Annealing Stage Research Articles

Catalytic Cu2O/Cu Site Trades off the Coupling and Etching Reactions of Carbon Intermediates for CO2-Assisted Graphene Synthesis.

In the chemical vapor deposition (CVD) synthesis of graphene, the surficial chemical state of the metal substrate has exerted key roles in all elemental reaction steps determining the growth mechanism of graphene. Herein, a CO2-participated annealing procedure is designed to construct catalytic Cu2O/Cu sites on Cu foil for the graphene CVD synthesis with CO2/CH4 as carbon sources. These Cu2O/Cu species can catalyze the CH4 decomposition and subsequent C─C coupling to form C2 intermediates for fast growth of monolayer hexagonal graphene domains with a diameter of ≈30µm within 0.5min. The graphene growth kinetics can be bidirectionally regulated merely with the variation of CO2 flow rate during annealing and growth stages, in association with the Cu+/Cu0 ratio, enabling simultaneous control over the size and shape of graphene domains. Density functional theory (DFT) calculations indicate that the catalytic Cu2O/Cu sites reduce the activation energy by ≈0.13eV for the first dehydrogenation of CH4, allowing the growing rate of graphene driven by coupling of C2 intermediates faster than their etching rate by O-containing *O and *OH species. The work provides novel insights into heterostructured nano-catalyst consisting of zero valent metal and variably valent metal oxide that facilitate the controllable synthesis of graphene materials.

СОВЕРШЕНСТВОВАНИЕ ТЕХНОЛОГИИ ПРОИЗВОДСТВА ТЕКСТУРИРОВАННОЙ МУКИ

The purpose of the study is to reduce energy costs for the production of textured flour by optimizing the technology of its production. Tasks: to develop a constructive and technological scheme for the production of textured flour and evaluate its technical and economic efficiency. The object of research is a technological line for the production of textured flour from wheat grain. Research was carried out at the Engineering Center of the FSBEI HE Krasnoyarsk State Agrarian University. Flour production was carried out according to two technologies, differing in that after cleaning, the grain was either extruded or pre-moistened and softened using a developed and patented grain processing device, and then extruded. The obtained extrudates were ground to obtain a textured flour. Its analysis showed a change in nutritional value. There was an increase in the content of protein, starch and fat by 4.7 %, 1.4 and 29.4 %, respectively, a decrease in the content of sugars – by 13.8 % and fiber – by 22.5 % when using preliminary grain conditionning. Based on the equipment used in production, taking into account all stages of processing of raw materials, an analysis of energy costs for the production of textured flour was carried out. The assessment of energy flows was used to justify the efficiency and feasibility of its production. To assess the energy efficiency of production, the energy income indicator E (MJ/kg) was used, showing the difference between the energy contained in the resulting product and the total energy costs invested in the production of textured flour at the stages of grain cleaning, moisturizing and tempering, extrusion and grinding. The cost of producing textured flour in the technology without pre-moistening and tempering of the grain amounted to 3.72 MJ/kg, with pre-moistening and tempering – 3.73 MJ/kg, at the same time, the energy income in the proposed technology increased and amounted to 8.81 MJ/kg. kg, compared with the original – 8.34 MJ/kg.

Influence of Copper and Tin Oxidation States on the Phase Evolution of Solution-Processed Ag-Alloyed CZTS Photovoltaic Absorbers

Kesterite-based semiconductors, particularly copper–zinc–tin–sulfide (CZTS), have garnered considerable attention as potential absorber layers in thin-film solar cells because of their abundance, nontoxicity, and cost-effectiveness. In this study, we explored the synthesis of Ag-alloyed CZTS (ACZTS) materials via the sol–gel method and deposited them on a transparent fluorine-doped tin oxide (FTO) back electrode. A key challenge is the selection and manipulation of metal–salt precursors, with a particular focus on the oxidation states of copper (Cu) and tin (Sn) ions. Two distinct protocols, varying the oxidation states of the Cu and Sn ions, were employed to synthesize the ACZTS materials. The transfer from the solution to the precursor film was analyzed, followed by annealing at different temperatures under a sulfur atmosphere to investigate the behavior and growth of these materials during the final stage of annealing. Our results show that the precursor transformation from solution to film is highly sensitive to the oxidation states of these metal ions, significantly influencing the chemical reactions during sol–gel synthesis and subsequent annealing. Furthermore, the formation pathway of the kesterite phase at elevated temperatures differs between the two protocols. Structural, morphological, and optical properties were characterized via X-ray diffraction (XRD), Raman spectroscopy, and scanning electron microscopy (SEM). Our findings highlight the critical role of the Cu and Sn oxidation states in the formation of high-quality kesterite materials. Additionally, we studied a novel approach for controlling the synthesis and phase evolution of kesterite materials via molecular inks, which could provide new opportunities for enhancing the efficiency of thin-film solar cells.

Study on the Crystallization Behavior of Polyether Ether Ketone Thin Films Under Thermal Annealing

ABSTRACTDue to its excellent biocompatibility, high‐temperature resistance, chemical corrosion resistance, radiation resistance, and ease of processing and shaping, polyether ether ketone (PEEK) has been widely used in the field of oral medicine. In this study, we conducted an in‐depth investigation of the thermal annealing process of PEEK films at different temperatures. The grazing incidence wide‐angle x‐ray scattering (GIWAXS) results indicate that the PEEK molecular chains tend to align in an edge‐on orientation in the film, and annealing at different temperatures leads to the formation of two crystalline phases, A and B, with a spacing of 4.46 Å for (200) A and 4.69 Å for (200) B. The crystallization behavior during the annealing process was characterized using in situ GIWAXS, revealing an increase in the film's crystallinity in the early stages of annealing. Due to enhanced polymer chains mobility, the B phase is formed. However, during annealing at 200°C, the intensity of the (200) B peak initially increases and then decreases, indicating the instability of the B phase, which can be disrupted by excessive molecular mobility. Mechanical property characterization results demonstrate that as the annealing temperature increases, the film's elongation at break and modulus decrease.

Study of minor Sc and Zr additions effect on silicon rich Al–Mg–Si aluminum alloy microstructure during Sc multistage thermal treatment

The study addresses the effect of multistage thermal treatment on microstructure formation of Al–Mg–Si series alloy with scandium and zirconium additions in Mg/Si = 0.3 proportion. Basic alloy AlM–Si without Sc and Zr and them modification AlMg1SiZrSc were cast. AlMgSiScZr alloy multi-stage thermal treatment included the following 4 annealing stages –550 °C 8 h + 440 °C 8 h + 500 °C 0.5 h + 180 °C 5 h. For AlMg1Si alloy it was performed following 550 °C 8 h + 180 °C 5 h practice. AlMgSiScZr microstructure was examined using scanning (SEM) and transmission (TEM) microscopy both in as-cast state and after each stage of thermal treatment, for AlMg1Si – both in as-cast state and after final thermal treatment. Coarse intermetallic particles were examined using SEM, while fine particles were examined using TEM. Besides, microhardness values were measured after various thermal treatment stages. It was found out, that coarse intermetallic compounds of Fe2Mg7Si10Al18 type are formed in both alloys during as-cast structure cooling down with such compounds partial dissolution during further thermal treatment. At the same time particles, that can be attributed either to (AlSi)3ScZr or to AlSc2Si2τ-phase, occur in inter-grain boundary of alloys with scandium-zirconium additions. No traces of scandium solid solution discontinuous decomposition have been identified during ingot cooling down. Thermal treatment during 8 h at 550 °C 8 and 8 h at 440 °C results in formation of the phase, which can represent both AlSc2Si2 and Al5SiZr2. At the same time nanoparticles (AlSi)3ScZr do not form during this thermal treatment stage. Heating to 500 °C during 30 min interval allows complete dissolution of magnesium in supersaturated aluminum solid solution. During the final stage β’’ particles (Mg5Si6), representing the major type, form in both alloys; in these conditions scandium does not produce significant effect on their formation.

Developing a Machine Learning 'Smart' Polymerase Chain Reaction Thermocycler Part 2: Putting the Theoretical Framework into Practice.

The introduction of PCR into forensic science and the rapid increases in the sensitivity, specificity and discrimination power of DNA profiling that followed have been fundamental in shaping the field of forensic biology. Despite these developments, the challenges associated with the DNA profiling of trace, inhibited and degraded samples remain. Thus, any improvement to the performance of sub-optimal samples in DNA profiling would be of great value to the forensic community. The potential exists to optimise the PCR performance of samples by altering the cycling conditions used. If the effects of changing cycling conditions upon the quality of a DNA profile can be well understood, then the PCR process can be manipulated to achieve a specific goal. This work is a proof-of-concept study for the development of a smart PCR system, the theoretical foundations of which are outlined in part 1 of this publication. The first steps needed to demonstrate the performance of our smart PCR goal involved the manual alteration of cycling conditions and assessment of the DNA profiles produced. In this study, the timing and temperature of the denaturation and annealing stages of the PCR were manually altered to achieve the goal of reducing PCR runtime while maintaining an acceptable quality and quantity of DNA product. A real-time feedback system was also trialled using an STR PCR and qPCR reaction mix, and the DNA profiles generated were compared to profiles produced using the standard STR PCR kits. The aim of this work was to leverage machine learning to enable real-time adjustments during a PCR, allowing optimisation of cycling conditions towards predefined user goals. A set of parameters was found that yielded similar results to the standard endpoint PCR methodology but was completed 30 min faster. The development of an intelligent system would have significant implications for the various biological disciplines that are reliant on PCR technology.

Sol–gel prepared ZnO: UV irradiation effect on structure and surface properties

The effect of UV irradiation on sol–gel prepared ZnO films subjected to mild thermal annealing was investigated, with special attention to their structural and surface properties. Sol–gel processes, including a high-temperature annealing stage, have been adapted to the requirements of flexible electronics for in situ synthesis of semiconductor ZnO films on polymer substrates at lower temperatures due to UV irradiation. Application of UV radiation with emission peaks at 185 and 254 nm to films annealed at 180 °C made it possible to obtain ZnO films with Zn/O ratios of ca. 1, which cannot be achieved by heat treatment alone.

Achieving 2.7 GPa tensile strength in ultrastrong high-carbon steel through prolonged low-temperature tempering

The mechanical properties of high‑carbon martensitic steel are improved by low-temperature tempering. This is due to carbon diffusion and carbide precipitation, which depend on temperature and time. To further improve mechanical properties and develop optimum tempering conditions of the conventional high‑carbon martensitic steel, long-term tempering was carried out at approximately 175 °C and 250 °C. Excellent mechanical properties, which had not been achieved before, were obtained after tempering samples at 175 °C for over 40 d, resulting in tensile strength of 2.7 GPa, yield strength of 2.3 GPa and total strain of 2.6%. Similarly, yield strength values exceeding 2.4 GPa were observed in samples tempered at 250 °C for 5 d. To understand the remarkable outcomes achieved, a detailed investigation into the tempering stages, with the use of Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), and X-ray Diffraction (XRD) analyses, was essential. The microstructure contained the typical tempered martensite matrix embedded by ultrafine carbides and retained austenite which decomposed slowly with increasing tempering time at 175 °C, contributing to a noticeable increase in strength. Conversely, no pronounced effect of retained austenite was observed on the strength evolution of tempered specimens at 250 °C. At the initial stage of long-term tempering, the primary strengthening mechanism was carbon solid solution strengthening with a value exceeding 1000 MPa. The solid solution strengthening weakened with tempering time, while precipitation strengthening increased with the growth and increasing volume fraction of carbides. The interplay of their effects and the softening of retained austenite led to a trend in which the total yield strength increased, followed by a decrease with increasing holding time. The resulting nuanced mechanical properties and microstructure obtained from long-term tempering offer strategies for synergistic strengthening and ductility of high‑carbon steels, thereby facilitating the expansion of their potential applications.

Influence of the as quenched state and tempering temperature on the final microstructure and hardness of a high strength medium carbon steel

The present study aimed to investigate the impact of the as-quenched microstructure and tempering temperature on the final microstructure and hardness of a medium-carbon, low-alloy steel using dilatometry, Electron backscatter diffraction (EBSD) and scanning electron microscopy (SEM). The results revealed substantial differences in the continuous heating stage of tempering in bainitic and martensitic samples, primarily attributed to the auto-tempering process during cooling. Tempering was carried out at 550 and 620 °C, and dilatometry results, along with microstructure analysis, indicated incomplete decomposition of retained austenite (RA) at both temperatures during a 30-min hold in the bainitic sample. The results show that non-decomposed RA, following the tempering of bainite, transformed into blocky fresh martensite, while no evidence of fresh martensite was observed in the martensitic sample. A new approach using EBSD and SEM images revealed that the decomposition of M/A (martensite/austenite constituent) zones in the bainitic sample resulted in the formation of a chain of aggregated chromium carbide zones at the grain boundaries. In contrast, the martensitic zone exhibited a uniform distribution of carbides in the microstructure. The stability of the phases was examined using the TCFE10 (thermodynamics) and MOBFE5 (mobility) modules of the DICTRA Themo-Calc software. Hardness measurements on all samples indicated decreases by about 18–24 % in the martensitic sample after tempering, while the bainitic sample exhibited a 5 % increase in hardness after tempering, attributed to secondary hardening and fresh martensite formation.

Thermal restoration kinetics and microstructural evolution of an Mg-RE alloy during annealing by quasi-in-situ observation

Quasi-in-situ electron backscatter diffraction method is applied to properly investigate thermal restoration kinetics and microstructural evolution of a commercial WE54 alloy after 10 % engineering pre-strain and post-annealing at 500 °C for 10, 35, and 70 min. Results show a reduction in the average grain orientation spread can effectively evaluate the restoration kinetics compared to other characteristics like average grain size or average misorientation angle. For microstructural evolution, nucleation behavior and abnormal grain growth of recrystallization nuclei as well as evolution of deformation twin have been investigated in detail. Low-angle grain boundary network due to the recovery effect provides recrystallization nuclei in the early stage of annealing, after which both continuous and discontinuous recrystallization nuclei are observed near deformation twin boundaries and original high-angle grain boundaries. Afterwards, grains with a tilting angle of 30° from the transverse direction grow abnormally, replacing the deformed grains, deformation twins, and part of some recrystallized grains. In addition, some twins can grow into the adjacent grains while de-twinning also occurs depending on twin orientations during thermal restoration.

Microstructure evolution and nano-precipitate of multi-stage heat-treated Ti–45Al–2Nb–2Cr-0.3C alloy

This work thoroughly examined the microstructure evolutions of the cast Ti–45Al–2Nb–2Cr-0.3C alloy after multi-stage heat treatments, involving solid solution, cyclic quenching and isothermal annealing. The experimental findings revealed that solid solution and isothermal annealing processes decreased the lattice constants of component parameters, while the cyclic quenching resulted in the lattice expansion. The blocky (B2+γ) phases, which had been distributed along the colony boundary of the as-cast microstructure, disappeared after multi-stage heat treatment, and the lamellae showed a trend of thinning first and then thickening. In addition, the cyclic quenching process resulted in a large number of dislocations and stacking faults within γ lamellae. These crystal defects could act as heterogeneous nucleation sites, lowering the energy barrier of Ti2AlC precipitated from the lamellar matrix during the isothermal annealing stage. The dispersed Ti2AlC particles, with an average size of 45 ± 15 nm, showed the following coherent relationship with the lamellar matrix, [1‾216‾]Ti2AlC//[001]γ and (101‾0)Ti2AlC//(2‾20)γ.

Annealing response and yielding behavior of cold rolled advanced HSLA steels

High-strength low-alloy (HSLA) steel is well established in car body manufacturing. They comprise a lean low-carbon alloy concept and can be produced by a wide variety of processing routes. However, cold-rolled HSLA steels are typically limited to a yield strength of 460 MPa by current standards. This research work will present a concept of extending the yield strength range of cold-rolled HSLA steels to above 500 MPa. A key aspect is to find the right balance between recovery and recrystallization of the cold rolled matrix during the annealing stage thereby mitigating the influence of solute and precipitated niobium. Additional solute draging power was introduced by alloying molybdenum to one of the investigated steels. A detailed microstructural analysis using transmission electron microscopy revealed that under recovery annealing conditions an ultrafine-grained microstructure with ferrite grain sizes between 0.5 and 1 μm can be established leading to large strength contribution via the Hall-Petch relationship. Strength losses related to partial recrystallization can be recovered to an extent of around 200 MPa by the precipitation of nano-sized niobium carbide particles. It is demonstrated that the presence of niobium and molybdenum in solute condition have the most prominent influence on obstructing recrystallization via solute drag. It is furthermore shown that the magnitude of precipitation strengthening correlates with the Lüders strain. The analysis of the work hardening behavior indicated that the n-value in ultrafine-grained condition approaches a lower limit value of 0.03 and raises to above 0.2 with progressing recrystallization as well as precipitation strengthening. The detailed evaluation of the tensile characteristics indicates that the strength limit for these HSLA steels ranging between 830 and 880 MPa is reached when the average grain size is reduced to 0.46 μm. The results of this study used to define robust processing conditions to securely produce steel grades in the 600–800 MPa yield strength range.

Quasi-in-situ observing unusual grain orientation rotation during the process of static recrystallization grain growth in Mg–Zn-Gd alloy

The orientation (including the c axis orientation and crystal direction parallel to rolling direction) evolution of grown recrystallization grains during annealing at 250 °C for 45–180 min in Mg–Zn-Gd alloy was characterized by quasi-in-situ electron backscatter diffraction method. An unusual grain orientation rotation during the process of static recrystallization grain growth, rather than common plastic deformation or recrystallization nucleation process, was observed. Due to the higher storage energy, the growth size in the early stage of annealing (1.41 μm) is larger than that in the late stage of annealing (0.73 μm) for most (∼76%) grains, and corresponding average c-axis rotation angles are 3.65° and 1.39°, respectively, indicating that the larger the increase in grain size, the greater the changing degree in grain orientation. It is speculated that the orientation rotation during grain growth process is mediated by the interaction between dislocations and grain boundaries. The results reported in the current paper can provide a new insight into the study on the relationship between preferential grain growth and non-basal texture formation in rare earth contained Mg alloys.

The Effect of Rare Earth Y on the Inhibitor Precipitation Behavior of Strip‐Cast Grain‐Oriented Silicon Steel

0.3 mm‐thick grain‐oriented silicon steel sheets with varying Y contents are produced via twin‐roll strip‐casting and two‐stage cold rolling process. This study primarily investigates the evolution of microstructure, texture, and precipitation along the processing. Specifically, the effect of rare earth Y on second‐phase particle precipitation in ultralow carbon grain‐oriented silicon steel is examined. Results indicate that higher Y content will consume beneficial inhibitor elements such as S and N, leading to the formation of coarse rare earth inclusions (≈10 μm) in the cast strip. This significantly diminishes inhibition ability and magnetic induction (B8 = 1.58 T≈1.71 T). On the contrary, the addition of trace Y can accelerate the precipitation of inhibitors. During the intermediate annealing stage, steel with trace Y exhibits a significant enhancement in precipitate distribution density (from 2.8 μm−2 to 13.6 μm−2), and the final magnetic induction B8 increases from 1.86 T to 1.91 T compared to steel without Y. In addition, the results of first‐principle calculations based on density functional theory reveal that the doped Y atom prefers to segregate at the Al–N interface, and the interface energy reduces from 1.871 J m−2 to 1.024 J m−2, thereby promoting the precipitation of AlN.

Microstructure evolution of V-containing low carbon ultra-fine bainitic steel during medium-temperature tempering and strengthening-toughening mechanism

In the present study, the microstructure evolution and the corresponding mechanical properties of V-containing low carbon ultra-fine bainitic steel during tempering were studied. The results show that during the initial stages of tempering, part of retained austenite in V-containing ultra-fine bainite steel transforms into bainite. The stability of the retained austenite improves when the tempering period is increased to 5 h. Simultaneously, nano-sized VC precipitates are precipitated in the microstructure. On the one hand, these phases can give full play to the transformation-induced plasticity (TRIP) effect by modulating the carbon content of the retained austenite. On the other hand, they can also reduce the lattice distortion in the matrix and combine it with the lower dislocation density, thereby improving the plasticity of the specimen. At the same time, the fine precipitated phase can also effectively improve the toughness of the cleavage crack region in the transition zone, preventing the micro-cracks from generating at the interface of the precipitated phase and then extending to the adjacent matrix to cause fracture, so that the uniform elongation, total elongation, impact toughness at room temperature and impact toughness at low temperature of the 5 h specimen are as high as 8.8 ± 0.2 %、16.2 ± 0.7 %、113 ± 4 J/cm2 and 76 ± 2 J/cm2, respectively. Furthermore, the primary contribution of the strengthening mechanism in the microstructure has shifted from fine grain strengthening and dislocation strengthening to precipitation strengthening, and part of the retained austenite undergoes a martensitic transformation during cooling, resulting in the highest yield strength of 1086 MPa for the 5 h specimen. The tensile strength is effectively maintained at 1402 MPa by increasing the tempering period, which has good tempering resistance, to achieve the comprehensive performance optimization of bainitic steel.

Microstructure, mechanical properties and corrrosion behavior of Al-Zn-Mg-Cu wire under different annealing conditions

Al-Zn-Mg-Cu aluminum alloy wires were annealed at 404 °C and then cooled at 10–100 °C/h. On the basis of the cooling speed of 10 °C/h, a second stage of 232 °C annealing was added and held for 4–8 h. The differences in grain organization, grain boundary precipitation phase, electrical conductivity, mechanical properties and intergranular corrosion properties of Al-Zn-Mg-Cu aluminum alloy wires with different annealing processes were comparatively investigated by using electron backscatter diffraction (EBSD) technique, transmission electron microscope (TEM), electronic tensile tester, conductivity meter. It is found that the grain size of Al-Zn-Mg-Cu wire after different annealing processes has not grown significantly, and the grain orientation has not changed obviously. As the cooling speed decreased from 100 °C/h to 10 °C/h, the precipitated η phase continued to merge and grow, from chain distribution to independent distribution, and the Cu element in η phase increase. The Cu content of η phase increases to 14.7 wt% by adding a second annealing stage. The conductivity of the alloy increases to 48.6 %IACS and the tensile strength is reduced to 168 MPa. In addition, the maximum corrosion depth of the alloy is reduced to 16 μm. It shows good mechanical properties and excellent corrosion resistance.

In-situ observation of restoration of tungsten plate via high-temperature confocal laser scanning microscopy

The restoration of an yttria dispersion strengthened tungsten plate and the corresponding microstructural evolution are investigated through in situ annealing using high-temperature confocal laser scanning microscopy. The geometrically necessary dislocation density and subgrain/grain evolution at each annealing stage are confirmed using the electron backscatter diffraction technique. The microstructure's evolution is divided into distinct stages of recovery, recrystallization, and grain growth based on their characteristic features. During the recovery process, the fomation of subgrains occurs. The primary mechanism of recrystallization nucleation is dominated by the strain-induced boundary migration mechanism, and the subgrains preexisting at grain boundaries are the main nucleation sites.

Unraveling the effect of annealing on the structural and microstructural evolution of NiFe2O4@SiO2 core-shell type nanocomposites

The comparison between as-received and multistage annealed NiFe2O4@SiO2 (NFO@SiO2) core-shell nanoparticles is presented. The studied ferrites were synthesized by co-precipitation followed by microemulsion. The presence of cubic inverse spinel ferrite structure with tetrahedral and octahedral iron occupancy is confirmed in all analyzed samples. The structural characterization revealed the gradual crystallization of NFO cores up to about 12 nm crystallite size at the last annealing stage. Simultaneously, a partial crystallization of the silica matrix is evidenced. The superparamagnetic (SPM) behaviour is demonstrated based on complex magnetic performance and confirmed by Mössbauer spectrometry. The spin-canting phenomenon on the surface dead magnetic layer (MDL) is revealed based on the Yafet-Kittel model. A slight change in MDL thickness versus heat treatment is proved. The X-ray photoemission and absorption studies confirmed the complex nature of the Fe-based states. The Si–O–Ni/Fe intermixing on the NFO – SiO2 nanoparticles interface is revealed by the core-level lines analysis, proving the existence of a disordered layer on the NFO surface.

A Correlation-Redundancy Guided Evolutionary Algorithm and Its Application to High-Dimensional Feature Selection in Classification

The processing of high-dimensional datasets has become unavoidable with the development of information technology. Most of the literature on feature selection (FS) of high-dimensional datasets focuses on improvements in search strategies, ignoring the characteristics of the dataset itself such as the correlation and redundancy of each feature. This could degrade the algorithm's search effectiveness. Thus, this paper proposes a correlation-redundancy guided evolutionary algorithm (CRGEA) to address high-dimensional FS with the objectives of optimizing classification accuracy and the number of features simultaneously. A new correlation-redundancy assessment method is designed for selecting features with high relevance and low redundancy to speed up the entire evolutionary process. In CRGEA, a novel initialization strategy combined with a multiple threshold selection mechanism is developed to produce a high-quality initial population. A local acceleration evolution strategy based on a parallel simulated annealing algorithm and a pruning method is developed, which can search in different directions and perform deep searches combing the annealing stage around the best solutions to improve the local search ability. Finally, the comparison experiments on 16 public high-dimensional datasets verify that the designed CRGEA outperforms other state-of-the-art intelligent algorithms. The CRGEA can efficiently reduce redundant features while ensuring high accuracy.

Evaluation of the strengthening components in 0.4%С–1.3%Mn–0.1%V steel after quenching and high temperature tempering

Transmission electron microscopy (TEM), electron backscatter diffraction (EBSD), and X-ray diffraction analysis are used to monitor the evolution of the microstructure of a microalloyed medium-carbon steel and to evaluate quantitatively the strengthening components and their relative contribution to the yield strength of this steel quenched and tempered at 650 °C. As the duration of isothermal tempering tem increases from 2 to 3000 min, the steel softens in two stages: a sharp drop of the strength properties, ~100 MPa/min, at stage I (tem ≤ 8 min) is followed by weak softening, ~0.1 MPa/min at stage II (tem ≥ 64 min). It is shown that the main contribution (q ~ 80%) to the yield strength of the steel is made by the combined effect of the dislocation and grain-boundary (due to the lath boundaries) strengthening mechanisms at the first stage of martensite tempering, and by subgrain strengthening at the second stage of tempering.