High-density Inclusions Research Articles

Numerical Modeling of Electron Beam Cold Hearth Melting for the Cold Hearth

The electron beam cold hearth melting (EBCHM) process is one of the key processes for titanium alloy production. The unique characteristic of this pyrometallurgy process is the application of the cold hearth, which is responsible for controlling the Low-Density Inclusions (LDIs) and High-Density Inclusions (HDIs) in the melt. As a key process of inclusion removal, the information such as melt residence time in the cold hearth is directly related to the control of metallurgical defects in the ingot, and may also affect the composition distribution of the ingot. In this paper, the details for the physical phenomena, namely the evolution of the pool, the evolution of the flow, and the evolution of the component in the cold hearth during EBCHM are investigated using a modified multi-physical numerical model. The effects of melting temperature and melting speed on these phenomena were investigated. The purpose is to provide more fundamental knowledge and to further enhance the applications of EBCHM for more titanium alloys.

Prior function designs for X-ray reconstructions from limited angular views

The objectivity of three-dimensional imaging has placed X-ray Computed Tomography (CT) into an indispensable diagnostic method in clinical and industrial applications. Despite the advances in the X-ray CT imaging, high- resolution three-dimensional reconstruction of small details in objects with large in-plane dimensions has been a fundamental challenge for the conventional X-ray CT method. An alternative scanning geometry, where X-ray source and a detector move synchronously irradiating a specimen at an inclined angle, has been proposed to address this challenge. This work presents new designs of prior (or penalty) functions developed for reconstructing the radiography data obtained under the limited angular conditions. The new prior targets reduction of shape distortion artifacts, common for laminographic reconstructions, as well as preservation of small features, such as voids, edge details, and high-density inclusions. The novel prior function designs are demonstrated on the computational phantom of a specimen scanned under tilted planar CT geometry simulating large planar dimensions of a specimen. To accommodate physical CT scanning of such specimens, a novel microfocus X-ray CT scanning device that rotates X-ray source and moves the detector synchronously while staying on the same side of the test specimen (Inclined CT), is introduced. This device allows scanning of critical areas of up to 3-meter-wide and potentially unlimited length specimens with high resolution required for identification of manufacturing and structural defects typical for modern composite structural elements used in the aerospace industry.

Comment on: Evolutionary paths for the formation of different types of fluid inclusions in the H2O-NaCl system by Mao et al. (2023)

Mao et al. (2023) illustrate phase assemblages in a variety of H2O-NaCl-rich fluid inclusions, and the “evolution” of these assemblages at temperatures below homogenization conditions. A fundamental knowledge of the application, merits and weakness of microthermometry seems to be absent. The authors do not clearly indicate which H2O-NaCl fluid model is used to calculate the “evolutionary paths”, but the results are identical to the results from the software AqSo_NaCl (Bakker, 2018, 2019). The claimed “first time” presented evolutionary path was already included in AqSo_NaCl, that contain all possible “evolutionary paths”, and offers abundant calculation procedures in the H2O-NaCl system. The suggested application to recognize or understand post-entrapment modifications does not contribute to our knowledge of re-equilibration processes, and does not offer a comprehensible method. The selected evolutionary paths (isochores) of relatively high-density inclusions must be corrected for host mineral expansivity and compressibility, that result in completely different homogenization temperatures and dissolution temperatures. The presence of abundant errors, deficiencies, and misplaced and omitted references highly reduces the quality of this manuscript.

Indigenous Development of Titanium Compressor Blade For Turbofan Engine

The Indigenous development of titanium compressor blade was taken up for turbofan engine for aeronautical applications. This titanium compressor blade is classified as flight safety critical part due to its rotating nature in dynamic load conditions. This blade is made from precision forging in titanium material with strength class of 880-1130 MPa. The material produced in accordance with this specification is melted by the triple VAR process or the cold hearth plus VAR process. The material specification calls for compliance on requirements on a forging lot/heat-treat lot/ingot for metallurgical defects like High Interstitial Defects (HID) "Type I" alpha defects, High-Density Inclusions (HDI), High-alpha defects ("Type II" alpha defect), Beta flecks, Clean shrinkage porosity and Strain-induced porosity. The forging required for compressor blade was developed as per approved test schedule, machined for finished dimensions and assembled and type tested in turbofan engine for its qualification. The titanium compressor blade was cleared for production after successfully completing stipulated qualification requirements. This paper covers the approach toward indigenous development of aero-engine titanium compressor blade forging, machining, assembly and its qualification testing in details

Typical X-ray Semiotic Signs of High-Density Inclusions of the Jaws According to Cone-Beam Computed Tomography

In the process of evaluating X-ray diagnostic images of the jaw bones of dental patients, foci of altered bone structure and atypical intraosseous inclusions of increased density are often found. The identified inclusions have different etiology, but at the same time a similar and in some cases implicit scialogical picture, which may cause an incorrect radiological conclusion. When analyzing the available literature, limited information was found about the typical radiosemiotic signs of dense intraosseous inclusions of the jaw bones found in everyday medical practice.

Automated X-Ray Tomographic Defect Analysis in High Density Carbon Capsules

High density carbon capsule ablators are of primary interest for National Ignition Facility experiments. Two of the major contributors to hydrodynamic instabilities in these capsules are voids and high-density inclusions, where the quantity and size of these defects can result in lower yields in inertial confinement fusion. To aid in capsule selection, General Atomics developed a LabVIEW analysis routine to quantify these defects based off a large field-of-view tomographic dataset and to provide insight into the quality of the capsule. This analysis determines if there are large voids or inclusions that may affect shot performance and helps rank which capsules should be used.

The Nature of Metal Artifacts in X-ray Computed Tomography and Their Reduction by Optimization of Tomography Systems Parameters

A significant gap in the known methods for assessing the levels of metal artifacts in X-ray computed tomography and approaches to their reduction is an almost complete disregard for the physical nature of this artifact—the proximity to zero of radioscopic transparency. The proposed work fills this gap. A mathematical model has been developed for evaluating metal artifacts in X-ray computed tomography as applied to the geometry of a parallel beam. The simulation model was transformed into an algorithm, and a Mathcad program was designed to simulate images of the internal structure of the test objects. The algorithm for estimating the studied artifact includes the stages of generating sinograms and estimating the distributions of the linear coefficient over the sections of the object based on the back projection method with filtering. The efficiency of the metal artifacts simulation algorithm is demonstrated in the example of symmetric and asymmetric objects with low- and high-density inclusions and inclusions from materials with high atomic number values. The possibility of reducing metal artifacts with the help of a rational choice of the maximum energy of X-ray radiation and the ADC bit depth is illustrated. For example, for an aluminum cylinder 200 mm in diameter with a central cylindrical cavity 80 mm in diameter, cylindrical inserts 12 mm in diameter with material densities from 1.5 g/cm3 to 10 g/cm3, and effective atomic numbers of materials from 13 to 47, the numerical simulation method proved the following: it is practically unattainable to significantly reduce the level of metal artifacts by increasing the ADC capacity to the maximum X-ray energy of 160 keV; the desired effect is achieved by simultaneously increasing the maximum X-ray energy to 225 keV and the ADC capacity to 24 or 32; increasing the maximum X-ray energy from 160 keV to 225 keV leads to an increase in the energy absorbed in the material of the test object by 26%. The results of this research can be used at the design stage of X-ray computed tomography systems designed to control objects with fragments of low radiation transparency.

Filtered selective search and evenly distributed convolutional neural networks for casting defects recognition

X-ray flaw detection is a key link in the detection of internal defects in titanium alloy castings which are used for most important components in aeroengines. However, the existing manual defect detection methods from the X-ray images have common drawbacks such as unstable artificial recognition, misdetection, misjudgment, fails of quantitative analysis, huge workload, and low-quality inspection efficiency. To avoid these drawbacks, this paper proposes a new artificial intelligent (AI) method to detect and recognize the aerospace titanium casting defects from the X-ray images. It includes the target defect positioning method named as filtered selective search algorithm (FSS) and the defect classification method named as evenly distributed convolutional neural network (ED-CNN). In the target positioning step, through statistical analysis of defect characteristics, a filtered selective search algorithm is built with two filters (size and edge curvature). In this way, the FSS algorithm can position the defects with almost 100 % of accuracy, hence avoid missed detection and false detection. In the target classification step, an ED-CNN is constructed with a similar structure of the same number of layers in each feature extraction stage, and its entire architecture is evenly distributed. Compared with other three classic high-performance convolutional neural network models (AlexNet, VGG16 and VGG19), the ED-CNN model has the best performance. The ED-CNN model was tested with 324 targets from 50 original images, a classification accuracy of nearly 90 % was obtained for low density holes, porosity, linear defects, high density inclusions and casting structure. The FSS/ED-CNN method of two phases defect detection proposed in this paper can achieve accurate positioning and high accurate classification of typical defect targets, and is expected to solve the common drawbacks of "manual defect detection". The newly-proposed FSS/ED-CNN method has important research significance and engineering value.

Geochronology and fluid evolution of the Machangqing Cu-Mo polymetallic deposit, western Yunnan, SW China

The Machangqing porphyry-skarn Cu-Mo polymetallic deposit is located to the east of the Jinshajiang-Ailaoshan alkaline porphyry metallogenic belt in western Yunnan, SW China. Three major paragenetic stages have been identified in the Machangqing skarn mineralization, namely the (I) prograde skarn stage dominated by anhydrous minerals (e.g., garnet and pyroxene); (II) iron oxide stage dominated by magnetite and quartz, and coexisting hydrous minerals (e.g., epidote, biotite, allanite and chlorite) and trace sulfides (e.g., chalcopyrite, pyrite and molybdenite); (III) the main sulfide stage, dominated by quartz, chalcopyrite, pyrite and minor molybdenite. Zircon U-Pb dating of the ore-related granite porphyry yielded an age of 36.1 ± 0.2 Ma (n = 21; MSWD = 1.13), consistent with the reported skarn-related hydrothermal titanite U-Pb dating of 34.3 ± 1.2 Ma, indicating that the granite porphyry and skarn mineralization are closely related. Trace element compositions of these zircon grains demonstrate a positive Ce4+/Ce3+ (110–816, avg. = 401) vs. Ce/Nd (13.9–101, avg. = 36.0) correlation. The high zircon Ce4+/Ce3+ and Ce/Nd ratios point to an oxidized magma that produced hydrothermal fluids enriched in sulfophilic elements. Stage I garnet contains aqueous (L-type), halite-bearing (SH-type) and undissolved mineral-bearing (SU-type) inclusions, which homogenized at >590 °C with 47.4 wt% NaCl eqv. (SH-type) salinity. The hematite daughter mineral in SU-type indicates that the fluid in this stage is oxidized. Stage II quartz contains multiphase vapor-rich CO2-bearing C-type (4.8–11.1 wt% NaCl eqv.), SH-type (38.8 wt% NaCl eqv.) inclusions and coexisting vapor-rich (V-type) and L-type inclusions, which homogenized at around 350 °C. Stage III quartz contains L-, V-, C-, SH- and SU-type inclusions, which homogenized between 340 and 400 °C, yielding salinities from 2.7 to 20.3 and 29.2 to 53.3 wt% NaCl eqv. The coexistence of low-density (C-/V-type) and high-density (SH-type) inclusions with similar homogenization temperatures suggests that fluid boiling took place in stages II and III. It is concluded that the ore-forming fluids are characterized by high temperature, high salinity, high oxygen fugacity and high CO2 content. Fluid-rock interaction leads to magnetite crystallization and reduces the fluids, while fluid boiling causes escapes of CO2, increasing pH and sulfide precipitation.

Aerospace Titanium Alloy Melt Process Quality Improvements

This Jet Engine Titanium Quality Committee (JETQC) paper describes industry quality improvements since 1990. Quality refers to freedom from melt-related hard-alpha and high-density inclusions (HDI). JETQC, formed under the auspices of the U.S. Federal Aviation Administration (FAA) following the Sioux City aircraft accident in 1989, is comprised of U.S., E.U. and Japanese aircraft engine manufacturers to address the quality of premium / rotor quality titanium alloy production. Titanium suppliers provide melt-related inclusion data. JETQC focuses on hard-alpha and HDI inclusion rates in premium quality (PQ) titanium alloy products for critical rotating aircraft engine applications. PQ materials typically are produced via triple vacuum arc re-melt (3XVAR) or hearth melt VAR (HMVAR) processes, but more recently, the Skull plus VAR (SVAR) process has been introduced. Hard-alpha rates have continued to decline over the last decade primarily for the HMVAR process. HDI rates declined in the early 90’s, but more recently the overall rate has stayed approximately constant with inclusions confined to the 3XVAR process. Combining the trends for both hard-alpha and HDIs, the HMVAR process has demonstrated in recent years to be higher quality compared with the 3XVAR process.

Inclusions in melting process of titanium and titanium alloys

This paper summarizes melting methods of titanium and titanium alloy, such as vacuum arc melting (VAR) and electron beam cold hearth melting (EBCHM), and the related inclusions formed when using these melting methods. Low-density inclusions are resulted from contamination of air, and high-density inclusions are caused by refractory elements. The formation process of inclusions was analysed. The removal mechanism of different kinds of inclusions was specified. Low-density inclusions are removed mainly by resolving. This is a comprehensive process containing reaction diffusion. The resolving rate of high-density inclusions is so low that these inclusions are mainly removed by sedimentation. The experiments and physical models of inclusions are detailed. In various melting methods, vacuum arc melting is prominent. However, this method cannot remove inclusions effectively, which usually results in repeat melting. Electron beam cold hearth melting has the best ability of removing inclusions. These results can provide instructions to researchers of titanium and titanium alloys.

Numerical methods for modeling focused ultrasound in biomedical problems

The focused ultrasound (FUS) based on the cavitation effect is a promising technology that has a number of drawbacks, and the main one is the unpredictability of side effects. Numerical simulation of the influence of FUS on a human body can help to determine main mechanisms and factors that cause an undesirable tissue damage and adjust the medical equipment to avoid it. In this project, two numerical methods were used and compared within the scope of this problem. The grid-characteristic method allows to manage border and contact conditions of any complexity and implement a wide variety of damage models. The method was verified on experimental data from different areas of industry. In this project, it was used for model problems with simple geometry. The discontinuous Galerkin method is a stable and reliable numerical method that is less convenient in terms of border and contact conditions, but imposes fewer requirements on a computational grid. It allowed us to use grids based on real biological data. Both methods allow to obtain the full three-dimensional elastic wave pattern, including shear and surface waves, which are essential for understanding the influence of high-density inclusions on a FUS procedure. The applicability of both methods and their further development is discussed.

Bayesian reconstruction of images of objects with high-density inclusions with suppression of artifacts

The technology of three-dimensional Bayesian tomographic reconstruction of homogeneous objects with high-density inclusions is developed. The approach is based on preliminary correction of projections by extracting the data corresponding to X-rays passing through a high-density region, and replacing it with synthesized data obtained by two-dimensional interpolation. An original method for selecting interpolation points is proposed and a mathematical algorithm is described that ensures the implementation of two-dimensional interpolation correction of projections.

MINGLING PROCESSES IN THE EARTH'S CRUST: GEOLOGICAL OBSERVATIONS AND MATHEMATICAL SIMULATION

This issue of Geodynamics & Tectonophysics presents the state-of-the-art studies of mingling processes and investigations of the interactions between the mafic and acidic melts of contrasting compositions at various depths of the Earth's crust. The diagnostic features and the genesis of magmatic and synmetamorphic mingling are discussed with respect to the reference objects of Altaides and Uralides. Several papers report on the results of mathematical simulation used to discover the mechanism for lifting the high-density basite inclusions in a chamber or a dyke filled with salic magma. This special issue is intended for researchers and specialists in geology, petrology and geodynamics of magmatic processes in the crust, as well as for lecturers, post-graduate students and university students.

Tensile failure observations in sintered steel foam struts revealed by sub-micron contrast-enhanced microtomography

Powder metallurgical open-cell steel foams made of hollow struts are of great interest for impact resistance. Here we report experimental results of high-resolution characterisation of single struts, extracted from a commercially available steel foam. Synchrotron radiation X-ray microtomography reveals that the hollow struts are made of triplets of lens shaped rods, connected to each other along the long axis, appearing triangular in cross-sections. The struts have a non-uniform geometry and they include macro and micropores as well as high-density inclusion powder particles, poorly fused with the matrix. Micro-tensile testing showed that tensile failure is accompanied by longitudinal unzipping due to shear along the thinner material found near the hollow corners. Included, higher-density powder particles deflect crack propagation along the interface with the matrix, where much porosity is observed. Results of finite element simulations well match our mechanical tests, revealing plastic deformation due to bending and significant shear stresses arising between neighbouring rods within the same strut. The failure behaviour and the mechanical response of sintered struts in steel foams produced using non-uniformly coated polyurethane templates is the result of an interplay between the triplet geometry, sub-micron pores, precipitates and high-density inclusions.

Forensic Considerations for Preprocessing Effects on Clinical MDCT Scans

Manipulation of digital photographs destined for medico-legal inquiry must be thoroughly documented and presented with explanation of any manipulations. Unlike digital photography, computed tomography (CT) data must pass through an additional step before viewing. Reconstruction of raw data involves reconstruction algorithms to preprocess the raw information into display data. Preprocessing of raw data, although it occurs at the source, alters the images and must be accounted for in the same way as postprocessing. Repeated CT scans of a gunshot wound phantom were made using the Toshiba Aquilion 64-slice multidetector CT scanner. The appearance of fragments, high-density inclusion artifacts, and soft tissue were assessed. Preprocessing with different algorithms results in substantial differences in image output. It is important to appreciate that preprocessing affects the image, that it does so differently in the presence of high-density inclusions, and that preprocessing algorithms and scanning parameters may be used to overcome the resulting artifacts.

Dissolution of High Density Inclusions in Titanium Alloys

This paper deals with the presence of High Density Inclusions (HDI) in VAR melted titanium ingots. For performance and economical reasons, the elimination of these inclusions is of utmost importance for the titanium industry. However, very few studies have considered dissolution aspects of HDIs and accurate data on their dissolution rates still lack in the literature. In the present study, we investigate the mass transport driven dissolution of some HDIs (tungsten and molybdenum) in CPTi, Ti64 and Ti17 baths. This has been done by allowing the partial dissolution of cylindrical rods in molten titanium for various controlled periods of time. Dissolution rates have been determined by measuring the dimensions of these samples before and after the experiments. In some cases, the chemical composition of the solidified bath near the sample has also been measured by Scanning Electron Microscope. It has been evidenced that the dissolution kinetics depends highly on the liquid metal agitation and temperature. The results also revealed that the dissolution of both tungsten and molybdenum is higher in pure titanium than in the investigated alloys. A numerical model describing the mass transport driven dissolution was used to determine dissolution rates numerically and to compare them to experimental results.

Carbonic fluid inclusions in amphibolite-facies pelitic schists from Bodonch area, western Mongolian Altai

We report first fluid inclusion data on amphibolite-facies pelitic schists from Bodonch area of western Mongolian Altai in the Central Asian Orogenic Belt. Three categories of fluid inclusions have been observed in quartz: dominant primary and secondary inclusions, and least dominant pseudosecondary inclusions. The melting temperatures of all the categories of inclusions lie in the narrow range of -57.5 °C to -56.6 °C, close to the triple point of pure CO2. Homogenization of fluids occurs into liquid phase at temperature between -33.3 °C to +19.4 °C, which convert into densities in the range of 0.78 g/cm3 to 1.09 g/cm3. The estimated CO2 isochores for primary and pseudosecondary high-density inclusions is broadly consistent with the peak metamorphic condition of the studied area (6.3-7.3 kbar at 655 °C). The results of this study, together with the primary and pseudosecondary nature of the inclusions, indicate CO2 was the dominant fluid component during the peak amphibolite-facies metamorphism of the study area. The examined quartz grains are texturally associated with biotite, kyanite and staurolite, which are regarded as high-grade minerals formed during prograde to peak metamorphism. Therefore quartz probably formed by high-grade metamorphism and the primary fluid inclusions trapped in the minerals probably preserve fluids at around peak metamorphism.

Reflection reduction by three-dimensional and two-dimensional phononic crystal slabs

A thin rubber coating with scatterer inclusions in a periodic lattice can redistribute sound energy, normally incident on a steel plate in water, in the lateral direction. The scattered energy can be absorbed by the rubber material and the reflection amplitude in the water can be reduced significantly. Coatings with different scatterer material types are here compared: air-filled cavities, high-density inclusions, and high-density inclusions coated by soft silicone rubber (which have attracted much interest in recent phononic crystal research). For each material type, scatterers of spherical (in a doubly periodic lattice) or cylindrical (in a lattice with a single period) shape are considered. Each coating type is optimized by differential evolution, varying a number of material and geometrical parameters to minimize the maximum reflectance within a certain frequency band. The layer multiple-scattering method is used as forward model. Good broad-band reflectance reduction is achieved with cavities (monopole scattering), but even better results are obtained with the coated high-density inclusions (dipole scattering). Combined with mixing scatterers of different sizes, the cylindrical shape, with scatterers in a lattice with a single period, is very powerful. The sensitivity of the performance to different parameters, as well as the incidence angle, is illustrated.

450 kW plasma melting system

Plasma melting technology can be used to meet the scrap recycle needs of reactive metals, superalloys and refractory materials such as titanium, zirconium and uranium alloys. Fabrication involving these reactive metals, share the common problem of generating a large amount of scrap where both low and high density inclusions become highly prevalent. Plasma melting technology can be used for re-melting, refining and production of premium grade metal ingot. 450kW multi-torch plasma melting furnace is developed and commissioned by Laser & Plasma Technology Division for the re-melting and refining of metals and scraps under controlled environment. This paper presents the vacuum system design for 450 kW plasma melting furnace. The efficacy of vacuum system in cold condition is also tested and the results are included in the paper. The vacuum feed through design for the plasma torch handling mechanism is also discussed.