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Diabetic osteoporosis (DO) presents significant clinical challenges. This study aimed to investigate the potential of magnetic nanoparticle-enhanced extracellular vesicles (GMNPE-EVs) derived from bone marrow mesenchymal stem cells (BMSCs) to deliver miR-15b-5p, thereby targeting and downregulating glial fibrillary acidic protein (GFAP) expression in rat DO models. Data was sourced from DO-related RNA-seq datasets combined with GEO and GeneCards databases. Rat primary BMSCs, bone marrow-derived macrophages (BMMs), and osteoclasts were isolated and cultured. EVs were separated, and GMNPE targeting EVs were synthesized. Bioinformatic analysis revealed a high GFAP expression in DO-related RNA-seq and GSE26168 datasets for disease models. Experimental results confirmed elevated GFAP in rat DO bone tissues, promoting osteoclast differentiation. miR-15b-5p was identified as a GFAP inhibitor, but was significantly downregulated in DO and enriched in BMSC-derived EVs. In vitro experiments showed that GMNPE-EVs could transfer miR-15b-5p to osteoclasts, downregulating GFAP and inhibiting osteoclast differentiation. In vivo tests confirmed the therapeutic potential of this approach in alleviating rat DO. Collectively, GMNPE-EVs can effectively deliver miR-15b-5p to osteoclasts, downregulating GFAP expression, and hence, offering a therapeutic strategy for rat DO. [ABSTRACT FROM AUTHOR]

The improved microstructure and enhanced elevated temperature mechanical properties of Ti-44Al-5Nb-(Mo, V, B) alloys were obtained by vacuum arc re-melting (VAR) and primary annealing heat treatment (HT) of 1 260 °C/6 h/Furnace cooling (FC). The phase transformation, microstructure evolution and tensile properties for as-cast and HTed alloys were investigated. Results indicate that three main phase transformation points are determined, Teut=1 164.3 °C, Tγ solv = 1 268.3 °C and Tβ trans = 1 382.8 °C. There are coarse lamellar colonies (300 µm in length) and neighbor reticular B2 and γ grain (3–5 µm) in as-cast alloy, while lamellar colonies are markedly refined and multi-oriented (20–50 µm) as well as the volume fraction and grain sizes of equiaxed γ and B2 phases (about 15 µm) significantly increase in as-HTed alloy. Phase transformations involving α+γ→α+γ+β/B2 and discontinuous γ coarsening contribute to the above characteristics. Borides (1–3 µm) act as nucleation sites for βeutectic and produce massive β grains with different orientations, thus effectively refining the lamellar colonies and forming homogeneous multi-phase microstructure. Tensile curves show both the alloys exhibit suitable performance at 800 °C. As-cast alloy shows a higher ultimate tensile stress of 647 MPa, while a better total elongation of more than 41% is obtained for as-HTed alloy. The mechanical properties improvement is mainly attributed to fine, multi-oriented lamellar colonies, coordinated deformation of homogeneous multi-phase microstructure and borides within lamellar interface preventing crack propagation. [ABSTRACT FROM AUTHOR]

Oxidation is an inevitable problem and accelerates the wear of materials under high temperature wear conditions. To enhance the oxidation resistance of TiC particle–reinforced steel matrix composites (TiC-SMCs), the role of Cr on the oxidation mechanism of TiC-SMCs at 600 °C was investigated through experimentation and first-principles calculations in this work. The results indicated that the addition of 3 wt% Cr could induce a transformation from internal oxidation to external oxidation because the diffusion energy barrier of O atoms was increased from 0.66 to 0.91 eV. Furthermore, The adsorption of the Fe and O atoms was reduced via Cr addition. Consequently, the oxidation resistance of TiC-SMCs was improved and internal oxidation was inhibited with increasing Cr content, where the oxidation rate coefficients of TiC-SMCs with 3 wt% and 0.3 wt% Cr content were 3.79 × 10−4 and 4.84 × 10−1 mg2 cm−4 h−1, respectively. The present study would not only provide the basic understanding for the role of Cr on oxidation behavior, but also contribute to the design of TiC reinforced steel matrix composites with excellent oxidation resistance. [ABSTRACT FROM AUTHOR]

In this work, a novel model reduction technique is proposed, which is based on the hybrid coordinate space modal synthesis method and structural dynamics modification method. This technique can be used to construct the corresponding reduced-order model (ROM) to solve some problems, which focus on the updating of time-varying dynamic parameters for thin-walled components in the milling process. These characteristics of the pending workpiece are analyzed, and then the entire workpiece is divided into two substructure parts: constant workpiece and removed material workpiece. The substructure part of the constant workpiece is analyzed by the double-coordinated free interface method, and the substructure part of the removed material workpiece is analyzed by the finite element method (FEM) among them. Afterwards, the two substructure models in the hybrid coordinate space are coupled based on the interface coordination condition, and the ROM can be obtained about the degrees of freedom (DOFs) of thin-walled components. Moreover, the structural dynamics modification method is introduced, which is used to explore the modal characteristics and vibration response characteristics of the ROM, and is performed to update the dynamic parameters for thin-walled components systems in the milling process. Comparing the dynamical parameters obtained by the full-order model (FOM) method and the reference method under the same conditions, the results indicate that the proposed method can be applied to a variety of boundary conditions effectively, its normalized relative frequency difference (NRFD) values are all lower than 5%, and these values are continuously and stably close to 0. Its modal assurance criterion (MAC) values are all higher than 0.99, and its frequency response assurance criterion (FRAC) values are all 1. For the update speed, its maximum growth rate is 97.38%. Accordingly, the proposed method has nice universality and efficiency, which is embodied in the updating of time-varying dynamic parameters of thin-walled components. [ABSTRACT FROM AUTHOR]

Extracellular vesicles derived from bone marrow mesenchymal stem cells (BMSC-EVs) are emerged as carriers of therapeutic targets against bone disorders, yet its isolation and purification are limited with recent techniques. Magnetic nanoparticles (MNPs) can load EVs with a unique targeted drug delivery system. We constructed gold-coated magnetic nanoparticles (GMNPs) by decorating the surface of the Fe3O4@SiO2 core and a silica shell with poly(ethylene glycol) (PEG)-aldehyde (CHO) and examined the role of BMSC-EVs loaded on GMNPs in diabetic osteoporosis (DO). The osteoporosis-related differentially expressed miR-150-5p was singled out by microarray analysis. DO models were then established in Sprague–Dawley rats by streptozotocin injection, where poor expression of miR-150-5p was validated in the bone tissues. Next, GMNPE was prepared by combining GMNPs with anti-CD63, after which osteoblasts were co-cultured with the GMNPE-BMSC-EVs. The re-expression of miR-150-5p facilitated osteogenesis in osteoblasts. GMNPE could promote the enrichment of EVs in the bone tissues of DO rats. BMSC-EVs delivered miR-150-5p to osteoblasts, where miR-150-5p targeted MMP14 and consequently activated Wnt/β-catenin pathway. This effect contributed to the enhancement of osteoblast proliferation and maturation. Furthermore, GMNPE enhanced the EV-based delivery of miR-150-5p to regulate the MMP14/Wnt/β-catenin axis, resulting in promotion of osteogenesis. Overall, our findings suggest the potential of GMNP-BMSC-EVs to strengthen osteoblast proliferation and maturation in DO, showing promise as an appealing drug delivery strategy against DO. 1. GMNPs-BMSCs-EVs-miR-150-5p promotes the osteogenesis of DO rats. 2. miR-150-5p induces osteoblast proliferation and maturation by targeting MMP14. 3. Inhibition of MMP14 activates Wnt/β-catenin and increases osteogenesis. 4. miR-150-5p activates the Wnt/β-catenin pathway by downregulating MMP14. [ABSTRACT FROM AUTHOR]

Data-driven deep learning method is the main way to study the condition monitoring of mechanical equipment, in which sufficient labeled signals to train the model parameters is a typical problem. The existing methods to obtain the labeled signals mainly focus on manual marking. For the non-batch impeller processing with variable working conditions, manually marking signals is not the wisest move. To solve this problem, this manuscript puts forward a deep conditional random field neural network (CRFNN) method. This framework fully utilizes the sensitivity of the conditional probability model to adjacent data marker information, and small cross-labeled samples are used to predict the labels of unknown signals. At the same time, the variational autoencoder is used to convert the one-dimensional time series signal into a three-dimensional image, which solves the problem that the empty tool signals have a great impact on the tool wear condition monitoring in the process of impeller blade machining. Experimental results on a CNC machining center demonstrate the effectiveness and feasibility of the proposed method and outperform the existing works under industrial small labeled samples. [ABSTRACT FROM AUTHOR]

Metal-free chemical vapor deposition (CVD) of single-layer graphene (SLG) on c-plane sapphire has recently been demonstrated for wafer diameters of up to 300 mm, and the high quality of the SLG layers is generally characterized by integral methods. By applying a comprehensive analysis approach, distinct interactions at the graphene-sapphire interface and local variations caused by the substrate topography are revealed. Regions near the sapphire step edges show tiny wrinkles with a height of about 0.2 nm, framed by delaminated graphene as identified by the typical Dirac cone of free graphene. In contrast, adsorption of CVD SLG on the hydroxyl-terminated α-Al2O3 (0001) terraces results in a superstructure with a periodicity of (2.66 ± 0.03) nm. Weak hydrogen bonds formed between the hydroxylated sapphire surface and the π-electron system of SLG result in a clean interface. The charge injection induces a band gap in the adsorbed graphene layer of about (73 ± 3) meV at the Dirac point. The good agreement with the predictions of a theoretical analysis underlines the potential of this hybrid system for emerging electronic applications. [ABSTRACT FROM AUTHOR]

In this study, a Ti/Al clad sheet was fabricated using horizontal twin-roll casting (HTRC) with the application of pulsed electric field (PEF) and electromagnetic oscillation field (EOF), and the effects of different external fields on interfacial bonding strength were investigated in detail. The external electromagnetic fields have little influence on the stability of HTRC process. With the application of PEF and EOF, the width of diffusion layer at the Ti/Al interface increases obviously, and the interfacial bonding strength increases from 20.1 to 21.4 N/mm and 24.5 N/mm, respectively. When the EOF is applied, the electromagnetic volumetric force is generated in the liquid cavity of cast-rolling zone, which is much larger than the electromagnetic force caused by single PEF. Under the action of the electromagnetic volume force, aluminum melt in the liquid cavity oscillates repeatedly, which scours the surface of the titanium strip and makes the newly formed crystal nuclei fall off the surface of strip. In addition, the oscillation effect reduces the temperature gradient at the contact area between strip and melt and slows down the solidification process, thus prolonging the contact time between aluminum and titanium. All of these effects make the melt spread more sufficient on the surface of titanium strip and promote the interdiffusion between atoms. As a result, more metallurgical bonding regions are formed and enhanced, which leads to the improvement of bonding strength of the clad sheet. [ABSTRACT FROM AUTHOR]

Two industrial ship plate steels, one having delamination and the other having no delamination during the impact tests at − 60 and − 80 °C, were studied to clarify the effect of delamination on ductile fracture. The instrumented impact tests recorded the load and absorbed energy. The microhardness maps at the selective section of the broken specimen were drawn to display the tendency of strain hardening and the stress state during fracture. The delamination morphology was observed to clarify the reason for the delamination in heavy-gauge steel. The texture transform characteristics were correlated with the initial and deformed microstructures. The results demonstrated that the delamination formed before the main fracture surface and divided the stress concentration into two parts during the impact test. Furthermore, by transmitting much plastic deformation into the specimen far away from the fracture edge and giving full play to the characteristics of crystallographic texture rotation, the severe stress concentration and grain breakage could be avoided. At the same time, the region that should have been formed a radial zone with a plane strain state at the lower part of the fracture could be eliminated and still maintain a ductile fracture contributing to the absorbed energy of 63 J. The segregation of Mn element, different plastic deformation ability between ferrite and bainite, and the crystallographic texture of <001>//ND orientation caused the delamination. [ABSTRACT FROM AUTHOR]

Chatter is a self-excited vibration that reduces the quality of the workpiece surface and accelerates tool wear, it is a phenomenon that is difficult to monitor and control. In order to achieve high-performance manufacturing, a reliable online monitoring system for chatter needs to be developed. This paper proposes a chatter identification method based on optimized variational modal decomposition (OVMD) and fuzzy entropy to achieve online monitoring of chatter accurately. The method embeds the whale optimization algorithm (WOA) into the VMD method, and the chattering features are extracted for both simulated and experimental signals to achieve the optimal decomposition of the force signal in a rapid way. In order to solve the problem that sample entropy and approximate entropy are not sensitive to chatter detection, fuzzy entropy is introduced to monitor the chatter feature components. Experimental results show that the fuzzy entropy is particularly sensitive to the occurrence of chatter in specific embedding dimensions, and this method can monitor the dynamics of milling with higher sensitivity and stability. [ABSTRACT FROM AUTHOR]

In milling processing, the wear state of the tool has an essential influence on the processing quality. The machining process is not continuous in the cycloid milling process, and the signal of the empty tool part increases the difficulty of identifying the tool wear state. At present, most of the researchers use experimental data and cut out the signal of the empty tool part in the signal by data processing. However, it will affect the original signal to a certain extent and destroy the confidential information in the original signal. A novel method using variational auto-encoder (VAE) for tool wear status identification is proposed. Due to VAE has structural characteristics that reduce the dimensionality of high-dimensional data to lower dimensionality. This requires VAE to find and learn the significant features, which are hidden in the complex raw data. In this paper, the signals of the empty tool do not need to be cut out; the effective value of the three-phase current signals obtained in the real processing is converted into the form of three-dimensional color images. VAE is applied to extract features from the image samples and then realize the classification of different wear states of the tool. A large number of comparison experiments are conducted, and the result shows that the presented method has a better recognition performance for the actual processing data. It is more suitable for the recognition of tool wear status in the actual milling process. [ABSTRACT FROM AUTHOR]

During cooling, the array jet impact can achieve a rapid and uniform cooling of the high-temperature plate. Previous research results mostly focused on single-jet cooling of thin plates, but the complex flow and heat transfer characteristics between multiple jets could not be obtained. To clarify the heat transfer mechanisms and cooling speed fields characteristics in different flow regions, double water-jet impingement experiments were carried out on an AISI 304 austenitic stainless-steel plate with a thickness of 50 mm. The jet exit velocity was set to 2.95, 5.90, 8.06, and 11.80 m/s, while the jet height was set to 50, 150, 250, 350, and 450 mm. Pure water was selected as the working fluid with a constant temperature of 12.8 °C. The results show that a complex trend with sequential increasing, decreasing, and increasing behaviors appears in the wetting front width, upon increasing the wetting region diameter. The confluence fluid was found to reduce the influence caused by different jet velocities and to increase the influence caused by different jet heights. In addition, it was found that an excessive amount of accumulated fluid reduces the heat transfer efficiency during transition boiling. Finally, the correlations between maximum heat flux and average maximum cooling speed were established, which provide useful data for optimizing the cooling technology. [ABSTRACT FROM AUTHOR]

CeO2-WO3 (CW) catalysts were prepared by situ self-assembly method for the selective catalytic reduction (SCR) of NOx with NH3. With the increasing content of WO3, the interaction between WO3 and CeO2 improved, resulting in the formation of more acid sites, CeO2-WO3 solid solution and excellent redox ability, which could enhance the catalytic activity. Furthermore, an excess of WO3 over CW catalysts could decrease the SCR activity due to the attenuation of interaction. Hence, CW-20 (WO3 was 20 wt% over CeO2-WO3) possessed the widest active temperature window and nearly 100% NOx conversion was obtained at 225–400 °C, which relied on the contents of WO3. [ABSTRACT FROM AUTHOR]

The process of dynamic recrystallization of bulb flat steel was simulated by the hot compression tests at a deformation temperature ranging of 950 to 1200 °C and strain rate ranging of 0.02 to 5 s−1, which is also the rolling speed and temperature range of the large-sized bulb flat steel. The results show that the PAGs increases gradually with the increase in deformation temperature. The PAGs are 16.7 μm in the temperature of 950 °C and up to 27.1 μm in the temperature of 1100 °C. The average austenite grain size was sharply decreased from 31.2 to 24.4 μm with the rise of strain rate from 0.2 to 2 s−1; the degree of decrease gets slow and becomes 21.9 μm at the strain rate of 5 s−1. Moreover, the constitutive equation of activation energy and grain sizes of dynamic recrystallization in the deformation process were established, and the dynamic recrystallization was elaborated in the deformation temperature of 950 to 1200 °C and strain rate ranging of 0.02 to 5 s−1. The dynamic recrystallization in the rolling process can be well reflected by the established models. [ABSTRACT FROM AUTHOR]

Temper embrittlement is one of the major challenges encountered during the heat treatment of ultra-high strength steels. In this work, the microstructural evolution and mechanical properties during the austenite region quenching and tempering (Q-T) and the intercritical quenching and tempering (IQ-T) processes in a tensile strength (TS) 1100 MPa grade steel targeted for the manufacturing of a mooring chain were investigated. The temper embrittlement presented in the Q-T sample was attributed to the carbide network decorating the prior austenite grain and martensitic lath boundaries. In contrast, the IQ-T sample, where intercritical holding before quenching at the temperature of 12 °C lower than Ac3 was applied, exhibited a reasonable CVN impact energy of 188 J at − 20 °C with a slightly reduced strength. The ferrite formed during intercritical holding not only added extra interphase boundaries, but also refined the substructure of the quenched martensite. These increased boundary areas provided more nucleation sites for carbide precipitation during tempering. Meanwhile, the refined martensitic substructure promoted the diffusion of Cr, encouraging the fast coarsening of Cr-rich carbides. The formation of a carbide network was eventually prevented in the IQ-T sample. Thus, the IQ-T process was an effective approach to eliminate temper embrittlement caused by the carbide network. [ABSTRACT FROM AUTHOR]

In this article, the coarse grained heat affected zone (CGHAZ) of a low carbon high strength steel was simulated at two heat inputs on a Gleeble-3800 thermo-mechanical simulator. A comparative study was conducted to reveal the role of Cu addition in toughness improvement by microstructure characterization and Charpy impact test. Microstructure observation suggested that there is no observable difference in the microstructure and prior austenite grain size between Cu-free steel and Cu-bearing steel, but a higher density of high-angle grain boundary (HAGB) was obtained in Cu-bearing steel with 50 kJ/cm. This was intrinsically associated with the configuration of three Bain groups from the aspect of crystallography. The optimum configuration can be achieved by adjusting transformation driving force, cooling rate and nucleation characteristics during martensite/bainite transformation. In this study, Cu addition played a determining role in increasing transformation driving force at high cooling rate, and altering the diffusion kinetics of alloying elements at low cooling rate. Accordingly, the density of HAGB can be optimized to be beneficial for high toughness in CGHAZ. Therefore, the optimum toughness was obtained in Cu-bearing steel with heat input of 50 kJ/cm, which was featured by the impact energy of ~ 198 J at − 40 °C. [ABSTRACT FROM AUTHOR]

Mixed-organic-cation perovskite absorbers as formamidinium doped methylammonium tin iodine (NH 2 CH) 1 - x (CH 3 NH 3) x SnI 3 ( x ≤ 1 ) can provide a pathway to highly efficient lead-free solar cells. Although this class of materials is known to be severely susceptible to degradation, induced among others by enhanced temperatures, humidity and illumination, an improved layer quality in view of crystal size and homogeneity is the key to diminish or even to block certain degradation channels. In this work, we present the fabrication of fully tin-based perovskites via pulsed laser deposition. The morphology is analyzed for different deposition energies and temperatures to find the optimum process window. The thin films already reveal crystalline structure at room temperature, while they are smooth and homogeneous above a critical thickness for carefully adapted deposition parameters. In contrast to the assumption that at elevated temperatures, the crystallinity is improved, and we find that the films reveal a strong organic depletion and simultaneously tin enrichment. As a measure for their suitability to be employed as photovoltaic absorbers, the band gap of the differently doped perovskites is estimated by spectroscopic ellipsometry in the range of 1.3 to 1.4 eV. [ABSTRACT FROM AUTHOR]

In this study, the heat transfer characteristics of nanofluids used in spray cooling systems were examined. Three nanofluids, i.e., Cu, CuO, and Al2O3, respectively, with volume fractions ranging from 0.1% to 0.5%, as well as different volume fractions of a surfactant Tween 20, were used. In addition, their contact angles were measured to examine the heat-transfer characteristics. Under the same experimental conditions, with the increase in the volume fraction of the Cu nanoparticles from 0.1% to 0.5%, the maximum heat flux qmax increased from 3.36 MW/m2 to 3.48 MW/m2 from the impinging central point to r = 30 mm (r is the distance from the impingement point), and the corresponding temperature of qmax increased from 400°C to 420°C. Results revealed that with increasing Tween 20 concentrations, the contact angle decreased because of the decrease in the surface tension of nanofluids and improvement of the wetting ability, and the corresponding qmax increased from 3.48 MW/m2 to 3.94 MW/m2 at the impact central point. [ABSTRACT FROM AUTHOR]

The influence of cooling models and moving velocity on the temperature variation and cooling rate through the thickness of a metal plate is experimentally investigated. In this investigation, the cooling process is divided into four stages: a starting stage (I), a rapid cooling stage (II), a slow cooling stage (III) and a stopping stage (IV). Based on the curves, cooling rate, temperature difference, the heat transfer coefficient and center temperature curves are discussed. The results indicate that the cooling model and moving velocity influence the heat transfer on the surface, and affects the cooling rate through the thickness by changing the temperature difference. When the flow rates of nozzles 1, 2 and 3 are set to be V1, V2 and V3 respectively, the highest heat transfer is observed when V1 > V2 > V3. Under this cooling model, the maximum temperature difference occurs at the time of transition from the rapid cooling stage (II) to the slow cooling stage (III). In the slow cooling stage (III), increased moving velocity improves the synchronization of the heat transfer and decreases the maximum heat flux. As well, the speed of motion affects the internal heat conduction and cooling rate by affecting surface heat transfer. [ABSTRACT FROM AUTHOR]

In this work, the effect of Cu addition on the microstructure and mechanical properties, in particular, low-temperature toughness, of low-carbon, high-strength steel was investigated. Steels with Cu concentrations varying from 1 to 2.5 wt pct in the place of carbon were prepared and then subjected to the two-step intercritical heat treatment. A mixed microstructure consisting of intercritical ferrite, tempered martensite, and retained austenite was obtained. There was an increased amount of retained austenite in the steels with Cu contents ranging from 0.23 to 2.5 wt pct. Therefore, Cu addition was beneficial for the stabilization of retained austenite. This phenomenon can be attributed to the enrichment of Cu in austenite and the increased driving force of reversed transformation caused by reduction in the T0 temperature (the temperature at which fcc austenite and bcc ferrite of identical composition have equal free energy). Furthermore, nanoscaled Cu precipitates were dispersed in the microstructure of Cu-containing steels. The combined effect of retained austenite and Cu precipitates could be the reason for excellent low-temperature toughness without loss in strength, which is featured by the impact energy of more than 120 J at 153 K (– 120 °C) for the Cu-containing steels. In addition to the deformation-induced transformation of retained austenite, bcc Cu precipitates act as misfit centers to improve the low-temperature toughness by enhancing the dislocation mobility and decreasing the ductile-to-brittle transformation temperature (DBTT). [ABSTRACT FROM AUTHOR]

In this paper, a process of two-step intercritical heat treatment was used to control the amount of retained austenite and nano-scaled precipitates for a low carbon Cu-containing structural steel such that the mechanical properties of this steel can be tailored. In this process, the first step is intercritical annealing and a mixed microstructure can be obtained which contains intercritical ferrite, tempered martensite, fresh martensite and a small amount of retained austenite. The subsequent intercritical tempering was introduced to be beneficial for producing more stable retained austenite at room temperature through secondary enrichment of stabilizers (Mn, Ni). Also, (Nb, V, Mo) (C, N) precipitates were formed during intercritical annealing, while smaller (Nb, V, Mo) (C, N) precipitates and Cu-rich particles with diameter of 5–15 nm were obtained after intercritical tempering. It is due to the contributions from multi-phase microstructure, strain-induced transformation of stable retained austenite and strengthening of nano-scaled precipitates that a combination of high strength, good ductility, low yield to tensile ratio (Y/T ratio) and excellent low-temperature toughness was achieved. The strengthening and toughening mechanism were discussed on the basis of retained austenite formation and interaction between Cu precipitates and the matrix, together with the crack propagation. The two-step intercritical heat treatment was employed in this low carbon low alloyed steel. The retained austenite and Cu precipitates were obtained, which was beneficial to a combination of high strength, good ductility and excellent low-temperature toughness. [ABSTRACT FROM AUTHOR]

Hot-core heavy reduction rolling (HHR2) is an energy-saving process that directly rolls continuously cast slabs at the end of solidification that have a large temperature gradient. Here, we elucidated the interaction of strain refined precipitates and recrystallized grains in Nb-Ti microalloyed steel during continuous casting, hot-core heavy reduction rolling, and reheating process. Furthermore, theoretical models were established to calculate recrystallization driving force and pinning force at temperatures in the range of 850-1300 °C by a two-stage interrupted compression test using a Gleeble-3800 thermomechanical simulator. The study indicated that a random dispersion of strain refined precipitates with a size range of ~ 6-10 nm was obtained in the hot-core heavy reduction rolled slab, which was different from the coarse and uneven distribution of precipitates in a conventional slab. Upon reheating, the austenite grains in the hot-core heavy reduction rolled slab were significantly refined and evenly distributed along the thickness direction. This is attributed to the random dispersion of strain refined precipitates formed in the HHR2 process. [ABSTRACT FROM AUTHOR]

In this article, an intercritical annealing (IA) process was introduced to the conventional quenching and tempering (QT) heat treatment for a Fe-C-Mn-Ni-Cu structural steel. The corresponding microstructures and mechanical properties of this steel were characterized by scanning electron microscope (SEM) equipped with electron back scattering diffraction (EBSD) and mechanical properties test. The results showed that IA process could lead to a considerable increase in low-temperature toughness for this steel. A mixed microstructure was obtained after IA process had been adopted containing intercritical ferrite and tempered martensite together with a small amount of retained austenite. This steel with mixed microstructure exhibited tensile strength of 961 MPa, relatively lower yield strength of 830 MPa, and a lower yield-to-tensile ratio (Y/T ratio) of 0.86, while a higher total elongation of 22.2 pct was achieved. The reason for this could be attributed to the multiple effect of multi-phase microstructure and deformation-induced transformation of the retained austenite during tensile deformation. The excellent low-temperature toughness was characterized by the Charpy impact energy as 183 J at 153 K (− 120 °C), which was associated with highly stable retained austenite and finer microstructure through reversed transformation during intercritical annealing treatment. These can be considered to increase the resistance to crack initiation and propagation and decrease the ductile-brittle transformation temperature (DBTT). [ABSTRACT FROM AUTHOR]

In this paper, experimental investigation and numerical simulation on heating process of small-sized workpieces in vacuum heat treatment furnace have been conducted. The proportional-integral-derivative (PID) control algorithm was employed for the temperature control of the numerical heat transfer model. Compared with the experimental data, the numerical results were validated. The computational maximum temperature difference of workpieces agreed well with the measured ones. In order to develop a new heating schedule for efficiently and uniformly heating loads, effects of heating rate, preheating rate and preheating temperature on heating performance have been researched. The results show that the maximum temperature difference decreases as the heating rate and preheating rate decrease appropriately. It is also found that decreasing preheating temperature can reduce the temperature difference of first-stage but increase the one of second-stage. Based on the results, an optimum heating process is proposed, through which the temperature difference within the workpiece drops below 50 °C during the whole heating schedule. [ABSTRACT FROM AUTHOR]

The effect of heat input on the microstructure and toughness of simulated subregions was investigated by welding thermal simulations and Charpy impact tests. The results indicate that the microstructures of the simulated coarse and fine grain heat affected zone (CGHAZ and FGHAZ) gradually changed from lath martensite to a mixture of lath martensite/lath bainite and finally to granular bainite with the increase in heat input. The microstructure of the simulated intercritical heat affected zone (ICHAZ) was mainly composed of granular bainite and blocky martensite regardless of heat input. When the heat input increased, the toughness of the simulated CGHAZ and ICHAZ continuously decreased. Nevertheless, the simulated FGHAZ still displayed good toughness (53.16 J) due to its fine structure. The occurrence of martensite-austenite (M-A) constituents was the main reason for the decrease in crack initiation energy of the simulated CGHAZ and ICHAZ at high values of heat input, and the toughness deteriorated as the size of M-A constituents increased. It should be noted that high-misorientation packet and block boundaries can effectively deviate or arrest the propagation of microcracks. When the heat input was in the approximate range of 8.63-14.95 kJ cm−1, all of the simulated subregions exhibited good toughness. [ABSTRACT FROM AUTHOR]

The effect of cold-rolled microstructures and subsequent reversion annealing on the microstructural characterization, reversion behavior, and microstructure-mechanical property correlation of Fe-17Cr-6Ni steel was evaluated with a heavy cold reduction of approximately 75 pct. Reversion annealing was conducted in a temperature range of 600 °C to 750 °C. The microstructures were evaluated using X-ray diffraction, optical microscope, scanning electron microscope, and transmission electron microscope. The mechanical properties were determined using tensile tests and microhardness tests. The results indicate that the reversion of lath martensite occurred in a diffusional manner over the entire temperature range, whereas that of dislocation martensite occurred in a diffusional manner at 600 °C, a combination of diffusional manner and shear manner at 650 °C, and a shear manner at 700 °C to 750 °C. The difference in the reversion conditions of lath martensite and dislocation martensite resulted in the heterogeneous microstructure made up of micrograins and nano/ultrafine grains. The tensile test results revealed that the mechanical behavior is closely related to the reversed microstructure, and can be classified into three different types, according to the engineering stress-strain curves. Moreover, a good combination of tensile strength and ductility was obtained in the samples that contained a suitable amount of retained martensite (~ 40 pct), which was due to long-range Lüders deformation. [ABSTRACT FROM AUTHOR]

The microstructure and mechanical properties of low carbon bainite high strength steel plate were studied via different cooling paths at the pilot scale. There was a significant increase in mechanical properties, and notably, the yield strength, tensile strength, and toughness at -40 °C for the tested steel processed by ultra-fast cooling were 126 MPa, 98 MPa and 69 J, respectively, in relation to steel processed by accelerated cooling. The ultra-fast cooling rate not only refined the microstructure, precipitates, and martensiteaustenite (M/A) islands, but also contributed to the refinement of microstructure in thick plates. The large size M/A constituents formed at lower cooling rate experienced stress concentration and were potential sites for crack initiation, which led to deterioration of low-temperature impact toughness. In contrast, the acicular ferrite and lath bainite with high fraction of high-angle grain boundaries were formed in steel processed by ultra-fast cooling, which retarded cleavage crack propagation. [ABSTRACT FROM AUTHOR]

Herein, a simple one-step immersion plating method is firstly used to prepare CuSn/Sn composite film electrode for lithium ion battery and thiourea (TU) is used as potential adjustment agent in the deposition process. The films with different morphologies are obtained by changing the content of tin(II) chloride (SnCl). After a series of physical and electrochemical characterizations, the results demonstrate that the content of SnCl in the plating solution plays an important role in determining the morphology and component of film electrode. In the condition of SnCl 6.5 g L, film electrode obtains both void space to accommodate volume expansion and stable structure which could inhibit abscission of active material from current collector. Therefore, the film electrode has an excellent areal capacity of 0.84 mA h cm after 70 cycles. In comparison with reported Sn-Cu alloy planar film electrodes for lithium ion battery in recent decade, the film electrode in this work exhibits a higher areal capacity. [ABSTRACT FROM AUTHOR]

Investigation on the correlation between microstructure and CVN impact toughness is of practical importance for the microstructure design of high strength microalloyed steels. In this work, three steels with characteristic microstructures were produced by cooling path control, i.e., steel A with granular bainite (GB), steel B with polygonal ferrite (PF) and martensite-austenite (M-A) constituent, and steel C with the mixture of bainitic ferrite (BF), acicular ferrite (AF), and M-A constituent. Under the same alloy composition and controlled rolling, similar ductile-to-brittle transition temperatures were obtained for the three steels. Steel A achieved the highest upper shelf energy (USE), while large variation of impact absorbed energy has been observed in the ductile-to-brittle transition region. With apparently large-sized PF and M-A constituent, steel B shows the lowest USE and delamination phenomenon in the ductile-to-brittle transition region. Steel C exhibits an extended upper shelf region, intermediate USE, and the fastest decrease of impact absorbed energy in the ductile-to-brittle transition region. The detailed CVN impact behavior is studied and then linked to the microstructural features. [ABSTRACT FROM AUTHOR]

We underscore here a novel approach to extend the boundaries of mechanical properties of Ti-Nb low-carbon steel via combination of ultrafast cooling and deformation during austenite-to-ferrite transformation. The proposed approach yields a refined microstructure and high density nano-sized precipitates, with consequent increase in strength. Steels subjected to ultra-fast cooling during austenite-to-ferrite transformation led to 145 MPa increase in yield strength, while the small deformation after ultra-fast cooling process led to increase in strength of 275 MPa. The ultra-fast cooling refined the ferrite and pearlite constituents and enabled uniform dispersion, while the deformation after ultra-fast cooling promoted precipitation and broke the lamellar pearlite to spherical cementite and long thin strips of FeC. The contribution of nano-sized precipitates to yield strength was estimated to be ~247.9 MPa and ~358.3 MPa for ultrafast cooling and deformation plus ultrafast cooling processes. The nano precipitates carbides were identified to be (Ti, Nb)C and had a NaCl-type crystal structure, and obeyed the Baker-Nutting orientation relationship with the ferrite matrix. [ABSTRACT FROM AUTHOR]

We have studied here the impact of finish cooling temperature on the microstructural evolution and precipitation behavior in Nb-V-Ti microalloyed steel through thermo-mechanical simulation in the context of newly developed ultrafast cooling system. The microstructural evolution was studied in terms of morphology and crystallography of precipitates using high-resolution transmission electron microscopy. At finish cooling temperature of 933 K and 893 K (660 °C and 620 °C), the microstructure primarily consisted of polygonal ferrite, together with a small amount of wedge-shaped acicular ferrite and lamellar pearlite, while, at 853 K and 813 K (580 °C and 540 °C), the microstructure consisted of lath bainite with fine interlath cementite and granular bainite with martensite/austenite (M/A) constituent. In all the finish cooling temperatures studied, the near-spherical precipitates of size range ~2 to 15 nm were randomly dispersed in ferrite and bainite matrix. The carbide precipitates were identified as (Nb,V)C with NaCl-type crystal structure. With a decrease in the finish cooling temperature, the size of the precipitates was decreased, while the number density first increased with a peak at 893 K (620 °C) and then decreased. Using Ashby-Orowan model, the contribution of the precipitation strengthening to yield strength was ~149 MPa at the finish cooling temperature of 893 K (620 °C). [ABSTRACT FROM AUTHOR]

The precipitation behavior and evolution of mechanical properties of Ti-Mo-bearing microalloyed medium-carbon steel during austenite to bainite transformation were studied, and two different cooling rates including ultrafast cooling (~80 °C/s) and accelerated cooling (~15 °C/s) during transformation were also investigated. The results suggest that Ti-Mo-bearing medium-carbon steel yield finer microstructure and nano-precipitates during austenite to bainite transformation during both ultrafast cooling and accelerated cooling processes. Yield strength and tensile strength obtained by ultrafast cooling process were higher than the accelerated cooling process, while the elongation was slightly reduced. Microstructural characterization indicated that grain refinement and precipitation hardening were the primary reasons for the increase in strength. Ultrafast cooling increased the density of dislocations and refined the grain size. Average size of precipitates containing Ti and Mo was 3-6 nm by ultrafast cooling process, while average precipitate size obtained by accelerated cooling process was 6-9 nm. [ABSTRACT FROM AUTHOR]

New generation thermo-mechanical control process(TMCP) based on ultra-fast cooling is being widely adopted in plate mill to product high-performance steel material at low cost. Ultra-fast cooling system is complex because of optimizing the temperature control error generated by heat transfer mathematical model and process parameters. In order to simplify the system and improve the temperature control precision in ultra-fast cooling process, several existing models of case-based reasoning(CBR) model are reviewed. Combining with ultra-fast cooling process, a developed R CBR model is proposed, which mainly improves the case representation, similarity relation and retrieval module. Certainty factor is defined in semantics memory unit of plate case which provides not only internal data reliability but also product performance reliability. Similarity relation is improved by defined power index similarity membership function. Retrieval process is simplified and retrieval efficiency is improved apparently by windmill retrieval algorithm. The proposed CBR model is used for predicting the case of cooling strategy and its capability is superior to traditional process model. In order to perform comprehensive investigations on ultra-fast cooling process, different steel plates are considered for the experiment. The validation experiment and industrial production of proposed CBR model are carried out, which demonstrated that finish cooling temperature(FCT) error is controlled within ±25°C and quality rate of product is more than 97%. The proposed CBR model can simplify ultra-fast cooling system and give quality performance for steel product. [ABSTRACT FROM AUTHOR]

A new-generation TMCP(NG-TMCP) with ultra fast cooling(UFC) as core technique was suggested instead of the conventional TMCP in which some problems are to be solved. And the ultra fast cooling technology has been successfully applied to the plate rolling production in Shouqin Metal Materials Co. Ltd. Industrial trials are reported for the production of X70 pipeline steels (about 70000 t) under UFC conditions. Pipeline steels with reasonably good properties have been produced on an industrial scale. UFC can improve the temperature uniformity, the mechanical properties and the plate profile of X70 pipeline steel. The performance features of the trial plates can meet the standard of X70 pipeline steel. Spot test results have shown that the qualification rate of shape control, the performance and charpy impact properties for the trial plates are 95%, 97% and 98%, respectively. The impact values of X70 pipeline steel at UFC mode exceed the standard requirements of X80 pipeline steel. The productivity is enhanced because cutting quantity of head and tail of the plate is reduced. The enhancement of control accuracy of the red back temperatures is favorable for industrial production of X70 pipeline steel. The reduced production of the steel-making has been industrially achieved, since a new composition was designed by reducing the vanadium content to less than 0.045 wt.%. [ABSTRACT FROM AUTHOR]

The interface heat transfer coefficient (IHTC) at the different casting/shell mold interfaces during the vacuum investment casting process was investigated by measuring the temperatures of K4169 superalloy melt and mold shell during the preheating, transferring, pouring, and solidification processes. The inverse model of ProCAST was used to calculate the interface heat transfer coefficient (IHTC) based on the temperature measurement results. The inverse calculation results show that the heat transfer between the shell mold and the outside air changes from natural convection to forced convection during the transfer process, but the heat transfer between the shell mold and the inside air is consistently natural convection heat transfer. Then, the convective heat transfer coefficient gradually decreases to 0.1 W/m2·K with the vacuum increases and is finally converted to radiation heat transfer at a vacuum of 10-3 Pa. In the early stages of solidification, the IHTC between the shell mold and the casting can reach 16,000 W/m2·K due to the close contact and the large temperature difference between them, and with the thermal expansion of the shell mold and cooling contraction of the casting, the formation of the gap leads to the interfacial heat transfer coefficient gradually stabilizing at 100–200 W/m2·K. The experimental validation results show that the IHTC has a great influence on the accuracy of the prediction of the location and shape of shrinkage porosities in the vacuum investment castings. [ABSTRACT FROM AUTHOR]

Microstructural stability is an important issue for nanocrystalline materials to be practically used in many fields. The present work shows how microstructure evolves with rolling strain in pre-annealed electrodeposited nanocrystalline nickel containing an initial strong fiber texture, on the basis of X-ray diffraction line profile analysis as well as transmission electron microscopy observation. The influence of shear strain on microstructural stability of the metal/roll contact interface is compared with that of the metal/metal contact interface; the latter would be closer to deformation in plane strain compression. From the statistical microstructural information, together with experimentally observed microstructure of deformed grains after the final rolling pass, it seems fair to conclude that the microstructure of the metal/metal contact interface is more stable during pack rolling than that of the metal/roll interface. [ABSTRACT FROM AUTHOR]