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It has been a common method to improve the mechanical properties of metals by manipulating their microstructures via static recrystallization, i.e., through heat treatment. Therefore, the knowledge of recrystallization and grain growth is critical to the success of the technique. In the present work, by using in-situ high temperature EBSD, the mechanisms that control recrystallization and grain growth of an extruded pure Mg were studied. The experimental results revealed that the grains of priority for dynamic recrystallization exhibit fading competitiveness under static recrystallization. It is also found that grain boundary movement or grain growth is likely to show an inverse energy gradient effect, i.e., low energy grains tend to swallow or grow into high energy grains, and grain boundaries of close to 30° exhibit superior growth advantage to others. Another finding is that {10–12} tensile twin boundaries are sites of hardly observed for recrystallization, and are finally swallowed by adjacent recrystallized grains. The above findings may give comprehensive insights of static recrystallization and grain growth of Mg, and may guide the design of advanced materials processing in microstructural engineering. [ABSTRACT FROM AUTHOR]

• Superplasticity of fine-grained Mg-10Li alloy was studied. • Severe plastic deformation was used to achieve the fine grains. • Its deformation mechanisms for superplastic flow were analyzed. • Deformation mechanism maps were constructed in 2D and 3D. The superplastic behavior and associated deformation mechanisms of a fine-grained Mg-10.1 Li-0.8Al-0.6Zn alloy (LAZ1011) with a grain size of 3.2 µm, primarily composed of the BCC β phase and a small amount of the HCP α phase, were examined in a temperature range of 473 K to 623 K. The microstructural refinement of this alloy was achieved by employing high-ratio differential speed rolling. The best superplasticity was achieved at 523 K and at strain rates of 10−4 -5 × 10−4 s−1, where tensile elongations of 550–600% were obtained. During the heating and holding stage of the tensile samples prior to tensile loading, a significant increase in grain size was observed at temperatures above 573 K. Therefore, it was important to consider this effect when analyzing and understanding the superplastic deformation behavior and mechanisms. In the investigated strain rate range, the superplastic flow at low strain rates was governed by lattice diffusion-controlled grain boundary sliding, while at high strain rates, lattice diffusion-controlled dislocation climb creep was the rate-controlling deformation mechanism. It was concluded that solute drag creep is unlikely to occur. During the late stages of deformation at 523 K, it was observed that grain boundary sliding led to the agglomeration of the α phase, resulting in significant strain hardening. Deformation mechanism maps were constructed for β-Mg-Li alloys in the form of 2D and 3D formats as a function of strain rate, stress, temperature, and grain size, using the constitutive equations for various deformation mechanisms derived based on the data of the current tests. [ABSTRACT FROM AUTHOR]

• HPT-processed Mg-Gd-Y-Zn-Zr nanostructure exhibits an excellent thermal stability. • Mg-Gd-Y-Zn-Zr nanostructure exhibits an unique phase transformation upon annealing. • The formation of solute segregation and β phase retards grain growth during annealing. • A hardness peak is achieved by annealing due to the effects of solute segregation. A Mg-8.2Gd-3.8Y-1.0Zn-0.4Zr (wt.%) alloy is processed by solution treatment and high pressure torsion (HPT) at room temperature to produce a nanostructured light material with high hardness. The stability of this alloy is subsequently tested through isochronal annealing for 0.5 h at 373 K to 673 K. The results reveal a thermal stability that is vastly superior to that of conventional Mg-based alloys processed by severe plastic deformation: the grain size remains at around 50 nm on heating to 573 K, and as the temperature is increased to 673 K, grain growth is restricted to within 500 nm. The stability of grain refinement of the present alloy/processing combination allowing grain size to be limited to 55 nm after exposure at 573 K, appears to be nearly one order of magnitude better than for the other SPD processed Mg-RE type alloys, and 2 orders of magnitude better than those of SPD processed RE-free Mg alloys. This superior thermal stability is attributed to formation of co-clusters near and segregation at grain boundaries, which cause a thermodynamic stabilization of grain size, as well as formation of β-Mg 5 RE equilibrium phase at grain boundaries, which impede grain growth by the Zener pinning effect. The hardness of the nanostructured Mg-Gd-Y-Zn-Zr alloy increases with increasing annealing temperature up to 573 K, which is quite different from the other SPD-processed Mg-based alloys. The high hardness of 136 HV after annealing at 573 K is mainly due to solute segregation and solute clustering at or near grain boundaries. [ABSTRACT FROM AUTHOR]

This study investigates the variations in the microstructural characteristics of a pre-twinned Mg alloy with the temperature of the subsequent annealing treatment. To this end, a rolled AZ31 alloy is compressed to 3% plastic strain along the rolling direction (RD) to activate {10-12} twinning and is subsequently annealed at 200, 250, 300, 350, and 400 °C. Numerous {10-12} twins are formed throughout the compressed material, leading to the formation of a RD-oriented texture. At an annealing temperature of 200 °C, no microstructural variations occur during annealing. As the annealing temperature increases from 250 to 400 °C, the residual strain energy and remaining twin boundaries of the annealed material decrease owing to the promoted static recovery and the increased area fraction of twin-free grown grains. Consequently, an increase in the annealing temperature results in a gradual microstructural transition from a fully twinned grain structure to a completely twin-free grain structure. The microstructural evolution during annealing is predominantly governed by the movement of high-angle grain boundaries via a strain-induced boundary migration mechanism, and a few twin boundaries migrate above 350 °C because of their lower boundary energy. The boundary migration behavior and resultant microstructural evolution are discussed in detail based on the variations in boundary mobility and driving force for boundary migration with annealing temperature. [ABSTRACT FROM AUTHOR]

Critical properties of metallic materials, such as the yield stress, corrosion resistance and ductility depend on the microstructure and its grain size and size distribution. Solute atoms that favorably segregate to grain boundaries produce a pinning atmosphere that exerts a drag pressure on the boundary motion, which strongly affects the grain growth behavior during annealing. In the current work, the characteristics of grain growth in an annealed Mg-1 wt.%Mn-1 wt.%Nd magnesium alloy were investigated by advanced experimental and modeling techniques. Systematic quasi in-situ orientation mappings with a scanning electron microscope were performed to track the evolution of local and global microstructural characteristics as a function of annealing time. Solute segregation at targeted grain boundaries was measured using three-dimensional atom probe tomography. Level-set computer simulations were carried with different setups of driving forces to explore their contribution to the microstructure development with and without solute drag. The results showed that the favorable growth advantage for some grains leading to a transient stage of abnormal grain growth is controlled by several drivers with varying importance at different stages of annealing. For longer annealing times, residual dislocation density gradients between large and smaller grains are no longer important, which leads to microstructure stability due to predominant solute drag. Local fluctuations in residual dislocation energy and solute concentration near grain boundaries cause different boundary segments to migrate at different rates, which affects the average growth rate of large grains and their evolved shape. [ABSTRACT FROM AUTHOR]

In metal additive manufacturing (MAM), laser direct energy deposition (L-DED) and wire arc direct energy deposition (W-DED) are commonly used methods that also possess challenges in the part quality due to the effect of different process parameters. Very little knowledge is currently available on the single-layer thermal behavior, cooling rate, melt pool dimension and their correlation with the microstructure for the DED processes (L-DED and W-DED). In this study, a comparative analysis of the microstructural characteristics along with hardness of austenitic stainless steel (SS 316L) samples is conducted to understand the variations between the L-DED and W-DED processes. It is observed that the microstructure of the W-DED samples possesses more columnar dendritic structure than the L-DED due to slower cooling rate in W-DED. It is also found that the ferrite (δ) phase fraction is 23% higher in W-DED than L-DED. There is also the formation of carbide precipitation at the fusion boundary in the L-DED samples. In L -DED, the grains are mostly oriented along the<001>/<111>direction, whereas in W-DED, the dominant orientation is<111>/<101>. The W-DED samples have significantly higher HAGB fraction (49%) than the L-DED samples. The detailed texture analysis of the samples showed that the L-DED has lower average grain misorientation than the W-DED along with ND rotated cube, twin copper, and cube structures. The hardness data reveals that the W-DED samples possess much higher hardness compared to the L-DED samples. [ABSTRACT FROM AUTHOR]

• The mechanism of grain growth of Mg alloys is reviewed systematically, including strain- induced grain boundary migration and heat-induced grain boundary migration. By clarifying the impact factors and mechanisms of grain growth, processing strategies to control the grain size can be optimized. • The relationship between grain size and mechanical properties is explained from the perspective of plastic deformation mechanisms. Grain growth directly influences the plasticity and strength of Mg alloys. As the grain size decreases from the microscale to the nanoscale, the plasticity of Mg alloys continually increases, whereas the strength first increases and later decreases. These trends are observed because the plastic deformation mechanism changes from dislocation–twinning dominance to grain boundary dominance. In this study, the factors influencing grain growth, such as the temperature of plastic deformation/annealing, second-phase particles and solute atoms, are examined to aid effective control of the grain size. Additionally, the mechanisms of grain growth, typically induced by strain and thermal activation, are clarified. Strain-induced grain boundary migration is attributable to the difference in the strain energy stored in adjacent grains with high-density dislocations. Heat-induced grain boundary migration is driven by the difference in the energy of the grain boundary/subgrain boundary and boundary curvature. Abnormal grain growth can be induced by anisotropy of the strain energy, anisotropy of the grain boundary mobility, depinning of the second phase and high misorientation gradient. [ABSTRACT FROM AUTHOR]

The nucleation, grain growth of 34 coarse grains during annealing were tracked using a quasi- in-situ EBSD method. These 34 coarse grains had different orientations and most grains were non-basal orientated. No preferable grain growth or special types of grain boundaries were identified. Only 9 coarse grains nucleated from deformed grain boundaries due to initial large grain size and limited grain boundary volume fraction. The main nucleation site of 34 coarse grains was dislocation cells or subgrains in deformed grain interiors. Their recrystallisation behaviour can be illustrated by abnormal subgrain growth (AsGG) rarely reported in Mg alloys. The coarse basal grains showed no growth advantage in terms of grain size or number over other non-basal grains, leading to a weak basal texture in AZ31B alloy. [ABSTRACT FROM AUTHOR]

The microstructural evolution and underlying grain growth mechanism of a {10–12}-twin-containing Mg alloy during annealing are investigated through quasi in situ electron backscatter diffraction measurements of a rolled AZ31 alloy subjected to precompression along the rolling direction (RD). The precompressed material shows a partially twinned structure consisting of a twinned region and a residual matrix region, and this structure changes to an almost twin-free structure consisting of grown grains with serrated grain boundaries in twin- and matrix-originated regions after annealing at 250 °C for 1 h. In addition, the average grain size almost doubles and the internal strain energy decreases significantly after annealing. These microstructural variations are induced mainly by grain growth through the strain-induced migration of high-angle grain boundaries without the movement of twin boundaries. The twinned region of the precompressed material has higher stored strain energy than the residual matrix region because the crystallographic orientation of the former region is favorable for basal slip and because of the occurrence of the dislocation transmutation reaction in the twins. For reducing the total strain energy accumulated in the precompressed material, the residual matrix region—having lower stored strain energy—preferentially grows while consuming the twinned regions formed in the surrounding grains during annealing. As a result, the area fraction of grains with a matrix texture increases whereas that of grains with a twin texture decreases after annealing. The twin texture intensity increases significantly and this texture becomes more concentrated along the RD because the highly RD oriented twins tend to grow during annealing on account of their fairly low stored strain energy. [ABSTRACT FROM AUTHOR]

The grain growth process plays an important role in the texture formation in magnesium alloys. The microstructural and micro-textural evolution of a cold-rolled Mg–Zn–Gd alloy during annealing at 350 °C for 60–190 min were tracked by quasi-in-situ electron backscatter diffraction method. The results show that grain growth takes place gradually with the annealing time increasing. Moreover, the TD-split texture maintains the texture type but alters in three aspects - the increased tilting angle, the decreased pole intensity and the widened distribution of high-intensity area. Grains with their c-axis tilting 45–70° from normal direction show preferential growth which is closely associated with the texture changes. The original grain size advantage is one of the important factors leading to the growth advantage, some grain boundaries, such as 50–60° [ 1 ¯ 2 1 ¯ 0 ], 50–60° [ 2 ¯ 7 5 ¯ 0 ], 60–70° [ 1 ¯ 2 1 ¯ 0 ] (∑18b), and 70–80° [ 10 1 ¯ 0 ] (∑10) are also considered to be related to this preferential growth. [ABSTRACT FROM AUTHOR]

• Photovoltaic performance of solution-coated CIGS films was improved via sulfurization. • The formation of selenium vacancies in CIGS films were diminished by sulfurization. • H 2 S concentration used in the solution-coated CIGS films was less than vacuum processes. • This investigation demonstrates the effect of H 2 S for solution-processed CIGS solar cells. The photovoltaic (PV) characteristics of solution-coated Cu(In,Ga)Se 2 films were effectively improved via a surface sulfurization in this study to overcome the complexity to control the appropriated amounts of sulfur ionsduring the sulfurization process.After sulfurization treatment, the Cu(In,Ga)(Se,S) 2 films with double-graded band gap were obtained because the incorporation of sulfur-ion intoCu(In,Ga)Se 2 films increasedthe band gap near the surface region.The formation of selenium vacancies in Cu(In,Ga)(Se,S) 2 films were effectively diminished by adjusting H 2 S concentration. Band gap gradients and defect passivation reduced the interface recombination and improved the carrier collection in the devices. As the H 2 S concentration was raised from 0 to 1.0 vol%, the open-circuit voltage was increased from 541 to 596 mV, thereby boosting the conversion efficiency from 10.71to 12.40%. The reduction of vacancy defects and surface roughness suppressed the formation of shunt paths, resulting ina decrease indiode factor and leakage current. Compared with the Cu(In,Ga)(Se,S) 2 films deriving from vacuum processes, solution-coated Cu(In,Ga)(Se,S) 2 films with relatively small grains facilitated the sulfur diffusion along the grain boundaries into the films.Therefore, the appropriate H 2 S concentration used in the solution-coated Cu(In,Ga)(Se,S) 2 films was less than vacuum processes. This investigation demonstrates that adjusting the concentrationof H 2 S is vital for enhancing the PV properties of thesolution-processed Cu(In,Ga)(Se,S) 2 PV cells. [ABSTRACT FROM AUTHOR]

The contribution of recrystallization and grain growth to the texture evolution in AZ31 alloy and a modified version AZ31+0.5 wt.% Ca was investigated utilizing a multi-step annealing process. The results showed that the addition of Ca triggered a considerable texture modification by increasing the texture spread and decreasing the overall texture intensity. This effect was found to be temperature dependent. When the annealing temperature remained lower than 450 °C, a weak double peak texture with large basal pole tilt towards the RD was formed. This is correlated to microstructure observations of a large number of Ca-containing nano-sized particles that seemed to suppress grain growth below 450 °C, which stabilized the weak recrystallization texture. This favorable texture was lost upon annealing at higher temperatures. In AZ31, recrystallization nuclei were found to preserve the orientation of their deformed parents, which offered limited potential to optimize the texture via annealing treatments. Grain growth of recrystallized grains resulted in a distinct sheet texture transition from a double-peak to a single-peak basal texture. Aspects of grain boundary energy and grain topology are discussed to explain the growth advantage of the sharp basal component over other orientations. [ABSTRACT FROM AUTHOR]

• Annealing effect was studied with respect to caliber-rolled AZ31 Mg alloys. • Low-temperature annealing gave rise to trade-off of strength and ductility. • High-temperature annealing led to simultaneous deterioration in strength and ductility. • The deterioration is attributed to a grain growth and resultant mechanical twinning. Recently, multi-pass caliber rolling has been shown to be effective for Mg alloys. This study investigated the effect of subsequent annealing on the mechanical properties of a caliber-rolled AZ31 Mg alloy to modulate the strength-ductility relationship. This annealing gave rise to different trends in mechanical properties depending on the temperature regime. Low-temperature annealing (T ≤ 473 K) exhibited a typical trade-off relationship, where an increase in annealing temperature resulted in increased ductility but decreased strength and hardness. Such a heat treatment did not degrade the high strength-ductility balance of the caliber-rolled alloy, suggesting that the mechanical properties could be tailored for different potential applications. In contrast, high-temperature annealing (T > 473 K) caused a simultaneous deterioration in strength, hardness, and ductility with increasing annealing temperature. These differences are discussed in terms of the varying microstructural features under the different investigated annealing regimes. [ABSTRACT FROM AUTHOR]

Grain growth can modify the texture orientation and the fraction of different texture component. The thermal stability of two texture component in an extruded magnesium AZ31 alloy was investigated. Three types samples with different texture distribution were prepared. The results show that normal grain growth takes place in the magnesium AZ31 alloy during annealing at 300 °C and 450 °C. But the grain growth does not lead to the strengthening of either texture component. Both the <0002> ⊥ED texture and <0002> //ED texture components show good thermal stability, without influence of the texture volume fraction. The two different texture component possess comparable boundary migration ability, so grains of the two texture component consume indifferently the other grains, or are equally consumed during annealing. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Molluscan shells, exhibiting a variety of complex three-dimensional architectures, are an exemplar model system to study biogenic mineral formation by living organisms. Recent studies have demonstrated that the deposition process of some shell ultrastructures can be described using classical analytical models borrowed from materials physics, which were developed to predict the structural evolution of man-made and geological polycrystalline composite assemblies. In the current study, we use this newly developed capacity to quantitatively describe the morphogenesis of the prismatic ultrastructure in three shells from the bivalve family Pinnidae towards establishing a correlation between structure, texture, growth kinetics, topology and phylogeny of the species. Using data collected by electron microscopy, synchrotron-based microtomography, electron backscatter diffraction analysis (EBSD) and X-ray diffraction we demonstrate that the prismatic ultrastructures in Pinnidae are formed following either ideal or triple-junction-controlled kinetics, which are shown to be closely linked to the morphological and topological characteristics, as well as crystallographic texture of these biocomposites. The experimental and analytical framework presented in this comparative study can serve as an additional tool for classifying molluscan shell ultrastructures on the levels of structural and textural morphogenesis. Statement of Significance The ability to quantitatively describe the structural evolution of the prismatic architecture in mollusc shells is used for the first time to derive and compare between analytical parameters that define the growth kinetics and morphological and topological evolution during the growth of three shells from the family Pinnidae from two different genera. Furthermore, these parameters are linked to the evolution of crystallographic texture in the studied architectures. The developed experimental and analytical framework not only enables us to quantitatively describe species-specific growth mechanisms but also suggests a direct correlation between the evolution of morphology and texture. [ABSTRACT FROM AUTHOR]

Abstract Cyanobacteria are potential prokaryotes found in diverse environment of freshwater and marine water ecosystem. They are well known applicant practised in ancient agriculture technique for improving the soil fertility, water holding capacity and texture of the soil. The availability, low cost and fast growth has considered them as superior candidate for biotechnological applications. In the recent years, cyanobacteria are been used to produce plant growth promoting hormones or substances for facilitating effective plant growth. The present study is focussed on validating the plant growth promoting ability of two heterocystous cyanobacteria strains (Anabaena variabilis , Nostoc calcicola) in five crop plant. The cyanobacterial strains were characterized by biochemical and plant growth promoting parameters like Chlorophyll content and IAA production. As result of this study, in vitro experiments revealed 100% of seed germination by Cyanobacteria growth promoting substances (CGPS) of Anabaena variabilis in the grains of Zea mays and Sorghum bicolour , while 90% germination in Nostoc calcicola. Statistical analysis proved the growth root length, plant height, weight of fresh and dry root, number of leaves in CGPS treated and untreated plant in pot. Further the CGPS was characterized using thin-layer chromatography (TLC), FT-IR and HPLC analysis. The dominant auxins in the two isolates were IAA in the range of 0.0372–1.2327 μg g−1 dry weight was detected. However, IAA production by Anabaena variabilis proved as potential candidate for promoting plant growth. In addition, Anabaena variabilis can also be utilized as a biofertilizer for the crops cultivated in normal fields. Highlights • Cyanobacteria are efficient plant growth promoting sources to help growth of food crops. • Cyanobacterial intracellular products contains large number of enzymes and growth promoting hormones. • Use of heterocystous cyanobacterial biomass as fertilizer will provide multiple benefits to plant and soil. [ABSTRACT FROM AUTHOR]

Copper based pesticides are used to protect vineyards from fungal infections. Plants like black oats ( Avena strigosa Schreb) can promote chemical changes in the rhizosphere, reducing copper (Cu) bioavailability in contaminated soils. The objective of this study was to evaluate how copper additions would affect growth, morphology and nutrient uptake by black oats and how the plants affect the chemical composition in rhizosphere and bulk soil. The soil was collected in grassland of southern Brazil. The soil was air-dried, adjusted pH and added phosphorus and potassium amendments, and then it was incubated. Three Cu levels were established in the soil with the addition of 0, 40 and 80 mg Cu kg −1 . The experimental design consisted of pots containing 8 plants with 10 kg of soil. Rhizosphere (2 kg of soil) and bulk (8 kg of soil) separated by a 30 µm nylon membrane. Black oat plants were grown for 54 days. The soil and solution were chemically characterized throughout cultivation for Cu speciation. At 54 days after emergence, the soil was sampled and proceeded chemical analysis and plants were collected to determine yield dry matter, morphological parameters and nutrient concentration. Black oat plants induce increase of pH and dissolved organic carbon in the rhizosphere. These root-induced processes increase the percentage of complexed chemical species and decrease free Cu +2 in soil solution, decreasing Cu toxicity. However, soil contamination with Cu induces morphological changes and nutritional imbalances. Black oats could thus be planted along with vineyards, for such increasing protect the soil and promote nutrient cycling, as well as reduce the free Cu available fraction due to the root-induced modifications in the rhizosphere. [ABSTRACT FROM AUTHOR]

Nanosized BaFe 1-x Cu x O 3 powders were prepared using the Pechini method. To limit grain growth and agglomeration, the temperature of calcination was limited to 800 °C. For all samples, the cubic form of BaFeO 2.75 was predominant with minor additional phases. Cu doping was found to have a remarkable effect on the structural cubic unit cell parameter as the Cu concentration increased. As shown by XRD,the samples were in the nanometer size range (17–63 nm). However, as the Cu concentration increases, the agglomeration increases with the highest surface area for the BaFe 0.95 Cu 0.05 O 3 composition, which also displays the highest photocatalytic atrazine degradation. For this sample, more than 90% degradation of atrazine was obtained at the optimum conditions (120 min irradiation under visible light at pH 11 using 0.75 mg of the catalyst). The Atrazine degradation was found to follow the pseudo-order kinetics. GC/MS was used to detect the intermediates and the reaction pathways. All the prepared samples and produced waters at the end of the experiment were found to be nontoxic. [ABSTRACT FROM AUTHOR]

Copyright of Tecnologia em Metalurgia, Materiais e Mineração is the property of Associacao Brasileira de Metalurgia e Materiais and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Yttria stabilized zirconia (YSZ) nanocrystals were prepared by hydrothermal synthesis and were calcinated at different temperatures and with different isothermal hold time. X-ray diffraction via whole powder pattern modeling approach was used to study the grain growth as well as the evolution of grain size distribution of YSZ nanocrystals. Results show that YSZ nanocrystals start to grow along with the grain size distribution broadening at about 300 °C. The grain growth rate and the grain size distribution of YSZ nanocrystals are dependent on the calcination temperature and the isothermal hold time. The grain growth exponent and the active energy of grain growth were calculated. Grain rotation induced grain coalescence is suggested as the predominant way of grain growth of YSZ nanocrystals. [ABSTRACT FROM AUTHOR]

The thickness of the lamellar band (LB) structure that is generated in an accumulative roll bonded nickel sheet represents the degree of structure refinement. The LBs reach a saturation in thickness after several roll bonding cycles due to adiabatic heating that balances the dislocations generated during rolling. The thermal restoration process starts with the rearrangement of dislocations and boundary migration. At the initial stages of thermal restoration, LBs with all the orientations in the deformation texture grow by the so-called continuous recrystallization process. However, in the latter stages, growth becomes orientation selective and dominated by S and copper orientations. Finally, grain growth after recrystallization results in the preferred growth of Cube-oriented grains to the full layer thickness of the ARB sheet, thereby generating a strong Cube texture. Thus, grain growth yields a final texture similar to that generated in conventionally rolled and annealed nickel sheets. [ABSTRACT FROM AUTHOR]

The exceptional properties associated with nanocrystalline materials are, to a large extent, a result of their high inter-crystalline volume fraction. However, the intrinsic instability of the nanostructured state may compromise the gain in properties by the occurrence of grain growth during exposure at elevated temperatures. Thermal stability is, therefore, a fundamental materials issue for nanocrystalline materials. This article describes what can be deduced from calorimetric measurements in the context of what is known about the microstructural evolution upon annealing of nanocrystalline Ni- and Co-based pulsed current electrodeposits. Special emphasis is put on interpreting the shape of the curves obtained by a differential scanning calorimetry (DSC). The temperature ranges for relaxation, segregation, precipitation, as well as abnormal and normal grain growth can be predicted. Also, by evaluating the shift in peak temperature with heating rate (Kissinger plot), the activation energies for grain growth can be obtained for the different materials. [ABSTRACT FROM AUTHOR]

The iron grain growth kinetics during the carbothermic reduction of ilmenite concentrates in the microwave field were investigated and described by using iron grain sizedtand a parameter (attenuation voltage U) of microwave-absorbing characteristics. The results demonstrated that there was a linear relationship between lndtand 1/Tduring the iron grain growth, and the kinetic model equation for the iron grain growth in the microwave field was deduced as: ln; the activation energy of the iron grain growth at the initial stage and the late stage in the microwave field were calculated to be 31.04 and 69 kJ/mol. It was found that there was also a linear relationship between lnUand 1/T. The iron grain growth described by using the attenuation voltage (U) of microwave-absorbing characteristics and the grain sizedthad the same rule, the activation energy at initial stage was small and became big at the late stage. The results suggested that the iron grain growth could be described by using a parameter of microwave-absorbing characteristics during the carbothermic reduction of ilmenite concentrates in the microwave field, if ignored the specific values of the activation energy, just used the changing trends of the activation energy, which could help us utilize the microwave technology in the ilmenite concentrate processing and the recovery of the byproducts of metallic iron. [ABSTRACT FROM AUTHOR]

Increasing attention has been focused on the health of vegetables and grains grown in the contaminated agricultural soil, it is thus meaningful to find ways to reduce the heavy metals (HMs) accumulation in plants. As sulfur is considered to be an essential macronutrient for plant stress defenses, the important role of sulfur assimilation in plants responding to HMs stress has been followed. However, the potential mechanism of the only sulfur-containing gasotransmitter hydrogen sulfide (H 2 S) and its main endogenously generated substrate, cysteine (Cys), in plant defense is poorly understood. The physiological and biochemical methods together with qRT-PCR were used to explore the response pattern of H 2 S-Cys cycle in plants resisting to chromium (Cr 6+ ) stress. Our results suggested that Cr 6+ stress inhibited Arabidopsis root elongation, increased the H 2 S and Cys contents time-dependently, and H 2 S production was activated earlier than Cys. Furthermore, H 2 S increased Cys accumulation more quickly than Cr 6+ stress. The qRT-PCR results revealed that H 2 S up-regulated the Cys generation-related genes OASTLa , SAT1 and SAT5 expression levels, and that SAT1 and SAT5 expression was elevated for a longer duration. Data suggested that H 2 S might regulate Cys metabolism-related genes expression to participate in Cr 6+ -mediated Cys accumulation. H 2 S and Cys relieved the root elongation inhibition caused by Cr 6+ in Arabidopsis . Both H 2 S and Cys enhanced glutathione generation and activated phytochelatins (PCs) synthesis by up-regulating PCS1 and PCS2 expression levels to fight against Cr 6+ stress. Besides regulating the expression of PCs synthase encoding genes, H 2 S might promote metallothioneins accumulation by significantly increasing the MT2A gene expression. Overall, H 2 S and H 2 S-induced Cys accumulation (H 2 S-Cys system) was critical in imparting Cr 6+ tolerance in Arabidopsis . This paper is the first to indicate that gasotransmitter H 2 S induced Cys accumulation in Arabidopsis Cr 6+ -stress defense and provides evidence for more extensive studies of the H 2 S signaling pathway. [ABSTRACT FROM AUTHOR]

Calibre rolling of Mg–3Al–1Zn alloy at 300 °C led to development of fine grain size of 3 µm. Subsequent annealing, from 5 to 6000 minutes at 300–450 °C, revealed faster grain growth initially up to 60 minutes, which became sluggish on prolonged annealing. The time exponent for grain growth kinetics ( n ) suggests bi-linear behaviour with n  = 0.11 and 0.008 over these time scales. The activation energy, based on various n values, varied over wide ranges that made the understanding of the mechanisms for grain growth difficult. This problem is explained by concurrent evolution of texture and grain boundary structure. The effect of grain growth on hardness at ambient temperature was found to follow the H–P type relationship. [ABSTRACT FROM AUTHOR]

Abstract Volume shrinkage, grain growth, and their interaction are major events occurring during free sintering of ceramics. A high temperature sintering dilatometry curve is influenced by these both phenomena. It is shown that the continuum theory of sintering can be utilized in the format enabling the extraction of the maximum amount of information on the densification and grain growth kinetics based on a simple dilatometry test. We present here the capability of such a fast approach (Dilatometry based Grain growth Assessment DGA) utilized for the modeling of sintering and grain growth of zirconia. [ABSTRACT FROM AUTHOR]

A Hard Sphere Simulator (HSS) is a mechanical model for demonstrating microscopic features and phenomena such as atomic arrangements in a crystal lattice and corresponding defects in the lattice at the macro-scale; hence, it is a potential learning tool for students. Here, we describe the construction of an HSS, using polymer gunshot balls as hard spheres. Using this HSS, we demonstrate material phenomena such as phase transitions and formation and movements of defects. We also show that, by carrying out Fourier transformation on the images obtained from the HSS, one can obtain the diffraction patterns of these structures. [ABSTRACT FROM AUTHOR]

A study of the austenite grain growth of an ASTM A213 T91 steel held at 1050 °C for increasing times is presented. The prior austenite grain size distribution (PAGSD) at various holding times was determined using scanning electron microscopy. Taking into account the critical role played by MX precipitates (M: metal, X: C and/or N) on grain growth, transmission electron microscopy on replicas was used to characterize the carbides or carbonitrides present during holding in austenite; thus, the particle size distribution and chemical composition of these precipitates were determined for each austenite holding time. Results indicate a change in the chemical identity of the MX precipitates –from V-rich to Nb-rich- during the first minutes of austenite holding, the M 23 C 6 dissolution and the further austenite grain growth in a heterogeneous mode. [ABSTRACT FROM AUTHOR]

Copyright of Tecnologia em Metalurgia, Materiais e Mineração is the property of Associacao Brasileira de Metalurgia e Materiais and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)