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The spatiotemporal resolution of diagnostic X-ray images obtained with rotating-anode X-ray tubes has remained limited as the development of rigid, high-performance target materials has slowed down. However, novel imaging techniques using finer detector pixels and orthovolt cancer therapy employing narrow X-ray focal spots demand improved output from brilliant keV X-ray sources. Since its advent in 1929, rotating-anode technology has become the greatest bottleneck to improvement. To overcome this limitation, the current authors have devised a novel X-ray generation technology based on tungsten microparticle targets. The current study investigated a hybrid solution of a stream of fast tungsten microparticles and a rotating anode to both harvest the benefits of the improved performance of the new solution and to reuse known technology. The rotating anode captures energy that may pass a partially opaque microparticle stream and thereby contributes to X-ray generation. With reference to fast-rotating anodes and a highly appreciated small focal spot of a standardized size of 0.3 for an 8° target angle (physical: 0.45 mm × 4.67 mm), we calculated a potential output gain of at least 85% for non-melting microparticles and of 124% if melting is envisioned. Microparticle charging can be remediated by electron backscattering and electron field emission. The adoption of such a solution enables substantially improved image resolution., QC 20240704

Electron beam powder bed fusion (PBF-EB) is used to manufacture dense nickel titanium parts using various parameter sets, including the beam current, scan speed and post cooling condition. The density of manufactured NiTi parts are investigated with relation to the linear energy input. The results implies the part density increases with increasing linear energy density to over 98% of the bulk density. With a constant energy input, a combination of low power and low scan speed leads to denser parts. This is attributed to lower electrostatic repulsive forces from lower number density of the impacting electrons. After manufacturing, densest parts with distinct parameter sets are categorized into three groups: i) high power with high scan speed and vacuum slow cooling, ii) low power with low scan speed and vacuum slow cooling and iii) low power with low scan speed and medium cooling rate in helium gas. Among these, a faster cooling rate suppresses phase transformation temperatures, while vacuum cooling combinations do not affect the phase transformation temperatures significantly. All the printed parts in this study exhibit almost 8% pseudoelasticity regardless of the process parameters, while the parts cooled in helium have a higher energy dissipation efficiency ( ), which implies faster damping of oscillations., QC 20230426

A crucial step in the powder bed metal additive manufacturing process is the formation of a thin layer of powder on top of the existing material. The propensity of the powder to form thin layers under the conditions used in additive manufacturing is critically important, but no test method has yet been established to measure this characteristic, which is sometimes referred to as spreadability. The current work spreads a single layer of powder using commercial equipment from the paint and food industries and derives the density of a layer of powder, which is of a similar thickness to that in additive manufacturing. Twenty-four powders from eight suppliers have been tested and the density of the layers has been measured as a function of various parameters. Twenty-two of the powders successfully form thin layers, with a density of at least 40% of each powder’s apparent density. Hall flow time did not correlate with the spread layer density, although the two powders that did not spread did not pass through the Hall funnel. The roughness of the plate onto which the powder was spread, the recoater speed, the layer thickness, particle size and aspect ratio all affect the measured layer density. Results of the new test are repeatable and reproducible. These findings can be used to develop a test for spreadability for metal powders that can be used for additive manufacturing, which will help to improve the quality of printed components., QC 20230524

This work systematically analyzes and optimizes the process of electron beam melting for pure copper. It is shown that, for reliable manufacturing, the preheating temperature should be optimized to avoid porosity as well as part deformation. The electron beam should be fully focused to prevent shrinkage voids (correlated to negative defocusing) and material spattering (linked to positive defocusing). Smoother surfaces from lower hatch spacing (e.g., 100µm) can improve the density reliability, while longer overhangs are reached by a higher hatch spacing. A suitable starting contour strategy is also applied to mitigate border porosities, reduce side roughness and increase geometric precision., QC 20220530

It is well documented that chemical additives (grinding aid “GA”) during grinding can increase mill throughput, reduce water and energy consumption, narrow the particle size distribution of products, and improve material flowability. These advantages have been linked to their effects on the rheology, although there is a gap in understanding GA effectiveness mechanism on the flow properties. The present study aims to fill this gap using different GAs (Zalta™ GR20-587, Zalta™ VM1122, and sodium hydroxide) through batch grinding experiments of magnetite ore and addressing the mechanisms of their effects on the rheology by an FT4 Powder Rheometer as a unique system. Experimental results showed that GA improved grinding efficiency (energy consumption and product fineness), which were well-correlated with basic flow energy, specific energy, aerated basic flow energy, and aerated energy. Moreover, the rheometry measurement showed strong linear correlations between basic flow energy, specific energy, and the resulting work index when GAs was considered for grinding, which confirmed the effect of GA on ground particles’ flowability. Zalta™ VM1122, a polysaccharide-based grinding aid, showed the best performance with 38.8% reduction of basic flow energy, 20.4% reduction of specific energy, 24.6% reduction of aerated basic flow energy, and 38.3% reduction of aerated energy. It also showed the strongest correlation between the grinding parameters and flow parameters (r > 0.93). The present investigation shows a strong indication that the predominant mechanism of GAs is based on the alteration of rheological properties and identify Zalta™ VM1122 as the best GA., Validerad;2022;Nivå 2;2022-04-19 (johcin);Finansiär: Kolarctic CBC (KO1030 SEESIMA)

Part of book: ISBN 978-91-89039-14-8, QC 20230228

Energy management is an essential part of the integration of renewable energy in energy systems, electric vehicles, energy-saving strategies, waste-heat recovery, and building energy. Although many publications considered energy management, no study addressed the connection between scientists, organizations, and countries. The present study provides a scientometric analysis that addresses the trend of publications and worldwide dynamic maps of connectivity and scientists, organizations, and countries and their contribution to energy management. The results showed that Javaid Nadeem published the most papers in the field of energy management (90) while Xiao Hu received the most citations (1394). The university with the highest number of publications in energy management is the Islamic Azad University (144 papers), while the Beijing Institute of Technology has received the most citations (2061 citations) and the largest h-index (28). China and the United States are in the first and second rank in terms of total publications, citations, and h-index. Pakistan has the most publications relative to the country's research and development investment level. The maps of co-authorship show islands of isolated groups of authors. This implies that the researchers in energy management are not well-connected. Bibliographic coupling of countries revealed China and USA are influential contributors in the field, and other countries were coupled mostly through these two countries., QC 20221024

The aim of this study is to analyze the thermo-magnetic-gravitational convection of a non-Newtonian power law ferrofluid within a circular cavity. The ferrofluid is exposed to the magnetic field of a permanent magnet. The finite element method is employed to solve the non-dimensional controlling equations. A grid sensitivity analysis and the validation of the used method are conducted. The effect of alterable parameters, including the power law index, 0.7 <= n <= 1.3, gravitational Rayleigh number, 10(4) <= Ra-T <= 10(6), magnetic Rayleigh number, 10(5) <= Ra-M <= 10(8), the location of the hot and cold surfaces, 0 <= lambda <= pi/2, and the length of the magnet normalized with respect to the diameter of the cavity, 0.1 <= L <= 0.65, on the flow and heat transfer characteristics are explored. The results show that the heat transfer rate increases at the end of both arcs compared to the central region because of buoyancy effects, and it is greater close to the hot arc. The location of the arcs does not affect the heat transfer rate considerably. An increase in the magnetic Rayleigh number contributes to stronger circulation of the flow inside and higher heat transfer. When the Kelvin force is the only one imposed on the flow, it enhances the heat transfer for magnets of length 0.2 <= L <= 0.3., QC 20220830

Additive manufacturing (AM) is a useful technology to produce artificial aortic models for the training of transcatheter aortic valve replacement (TAVR) surgery. With AM, the models can be tailored towards the individualized aortic anatomy of patients. Most of these reported models so far are manufactured using single rubber-like materials. However, such materials do not replicate the mechanical properties of natural aortic tissue, especially the stress-strain response in higher strain (>0.1) regions. This could be problematic for surgeons training for surgeries using a model which does not exhibit properties of the real aorta. To overcome this limitation, we developed a 3D-printed, mechanically representative aortic model comprising gelatin fibers and silicone. The model is promising as a realistic analog of aortic sinus for mock TAVR surgery. Computerized tomography data was analyzed beforehand using medical imaging to identify the anatomy of a specific patient's aortic sinus and the surrounding blood vessels. A novel silicone matrix composite reinforced with gelatin fibers designed in this work was tested and compared with the stress-strain response of aortic tissue. Such a model comprising both patient-specific geometries as well as realistic material properties of aortic tissue can be helpful for the development of next-generation medical phantoms., QC 20220707

Flow occurs in most powder-based processes, opposed by various cohesive forces. Magnetism is often overlooked for metal powders. Here, flowability and magnetization were measured for a dual-phase steel powder in size fractions from (Formula presented.) to > 200 µm. The finest fraction did not flow through a Hall flowmeter, then flow time increased continuously with particle size from 12 ± 1 s for the next fraction ((Formula presented.)) to > 28 ± 0.5 s for > 200 µm. Drying had little effect. Key metrics derived from shear tests gave no overall relationship between flow behavior and particle size. Magnetism was considered the most likely reason for this behavior. Magnetometry showed a remanent magnetization of (Formula presented.) which causes ∼ 5 µN cohesion between 200 µm diameter particles. X-ray diffractometry showed that the powder contained 77 wt%-80 wt% of (magnetic) martensite. Liquid bridging, van der Waals forces and friction (in the Hall flowmeter geometry) contribute 50 µN, 0.08 µN and 4 µN, respectively, to cohesion in 200 µm particles. These results can be used to help explain flow behavior in other magnetic powders and allow optimization of powders and/or powder-based processes., QC 20220504

Atmospheric humidity is introduced into powders during handling, transportation, and storage. High moisture content can increase cohesive forces between particles and make it difficult to spread a powder into thin layers in powder bed processes or to fill a mold in processes such as press-and-sinter. Furthermore, water can cause porosity and uptake of oxygen in the final component, damaging its mechanical properties. In this study, a Freeman FT4 powder rheometer was placed inside a climate chamber. Both flowability and shear tests were performed on four steel powders under a range of humidity and temperatures. Basic flowability energy and specific energy were both found to increase significantly with humidity (typically increase by 50% for 80% of relative humidity compared to dry conditions) and were insensitive to temperature change (10–30 °C). Conversely, the behavior of the powders under shear was neither sensitive to relative humidity nor temperature. Measurements of moisture content revealed that finer powders contained more moisture than coarser ones, but the moisture content was not correlated with humidity, probably due to shortcomings with the measurement method. This knowledge can be used to optimize powder processing conditions., QC 20220603

In this work, three characterization techniques were applied to a set of alloys in fine powder form (TiAl6V4, AlSi10Mg, AlSi7, 316L, ferritic stainless steel, martensitic stainless steel and WC-Co-mixes). We sought deeper understanding of response to humidity and flowability as a result of the powder alloy. Slight tribo-charging (induced and measured using a GranuCharge setup) against metal surfaces was found to occur for all alloys. Although the accumulated charge was small and dissipated quickly. Greater charging occurs if the environment is humid, and if the powder slides against plastic surfaces. Dynamic Vapor Sorption (DVS) was employed to understand the adsorption capacity of powders. It showed that WC-Co-mixes adsorbed much more humidity than the other materials. Some alloys retained some of the adsorbed mass when humidity returned to normal conditions. RPA was tested on powders during exposure to 20-98% RH, which above 80% RH caused declining flowability., Part of ISBN 9781899072552QC 20230907

Alloy 825 is widely used in several industries, but its useful service life is limited by both mechanical properties and corrosion resistance. The current work explores the effect of the addition of magnesium on the recrystallization and mechanical behavior of alloy 825 under hot compression. Compression tests were performed under conditions representative of typical forming processes: temperatures between 1100 and 1250 °C and at strain rates of 0.1–10 s−1 to a true strain of 0.7. Microstructural evolution was characterized by electron backscattered diffraction. Dynamic recrystallization was found to be more prevalent under all test conditions in samples containing magnesium, but not in all cases of conventional alloy 825. The texture direction ⟨101⟩ was the dominant orientation parallel to the longitudinal direction of casting (also the direction in which the samples were compressed) in samples that contained magnesium under all test conditions, but not in any sample that did not contain magnesium. For all deformation conditions, the peak stress was approximately 10% lower in material with the addition of magnesium. Furthermore, the differences in the peak strain between different temperatures are approximately 85% smaller if magnesium is present. The average activation energy for hot deformation was calculated to be 430 kJ mol−1 with the addition of magnesium and 450 kJ mol−1 without magnesium. The average size of dynamically recrystallized grains in both alloys showed a power law relation with the Zener–Hollomon parameter, DD~Z−n, and the exponent of value, n, is found to be 0.12. These results can be used to design optimized compositions and thermomechanical treatments of alloy 825 to maximize the useful service life under current service conditions. No experiments were conducted to investigate the effects of such changes on the service life and such experiments should now be performed., QC 20210517

Thermal energy storage units conventionally have the drawback of slow charging re- sponse. Thus, heat transfer enhancement techniques are required to reduce charging time. Using nanoadditives is a promising approach to enhance the heat transfer and energy storage response time of materials that store heat by undergoing a reversible phase change, so-called phase change materials. In the present study, a combination of such materials enhanced with the addition of nanometer-scale graphene oxide particles (called nano-enhanced phase change materials) and a layer of a copper foam is proposed to improve the thermal performance of a shell-and-tube latent heat thermal energy storage (LHTES) unit filled with capric acid. Both graphene oxide and copper nanoparticles were tested as the nanometer-scale additives. A geometrically nonuniform layer of copper foam was placed over the hot tube inside the unit. The metal foam layer can improve heat transfer with an increase of the composite thermal conductivity. However, it suppressed the natural convection flows and could reduce heat transfer in the molten regions. Thus, a metal foam layer with a nonuniform shape can maximize thermal conductivity in conduction-dominant regions and minimize its adverse impacts on natural convection flows. The heat transfer was modeled using partial differential equations for conservations of momentum and heat. The finite element method was used to solve the partial differential equations. A backward differential formula was used to control the accuracy and convergence of the solution automatically. Mesh adaptation was applied to increase the mesh resolution at the interface between phases and improve the quality and stability of the solution. The impact of the eccentricity and porosity of the metal foam layer and the volume fraction of nanoparticles on the energy storage and the thermal performance of the LHTES unit was addressed. The layer of the metal foam notably improves the response time of the, QC 20210521

The spreading of powders into thin layers is a critical step in powder bed additive manufacturing, but there is no accepted technique to test it. There is not even a metric that can be used to describe spreading behaviour. A robust, image-based measurement procedure has been developed and can be implemented at modest cost and with minimal training. The analysis is automated to derive quantitative information about the characteristics of the spread layer. The technique has been demonstrated for three powders to quantify their spreading behaviour as a function of layer thickness and spreading speed., Das Aufbringen von Pulvern in dünne Schichten ist ein kritischer Schritt bei der Herstellung von Pulverbettadditiven, es gibt jedoch keine akzeptierte Technik, um dies zu testen. Es gibt nicht einmal eine Metrik, mit der das Ausbreitungsverhalten beschrieben werden kann. Es wurde ein robustes, bildbasiertes Messverfahren entwickelt, das mit geringen Kosten und minimalem Schulungsaufwand implementiert werden kann. Die Analyse wird automatisiert, um quantitative Informationen über die Eigenschaften der Ausbreitungsschicht abzuleiten. Die Technik hat gezeigt, dass drei Pulver ihr Ausbreitungsverhalten als Funktion der Schichtdicke und der Ausbreitungsgeschwindigkeit quantifizieren können., QC 20210710

It is well documented that chemical additives (grinding aid “GA”) during grinding can increase mill throughput, reduce water and energy consumption, narrow the particle size distribution of products, and improve material flowability. These advantages have been linked to their effects on the rheology, although there is a gap in understanding GA effectiveness mechanism on the flow properties. The present study aims to fill this gap using different GAs (ZaltaTM GR20-587, ZaltaTM VM1122, and sodium hydroxide) through batch grinding experiments of magnetite ore and addressing the mechanisms of their effects on the rheology by an FT4 Powder Rheometer as a unique system. Experimental results showed that GA improved grinding efficiency (energy consumption and product fineness), which were well-correlated with basic flow energy, specific energy, aerated basic flow energy, and aerated energy. Moreover, the rheometry measurement showed strong linear correlations between basic flow energy, specific energy, and the resulting work index when GAs was considered for grinding, which confirmed the effect of GA on ground particles’ flowability. ZaltaTM VM1122, a polysaccharide-based grinding aid, showed the best performance with 38.8% reduction of basic flow energy, 20.4% reduction of specific energy, 24.6% reduction of aerated basic flow energy, and 38.3% reduction of aerated energy. It also showed the strongest correlation between the grinding parameters and flow parameters (r > 0.93). The present investigation shows a strong indication that the predominant mechanism of GAs is based on the alteration of rheological properties and identify ZaltaTM VM1122 as the best GA., QC 20210906

The production of metal powder by gas atomisation generates feedstock for many manufacturing techniques, including hot isostatic pressing, laser cladding and, of current interest, powder bed additive manufacturing. While many thousands of alloys are commercially available in bulk form, fewer than fifty are widely available as powders suitable for additive manufacturing. This is due to difficulties in controlling droplet size distribution and avoiding particle defects. Indeed, a typical gas atomisation process that attempts to make powder for powder bed additive manufacturing achieves a yield of suitable powder below 50%. Several studies have simulated the gas atomisation process or part of it, but few validate the models directly. The current work aims to take a first step towards making a holistic and fully validated model for gas atomisation. The gas flow from de Laval nozzles under conditions similar to those used in gas atomisation has been simulated using computational fluid dynamics and experiments to validate these simulations have been performed using shadowgraphy. A validated model can be used as part of a larger model to predict the phenomena that occur in gas atomisation and thereby refine the process to improve the production yield of powders, especially for additive manufacturing., QC 20210907

Since there is no report on the influence of machining depth on electron beam melting (EBM) parts, this paper investigated the role of superficial defects and machining depth in the performance of EBM made Inconel 718 (IN718) samples. Therefore, as-built EBM samples were analyzed against the shallow-machined (i.e., only removal of outer surfaces) and deep-machined (i.e., deep surface removal into the material) parts. It was shown that both as-built and shallow-machined samples had a drastically lower yield strength (970 ± 50 MPa), ultimate tensile stress (1200 ± 40 MPa), and ductility (28 ± 2%) compared to the deep-machined samples. This was since premature failure occurred due to various superficial defects. The superficial defects appeared in two levels, as (1) notches and pores on the surface and (2) irregular pores and cracks within the subsurface. Since the latter occurred down to 2 mm underneath the surface, shallow machining only exposed the subsurface defects to outer surfaces. Thus, the shallow-machined parts achieved only 68% and 8% of UTS and elongation of the deep-machined parts, respectively. This low performance occurred to be comparable to the as-built parts, which failed prematurely due to the high fraction surface voids and notches as well as the subsurface defects., QC 20210824

The spreading of powders into thin layers is a critical step in powder bed additive manufacturing, but there is no accepted technique to test it. There is not even a metric that can be used to describe spreading behaviour. A robust, image-based measurement procedure has been developed and can be implemented at modest cost and with minimal training. The analysis is automated to derive quantitative information about the characteristics of the spread layer. The technique has been demonstrated for three powders to quantify their spreading behaviour as a function of layer thickness and spreading speed., QC 20220302

The impact of moisture on flowability and spread- ability is discussed. More notably we also present research on the impact of moisture on built nickel-base material. One lot of a newly opened Hastelloy X (HX) L-PBF powder was split into two equal batches. One batch was moisturized using a programmable climate chamber, the other was un- treated. We built bars with both batches for mechanical testing, in an EOS M100, with a cold build plate. The mois- ture content of the two powder batches, before and after the build-jobs, were determined using Karl Fischer titration (KF). Regarding the periodical monitoring of moisture con- tent, it is not needed according to the findings of this paper. More moisture contributes to a slightly higher O-content in the built material, and in turn, a very slight reduction in im- pact toughness. If a newly purchased powder exhibits poor flowability or high oxygen content, the analysis using oven- desorption followed by KF is recommended. If the moisture content is high, a drying of the powder is recommended, QC 20210916

Humidity and temperature can vary across the world. For this reason, during storage and processing, batches of the same powder may interact with diverse environmental conditions and eventually vary in their properties. For example, a higher atmospheric water vapour content could increase the water adsorbed on the surface of individual powder particles. This adsorbed water can alter the surface interactions between particles, affecting its flow behaviour. In this study, we measured the flow behaviour of various sieve fractions and steel powders in different environmental conditions. We set the environmental conditions in a C1000-40 climate chamber to different levels of relative humidity and temperature. The powder samples and a Freeman FT4 powder rheometer were placed in the climate chamber and equilibrated for 72h. Subsequently, we tested the flow behaviour using two different programs of the powder rheometer. Ultimately, we found that powder flowability is adversely affected by increased humidity., QC 20220615Part of proceedings: ISBN 978-189907251-4

Magnesium is the lightest metal currently processed by powder bed fusion - laser beam (PBF-LB). Its low density implies very different powder characteristics compared to materials more established within AM. To gain a greater understanding of the characteristics of magnesium powder and its implications for AM, a gas-atomized WE43 powder was characterized and processed by PBF-LB. The spreadability of the powder was evaluated using TQC Sheen Automatic Film Applicator, while in parallel, the powder was processed in PBF-LB. The flowability was evaluated using Hall and Gustafsson flowmeters. Apparent density was measured and general behaviour during handling was evaluated. The results were compared with powders commonly used in PBF-LB. The spreadability of the powder was greater than expected: the powder flowed in both the Hall and Gustavsson flowmeters, although the flow time was extremely long. Parts were successfully built in an EOS M290 printer using the powder with the as-atomized particle size distribution., Part of proceedings: ISBN 9781899072514, QC 20220613

The behaviour of metal powders when they are spread into thin layers is critical for powder bed additive manufacturing and other processes. However, there is no accepted test procedure to quantify this behaviour. There is not even an accepted metric that can be used to assess this property. This increases the difficulty of developing new powders for additive manufacturing. The current study proposes test and analysis procedures that minimise the influence of operators and are aimed at providing maximum repeatability and reproducibility while minimising the need for specialist analysis equipment. Initial testing shows that a powder with good flow properties behaves as expected as a function of recoater speeds and always exhibits superior spread metrics to powders with poor flow properties. This provides an important step towards the establishment of a robust, inexpensive test that can help additive manufacturing to grow in new industries., QC 20220613

The flowability of a powder is an important characteristic that depends on both the physical properties of the particle ensemble and the testing method, equipment and conditions. In additive manufacturing processes, flowability can be an indicator of the quality of the deposited powder layer and, therefore, the final component. In this study, we carried out a comparison of the flowability of different steel powders and the data generated by a range of testing methods. Each sample had a unique combination of composition and particle size range. Flowability testing equipment and methods were selected according to standards (angle of repose, Hausner Ratio, Hall flow) or published literature (FT4 Powder Rheometer). We measured the flowability of different samples for each testing method, in order to obtain a first dataset. Secondly, we evaluated the correlations between different flowability testing methods., QC 20210914

A novel, low-alloy steel has been designed for use in the oil and gas industry. Its high strength and hydrogen trapping potential are derived from a martensitic microstructure containing a dispersion of fine vanadium-molybdenum alloy carbides that evolve during tempering. In this second paper, the effect of quench rate from austenitisation and tempering conditions are investigated with respect to the microstructure. The alloy loses its tempering resistance following slow-cooling from austenitisation as a result of MC precipitation, leading to vanadium depletion and significant M2C coarsening. This is predicted using computer simulation and confirmed by high energy X-ray diffraction, combined with electron microscopy., QC 20190412

Understanding the nature of the magnetic-field-induced precipitation behaviors represents a major step forward towards unravelling the real nature of interesting phenomena in Fe-based alloys and especially towards solving the key materials problem for the development of fusion energy. Experimental results indicate that the a pplied high magnetic field effectively promotes the precipitation of M 23 C 6 carbides. We build an integrated method, which breaks through the limitations of zero temperature and zero external field, to concentrate on the dependence of the stability induced by the magnetic effect, excluding the thermal effect. We investigate the intimate relationship between the external field and the origins of various magnetics structural characteristics, which are derived from the interactions among the various Wyckoff sites of iron atoms, antiparallel spin of chromium and Fe-C bond distances. The high-magnetic-field-induced exchange coupling increases with the strength of the external field, which then causes an increase in the parallel magnetic moment. The stability of the alloy carbide M 23 C 6 is more dependent on external field effects than thermal effects, whereas that of M 2 C, M 3 C and M 7 C 3 is mainly determined by thermal effects., QC 20180604

A new thermally stable, nanocrystalline bainitic steel has been developed, rich in nickel and aluminium. During tempering, it is expected that a significant quantity of intermetallic precipitates will form. This was confirmed by X-ray diffractometry, scanning transmission electron microscopy, Fourier transform analysis of atomic column images, energy dispersive X-ray spectroscopy and selected area electron diffraction. These are the first intermetallics to be produced in a nanocrystalline bainitic steel., QC 20190110

QC 20180604

Two novel nanocrystalline steels were designed to withstand elevated temperatures without catastrophic microstructural changes. In the most successful alloy, a large quantity of nickel was added to stabilize austenite and allow a reduction in the carbon content. A 50 kg cast of the novel alloy was produced and used to verify the formation of nanocrystalline bainite. Synchrotron X-ray diffractometry using in situ heating showed that austenite was able to survive more than 1 hour at 773 K (500 ˚šC) and subsequent cooling to ambient temperature. This is the first reported nanocrystalline steel with high-temperature capability., QC 20180604

A combined approach to calculate the thermodynamic properties of iron and alloy carbides including the thermal and magnetic contribution is derived. Special emphasis is placed on the role of Fe and Mo to the Gibbs free energy. Lower Mo concentration in the carbides corresponds to a higher thermal Gibbs free energy change. The higher Fe content and external magnetic field greatly increase the induced magnetization, reducing the magnetic Gibbs free energy substantially and therefore increase the formation temperature. The stability of M 2 C and M 3 C are mainly determined by the thermal factors, whereas magnetic field has a predominant contribution for M 6 C., QC 20180604

A hybrid method combining first-principles calculations and Weiss molecular field theory with thermodynamic data has been implemented to explore the origin of magnetic-field-induced precipitation behaviors for alloy carbides. The paramagnetic Mo atom disturbed the order of magnetic moment and resulted in a decrease in the Curie temperature for alloy carbide Fe6-xMoxC. The temperature dependence of magnetic moment and saturation magnetization of Fe atoms at different Wyckoff positions, as well as the saturation or induced magnetization of Fe6-xMoxC, decreased with increasing temperature. The higher Fe content and external magnetic field greatly increased the magnetization of alloy carbides. Two kinds of stella quadrangula lattices were employed to account for the total magnetism which was derived from the contribution of different Wyckoff sites of Fe atoms and Fe-C distances. The calculated total free energy taking into account magnetic field, temperature and composition was sufficient to provide quantitative agreement with experiment. The investigation of the effects of external field on the carbide precipitation behaviors led to a better understanding of the magnetic-field-induced phase transformation mechanism in heat resistant steels., QC 20180604

There is growing evidence that bainitic ferrite which retains a substantial amount of carbon in solid solution does not have cubic symmetry. We provide additional data on a different nanostructured bainitic steel to support this evidence, based on synchrotron X-ray diffraction experiments. The data are consistent only with a displacive transformation mechanism for bainite., QC 20180604