In this work, the hot deformation behavior of Alloy 925 with intermediate strain rates of 0.01s−1-10s−1 ranging from 900 °C to 1150 °C has been investigated through the isothermal hot compression tests. Some features of the flow curves corresponding to negative strain rate sensitivity have been observed and discussed associated with the microstructural evolution, showing the nucleation mechanism of dynamic recrystallization and the occurrence of dynamic strain ageing. Besides, we have employed two typical constitutive models, namely, Arrhenius model and backpropagation artificial neural network (BP ANN) model to describe the flow behavior, and also developed a modified BP ANN model based on genetic algorithm (GA-BP ANN). The results show that the GA-BP ANN model has the highest accuracy and stability for predicting the flow stress. The correlation coefficient between the predicted and experimental values is 99.99 %, and the average absolute relative error is only 0.54 %. The comparative investigation on the predicted values of different ANN models reflects that GA can reduce the randomness of initial weights and thresholds of BP ANN and also can further increase the accuracy and stability of ANN model. Moreover, the increasing number of input training data can improve the prediction performance of neural network. For a single-layer neural network, 12 hidden layers can effectively ensure the reliability of the constitutive model.

Dynamic behavior and modified artificial neural network model for predicting flow stress during hot deformation of Alloy 925

The mechanism of dynamic strain aging for type A serrations in tensile flow curves of Fe-18Mn-0.55C (wt.%) twinning-induced plasticity steel

Abstract Thermosetting polymers have higher heat resistance, chemical resistance, mechanical characteristics and structural integrity than thermoplastic polymers due to their three-dimensional networks of covalent bonds. The current status and challenges in the field of thermosetting polymer modified asphalts are reviewed in this article. Firstly, classification and application of thermosetting polymers are briefly introduced, and modification approaches of polymer modified asphalts are compared. Crucial factors in selecting polymers for asphalt modification are then analyzed. Further, the cure mechanisms, preparation methods and properties of thermosetting polymers, including epoxy resin, polyurethane, polyurea, unsaturated polyester resin, phenolic resin, furan resin and amino resin, for asphalt modification are discussed. Especially, the effect of components of epoxy resin and polyurethane on the properties of modified asphalts is described. To develop eco-friendly and sustainable asphalt materials, this article also reviews the use of bio-based thermosetting polymers, including epoxy resin, polyurethane and phenolic resin, in asphalt modification. Finally, self-healing and recyclable thermosetting polymer modified asphalts are highlighted as promising solution to the challenges of healability and recyclability of thermosetting polymers in asphalt modification after long-term service.

Thermosetting Polymer Modified Asphalts: Current Status and Challenges

This review article provides an in-depth discussion on the hot deformability, processing map analysis, and microstructural development in superalloys, as well as the associated constitutive equations employed in flow stress prediction. It describes how hot working can improve the grain structure of superalloys by dynamic recrystallization (DRX), reduce defects, and enhance their mechanical characteristics. The formation of necklace structures, work-hardening analysis to identify the existence and commencement of dynamically recrystallized grains and the influence of processing conditions on DRX grain size are all addressed in this article. The influence of deformation variables, described by the Zener-Hollomon parameter - the occurrence of phases, dynamic precipitation, and alloying elements on the thermomechanical response, and the restoration processes of DRV and DRX are discussed in detail. The utilisation of processing maps as a means to determine the most favourable processing conditions and identify the instability regime, encompassing flow instability, defects and cracking, that may arise during the hot-working of superalloys are discussed. Specifically concerning the constitutive modelling of flow stress for characterizing material flow (at various deformation strain rates, temperatures, and strain), the application threshold stress (as a result of phase transformation during hot deformation), temperature-dependent Young's modulus, and comparing the experimentally observed activation energy and deformation stress exponent to the values predicted by creep theories, are discussed. Also, an analysis of the various modelling techniques and equations for predicting flow curves during hot-working processing is evaluated. Finally, some recommendations are made regarding the potential future research directions. 

Hot deformation behaviour, constitutive model description, and processing map analysis of Superalloys: An overview of nascent developments

Piezoelectric energy harvesting and dissipating behaviors of polymer-based piezoelectric composites for nanogenerators and dampers

In this research, we performed an experimental investigation into the influence of dynamic strain aging (DSA) and precipitation behavior on the plastic deformation and microstructure evolution in alloy 253MA considering its service temperature. The serrated flow behavior, stress anomaly behavior and negative strain rate sensitivity are considered as the manifestation of DSA within a certain temperature range (TDSA), which can be classified as low (550–700 °C), intermediate (600–750 °C) and high temperatures (700–790 °C) at 0.001 s−1, 0.01 s−1 and 0.1 s−1, respectively. The activation energy of DSA was determined to be 242 kJ/mol, indicating that the diffusion of substitutional solutes, such as Cr and Ni, is mainly responsible for the DSA phenomenon. The characteristic of dislocation substructures is prone to change from linear structure to cellularization structure with a rising deformation temperature in the DSA regime. The stress anomaly behavior can be attributed to the rapid dissolution of σ phase. The initiation of dynamic recrystallization should contribute to the disappearance of DSA by suppressing the dynamical solute atom–dislocation interaction.

Effect of dynamic strain aging and precipitation on the hot deformation behavior of 253MA heat-resistant alloy

Electrode-Free Piezoelectric Nanogenerator Based on Carbon Black / Polyvinylidene Fluoride-Hexafluoropropylene Composite Achieved Via Interface Polarization Effect

The rapid growth in traffic volume and loads has increased the demand for high strength and durability paving materials. As the primary paving material of long-life pavements and long-span steel bridge decks, epoxy asphalt (EA) has the problems of poor tensile strength and low fracture toughness. In this study, graphene oxide nanosheets (GOs) and multiwalled carbon nanotubes (CNTs) were used to improve the mechanical properties of EA. Tensile tests, segregation experiments, Fourier transform infrared analysis, X-ray diffraction, and fluorescence microscope (FM) were used to analyze the mechanical properties and micromorphology of nano-modified EA, and to explore the optimal content of these two nano-modifiers in EA. The results of tensile properties tests show the tensile properties of advanced nano-modified EA are better when 0.01 wt% CNTs and 0.02 wt% GOs are added. Among them, EA modified by CNTs has the best toughening effect, and its fracture toughness is increased by 21%. Finally, combining macroscopic and microscopic experimental analysis, it is concluded that the mechanical homogeneity of the advanced nano-modified EA is better, and the asphalt is uniformly dispersed in the continuous phase of epoxy resin. Furthermore, CNTs are chemically reacted with the amino group in oleylamine and modified EA through fiber network reinforcement, and GOs modified EA through the amidation reaction with oleylamine. 

Study on preparation and performance of advanced nano‐modified epoxy asphalt

The invention belongs to the technical field of electrolytic polishing, and discloses an electrolytic polishing method of an Al/Ti cold rolled composite plate. Through the novel electrolytic polishingmethod, a sample is clamped by using a clamping tool to be placed into a Stael Lectropol-5 electrolytic polishing instrument, the control speed flow is 12, the voltage is 10-15 V, the temperature is2-5 DEG C, and the time is 100-120 s, and the sample is washed with the water after polishing, moisturized with the alcohol, and dried by cold wind blowing; and analysis and calibration of the electronic backscatter diffraction (EBSD) are conducted. The surface of the Al/Ti cold rolled composite plate after electrolytic polishing is bright as a mirror and has no obvious corrosion spots and other defects, when the EBSD is conducted, the EBSD calibration can be conducted on the Al layer and Ti layer on the two sides of the interface simultaneously, and the calibration rate is very high and can reach more than 99%.

Electrolytic polishing method of Al/Ti cold rolled composite plate

In this paper, CaxZn10-xFe20 catalysts were prepared by the co-precipitation method and applied to CO2 hydrogenation. The experimental results show that the CO2 conversion of the catalyst Ca1Zn9Fe20 at a Ca doping amount of 1 mmol can reach 57.91%, which is 13.5% more than the CO2 conversion of the catalyst Zn10Fe20. Moreover, the catalyst Ca1Zn9Fe20 has the lowest selectivity for both CO and CH4, with 7.40% and 6.99%, respectively. The catalysts were characterized by XRD, N2 adsorption-desorption, CO2-TPD, H2-TPR, and XPS. The results demonstrate that the doping of Ca increases the basic sites on the catalyst surface and thus allows the catalyst to adsorb more CO2 to promote the reaction. Besides, the Ca doping amount of 1 mmol can suppress the formation of graphitic carbon on the catalyst surface and prevent the excess graphitic carbon from covering the active site Fe5C2.

The effect of Ca doping on the CO2 hydrogenation performance of CaxZn10-xFe20 catalysts (x= 0, 0.5, 1 and1.5).

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