temperature of 3660 ± 120 K (the error includes the effects of the temporal flux variation that is assumed to be the same as Betelgeuse) and a luminosity of log L⋆/L⊙ = 4.88 ± 0.23. Comparison with theoretical evolutionary tracks suggests a mass of 15 ± 5 M⊙ with an age of 11–15 Myr, which is consistent with the recently estimated age for the Upper Scorpius OB association. Conclusions. The properties of the outer atmosphere of Antares are similar to those of another well-studied red supergiant, Betelgeuse. The density of the extended outer atmosphere of Antares and Betelgeuse is higher than predicted by the current 3D convection simulations by at least six orders of magnitude, implying that convection alone cannot explain the formation of the extended outer atmosphere.
The effect of an automotive paint bake (PB) thermal cycle on the microstructural evolution and the mechanical properties of resistance spot welded advanced high strength steel is presented in this ...work. Mechanical behavior of the heat-treated welds reveals an increase in maximum cross-tension strength, displacement and subsequently energy absorption capability when 453 K (180 °C)-20 minutes a bake thermal cycle is applied after welding. The microstructures of resistance spot welds with and without a PB heat treatment were characterized using scanning and transmission electron microscopy (TEM). TEM analysis revealed that the weld nugget and HAZ of the resistance spot welds consist of a martensitic microstructure. The microstructural analysis of the post-weld heat-treated samples shows the presence of
ε
carbides in a martensitic matrix within the weld nugget and the HAZ. It is shown that the improved mechanical response of the paint-baked welds is associated with carbide precipitation during heat treatment.
The magnetoelectric behavior of a dual-phase dimensionally graded magnetostrictive-piezoelectric composite is modeled in this article. The cantilever is formed by piezoelectric macro-fiber composite ...bonded to a Ni cantilever. Theoretical estimates show a large magnetoelectric voltage coefficient of 100V/(cmOe) at electromechanical resonance frequency. An additive effect was realized when an acceleration and magnetic field was applied to the structure simultaneously. Applied magnetic field of 10Oe and shaker acceleration of 0.02g induce the approximately equal output voltage of 20–35V.
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