Evolution Of Microstructure Morphology Research Articles

Morphology evolution and non-uniformity removal mechanism analysis of diamond nanocone arrays by reactive ion etching

Microstructures of diamond can be fabricated by reactive ion etching and during this process the evolution of surface morphology can affect the electric field near the microstructure. These changes in the electric field will alter the trajectory of ions, thereby affecting the number of ion bombardments on the surface regions of the microstructure. Consequently, this will affect the removal rate of the material on the microstructure surface and consequently affects the evolution of microstructure morphology. In order to understand the morphology evolution process of diamond during etching. H2 and Ar were used as the reactive gases to etch the nanocrystalline diamond (NCD) films with masks. The electric field near the microstructure and the trajectories of reactive ions was stimulated. The number of H+ and Ar+ bombardments at various regions on the diamond microstructure surface has been recorded and analyzed. By observing the cross-sectional morphology of the microstructure at different periods, the etching process of nanocones was analyzed. The study found that the microstructure of the diamond surface would gradually be etched into convex shaped and waist drum shaped and cone. By stimulating the electric field near the microstructure, it was found that the electric field distorted near the microstructure, causing the electric field lines initially perpendicular to the diamond surface to be diverted. As a result, the trajectory of the particles originally arrived perpendicularly to the diamond surface was distorted and hence they bombarded against the sidewall of the diamond microstructures. The angle between the ion trajectory and the electric field line also increased gradually.

Microstructure evolution and properties of Fe-Ni-Cr-Co-Mo-W high-entropy alloy coatings by plasma surface alloying technology

The purpose of this study is to develop a new type of high-entropy alloy (HEA) coating with high temperature oxidation resistance. In this paper, the Fe-Ni-Cr-Co-Mo-W HEA coatings were prepared by plasma surface alloying technology with different holding temperatures (1150 °C, 1200 °C, 1250 °C, 1300 °C). The microstructure morphology evolution and properties of Fe-Ni-Cr-Co-Mo-W HEA coatings were systematically studied. The results indicate that all the Fe-Ni-Cr-Co-Mo-W HEA coatings are composed of a deposition layer and diffusion layer, forming gradient structure HEA coating. The element gradient distribution in the diffusion layer achieves the metallurgical bonding effect. The deposition layer conforms to the definition of HEAs based on the composition or configuration entropy, and forms the surface HEAs. The phase of Fe-Ni-Cr-Co-Mo-W HEA coatings is all composed of HCP phase + FCC phase. The higher the holding temperature, the greater the supply of alloying elements are deposited by sputtering, and the higher the density of surface vacancy formation, which promotes the diffusion of atoms and the growth of grain structure. The surface morphology of the Fe-Ni-Cr-Co-Mo-W HEA coating changes from the pinecone-like large particle dense accumulation morphology to flat and compact plane, and then to fine particles compact accumulation morphology. The properties of the 1300 °C Fe-Ni-Cr-Co-Mo-W HEA coating is the best, the abrasive resistance and high temperature oxidation resistance are 3.66 and 5.5 times higher than those of the matrix respectively. The results indicate that the Fe-Ni-Cr-Co-Mo-W HEA coating with gradient structure and metallurgical bonding has a good application prospect.

A calculation method of solidification parameter threshold for welding microstructure evolution

The relationship between the evolution of microstructure morphology (planar, cellular, columnar and equiaxed) and grain size (2.5 μm, 5.0 μm, 7.5 μm and 10.0 μm) of a specified metal and the calculated solidification parameter (G/R, G × R) of temperature gradient (G) and solidification rate (R) is calculated by comparing the “solidification process percentage” of the welding experiment and simulation. Taking pulsed laser single spot welding as the object, the varying solidification parameters and corresponding microstructure of liquid–solid interface are obtained by adjusting the pulsed closing shapes. The results show that the calculating method of the solidification parameter threshold of the welding microstructure evolution by using the solidification process percentage is reliable and the evolution threshold of microstructure morphology and the grain size of AZ31 magnesium alloy are obtained. The research lays a theoretical and practical foundation for the establishment of the solidification parameter threshold system of the welding microstructure evolution.

Dynamic evolution of microstructure morphology in thin-sample solidification: Deep learning assisted synchrotron X-ray radiography

The dendrite morphology significantly affects the formation of micro-segregation, intermetallic precipitation, and rheology of the mushy zone during solidification. Among the parameters that describe the morphology of dendrites, the specific interface area is critical since it characterizes the overall morphology of dendrites in a universal and general sense. In this work, a novel radiography-based method has been proposed to achieve in-situ determination of the evolving specific interface area during thin-sample solidification. Employing our proposed deep-learning-based dendrite segmentation model and image processing method, a generally authentic three-dimensional solidification microstructure can be obtained, which underlies the measurement of specific interface area from radiographs with negligible relative error. This method can be employed to study the evolution of 3D microstructure under large cooling rates requiring high temporal resolution. Based on this method, the morphology evolution of the overall solidification microstructure during directional solidification of Al-15 wt% Cu alloy has been studied. The results indicate that the evolution of interfacial area density SV conforms to the relation suggested by Rath with asymmetric law. Besides, the asymmetric evolution of SV concerning solid fraction can be attributed to the concurrent growth and coarsening of the solid phase with uneven change rates under temperature gradient.

Grain boundary diffusion effect on mineral transition of calcium sulpho-aluminate with sodium dopant

The mineral formation-transition mechanism, microstructure morphology evolution, pulverization property and chemical reactivity of calcium sulpho-aluminate with sodium dopant are systematically studied with the molar ratio of CaO to Al2O3 is 0.8, the molar ratio of CaO to SiO2 is 1.5, the mass ratio of Al2O3 to SiO2 is 2.0, and the SO3 accounts for 4%. The results show that sodium dopant could promote 3CaO·3Al2O3·CaSO4, CaO·2Al2O3 and 2CaO·Al2O3·SiO2 transform into 2CaO·SiO2, CaO·Al2O3, 12CaO·7Al2O3 and 2Na2O·3CaO·5Al2O3, and it also can decrease the decomposition temperature of reactive materials and the initial phases formation temperature significantly. Sodium diffusion can destroy the clear grain boundary of calcium aluminate and calcium silicate phases, change the macro-microstructure morphology, improve the crystalline degree of the samples, and then improve the pulverization and alumina leaching property. However, excessive sodium dopant can decrease the melting temperature, inhibit the transformation process of 2CaO·SiO2 from β to γ, and then deteriorate the pulverization property significantly again.

EBSD analysis of graphitized steel microstructure after compression deformation at room temperature

The graphitized steel has attracted considerable attention due to its excellent cutability and good properties at cold forming. Compression deformation at room temperature of graphitized steel (0.43 % C) with a ferrite-graphite microstructure was performed on a universal testing machine. Microstructures of deformed samples were studied using the analysis technique of Electron Back-Scattered Diffraction (EBSD). The evolution of microstructure morphology, texture, distribution of Kernel Average Misorintations (KAM) and the Taylor factor in the zone of large deformations of deformed samples with different degrees of deformation is discussed. The results show that the studied steel has a good ability to compression deformation. During compression deformation, with an increase in deformation degree the deformation morphology of the ferrite grain and graphite inclusions gradually stretch in the direction perpendicular to the compression axis and they are represented as fibrous forms. The orientation of ferrite grains in the matrix is gradually obvious, and the orientation of ferrite grains around graphite inclusions is not obvious, that is, the number of grains oriented to <100>, <111> in the matrix is much greater than around graphite inclusion. In addition, KAM and the Taylor factor in the large deformations region of compression samples show that the deformation degree of ferrite grains around graphite inclusions is less than that of ferrite grains in the matrix. The reason for this is that the soft graphite inclusions can reduce the degree of dislocation pile-up.

Development and evaluation of data transfer protocols in the fully coupled random cellular automata finite element model of dynamic recrystallization

Development and application of the hybrid fully coupled, random cellular automata finite element (RCAFE) approach to modelling dynamic recrystallization phenomenon, during a high temperature deformation is the overall goal of the paper. The finite element (FE) solver provides information on equivalent stress, equivalent strain, temperature fields as well as on geometry of deformed computational domain after each time step. These data are transferred to the developed random cellular automata (RCA) model, which is responsible for evaluation of corresponding microstructure morphology evolution and dislocation density changes under dynamic recrystallization (DRX) conditions. Finally, a set of data from the RCA part is send back to the FE solver and used as an input for the next time step. As a result, the fully coupled RCAFE model for simulation of a DRX progress is established. Crucial developments of the RCA model related to the space deformation and efficient neighbors selection are presented within the paper. However, particular attention is put on the development of efficient communication algorithms and methods for input/output data transfer between the FE and RCA modules. The communication protocols based on text files and sockets have different levels of complexity but both are based on the Abaqus VUMAT subroutine. Their capabilities and limitations are evaluated within the paper. Finally, an application of the proposed RCAFE method to simulation of a dynamic recrystallization progress at the level of single grains is presented and discussed to highlight capabilities of the model.

Simulation and Experiment on Solid Electrolyte Interphase (SEI) Morphology Evolution and Lithium-Ion Diffusion

In this study, a phase-field model is developed to simulate the microstructure morphology evolution that occurs during solid electrolyte interphase (SEI) growth. Compared with other simulation methodologies, the phase-field method has been widely applied in the solidification modeling that has great relevance to SEI formation. The developed model can simulate SEI structure and morphology evolution, and can predict SEI thickness growth rate. X-ray photoelectron spectroscopy (XPS) experiments are performed to confirm the major SEI species as LiF, Li2O, ROLi, and ROCO2Li. Transmission electron microscopy (TEM) experiment is performed to present the SEI layer structures. The experiments reduce the complexity of the model development and provide validation to some extent. Fick's law and mass balance are applied to investigate lithium-ion concentration distributions and diffusion coefficients in different types of SEI layers predicted by the phase-field simulations. Simulation results show that lithium-ion diffusion coefficients between 298 K and 318 K are 1.340–7.328(10−16) cm2/s, 1.734–3.405(10−12) cm2/s, and 2.611–2.389(10−15) cm2/s in the compact, porous, and multilayered structures of SEI layer, respectively. The resistances between 298 K and 318 K are 0.740–1.693 Ω⋅cm2, 2.827–5.517 Ω⋅cm2, and 3.726–5.839 Ω⋅cm2 in the compact, porous, and multilayered structures of SEI layer, respectively.

Microstructure Morphology Evolution of Single Crystal Copper Rod by Ohno Continuous Casting in Copper Manufacturing System

Heated-mould continuous casting (Ohno continuous casting, OCC) is a kind of special continuous directional solidification technique in copper manufacturing system. Copper rod solidification process is cooperative controlled by heated mould and water cooler. Single crystal metal rod of any length can be produced by OCC. In this paper, based on continuous nucleation model, microstructure morphology evolution process of single crystal copper rod has been studied by coupled cellular automata method and finite element method. Competitive growth process has been described that tiny equiaxed crystal merged into big columnar crystals towards heat flow direction. Single crystal evolution distance changing rule has been study under different drawing speed and mould temperature by simulation and experiment results. This study provides reference for high quality single crystal copper rod in copper deep manufacturing processing.