Microstructural Elements Research Articles

Effects of long-term high temperature annealing on Li2TiO3 and advanced core-shell Li2TiO3-Li4SiO4 tritium breeders

The present work investigates the evolution of mechanical performance and provides a comprehensive study of the changes in microstructure, phase, and compositional elements of Li2TiO3 and core-shell Li2TiO3-Li4SiO4 pebbles resulting from annealing at 900 °C in He incl. 0.1 vol % H2 flow atmosphere for specific durations. Compression tests show that long-term annealing improves the mechanical performance of Li2TiO3 instead of degrading it. The mean crush load of Li2TiO3 increases from 41 N to 45 N after 1000 h of annealing. Li2TiO3 pebbles can maintain their microstructure stability, with only limited grain growth and a decrease in open porosity identified. These changes are believed to be responsible for the improvement in mechanical performance after 1000 h. The mechanical performance of core-shell Li2TiO3-Li4SiO4 pebbles primarily degrades during the initial 100 h, with a decrease in mean crush load from 118 N to 91 N. Subsequently, it gradually stabilizes with a mean crush load of 91 N over the remaining annealing period. An increase in open pores and slight Li4SiO4 grain growth was observed after 1000 h of annealing, which is the primary cause of the mechanical performance degradation in core-shell Li2TiO3-Li4SiO4 pebbles. The loss of lithium in core-shell Li2TiO3-Li4SiO4 pebbles is a combined effect of the Li2TiO3 phase and Li4SiO4 phase, with a stronger association to the Li4SiO4 phase.

High-entropy alloys: A review of their performance as promising materials for hydrogen and molten salt storage

Abstract Fossil fuels have been the most employed energy source with a consistent and growing consumption; however, they will be replaced by renewable energy sources (RESs). Massively using this type of energy will require new materials, especially metallic-based materials, because the typical materials have shown poor performance. In particular, hydrogen obtained from RESs has technological concerns like absorption/desorption cycling, kinetics, and cost. Similarly, the solar industry demands highly corrosion-resistant materials at high temperatures. As mentioned above, these could be solved using high-entropy alloys (HEAs). HEAs are barely around 15 years old and have been intensively investigated to be used for wide technological and scientific applications due to their unusual mechanical, physical, and chemical properties. Thus, this study summarizes advances in HEAs as promising materials for hydrogen and energy molten salt storage technologies and discusses the corrosion performance of current HEAs, considering both the microstructure and constituent element effect.

Multiscale study of additively manufactured 316 L microstructure sensitivity to heat treatment over a wide temperature range

The main subject of this study is to investigate the correlations between the evolution of mechanical behavior and the multiscale microstructure of 316 L stainless steel obtained by laser powder bed fusion process (LPBF) after various post-manufacturing heat treatments across a wide temperature range. The microstructure of 316 L LPBF parts exhibits a hierarchical microstructure based on unique grain structures, chemical segregations, dislocation arrangements at the microscopic scale and fine nano-oxides at the nanoscopic scale. These microstructural elements play a crucial role in determining the material's mechanical and corrosion properties. To understand how different microstructural features contribute to the material's behavior, the researchers conduct post-manufacturing heat treatments to isolate and study these components. The results show that dislocation and/or micro-segregation networks significantly influence the high tensile properties of 316 L LPBF steel in its as-built state and after heat treatments above 900∘C. Despite their disappearance during heat treatments, the material maintains high tensile strength due to an increase in strain-hardening capabilities. The study also examines the impact of nano-oxides and the σ phase on the material's properties. The contribution of nano-oxides to yield strength diminishes with increasing temperature. Interestingly, the σ phase does not necessarily lead to a detrimental effect on failure elongation for 316 L LPBF steel. Overall, this research provides insights into the relationship between microstructure and mechanical properties for additively manufactured stainless steel. By understanding these relationships, it becomes possible to tailor the microstructure to achieve desired mechanical properties for specific applications and extend the use of 316 L LPBF to higher temperatures compared to conventional methods.

Improved interlayer performance of short carbon fiber reinforced composites with bio-inspired structured interfaces

The weak layer interfaces of 3D-printed short carbon fiber (SCF) reinforced polymer composites have remained an issue due to planar layer printing by traditional 3D printers. Recently, multi-axis 3D printing technology which can realize non-planar layer printing has been developed. This study’s aim was to evaluate and compare the bonding performance of non-planar interfaces produced by multi-axis 3D printing with that of planar interfaces. The tested non-planar interfaces were designed as bio-inspired structured interfaces (BISIs) based on microstructural interfacial elements in biological materials. The standard specimens with the 0°/90° and 0° infill line directions were printed by a robotic arm multi-axis 3D printer. Double cantilever beam (DCB) and end-notched flexure (ENF) tests were conducted to obtain Mode Ⅰ and Mode Ⅱ interlaminar toughness of SCF-reinforced composites. Test results showed that the critical energy release rates of the integrally formed BISI were significantly improved compared with the planar interface (PLAI) for both Mode I and Mode II delamination. In particular, the BISI with 0° infill line direction exhibited the greatest increase in critical energy release rate, and the damaged areas were spatially swept through the curved interfaces of the BISI with different infill line directions by scanning electron microscopy (SEM) and computed tomography (CT), which showed that the higher critical energy release rate was always accompanied with a larger damaged area. In addition, the tensile and flexural properties of 0°-infilled PLAI and BISI specimens were also measured. This work provides an in-depth investigation of the PLAI and BISI properties of SCF-reinforced composites, demonstrating the potential benefits of integrally formed BISI by multi-axis 3D printing and fostering new perspectives to enhance layer interfaces of 3D printed composites.

The utility of wearable headband electroencephalography and pulse photoplethysmography to assess cortical and physiological arousal in individuals with stress-related mental disorders.

Several stress-related mental disorders are characterised by disturbed sleep, but objective sleep biomarkers are not routinely examined in psychiatric patients. We examined the use of wearable-based sleep biomarkers in a psychiatric sample with headband electroencephalography (EEG) including pulse photoplethysmography (PPG), with an additional focus on microstructural elements as especially the shift from low to high frequencies appears relevant for several stress-related mental disorders. We analysed 371 nights of sufficient quality from 83 healthy participants and those with a confirmed stress-related mental disorder (anxiety-affective spectrum). The median value of macrostructural, microstructural (spectral slope fitting), and heart rate variables was calculated across nights and analysed at the individual level (N = 83). The headbands were accepted well by patients and the data quality was sufficient for most nights. The macrostructural analyses revealed trends for significance regarding sleep continuity but not sleep depth variables. The spectral analyses yielded no between-group differences except for a group × age interaction, with the normal age-related decline in the low versus high frequency power ratio flattening in the patient group. The PPG analyses showed that the mean heart rate was higher in the patient group in pre-sleep epochs, a difference that reduced during sleep and dissipated at wakefulness. Wearable devices that record EEG and/or PPG could be used over multiple nights to assess sleep fragmentation, spectral balance, and sympathetic drive throughout the sleep-wake cycle in patients with stress-related mental disorders and healthy controls, although macrostructural and spectral markers did not differ between the two groups.

Effects of dual biomimetic tool surface microstructure on specific cutting energy in green turning

The energy consumption in the tool-workpiece system is dominated by specific cutting energy (SCE). Reducing SCE is critical for energy conservation in continuous dry turning which is a typical green turning process. The application of biomimetics shows great promise for reducing SCE. This study investigated effects of dual biomimetic tool surface microstructure on SCE in green turning. The dual biomimetic microstructure was established considering the rheological feature of the flow zone, the fierce cutting load and two kinds of biological structure. A theoretical rheological indicator was proposed for the flow zone in the secondary deformation zone. Furthermore, theoretical model was derived for SCE on the basis of the rheological indicator. It was found that the fabricated dual biomimetic microstructure reproduced the designed geometry characteristics. The SCE in green turning was reduced due to the existence of the dual biomimetic microstructure. A suitable area density Ad (27.66 %) of the microstructure should be adopted for efficiently reducing SCE. The variation of SCE was sensitive to the change of the rheological indicator. Larger parameter Pbm, the ratio of laser angle to microstructure element area, should be utilized for the microstructure element to acquire even lower rheological indicator and thereby obtain even greater reduction of SCE. Moreover, growth of the reduction rate was obvious only when Pbm was lower than 1.2 ∗ 109°/m2. The combination of Ad with a value of 27.66 % and Pbm with a value of 1.2 ∗ 109°/m2 can result in 34.72 % reduction of the total SCE compared to conventional tool.

Percussion solo parts in Rogerio Duprat’s Antinomies I

This article aims to analyse the solo percussion parts in Antinomies I, written for chamber orchestra by Brazilian composer Rogério Duprat (1932–2006) in 1962. Characterised by its graphic notation, the composer uses indeterminacy to lead the orchestra into an unconventional paradigm of sound creation. The analysis focuses on the percussionist's range of choices in order to understand how they affect the macro and microstructural elements of the work. There is considerable scope for choices in the percussion part of Antinomies I, which requires the use of "multi-percussion". Eight of the thirty-two circular structures that form the score are percussion solos. It is a significant number, greater than any other individual instrumentalist from the chamber orchestra. These circles form a heterogeneous group with different degrees of indeterminacy whose analysis reveals the interpretive process of transforming a graphic score into percussion sounds.

A MULTISCALE MULTIPHYSICS FINITE ELEMENT FOR LUNG

The previously formulated finite element for lung mechanics (MSCL) by the author is extended to include airflow and molecular transport by diffusion. The lung mechanics is analyzed in detail providing an insight into the deformation of the microstructural elements. Also, some refinements are introduced with respect to the previous model. Here, the finite element is extended to incorporate airflow and convective-diffusive particulate (molecular) transport. The smeared concept (the Kojic Transport Model – KTM) is implemented with lung small airway generations considered as subdomains within the KTM. The subdomains refer to a selected number of generations according to the airway diameters. Each domain has its own volumetric fraction and transport tensor specified in terms of the airway size. The computational procedure implemented in the PAK-BIO software consists of three passes within each time step: mechanics, airflow, and diffusion. The current geometry is used for the airflow where the alveolar sacs are considered as the source terms for the last domain, according to the rate of volumetric deformation and volumetric fraction of the sacs. The pressure distribution calculated in the pass 2 is used for the convective term in the diffusion. Here, the alveolar sacs are included as the last subdomain. The new element is now termed the General Lung Finite Element (GLFE). Coupling airflow in large airways, governed by the Navier-Stokes equations, to small airways (with the Hagen-Poiseuille equations) is presented; the same coupling is given for diffusion. Numerical examples illustrate the generality of the formulated finite element.

Multimodal investigation of the early associations between sleep‐wake regulation, cognition and Alzheimer’s disease neuropathology and risk

AbstractBackgroundAlterations in sleep‐wake regulation are hallmarks of the ageing process and emerge as risk factors for Alzheimer’s disease (AD). While the fine‐tuned coalescence of sleep microstructure elements may influence age‐related cognitive trajectories, its association with AD‐related processes is not fully known. Likewise, whether markers of sleep‐wake regulation assessed during wakefulness are associated with the risk of developing AD is not established.MethodHere, we sought associations between key elements of the electrophysiology of sleep microstructure and of sleep‐wake regulation and hallmarks of AD neuropathology (early Aβ/Tau/neuroinflammation brain burden) or the polygenetic risk in 360 young adults (18‐31y) and 100 late‐midlife healthy individuals (50‐70y). We further investigated relationships with cognitive performance.ResultWe first found that spontaneous arousal during sleep are heterogenous and differently associated with Aβ and cognition. We further found the young‐like co‐occurrence of sleep spindles and slow‐depolarisation slow waves was associated to lower early burden of Aβ and was predictive of memory decline at 2‐year follow‐up. We also find that the dynamics of the daily change in cortical excitability and EEG markers of sleepiness are respectively not associated with early Ab burden and associated with the polygenic risk of developing AD. Cortical excitability dynamics is, however, association with cognitive performance.ConclusionThese findings unravel early links between sleep‐wake regulation, AD‐related processes or genetic risks and their association with cognitive performance. Spontaneous arousals and the altered coupling of sleep microstructure elements that are key to its mnesic functions may contributes to poorer brain and cognitive trajectories in ageing. In addition, associations between markers of sleep‐wake regulation and AD can be detected during quiet wakefulness.Support: ULiège, Wallonia‐Brussels Federation, Fonds de la Recherche Scientifique (FNRS Belgium), Fondation Recherche Alzheimer (SOA‐FRA Belgium), Fondation Léon Fredericq, EU FEDER programme

MARKET MICROSTRUCTURE AND FINANCING EFFICIENCY IN MSMES IN INDONESIA: COMPARISON OF SHARIA AND CONVENTIONAL SECTORS

The objective of this research is to examine the financing efficacy and market microstructure of Micro, Small, and Medium Enterprises (MSMEs) in Indonesia. Specifically, it compares the conventional sector with the sharia-compliant sector. This study employs Structural Equation Modeling with Partial Least Squares (SEM-PLS 4) to examine access to financing, utilization of collateral, and ability to pay with a sample of 132 MSMEs. The results of the study demonstrate distinct variations between conventional and sharia-compliant MSMEs, underscoring the influence of market microstructure elements on financial accessibility. SMBs that adhere to sharia law demonstrate, in particular, increased levels of access to capital and utilization of collateral. This research makes a valuable contribution to the comprehension of sectoral dynamics and provides policymakers, financial institutions, and MSMEs in Indonesia with practical implications.

Dynamic Assessment of Narrative Skills for Identifying Developmental Language Disorder in Monolingual and Bilingual French-Speaking Children.

Purpose: Typically developing (TD) bilingual children usually produce narratives with preserved macrostructure (i.e., narrative scheme) but with impaired microstructure (i.e., language complexity). As for monolingual and bilingual children with developmental language disorder (DLD), they usually produce narratives with both impaired macro- and microstructure. It is therefore difficult to differentiate TD from DLD, on the basis of narrative production, especially in bilingual children. In this study, we examine whether a dynamic assessment (DA) task of narratives, using a pretest–teaching–posttest design, can differentiate TD from DLD, without disadvantaging bilinguals over monolinguals. Method: We recruited 118 French-speaking children ( M age = 8;5 [years;months]), with one experimental condition in which children benefited from a teaching phase (30 TD, 18 monolinguals and 12 bilinguals; 30 DLD, 15 monolinguals and 15 bilinguals) and one control condition (58 TD, 31 monolinguals and 27 bilinguals), in which children participated in another activity. In the pre- and posttest, children were asked to tell a story based on a series of pictures. During the teaching phase, an examiner asked children 12 specific questions about the story, targeting macro- and microstructural elements. Scores were attributed to the number of macro- and microstructural elements correctly produced and to the number of specific trained elements (TE) that were produced as a result of training. Results: Scores improved on macrostructure and on the number of TE following teaching for all groups of the experimental condition (TD and DLD), whereas there was no progress in children of the control condition. TD participants and participants with DLD differed on all measures in both pre- and posttest, with no differences between monolinguals and bilinguals. Conclusions: Our dynamic task led to both improved narrative skills and TD/DLD differentiation, with bilinguals not being disadvantaged. Our study thus supports the existing literature indicating that DA can be used to diagnose narrative deficits in children with DLD.

Childhood development of brain white matter myelin: a longitudinal T1w/T2w-ratio study

Myelination of human brain white matter (WM) continues into adulthood following birth, facilitating connection within and between brain networks. In vivo MRI studies using diffusion weighted imaging (DWI) suggest microstructural properties of brain WM increase over childhood and adolescence. Although DWI metrics, such as fractional anisotropy (FA), could reflect axonal myelination, they are not specific to myelin and could also represent other elements of WM microstructure, for example, fibre architecture, axon diameter and cell swelling. Little work exists specifically examining myelin development. The T1w/T2w ratio approach offers an alternative non-invasive method of estimating brain myelin. The approach uses MRI scans that are routinely part of clinical imaging and only require short acquisition times. Using T1w/T2w ratio maps from three waves of the Neuroimaging of the Children’s Attention Project (NICAP) [N = 95 (208 scans); 44% female; ages 9.5–14.20 years] we aimed to investigate the developmental trajectories of brain white matter myelin in children as they enter adolescence. We also aimed to investigate whether longitudinal changes in myelination of brain WM differs between biological sex. Longitudinal regression modelling suggested non-linear increases in WM myelin brain wide. A positive parabolic, or U-shaped developmental trajectory was seen across 69 of 71 WM tracts modelled. At a corrected level, no significant effect for sex was found. These findings build on previous brain development research by suggesting that increases in brain WM microstructure from childhood to adolescence could be attributed to increases in myelin.

Detection of Xylene Using Ni(OH)2-Enhanced Co3O4 Nanoplate via p–n Junctions

This study reports a novel Ni(OH)2/Co3O4 heterostructured nanomaterial synthesized through a simple two-step hydrothermal method combined with subsequent heat treatment. The Ni(OH)2/Co3O4 heterostructured nanomaterial showed excellent performance in the detection of xylene gas. XRD, SEM, and EDS characterized the crystal structure, microstructure, and composition elements of Co3O4 and Ni(OH)2/Co3O4, and the gas sensing properties of the Co3O4 sensor and Ni(OH)2/Co3O4 sensor were systematically tested. The test results indicate the Ni(OH)2/Co3O4 sensor has an optimal operating temperature of 175 °C, which is 10 °C lower than that of the Co3O4 sensor; has a response of 14.1 to 100 ppm xylene, which is 7-fold higher than that of the Co3O4 sensor; reduces the detection limit of xylene from 2 ppm to 100 ppb; and has at least a 4-fold higher response to xylene than other gases. The Ni(OH)2/Co3O4 nanocomposite exerts the excellent catalytic performance of two-dimensional nanomaterial Ni(OH)2, solves the deficiency in the electrical conductivity of Ni(OH)2 materials, and realizes the outstanding sensing performance of xylene, while the construction of the p–n heterojunction between Ni(OH)2 and Co3O4 also improves the sensing performance of the material. This study provides a strategy for designing high-performance xylene gas sensors using two-dimensional Ni(OH)2 materials.

Application of Ice Pigging in a Drinking Water Distribution System: Impacts on Pipes and Bulk Water Quality

Ice pigging is an emerging technique for pipe cleaning in drinking water distribution systems. However, substantial confusion and controversy exist on the potential impacts of ice pigging on bulk water quality. This study monitored the microstructural features and composition of sediments and microbial community structures in bulk water in eight multimaterial Chinese networks. Chloride concentration analysis demonstrated that separate cleaning of pipes with different materials in complex networks could mitigate the risk of losing ice pigs and degrading water quality. The microstructural and trace element characterization results showed that ice pigs would scarcely disturb the inner surfaces of long-used pipes. The bacterial richness and diversity of bulk water decreased significantly after ice pigging. Furthermore, correlations were established between pipe service age, temperature, and chloride and total iron concentrations, and the 15 most abundant taxa in bulk water, which could be used to guide practical ice pigging operations.

Three-dimensional microstructural simulation of the thermodynamic behavior of recycled concrete under freeze-thaw action

A thermal-water-mechanical coupling model was utilized to simulate pore water crystallization and melting heat transfer processes in recycled concrete. Based on the random spherical microstructure of recycled concrete, The characteristics of aggregates, new mortar, old mortar, and the interface transition zones (ITZ1, ITZ2, and ITZ3) between natural aggregates and new mortar, old aggregates, and mortar, as well as new and old mortar, were clearly described. The proposed model was validated by comparing it with experimental data available in the literature. Three-dimensional microstructural finite element simulations were performed to assess the influence of the water-to-cement ratio of new mortar, the water-to-cement ratio of old mortar, aggregate gradation, replacement ratio of recycled aggregates, aggregate volume fraction, and temperature difference on the performance of recycled concrete. The research results demonstrated that the aggregate gradation, replacement ratio of recycled aggregates, and aggregate volume fraction significantly affected recycled concrete's freeze-thaw characteristics. In contrast, the influence of the water-to-cement proportions of fresh and old mortar was relatively small. The impact of environmental temperature differences should also be given due attention.

A multi-scale formulation for polycrystalline materials accounting for cohesive micro-cracks: Homogenisation of the traction-separation law

This contribution investigates the modelling of failure in polycrystalline materials due to the nucleation and propagation of cohesive cracks at the micro-scale. First, a two-scale formulation that enables the analysis of failure, even when the evolution and propagation of cohesive micro-cracks induce material instability, is proposed. The development of this macro-continuous/micro-discontinuous formulation is based on the Method of Multi-Scale Virtual Power, from which dynamic equilibrium and homogenisation equations are derived, ensuring a variationally consistent scale transition. The respective minimal kinematical constraint is retrieved and enforced with the Lagrange multiplier method. The formulation is also extended for periodic boundary conditions. The discretisation of the resulting equilibrium equations, with the finite element method and the generalised-α method, is described in detail.Second, a fracture-based computational homogenisation procedure is developed to obtain homogenised traction-separation laws and fracture properties from microstructural volume elements. It is derived from a crack-based Hill-Mandel principle and employs a novel energetic-based damage variable, within the Park-Paulino-Roesler cohesive model, proposed to define the crack domain and compute the crack homogenised quantities. A strategy for accurately computing the homogenised unit normal vector of the equivalent macroscopic crack is also suggested.Numerical examples demonstrate the formulation’s ability to analyse fracture problems, including a study on the impact of different microscopic boundary conditions. This work also reveals the convergence of the traction-separation law with increasing microstructure model size when using the fracture-based computational homogenisation. Furthermore, it investigates how advanced deformation mechanisms, like slip plasticity and martensitic transformation, affect intergranular crack propagation mechanisms.

Insights into building a digital twin of closed-cell aluminum foam during impact loading: Microstructural, experimental and finite element investigations

The mechanical behavior of metal foams under impact loading depends on multiple and complex parameters like impact velocity, strain-rate, local plastic deformation, oscillating and micro-inertial effects, etc. The prediction of the behavior of metal foams that are subject to impact loads is still challenging and engineering application of these materials typically requires time-consuming experimental tests. Numerical models based on the finite element method (FEM) can contribute to minimizing the experimentation effort. Realistic FEM models were built that account both for the macro- and micro-scopic characteristics of the porous material, explain the acting mechanisms that take place during impact, and study the yield properties as well as the energy absorption during the impact of closed-cell aluminum foams. The simulation results are compared with the ones derived from respective experimental uniaxial tests. Two different modeling approaches were applied thus creating two models. The first model relies on a cell-based method where the initial geometry of the foam was generated based on the Voronoi tessellation algorithm and the second one relies on the isotropic, strain-hardening, and continuum-based model developed by Deshpande-Fleck. The outcome of the investigation sheds light on the metal foam behavior under impact by explaining macro- and micro-structural phenomena that develop during impact.

Understanding the Microstructure and Macrostructure Narrative Skills of Bilingual Adolescents in Relation to Their Language Experience.

Narratives have been a useful tool for evaluating language skills in young bilingual children. This study extends that work to bilingual adolescents by (a) describing their narrative skills and (b) evaluating the role of current language experience on measures of narrative micro- and macrostructure across Spanish and English. Sixty-five Spanish-English bilingual adolescents, ages 10-15 years, were administered the Test of Narrative Language (TNL) in English and Spanish. Language samples were transcribed and coded for elements of narrative microstructure. Parents provided information about participants' current language experience. Means and standard deviations were reported for microstructure composites, TNL comprehension subtests, and TNL production subtests in Spanish and English. Findings showed differential effects of current English experience on narrative performance across Spanish and English, such that experience significantly explained 12%, 10%, and 20% of the variance in participants' microstructure scores, narrative comprehension, and narrative production in Spanish, respectively. Language experience was unrelated to performance across all English narrative measures. Findings suggest that continued use of Spanish may be important for bilinguals' maintenance of the home language during adolescence, particularly on narrative tasks that require bilinguals to produce Spanish. However, experience is insufficient to explain the variability in bilinguals' narrative skills across Spanish and English.

Quantitative representation of directional microstructures of single-crystal superalloys in cyclic crystal plasticity based on neural networks

Nickel-based single-crystal alloys undergo microstructural degradation induced by thermal exposure. The directional rafting of microstructures significantly affects the mechanical properties and makes the material anisotropic. For structural design, establishing a quantitative description of microstructural effects in a constitutive model becomes essential and is still a tough research topic in multi-scale materials modeling. In the present work, the fabric tensor was correlated with the anisotropic cyclic crystal plasticity of nickel-based single-crystal alloys with the help of neural networks. The microstructural representative volume elements with various single-crystal morphologies were generated by the phase-field method and the deformation behaviors were studied under different crystal orientations and loading configurations. The neural network analysis confirmed that the fabric tensor can present anisotropic single-crystallographic microstructural features and describe mechanical behavior under both monotonic and cyclic multi-axial loading conditions. The history-dependent anisotropic cyclic hardening or softening behavior of the material can be captured by the introduced microstructural state variable. A principal component analysis (PCA) aided gradient-based attribution method was proposed to evaluate the importance of input variables. The characterization of different material components and their contribution to the stress–strain relationships are investigated and validated. The fabric tensor was verified to be an effective microstructural indicator for the continuum plasticity of single-crystal alloys.

Influence of starting microstructure on the microstructure evolution during annealing and the yield strength in Nb-Ti microalloyed cold-rolled steel

The microstructure evolution of cold-rolled microalloyed steel during annealing at different soaking temperatures was investigated, with emphasis on the influence of the starting microstructure prior to annealing. The starting microstructure of cold-rolled martensite exhibited the fastest recrystallization kinetics, followed by the cold-rolled ferrite-pearlite initial microstructure, while the recrystallization was nearly suppressed in the cold-rolled ferrite-cementite microstructure. The different recrystallization kinetics appear to be influenced by the competing effects of the driving pressure for recrystallization and the solute drag of microalloying elements, which leads to dissimilar post-annealing microstructures even with comparable fractions of new ferrite originating from the reversely transformed austenite. The yield strength following annealing was found to be affected by the starting microstructure. In addition to the dislocation strengthening associated with recrystallization retardation, contributions from other strengthening mechanisms, such as grain refinement and precipitation, varied depending on the starting microstructure. Consequently, the strengthening effects are subject to interplay between the starting microstructure and microalloying elements during annealing, which requires quantitative evaluation for a comprehensive understanding of changes in yield strength.