Study Of Phase Transformations Research Articles

Study of phase transformations in 14Kh2G2NMFB steel providing high-strength state

Study of phase transformations in 14Kh2G2NMFB steel providing high-strength state

Measurement bias in self-heating x-ray free electron laser experiments from diffraction studies of phase transformation in titanium

X-ray self-heating is a common by-product of X-ray Free Electron Laser (XFEL) techniques that can affect targets, optics, and other irradiated materials. Diagnosis of heating and induced changes in samples may be performed using the x-ray beam itself as a probe. However, the relationship between conditions created by and inferred from x-ray irradiation is unclear and may be highly dependent on the material system under consideration. Here, we report on a simple case study of a titanium foil irradiated, heated, and probed by a MHz XFEL pulse train at 18.1 keV delivered by the European XFEL using measured x-ray diffraction to determine temperature and finite element analysis to interpret the experimental data. We find a complex relationship between apparent temperatures and sample temperature distributions that must be accounted for to adequately interpret the data, including beam averaging effects, multivalued temperatures due to sample phase transitions, and jumps and gaps in the observable temperature near phase transformations. The results have implications for studies employing x-ray probing of systems with large temperature gradients, particularly where these gradients are produced by the beam itself. Finally, this study shows the potential complexity of studying nonlinear sample behavior, such as phase transformations, where biasing effects of temperature gradients can become paramount, precluding clear observation of true transformation conditions.

HIGH-TEMPERATURE PHASE TRANSFORMATIONS IN THE COMPOSITION “KAOLIN-DOLOMITE-ALUMINA”

The article presents the results of a study of phase transformations in sintered compositions “kaolin-dolomite-alumina”. It has been established that the nature of the location of melting isotherms on the triple diagram indicates the spread of neoformation processes into the region of the internal compositions of the triangle and the formation of crystalline phases of the mineral’s spinel, corundum, mullite. It is shown that based on alumina-containing waste and kaolin, as well as partially introduced dolomite, it is possible to develop compositions of low-temperature sintering ceramic masses for technical materials.

A modern reappraisal of the U-Zr phase diagram

By integrating published experimental data on the uranium-zirconium (U-Zr) system into a machine learning framework, insight into the two differing views on the thermochemical equilibrium, particularly on the U-rich portion of the phase diagram (PD) was developed, ultimately resulting in a new U-Zr PD. Phase diagram sensitivity to model parameters, tolerances, physical preconceptions and experimental biases, are considered to establish the validity of the generated PDs. A systematic assessment of the most reliable and most recent thermochemical data was made, and the traditional modeling bias to search the space of free energy parameters was removed by using recently developed machine learning strategies. The readily validated methodology enables a thermodynamically consistent search of free energy parameters by leveraging modern experimental work from an array of sources including phase transformations, phase transition temperatures, and enthalpy changes between 723-1173 K (450-900°C). These changes include the truncation of β-U stability at 6 at.% Zr, prominent isotherms at 884 K (611°C) and 961 K (688°C), and δ-U-Zr phase boundaries ranging from 66.5 to 80.2 at.% Zr at 823 K (550°C). The newly proposed PD captures fundamental constants measured experimentally and improves the agreement with phase transformation studies such as neutron diffraction with in situ heating. As such, it is proposed that the new U-Zr PD developed in this work be used to resolve the historically opposing views.

Automated pipeline processing X-ray diffraction data from dynamic compression experiments on the Extreme Conditions Beamline of PETRAIII.

Presented and discussed here is the implementation of a software solution that provides prompt X-ray diffraction data analysis during fast dynamic compression experiments conducted within the dynamic diamond anvil cell technique. It includes efficient data collection, streaming of data and metadata to a high-performance cluster (HPC), fast azimuthal data integration on the cluster, and tools for controlling the data processing steps and visualizing the data using the DIOPTAS software package. This data processing pipeline is invaluable for a great number of studies. The potential of the pipeline is illustrated with two examples of data collected on ammonia-water mixtures and multiphase mineral assemblies under high pressure. The pipeline is designed to be generic in nature and could be readily adapted to provide rapid feedback for many other X-ray diffraction techniques, e.g. large-volume press studies, in situ stress/strain studies, phase transformation studies, chemical reactions studied with high-resolution diffraction etc.

Effect of Accelerated Aging on High-Translucity Zirconia: an in Vitro Study of Phase Transformation and Fracture Resistance

Effect of Accelerated Aging on High-Translucity Zirconia: an in Vitro Study of Phase Transformation and Fracture Resistance

THEORETICAL AND EXPERIMENTAL MODELING OF THE PROCESS OF MELTING COMPLEX ALLOYED STEELS (Fe-Si-Al-Mn)

In the practice of complex theoretical research of multicomponent systems, the so-called thermodynamic-diagram method of analysis is known, which significantly simplifies the study of phase transformations in multicomponent systems by dividing them into thermodynamically stable elementary partial subsystems of equal dimensionality as the main ones. Thermodynamic-diagram analysis combines the thermodynamic assessment of chemical interactions between components in the studied system with a geometric diagram. Such a combination, as studies of the physicochemical principles of refractories and ferroalloys production have shown, proves to be productive in interpreting chemical interactions in complex systems.

Unveiling dual crystallization peaks in Zn2P2O7 glass: Insights into stability, nucleation, and growth kinetics

This study reports on the successful synthesis of Zn2P2O7 glass using the conventional melt-quenching method. The state of the material has been investigated using X-ray Diffraction (XRD) and Differential Scanning Calorimetry (DSC), to verify its amorphous and glassy state with the onset of two distinct crystallization peaks. These peaks were indicative of the transition to α-Zn2P2O7 and γ-Zn2P2O7 phases during the annealing process, a finding that was supported by Fourier-transform infrared spectroscopy (FTIR) analysis. This marked the inaugural occasion where the stabilization of both Zn2P2O7 phases from their respective annealed glassy state was achieved. The crystallization kinetics and associated parameters of Zn2P2O7 glass were deeply delved into, with various models including Kissinger, Ozawa, and the Matusita-Sakka approach. The applied models elucidate the mechanisms of growth and nucleation within the glass matrix. This kinetic study provided valuable insights into the crystallization process, revealing that α-Zn2P2O7 is both kinetically and thermally more stable than the γ-phase. However, it is less thermodynamically stable compared to the γ-phase. Besides, the study of phase transformations and crystallization kinetics was enhanced by the analysis of the Avrami index.

Nanocalorimeter and Raman microscope combination technique to study polymorphic transition processes in pharmacy materials

This article describes an experimental setup for combining ultrafast on-chip calorimetry (nanocalorimetry) and Raman spectroscopy (Raman spectroscopy) to study phase transformations in polymer materials. A new method for calibration of a nanocalorimetric sensor under a laser beam of a Raman microscope for in situ measurements at various temperatures is developed.

A multi-scale microscopic study of phase transformations and concomitant α/β interface evolution in additively manufactured Ti-6Al-4V alloy

Ti-6Al-4V alloy produced by laser-based powder bed fusion (LPBF) technique consists of an α′-martensite phase which is usually brittle and hence required, microstructure optimization by heat treatment to improve ductility. In this study, detailed microstructure analysis in the as-built condition and its evolution after sub-transus annealing was investigated. On annealing, the α′-martensite decomposes into α- and β-phases with the evolution of the α/β interface. Considering that the composition and microstructure play a crucial role in deciding the mechanical properties and service performance, a multi-scale correlative microscopy approach involving Transmission Electron Microscopy (TEM), Transmission Kikuchi Diffraction (TKD), and Atom Probe Tomography (APT) was employed. In the as-built condition, predominant segregation of β-stabilizers at the defect site especially along grain boundaries was observed; and these act as potential nucleation sites for β-phase during subsequent annealing. Low temperature annealing (750ᵒC) transforms the V-rich regions into the β-phase in the form of nanoscale precipitates. However, as the annealing temperature increases above 800ᵒC, the β-phase adopts a rod-like morphology. Comparing α-stabilizers, it is realized that β-stabilizers have a twofold greater contribution to elemental partition. Further, the composition and width of the α/β interface significantly impacts the mechanical properties of the alloy. Annealing at 750 °C and 850 °C resulted in significant improvement in ductility by 57.5% and 62.7% respectively without much of a trade-off in strength (>1 GPa). The strength and ductility are seen to decline when annealing temperature is raised above 850 °C due to a rise in compositional fluctuation and broadening of the α/β interface.

Electron Microscope Study of the Pressure-Induced Phase Transformation and Microstructure Change of TiO2 Nanocrystals.

Microstructure transformation of materials under compression is crucial to understanding their high-pressure phase transformation. However, direct observation of the microstructure of compressive materials is a considerable challenge, which impedes the understanding of the relations among phase transformation, microstructure, and material properties. In this study, we used transmission Kikuchi diffraction and transmission electron microscopy to intuitively characterize pressure-induced phase transformation and microstructure of TiO2. We observed the changes of twin boundaries with increasing pressure and intermediate phase TiO2-I of anatase transformed into TiO2-II (α-PbO2 phase) for the first time. The following changes occur during this transformation: anatase (diameter of ∼100 nm) → anatase twins 60° along the [110] zone axis → intermediate TiO2-I twins 60° along the [010] zone axis → TiO2-II twins 90° along the [010] zone axis. These results directly reveal the crystallographic relation among these structures, enhancing our understanding of the phase transformation in TiO2 nanocrystals.

3D Model of Carbon Diffusion during Diffusional Phase Transformations.

The microstructure plays a crucial role in determining the properties of metallic materials, in terms of both their strength and functionality in various conditions. In the context of the formation of microstructure, phase transformations that occur in materials are highly significant. These are processes during which the structure of a material undergoes changes, most commonly as a result of variations in temperature, pressure, or chemical composition. The study of phase transformations is a broad and rapidly evolving research area that encompasses both experimental investigations and modeling studies. A foundational understanding of carbon diffusion and phase transformations in materials science is essential for comprehending the behavior of materials under different conditions. This understanding forms the basis for the development and optimization of materials with desired properties. The aim of this paper is to create a three-dimensional model for carbon diffusion in the context of modeling diffusional phase transformations occurring in carbon steels. The proposed model relies on the utilization of the LBM (Lattice Boltzmann Method) and CUDA architecture. The resultant carbon diffusion model is intricately linked with a microstructure evolution model grounded in FCA (Frontal Cellular Automata). This manuscript provides a concise overview of the LBM and the FCA method. It outlines the structure of the developed three-dimensional model for carbon diffusion, details its correlation with the microstructure evolution model, and presents the developed algorithm for simulating carbon diffusion. Demonstrative examples of simulation results, illustrating the growth of the emerging phase and affected by various model parameters within particular planes of the 3D calculation domain, are also presented.

Study of microstructure, phase transformation and high temperature strength of hastelloy X and Ni3Al joint by TLP process

Study of microstructure, phase transformation and high temperature strength of hastelloy X and Ni3Al joint by TLP process

Effect of martensitic phase formation on the nano-mechanical attributes during the electron beam melting process of Ti-6Al-4V

Electron Beam Melting based Ti-6Al-4V parts plays a predominant role in the field of bio medical and aerospace applications, especially in the aero due to its sustainability. However, there were not enough studies on nano-mechanical properties that looked at how phase changes during the heat and cooling process affected the printing process. With the assistance of OM and FESEM with EDX, the EBM Ti64 coupons were analysed for the grain orientation and phase transformation studies. The FESEM with EDX supported the existence of columnar grains and orthogonally oriented martensitic needles. Additionally, both XRD and TEM confirmed the presence of vanadium-rich precipitates and the HCP α-Ti and BCC β-Ti phases. EBSD analysis was adopted to further investigate the orientation of grains. The nano-hardness and elastic reduced modulus mapping confirmed the phase transformation to martensitic phase. The strong “martensitic” phase had a maximum reduced modulus of 183.5 GPa and a hardness value of 7.31 GPa. However, the EBM based Ti64 possesses an average nano-hardness and reduced modulus of 4.26 GPa and 118.3 GPa under the applied load of 2500μN. In addition, topographic wear and scratch tracks confirmed the soft nature of α colonies by forming more piles of materials, while nano-wear and scratch analysis predicted the functions caused by the presence of hard martensitic phases. The SR sensitivity of the Ti64 specimens was investigated using three different quasi-static strain rates. It was determined that the EBM Ti64 parts have a considerable effect over the strain rate, whereas, a quasi-static strain rate allowed for the achievement of the highest possible Ultimate Tensile Strength (UTS) and ductility.

Comprehensive study of microstructure, phase transformations, and mechanical properties of nitinol alloys made of shape memory and superelastic wires and a novel approach to manufacture Belleville spring using wire arc additive manufacturing

In the present work, using wire arc additive manufacturing (WAAM), a novel approach is implemented to manufacture the Belleville spring/washer made from superelastic (SE) and shape memory (SM) Nitinol (NiTi) wires. A detailed correlation between the chemical composition, microstructure, and martensite transformation of deposited layers and their mechanical properties has been established. The energy dispersive spectroscopy (EDS) results revealed that the first track deposited using both SE and SM effect wire consisted of significant Fe constituents, which was further reduced while increasing the number of tracks. Moreover, as compared to the sample manufactured with SE effect NiTi wire (S1), the X-ray diffraction (XRD) of the sample manufactured with SM effect NiTi wire (S2) showed a secondary phase like NiTi2 along with the major NiTi (B19′ martensitic). It has been found that the presence of Ni4Ti3 precipitate in the microstructure of SE causes an enhanced superelasticity desired for the Belleville spring applications. Furthermore, the mechanical properties, microstructure, and phase transformation temperature of both S1 and S2 were investigated and compared. It was found that S2 has a finer microstructure than S1. Also, the compressive strength and hardness of S2 were higher than that of S1. In contrast, the tensile strength of the S2 was found to be lower than the S1. Regarding manufacturing the Belleville spring using WAAM, S1 showed promising mechanical and martensitic transformation results.

Study of phase and structural transformations in overcooled austenite for high-strength cold resistant steel during continuous cooling

Study of phase and structural transformations in overcooled austenite for high-strength cold resistant steel during continuous cooling

Unveiled the Structure-Selectivity Relationship for Carbon Dioxide Reduction Triggered by Bi-Doped Cu-Based Nanocatalysts.

To investigate synergistic effect between geometric and electronic structures on directing CO2RR selectivity, water phase synthetic protocol and surface architecture engineering strategy are developed to construct monodispersed Bi-doped Cu-based nanocatalysts. The strongly correlated catalytic directionality and Bi3+ dopant can be rationalized by the regulation of [*COOH]/[*CO] adsorption capacities through the appropriate doping of Bi3+ electronic modulator, resulting in volcano relationship between FECO/TOFCO and surface EVBM values. Spectroscopic study reveals that the dual-site binding mode ([Cu─μ─C(═O)O─Bi3+]) enabled by Cu1Bi3+ 2 motif in single-phase Cu150Bi1 nanocatalyst drives CO2-to-CO conversion. In contrast, the study of dynamic Bi speciation and phase transformation in dual-phase Cu50Bi1 nanocatalyst unveils that the Bi0-Bi0 contribution emerges at the expense of BOC phase, suggesting metallic Bi0 phase acting as [H]˙ formation center switches CO2RR selectivity toward CO2-to-HCOO- conversion via [*OCHO] and [*OCHOK] intermediates. This work provides significant insight into how geometric architecture cooperates with electronic effect and catalytic motif/phase to guide the selectivity of electrocatalytic CO2 reduction through the distinct surface-bound intermediates and presents molecular-level understanding of catalytic mechanism for CO/HCOO- formation.

Thermodynamic analysis and in situ PXRD study of mineralogy phase transformation of arsenopyrite in acid pressure oxidation

Acid pressure oxidation (POX) is a cost-efficient pre-treatment method for releasing refractory gold from arsenopyrite and pyrite prior to cyanidation. However, ongoing debate surrounds the mechanism of the dissolution, crystallization, and phase transformation during POX, in part due to the lack of thermodynamic data and in situ studies of the acid POX. In this study, we developed Eh-pH diagrams and used in situ powder X-ray diffraction (PXRD) to investigate mineralogical phase changes during acid POX of arsenopyrite. Based on the existing thermodynamic data, we established the Eh-pH diagrams for the Fe-As-S-H2O systems at 225 °C and 100 °C, which correctly predicted the predominant solid phases precipitating during POX of arsenopyrite at a pH range of 0 to 0.5, such as basic ferric sulphate (BFS: Fe(OH)SO4), szomolnokite (FeSO4·H2O), hydronium jarosite ((H3O)Fe3(SO4)2(OH)6) and angelellite (Fe4O3(AsO4)2). FeSO4·H2O solid is the stable phase during annealing stages as predicted by the Eh-pH diagram, which is in line with the observed solid phases using in situ PXRD. The influence of initial concentration of ferric ions and the presence of pyrite on mineral phase change was revealed. Our results confirmed the formation of FeSO4·H2O, BFS and hydronium jarosite during annealing stages, while BFS and/or hydronium jarosite dissolved during curing and cooling process. Especially, the formation of angelellite was observed in the presence of pyrite during cooling process, which is well-agreed with thermodynamic analysis.

Electron-microscopic study of phase transformations in 316L austenitic steel manufactured by laser 3D printing

We studied the structure and phases in porous samples of 316L austenitic steel manufactured by laser 3D printing. Transmission electron microscopy revealed the presence of residual δ-ferrite along with austenite in the sample. A high density of dislocations is also observed in the sample. EBSD analysis revealed a lack of texture.

Investigation of structural-phase transformations in a foundry structural alloy based on Ni3Al intermetallic compound after high-temperature exposures and during the operation of the alloy as a nozzle blade

The paper presents studies of structural and phase transformations in intermetallic compositions based on the Ni3Al compound depending on alloying and high-temperature treatments, carried out in the process of creating a cast structural alloy for operation in the temperature range of 900–1200°C. Experimentally, when testing the developed intermetallic alloy as nozzle blades of the 1st stage of a high-pressure turbine, it was confirmed that the alloy is thermally stable at temperatures up to 1200°C.