Multiple Recrystallization Research Articles

Study on microstructure evolution mechanism and inhomogeneous characteristic of 2219 aluminum alloy in hot flow forming

In order to reveal the evolution mechanism of the deformation microstructure of 2219 aluminum alloy tube under compression-shear stress, in this paper, flow forming tests and their numerical simulations were carried out, respectively, at temperatures from 250 °C to 400 °C. Meanwhile, a midrange layer index was proposed to analyze the gradient of deformation microstructure. The results show that multiple recrystallization mechanisms of the 2219 aluminum alloy are presented simultaneously during hot flow forming. The shear stress during forming is the main factor that generated the microstructure gradient along the thickness direction, and the recrystallization level is higher with higher shear strain. In addition, it is beneficial to improve microstructure homogeneity and mechanical properties by increasing thickness reduction or decreasing the temperature. This study provides guidance for microstructure control of the 2219 aluminum alloy tube flow forming process.

Selective growth of recrystallizing grains into well-characterized deformed aluminum at hardness indentation

The selective 3D growth of multiple recrystallization nuclei/grains around a hardness indentation into a deformed Al grain has been quantified through a new approach that combines two synchrotron techniques: 3D X-ray Laue micro-diffraction and diffraction contrast tomography. The former is used to characterize the deformed microstructure and nucleation, while the latter to track the nuclei's growth during interrupted in situ annealing. The combined 4D (x,y,z,t) datasets enable a detailed quantification of the local deformed microstructure consumed by the nuclei/grains and the boundary characteristics between them, including the stored energy and anisotropy of the orientation distribution of the deformation matrix, as well as the misorientation of the moving and non-moving boundary segments. It is found that only certain nuclei can grow into large sizes, and the growth is heterogeneous both among recrystallizing grains and along different directions. Neither the local stored energy nor the boundary misorientation, whether considered individually or in combination, can fully account for the observed growing and shrinking behavior. The growth difference along different directions is related to the deformation microstructure, specifically the geometrical alignment of dislocation boundaries. Furthermore, the effects of impingement of other recrystallizing grains, recovery of the matrix, and elastic strain/stress, on the growth heterogeneities are discussed in detail with a view towards developing advanced modeling with improved predictability of local recrystallization phenomena. The present study demonstrates the effectiveness of the new approach in enabling 3D analysis of recrystallization in complex materials, with potential applications in the development of advanced engineering materials.

Deep learning-based modeling of the strain rate-dependent thermomechanical processing response for a novel HIPed P/M nickel-based superalloy

Understanding and modeling the thermomechanical processing (TMP) response of a novel HIPed powder metallurgy (P/M) superalloy is crucial for its industrial application. This research characterizes the TMP-responding behavior of a novel HIPed FGH4113A P/M superalloy at 1000–1150 ℃ with strain rates of 0.01–5 s−1. The results depict that the adiabatic temperature rise during high-strain-rate TMP will accelerate the stress softening. A two-stage deep learning (DL)-based constitutive model framework, coupled with the deformation-induced temperature rise and its influence on flow stress, was first proposed and compared with the traditional Arrhenius-type model. Two types of DL approaches including the backpropagation (BP) and long short-term memory (LSTM) neural networks were trained and compared separately. It is noted that the LSTM neural network, considering previous deformation history in its unique gate structure, depicts the best prediction accuracy and generalization ability under large strains than other models. Then the strain rate-dependent hot workability and flow softening mechanisms were modeled and discussed. High-strain-rate deformation (5 s−1) in certain temperatures (1110–1150 ℃) can avoid unstable defects and transform the generated deformation heat into the driving force for the activation of multiple dynamic recrystallization mechanisms. Therefore, the near fully recrystallized microstructure can be achieved similarly to that at 0.01 s−1, indicating the feasibility and superiority of the high-strain-rate TMP of P/M superalloys in a certain temperature range.

Evolution of austenite microstructure and microalloy precipitation state during double-twist torsion testing on Nb-Ti-bearing steels

Double-twist torsion testing was applied to two Nb-Ti-bearing microalloyed steels to develop the relationship between the mechanical response and the resulting microstructure. The double-twist torsion test applies pairs of isothermal deformation passes to a single specimen at progressively lower temperatures. The test captures the effect of multiple deformation and recrystallization events and allows changes in recrystallization behavior to be assessed with fractional softening calculations. Conventional methods for determining fractional softening were applied to the torsional data to infer changes in recrystallization behavior and estimate the temperature regime where partial recrystallization occurs. The non-recrystallization temperature (Tnr) was determined with multi-step hot torsion testing and compared to the partial softening regime from the double-twist torsion test. The traditional concept of Tnr as a single temperature was thereby assessed with respect to the fractional softening calculations and corresponding microstructural changes at the micro- and nano- scales. Tnr was within the partial softening regime assessed with double-twist torsion testing, suggesting partial recrystallization near Tnr. Measurements of grain aspect ratio matched the trends observed in the fractional softening data and confirmed that strain accumulation occurred throughout the partial softening regime. Higher Nb contents corresponded to greater strain accumulation at lower temperatures within the partial softening regime. The precipitation of Nb(C,N) occurred at high temperatures in the form of caps precipitating on pre-existing Ti-rich cores, while fine-scale precipitation occurred at lower temperatures. Increasing the Nb-content increased both the extent of cap formation and the extent of fine-scale precipitation.

A petroliferous Ediacaran microbial-dominated carbonate reservoir play in the central Sichuan Basin, China: Characteristics and diagenetic evolution

Some of the largest gas accumulations in the central Sichuan Basin, south China are hosted in the Ediacaran microbial-dominated dolomite reservoirs. However, recent exploration of the Secondary Member of the Ediacaran Dengying Formation (Z2dn2) has been hampered by an overall lack of understanding of the microbial-dominated dolomite reservoir and its diagenetic evolution process due to its prolonged burial history and complex diagenetic alternation. On the basis of detailed petrographic and geochemical analysis, we have conducted an in-depth investigation on the characteristics, diagenetic sequence and pore evolution process of the microbial-dominated dolomite reservoirs. The main reservoir comprises thromatolitic dolomite, stromatolitic dolomite and straticulate dolomite. Five generations of cement are identified in the microbial dolomite lithofacies. Multiple dissolution, cementation, differential dolomitization, recrystallization and silicification are recognized. Based on elemental geochemistry, carbon and oxygen isotope characteristics, as well as fluid inclusion homogenization temperatures, cements are attributed to six diagenetic stages. The coupling of high-energy deposition, early supergene karsting and dolomitization processes are found to be essential for developing some world-class favorable high-quality microbial-dominated dolomite reservoirs in Z2dn2 in the central Sichuan Basin.

Evolution of the Microstructure and Mechanical Properties of AZ31 Magnesium Alloy Sheets during Multi-Pass Lowered-Temperature Rolling

AZ31 magnesium alloy sheets with 2 mm thickness were successfully fabricated by multi-pass lowered-temperature rolling. The evolution of the microstructure, texture, and mechanical properties during the rolling process was investigated. Based on the effect of multiple dynamic recrystallization, multi-pass lowered-temperature rolling not only refined the grain size obviously but also markedly improved the microstructure homogeneity. The resulting sheets had the optimal microstructure morphology with an average grain size of 4.38 μm. For the texture evolution, the stress state of the rolling process made the (0002) basal plane gradually rotate toward the rolling plane. However, the activation of non-basal slips due to the higher rolling temperature slightly rotated the (0002) basal plane point to the rolling direction (RD). As a result, the grain refinement strengthening and the texture strengthening together increased the yield stress to 202 MPa in the transverse direction (TD) and 189.8 MPa in the RD. Importantly, the resulting sheet concurrently exhibited excellent fracture elongation, about 38% in the TD and 39.2% in the RD. This was mainly ascribed to the finer grain size, giving rise to a significant effect of grain boundary sliding and the activation amount of non-basal slips.

Supramolecular architecture and SHG activity of organic crystals formed between the amidinothiourea and nicotinic acid

The single crystals of [1-(diaminomethylene)thiouron-1-ium] pyridine-3-carboxylate were grown using a solution growth technique. Depending on the concentration of the 1: 1 amidinothiourea: nicotinic acid solution, two different forms of 1: 1 crystal (orthorhombic non-centrosymmetric, P212121,(1), and monoclinic centrosymmetric, C2/c, (2)) were obtained. These phases differ in ordering, the orthorhombic phase is ordered, and in the monoclinic phase the 1-(diamino-methylene)-thiouron-1-ium cation is disordered and has two non-equivalent orientations with occupations of around 0.80 and 0.20. This ordering/disordering is due to the rate of crystallization: slow crystallization from a dilute solution leads to an ordered orthorhombic phase and quick crystallization from a saturated solution leads to a disordered monoclinic phase. Multiple recrystallizations of 1 and 2 from heavy water gives deuterated analogs 1d and 2d The conformation of the 1-(diaminomethylene)thiouron-1-ium cation in both phases is very similar and slightly non-planar. In the orthorhombic phase the plane of the carboxylate group is more twisted in relation to the plane of the pyridine ring than in the monoclinic phase. The oppositely charged components of the crystals, i.e., 1-(diaminomethylene)thiouron-1-ium cations and pyridine-3-carboxylate anions interact each other forming three-dimensional supramolecular architecture. Both compounds were also characterized by IR and Raman spectroscopy. Assignment of the vibrational bands were supported by the DFT calculations and the isotropic frequency shift. The SHG efficiency of the powdered orthorhombic phase relative to potassium dihydrogen phosphate (KDP) was found to be 1.70.

Smelting recrystallization of CsPbBrI2 perovskites for indoor and outdoor photovoltaics

A smelting multiple recrystallization strategy and its effects on the morphology, composition, and defects of CsPbBrI2 film were investigated. An optimal number (n = 2) of recrystallization cycles improved the crystallinity and phase purity, minimized the grain boundaries, and optimized the crystal structure, yielding a high-quality perovskite film with significantly reduced defects density. The corresponding photovoltaic devices exhibited a champion efficiency of 16.02% under AM 1.5 G illumination and presented an even higher indoor efficiency of 33.50% under an LED (2956 K, Pin: 334.41 μW/cm2). This recrystallization method offers a promising strategy for developing high-performance indoor and outdoor photovoltaics. Direct recrystallization in the cells was also explored to achieve enhanced stability and longer lifetime in humid conditions.

FepiM: A Novel Inverse Piecewise Method to Determine Isothermal Flow Curves for Hot Working

In forming simulations, flow curves are cardinal inputs to predict features, such as forming forces and material flow. The laboratory-scale experiments to determine them, like compression or tensile tests, are affected by deformation heating, restricting direct flow curve determination. In principle, the current analytical and inverse methods determine flow curves from these tests, but while the analytical methods assume a simplified temperature profile, the inverse methods require a closed-form flow curve equation, which mostly cannot capture complex material behavior like multiple recrystallization cycles. Therefore, the inverse piecewise flow curve determination method “FepiM” previously developed and published by the current authors is extended by introducing a two-step procedure to obtain isothermal flow curves at elevated temperatures and different strain rates. Thereby, the flow curve is represented as tabular data instead of an equation to reproduce complex flow curve shapes while also compensating the effect of inhomogeneous temperature profiles on the flow stress. First, a flow curve at the highest temperature is determined. In the second step, using this first flow curve as a reference, the flow curves at lower temperatures are obtained via interpolation. Flow curves from conventional compression tests for aluminum and copper in the temperature range of 20–500 °C are predicted, and it is shown that these flow curves can reproduce the experimental forces with a maximum deviation of less than 1%. Therefore, the proposed new piecewise method accurately predicts isothermal flow curves for compression tests, and the method could be further extended to highly inhomogeneous methods in the future.

Multi-episodic recrystallization and isotopic resetting of early-diagenetic dolomites in near-surface settings

ABSTRACTThe lower Eocene Rus Formation in Qatar reflects carbonate deposition in a semirestricted to fully restricted marine setting on a shallow ramp. Petrographic, mineralogical, and geochemical evidence from three research cores show early diagenesis has extensively altered nearly every petrological attribute of these rocks despite not having been deeply buried. In southern Qatar, the lower Rus (Traina Mbr.) consists of fabric-retentive dolomite intervals that preserve mudstone, wackestone, and packstone textures that are interbedded with depositional gypsum beds. In northern Qatar, the same member is dominated by fabric-destructive planar-e dolomite, and evaporites are absent. In both northern and southern Qatar, the upper Rus (Al Khor Mbr.) is composed of fabric-retentive dolomite intervals as well as limestone intervals rich with Microcodium textures that display evidence of dedolomitization. Geochemical analysis reveals that the limestones have an average δ18Ocal of –10.73‰ VPDB and δ13Ccal of –7.84‰ VPDB, whereas average dolomite δ18Odol is significantly higher (–1.06‰ VPDB) but δ13Cdol values (–3.04‰ VPDB; range –10 to 0‰) overlap with δ13Ccal values. Additionally, δ13Cdol trends toward normal marine values with depth away from the calcite–dolomite contact in all three cores. Petrographic observations demonstrate that dolomite crystals are commonly included in calcite and partially to completely replaced by calcite in these intervals and suggests that dolomite formed before calcite in the Microcodium-bearing intervals. Furthermore, the dolomites are commonly cemented by gypsum in the Traina Mbr. in southern Qatar, suggesting that dolomitization may have also occurred before, or concurrent with, bedded gypsum formation and indicates that dolomitization occurred early. Early dolomites were subsequently replaced by Microcodium-bearing limestones at and immediately below paleo-exposure surfaces, and at greater depths recrystallized in mixed marine–meteoric fluids, producing a negative δ13Cdol signature that trends toward more positive values away from the limestone–dolomite contact. Lastly, the dolomites underwent another phase of recrystallization in either marine-dominated fluids or possibly a well-mixed aquifer setting, resulting in a near-0‰ δ18Odol signature but retaining the negative δ13C signature. These findings thus have implications for reconstructing the diagenetic history of carbonate rocks, as they suggest that early diagenesis of carbonates can be extremely complex, resulting in multiple stages of mineral replacement and isotopic exchange in meteoric and shallow marine fluids before significant burial. Furthermore, this study shows that dolomitization of a limestone does not necessarily prevent additional early diagenesis and multiple recrystallization events. Lastly, it emphasizes the importance of incorporating petrographic observations with geochemical data when interpreting the diagenetic history of carbonate rocks.

Double twist torsion testing to determine the non recrystallization temperature

A double-twist torsion testing technique has been developed using a 316 stainless steel as an exemplar material to experimentally assess recrystallization behavior and determine the non-recrystallization temperature (Tnr). This new method was compared to the traditional methods of double-hit compression and multi-step hot torsion testing. The double-twist torsion test allows Tnr to be related to the extent of austenite recrystallization through measurements of fractional softening while accommodating multiple deformation and recrystallization steps with a single specimen. The double-twist torsion test resulted in average Tnr values similar to those determined with multi-step hot torsion, and a partially recrystallized microstructure was observed in the vicinity of the calculated Tnr for all three methods. The ability of the double-twist torsion test to relate the experimental Tnr to the evolution of austenite recrystallization via fractional softening measurements while incorporating effects of multiple deformation steps offers an advantage over traditional methods for quantifying changes in austenite recrystallization during thermomechanical processing.

Synthesis, characterization and thermal behaviour of solid phases in the quasi-ternary system Mg(SCN)2-H2O-THF.

Mg(SCN)2·4H2O can be converted into previously unknown compounds Mg(SCN)2·(4 - x) H2O·xTHF with x = 0, 2 and 4 by multiple recrystallization in tetrahydrofuran (THF). The phases were characterized by infrared spectroscopy (IR), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), and their crystal structures were solved from X-ray powder diffraction (XRPD) data. In the crystal structures isolated Mg(NCS)2(H2O)4-x(THF)x units form layered motifs. The thermal behavior of Mg(SCN)2·4H2O and Mg(SCN)2·4THF was investigated by temperature dependent in situ XRPD, where Mg(SCN)2·4THF was found to acquire a room temperature (α-form) and high temperature modification (β-form). The phase transformation is associated with an order-disorder transition of the THF molecules and with a reversion of the stacking order of the layered motifs. Further heating eventually leads to the formation of Mg(SCN)2·2THF. There thiocyanate related sulfur atoms fill the voids in the coordination sphere of magnesium, which leads to the formation of one dimensional electroneutral ∞[Mg(NCS)2/2(SCN)2/2(THF)2] chains. All investigated Mg(SCN)2·(4 - x) H2O·xTHF phases exhibit a remarkable anisotropic thermal expansion, and Mg(SCN)2·4H2O and Mg(SCN)2·2THF were found to show both positive and negative thermal expansion coefficients.

Differential diagenetic evolution and hydrocarbon charging of the tight limestone reservoir of the Da’anzhai Member in the central Sichuan Basin, China

The tight lacustrine carbonate reservoir of the Da’anzhai Member, Lower Jurassic Ziliujing Formation, in the central Sichuan Basin is a typical tight oil reservoir, and it is one of the crucial petroleum exploration targets in the Sichuan Basin. The porosity of the limestone ranges from 0.5% to 2%, and the permeability ranges from 0.001 to 1 mD. The Da’anzhai limestone experienced multiple diageneses, including compaction, cementation, dissolution, and recrystallization. Different diageneses occurred in the burial process due to the various fabrics and depositional environments, eventually forming distinct rock types; therefore, the pore evolution and hydrocarbon charging characteristics are inconsistent. In our research, there are two stages of major maturation and hydrocarbon expulsion in the source rocks of the Da’anzhai Member. The first large-scale expulsion of hydrocarbon is oil-based and gas-supplemented, whereas the second expulsion is dominated by gas. Hydrocarbon-filling characteristics are different in different types of reservoir rocks. Compared with the bioclastic grainstone and crystalline limestone, we have considered that the argillaceous shell packstone and bioclastic packstone deposited in the shallow and semideep lake environment still contain residual intergranular pores, which have not become fully compacted and are partly filled with hydrocarbons. The presence of hydrocarbon fluid hindered the secondary porosity reduction and was helpful for reserve space preservation.

Nonclassical Recrystallization.

Applications in the fields of materials science and nanotechnology increasingly demand monodisperse nanoparticles in size and shape. Up to now, no general purification procedure exists to thoroughly narrow the size and shape distributions of nanoparticles. Here, we show by analytical ultracentrifugation (AUC) as an absolute and quantitative high‐resolution method that multiple recrystallizations of nanocrystals to mesocrystals is a very efficient tool to generate nanocrystals with an excellent and so‐far unsurpassed size‐distribution (PDIc=1.0001) and shape. Similar to the crystallization of molecular building blocks, nonclassical recrystallization removes “colloidal” impurities (i.e., nanoparticles, which are different in shape and size from the majority) by assembling them into a mesocrystal. In the case of nanocrystals, this assembly can be size‐ and shape‐selective, since mesocrystals show both long‐range packing ordering and preferable crystallographic orientation of nanocrystals. Besides the generation of highly monodisperse nanoparticles, these findings provide highly relevant insights into the crystallization of mesocrystals.

Multiple crystallization as a potential strategy for efficient recovery of succinic acid following fermentation with immobilized cells.

This study aimed to enhance the crystallizability of bio-based succinic acid for its efficient recovery while maintaining the end product at the highest purity. Immobilization of Actinobacillus succinogenes was initially evaluated based on three different carriers: volcanic glass, clay pebbles, and silica particles. The adsorption capacity of metabolites with a low concentration (10g/L) and a high concentration (40g/L) was investigated. It was demonstrated that clay pebbles adsorbed the least succinic acid (< 11mg/g clay pebbles). The repeated batch-fermentation trials with immobilized cells highlighted that succinic acid with an average concentration of up to 36.3g/L with a metabolite-production ratio of 3:1 (succinic acid to by-products) could be attained within 130h. Subsequently, the purification of succinic acid through crystallization was assessed in terms of pH, temperature, crystallization time, initial succinic acid concentration and multiple recrystallization processes. Increasing the crystallization time from 6h to 9h afforded an improvement of 17% in the recovery of succinic acid crystals. Moreover, a fourfold concentration coefficient of the broth yielded the highest purity percentage (99.9%). The crystallization in three consecutive stages at 9h (with a fourfold concentration coefficient) successfully improved the total recovery percentage of succinic acid from 55.0 to 84.8%.

Experimental investigation of the dynamic impact responses of as-cast and homogenized A535 aluminum alloy

Aluminum A535 alloy plates were received in the as-cast condition. Some specimens cut from the cast plates were homogenized at 400 °C for 5 h and then quenched in water to room temperature. SEM, EDS, and EBSD analyses of ground and polished specimens show that in addition to a change in crystallographic texture of the A535 alloy, significant reduction in pores and removal of microsegregation occurred during homogenization heat-treatment of the as-cast specimens. Homogenizing heat treatment also decreased the average grain size of the alloy by discontinuous static recrystallization mechanism. The dynamic impact responses of as-cast and homogenized aluminum A535 alloy were experimentally determined using the split Hopkinson pressure bar system. At a true strain rate between 4 × 103 and 14.2 × 103 s-1, the homogenized specimens exhibited better dynamic mechanical strength and ductility than the as-cast specimens. Higher strength in the homogenized specimen is attributed to higher grain boundary area and stronger evolution of CD||[110] grains than in the as-cast specimens. On the other hand, severe mechanical damage such as loss of roundness of cylindrical specimen, severe micro-cracks and formation of adiabatic shear bands occurred more in homogenized specimens than in as-cast specimens. Using the electron back-scattered diffraction technique, activation of multiple dynamic recrystallization (DRX) mechanisms and the role of crystallographic texture were observed in the investigated alloy. While continuous DRX occurred at the center of the deformed specimens, discontinuous DRX occurred homogenously on the entire polished surface of the specimen at particle sites. Microsegregation and texture-related conditions enhanced DRX more readily in as-cast specimens than in the homogenized specimens. The mode of dynamic failure and fracture in the investigated alloy deviates from those reported in the literature for wrought alloys.

To the problem of origin of the Bug series rocks

The age of the Bug series rocks is an object for discussion. Isotopic methods do not give a distinct answer, because in the same outcrop, the same sample and even in the same crystal of zircon several dates of formation are to be found with evident significance. Involvement of additional criteria is required to determine the time of the Bug series formation. While examining the phase composition and the initial source of the material we need taking into account temperature and pressure distribution in the depth of formation of rocks, which are on the surface nowadays. Mineral and chemical composition of rocks and tectonic structure of including patterns have been considered. It has been shown that the composition of the Bug series is an indicator of time of formation. Carbonatites and calcyphyres, carbonate-magnetite rocks are not produced earlier than ~2.0 Ga ago. A considerable part of the stratum is presented by high-clayish and graphite shale, quartzite, and ultrabasite that occur jointly only in this period of time. Arrangement of the structures is subdued to tectonic control by zones of deep faults. Smaller fault zones are determinative in the pattern of structures themselves and in manifestations of metasomatic processes. By the moment of their formation the level outcropped on the modern surface occurred at a depth more than 20 km that makes sedimentary nature of composing rocks doubtful. It has been shown that the most part of rocks attached to the Bug series are crystallization products of magmatic melts as well as carbonate, silicate (water-silicate with chlorine), hydrocarbon fluids in faults (permeable zones) of crystalline basement in diapason of PT -conditions, corresponding to high amphibolites-granulites metamorphic facies. The pattern of these structures in projection is similar to the section of volcano-tectonic apparatuses at a depth not less than 20 km. In the structures small by their area, the rocks formed at different depths (from 300 to 200 km) from melts and fluids in different chemical media are presented. High temperature multiple metasomatism has been superposed. A conclusion has been made that the pattern of the structures of Khashchevato-Zavalye block and the Golovaniv suture zone does not reflect the succession of primary sedimentary rocks occurrence but a result of multiple crystallization and metasomatic re-crystallization of melts and fluids.

Growth, Linear and Nonlinear Optical Studies of D-Tartaric Acid Crystal

A single crystal of D-Tartaric acid, a stereoisomer of tartaric acid, has been grown by a slow solvent evaporation technique. Good crystals to be used for optical testing were harvested after multiple recrystallizations, whose maximum size is 30x20x4mm 3 . In view of finding second harmonic generation efficiency and properties supporting for a nonlinear optical device, the grown crystals were subjected to various characterizations. Firstly, the compound was confirmed by single crystal and powder X-ray diffraction analysis and thereafter further studies were undertaken. Various possible functional groups available in the grown crystalline compound were identified using Fourier transform infrared analysis and reported. The second harmonic generation, a nonlinear optical property of a crystal, was studied and compared with standard KDP crystal. The percentage of linear optical transmittance in the ultraviolet, visible and infrared radiation of wavelength ranging from 200 to 1100 nm was studied and explained in detail. Thermal studies such as Thermogravimetric and Differential thermal analysis were carried out to find the thermal stability of the crystalline material. Vicker’s microhardness testing was made on the as-grown crystalline surface to find the surface hardness, yield strength and other related mechanical properties of the crystal. Copyright © VBRI Press.

Formation of the elliptical texture and its effect on the mechanical properties and stretch formability of dilute Mg-Sn-Y sheet by Zn addition

All the time, it is difficult for magnesium alloys to equilibrate the relationship among strength, ductility and stretch formability at room temperature. Here, we added 0.6 wt% Zn into Mg-0.4Sn-0.7Y (TW00, wt%) alloy attempting to achieve a good combination among strength, ductility and stretch formability at room temperature. After extrusion, we found that Mg-0.4Sn-0.7Y-0.6Zn (TWZ000, wt%) alloy sheet exhibited a weak elliptical texture, accompanied with significant grain and second phase refinement. The formation of this weak elliptical texture was mainly originated from the joint contributions of multiple dynamic recrystallization (DRX) mechanisms consisted of twin-, compound- and dislocation slip-induced DRX behaviors. Grain boundary strengthening and second phase strengthening were mainly dedicated to the enhanced yield strength (~ 150.0 MPa) and ultimate tensile strength (~ 235.1 MPa), while non-basal slip, grain boundary cohesion, texture modification and twins commonly guaranteed the high ductility (~ 39.8%). Besides texture modification and non-basal slip, a large number of twins altered the initial microstructure along with the formation of new twinning textures during stretch forming. These new twinning texture facilitated the higher Schmid factor (SF) for basal slip beneficial to the enhancement in stretch formability (~ 7.0 mm). Therefore, TWZ000 alloy sheet provided an enormous potential to broaden magnesium alloys applications.

The first spontaneous resolution of a sulfoxide: Dianin's compound analogue, (R)-4-(4-hy-droxy-phen-yl)-2,2,4-tri-methyl-thia-chroman-1-oxide.

The title sulfoxide, C18H20O2S, was prepared by controlled oxidation of thia-Dianin's compound using hydrogen peroxide in glacial acetic acid. On recrystallization from glacial acetic acid, it was found to form unsolvated, spontaneously resolved crystals, the initial crystal structure analysis revealing the presence of both sulfoxide epimers in the crystal. On multiple recrystallization a single epimer was observed, with crystallization occurring in the unchanged ortho-rhom-bic space group P212121, with Z' = 1. The mol-ecule possesses a distal conformation, referring to the juxtaposition of the p-hydoxyphenyl substituent with respect to its syn-related methyl group, with the sulfoxide oxygen atom anti to the aromatic substituent. The mol-ecular packing features O-H⋯O hydrogen bond chains running parallel to the b axis of the unit cell.