Diffusion Zone Research Articles

Dynamic track model of miscible CO2 geological utilizations with complex microscopic pore-throat structures

Monitoring field-scale CO2 geological utilizations is of paramount importance but challenging due to the complexities in microscopic heterogeneity. In this paper, complex geological characterizations and fluid properties are specifically analysed and a prediction model is developed, which is capable to track the dynamic behaviour of miscible CO2 multiphase flow in microscopically-heterogeneous porous media. More specifically, first, pore-throat sizes and distributions were characterised from the constant-rate mercury injection and the CO2-displacement seepage resistance was evaluated from a capillary bundle model. The differences of seepage resistance caused from the throat changing and coupling diffusion-dissolution effects and viscosity-resistance reductions were specifically studied in the process of continuous miscible CO2 displacement. Accordingly, a comprehensive mathematical model was developed with the time-node analysis method and validated through comparison with the experimental results. The leading edge of CO2 displacement as well as the timing of gas breakthrough and displacement completion are determined to be different with varying throat sizes. It is further found that the gas breakthrough time and the time required to complete the displacement are reduced with increasing throat size and their differences also decrease. Moreover, the interval area of injection and production wells could be characterised as pure CO2, diffusion and pure oil zones, whose positions could be dynamically tracked from the recovery performance. The calculated oil recovery and gas-oil ratio from the developed model share good agreement with experimental results, with deviations of 2.2 and 0.7%. Such the validated mathematical model is then applied to successfully predict the dynamic performance of an actual reservoir (H3).

Parameter Studies on Hydraulic Fracturing in Brittle Rocks Based on a Modified Hydromechanical Coupling Model

In this paper, we present a numerical study of hydraulic fracturing in brittle rock by using particle flow simulation. The emphasis is put on the influence of in situ stress, differential stress, fluid injection rate, fluid viscosity and borehole size on hydraulic fracturing behavior. To this end, an improved hydromechanical coupling model is first introduced to better describe fluid flow and local deformation of particle-based rocks. A series of parameter sensitivity studies are then conducted under the framework of particle flow simulation. Modelling results suggest that the breakdown pressure and time to fracture both linearly increase with confining stress, and hydraulic fracturing patterns present a distinct transition from brittle to ductile. Fluid injection rate and fluid viscosity have similar influences on hydraulic fracturing propagation, their value decrease leads to borehole pressure decrement and time to fracture prolongation. However, the former mainly controls the time to initial cracking, while the latter largely decides the duration of fracturing propagation. As for borehole radius, its increases can directly enhance the fluid diffusion zone, which further intensifies the nonlinear property of borehole pressure, leads to breakdown pressure decrease, prolongs time to fracture and forms more complex hydraulic fractures.

Brazing of TiAl and Ti2AlNb alloys using high-entropy braze fillers

To address the excessive formation of brittle compounds when brazing TiAl alloys, a TiZrHfCoNiCu high-entropy brazed filler was developed to realize the brazing of TiAl/Ti 2 AlNb couples. The TiAl/Ti 2 AlNb brazed joints can be divided into 4 zones, i.e., 2 diffusion zones at the TiAl/braze filler, Ti 2 AlNb/braze filler interfaces and 2 zones divided inside the brazed seam. α 2 + γ-TiAl were the main reaction products formed at the TiAl/braze filler interface and α 2 + Ti 0.5 Al 0.12 Nb 0.38 were the main reaction products at the Ti 2 AlNb/braze filler interface. Effects of brazing temperatures on the interfacial microstructure and mechanical properties of the TiAl/Ti 2 AlNb brazed joints were investigated. When brazing at 1100°C/15 min, the highest shear strength can reach 157 MPa (room temperature), and 123 MPa (650°C) respectively. The relationship between the microstructure and the corresponding mechanical response were discussed in detail. This research can offer new insights on developing desirable brazing filler when joining TiAl and TiAl based alloys. • A TiZrHfCoNiCu high-entropy alloy braze filler was developed to realize the brazing of TiAl/Ti2AlNb couples. • Ti 0.5 Al 0.12 Nb 0.38 and α 2 + γ-TiAl formed at the braze filler/base metal interfaces were the key to realize the joining. • The α 2 + γ-TiAl at the TiAl/braze filler interface was preferential to crack for the strongest brazed joints. • Highest shear strength of 157 MPa (room temperature) and 123 MPa (650°C) were achieved at 1100°C/15 min.

Active Tectonics of the North Tunisian Continental Margin

AbstractA poorly defined boundary between the Nubia and Eurasian plates runs along the Northern Tunisian continental margin. The Tunisia margin is deformed by a slow NW–SE trending convergence resulting in a diffuse deformation zone with scarce and scattered seismicity compared to the seismic activity into the neighboring regions to the east and west along the boundary. The area has been poorly studied and therefore its recent evolution is almost unknown, particularly offshore. Here, we present a structural analysis of the active tectonics in this submarine continental margin. The data used for this analysis are high‐resolution bathymetric maps together with parametric echosounder images which have allowed to obtain a map of active faulting with unprecedented detail. The structural analysis supports a dominantly transpressive to compressive component of faulting, resulting from the current regional NW–SE trending compressive regime between plates. The North‐eastern Domain of the study region contains the highest number of active faults with numerous pockmarks aligned along them. This study shows that the plate boundary across the North Tunisia margin is incipient and poorly developed, which may be due to the fact that deformation is partitioned over a large number of structures, each accommodating a small percentage of convergence, with the exception of the Hayat fault system. The Hayat reverse fault, striking WSW–ENE, is the largest fault system that comparatively may accommodate a greater amount of displacement, and is probably responsible for the uplift of the North‐eastern Domain of the continental margin.

Interfacial microstructure and mechanical behavior of low-temperature diffusion bonded Mo/SS304 joints using NixCu1-x interlayers

To join dissimilar metals with significant differences in characteristics, such as molybdenum (Mo) and stainless steels (SS), is essential to take full advantage of their combined performances. In this work, Mo and SS304 have been jointed with Ni interlayer using a diffusion bonding technique at different bonding temperatures. The results show that a MoNi brittle intermetallic compound is easy to form in the interface of the Mo/SS304 joint with increasing the bonding temperature, which will reduce the shear strength of the joint because a crack is easy to form between Mo and the intermetallic compounds. Meanwhile, Mo/SS304 joints have also been prepared by using Ni x Cu 1-x (x = 0.45, 0.24, or 0) as an interlayer. The result shows that reducing Ni content can avoid the formation of intermetallic compounds, and the fracture occurs between the interlayer and Mo diffusion zone far away from the Mo side. This work shows that the fracture properties of the Mo/SS304 joint can be modified by changing the composition of the interlayer. The best shear strength of the Mo/SS304 joint is 140 MPa. This work is essential for effectively joining Mo and SS304 using a low-temperature diffusion bonding method.

Structural and morphological study of the Al–Si–Mg–SiC composite material produced by mechanical alloying

The research focuses on aluminum composite granules obtained by the mechanical alloying of VAS1 aluminum alloy and silicon carbide initial powders. It was found that the morphology and average size of composite granules change as the time of mechanical alloying increases. There are the processes of aluminum matrix plastic deformation and the introduction of silicon carbide particles into the matrix, «cold welding» of agglomerates to each other and the growth of an average granule size up to 550 μm that occur for 40 hours of processing. After longer mechanical alloying (60 h), the structure of composite granules becomes uniform, and the average particle size reaches ~150 μm remaining virtually unchanged as the process time increases. X-ray analysis showed that there is a change not only in the morphology of composite granules, but also in their internal structure: coherent scattering regions decrease, the lattice constant of the aluminum matrix alloy changes, microdeformations and stacking faults increase. Transmission electron microscopy studies were conducted in order to study the material microstructure more deeply. Their results proved that the material has a uniform ultra-fine grain structure. The solid solution of aluminum has a maximum grain size of 160 nm. Dislocation density in the composite is rather high. The structure features nanosized plate-like Si particles and silicon carbide existing in the material as distributed splintery coarse particles. No diffusion zone between SiC particles and the base material was found.

Effect of Diffusion on Dissimilar Welded Joint between Al0.8CoCrFeNi High-Entropy Alloy and S235JR Structural Steel

This research focused on the investigation of the metallurgical behavior of the Al0.8CoCrFeNi high-entropy alloy and S235JR structural steel, welded with (Ni, Fe)-rich filler metal, by the Gas Tungsten Arc Welding (GTAW) method. The electric arc and the welding pool were protected against the contamination with gases from the environment, by employing high-purity Ar 4.8 inert gas that plays an important role in reducing the oxidation effects and the development of cracks in the weld and the adjacent areas. The microstructure and microhardness analysis did not reveal the existence of fragile phases, cracks, inadequate penetration, or other imperfections, showing an appropriate adhesion between the deposited metal and the substrates. At the interface between the Ni-rich weld metal and the high-entropy alloy, a higher hardness (448 HV0.2) than in the base material (358 HV0.2) was measured. Energy-dispersive X-ray analysis (EDS), performed at the interface between the weld metal and the base materials, did not show significant modifications of Co, Fe, and Cr percentages. However, during the investigation, significant variations in Al and Ni concentrations were observed, caused by the fast diffusion of chemical elements, and the development of hard (Ni, Al)-rich compounds. In some areas of the deposited metal, located at a distance of about 10 µm from the interface, the percentages of Ni and Al were higher than in the high-entropy alloy base material, being around 41% by weight Ni and over 13% by weight Al, while the concentrations of the Co, Cr, and Fe elements proportionally decreased (i.e., approximately 14% by weight Co, 12% by weight Cr, and 17% by weight Fe). The development of Ni3Al and NiAl compounds was also noticed, whose formation was determined by the local chemical concentration and the temperature reached in the vicinity of the diffusion zone. The XRD analysis showed a group of X-ray peaks in the Al0.8CrFeCoNi alloy that corresponded to both α-type—BCC and FCC phases. The crystallite size of the high-entropy alloy investigated was found to be 22.05 nm. Despite the diffusion phenomenon, if filler materials and process parameters are appropriately selected, quality joints of high-entropy alloys and structural steels can be carried out under good welding conditions.

The Feasibility and Long-Term Outcomes of the Crossboss/Stingray for Treating Coronary Chronic Total Occlusions Lesions with Distal Diffuse Disease Landing Zone

The feasibility and long-term outcomes of the CrossBoss/Stingray for treating coronary chronic total occlusions (CTO) with distal diffuse disease landing zone remain unclear. Consecutive CTO patients with distal diffuse lesions that underwent percutaneous coronary intervention by the CrossBoss/Stingray system at Xijing Hospital from April 2016 to October 2020, were included. Patients were analyzed by two groups according to the extent of stenosis in the distal landing zone: 50%-70% stenosis (moderate stenosis group) and >70% stenosis (severe stenosis group). The primary efficacy outcome was technical success, defined as the frequency of true lumen guidewire placement distal to the CTO. The composite endpoint of all-cause death, any stroke, or any revascularization was also explored. A total of 91 consecutive patients were included, with 32 patients in the moderate stenosis group and 59 patients in the severe stenosis group. The mean J-CTO score was 2.5 ± 1.1. The technical success rate was 79.1% (72/91) in the overall population and was similar between the 2 groups: 78.1% (25/32) and 79.7% (47/59) (p = 0.608). No coronary perforation occurred. With a median follow-up of 29 months (IQR: 53-92), the estimated rate of the composite endpoint of all-cause death, any stroke, or any revascularization was 50.4% (all-cause death: 16.6%, any stroke: 1.1%, any revascularization: 36.5%) in the overall population. No significant difference was observed in the rate of the composite endpoint between the moderate stenosis group and the severe stenosis group (45.1% vs. 54.3%, respectively, p = 0.797). In CTO lesions with distal diffuse disease landing zone, the technical success rates of CrossBoss/Stingray and the long-term clinical outcomes were not significantly different between the moderate stenosis group (50%-70%) and the severe stenosis group (>70%). However, the relatively high rate of long-term clinical outcomes, especially any revascularization, warrants further investigations on this indication in future studies.

Sourcing of chalkstone used in medieval buildings in the Eastern Duchy of Normandy (10th−14th centuries) through geological and geochemistry analyses

AbstractThe provenance of medieval building stones links historic constructions with their quarrying areas, thereby revealing medieval trade routes and the spatial organization of past societies. In northern France, the Duchy of Normandy played a significant role in the medieval history of Europe, situated at the centre of the disputes between the English and French kingdoms. However, the historical documentation from this period is scarce, particularly in terms of the quarrying industry. Our study aims to define the quarrying areas and their diffusion zones and map the territorial organization of Eastern Normandy during the 10th–14th centuries. A multidisciplinary procedure using archaeological, geological and geochemical techniques was designed to establish the provenance of Normandy Chalkstone. First, we obtained a representative assembly of building stones by the selection and strategic sampling of 22 buildings. Second, we determined areas of chalk bedrock from a geological map rendered through GIS and sampled chalkstones from natural outcrops and quarries. In total, 118 samples from buildings, quarries and natural outcrops were characterized via optical microscopy and geochemical analyses for major, minor and trace elements (XRF, ICP‐MS and ICP‐OES), as well as for 87Sr/86Sr isotope ratios (MC‐ICP‐MS). The application in situ of pXRF analysis allows for the identification of Normandy Chalkstone sources preserved in archaeological sites. The results indicate that all chalkstones came from five local varieties of Normandy Chalkstone and one of Shelly Limestone imported from nearby regions. The suitability of chalkstone as construction material was evaluated in situ using a sclerometer, which revealed that the singular and local geological features of the chalkstone make it suitable for walling. Our study demonstrates the development of a prominent and relatively continued quarrying industry over the 10th to 14th centuries in Eastern Normandy. The main quarrying areas were constituted of three chalkstone diffusion zones that run coevally with smaller and apparently sporadic quarries. The chalkstone diffusion was strongly related to the occurrence of singular and local geological resources and the stone transport system, which favoured the use of effective fluvial and maritime navigation for transport over 50 km from the quarrying areas.

Features of formation of diffusion zone obtained on steel 20 by boriding in induction furnace

The article presents data on studies of iron borides synthesis during induction heating to 1000 °C for 5 min of steel 20 samples with a coating from a charge containing Fe – H3BO3. Content of boric acid in the charge varied from 25 to 75 % wt. Charge in the experiments could be diluted with a solution of liquid glass in water with addition of small amount of ammonium hydroxide and coal. Study of the surface layer microhardness showed that during saturation of the surface layer of carbon steel 20 with boron, a macroscopically extensive diffusion zone 900 – 1000 μm in size is formed, in which the boride content gradually decreases when moving deeper into the matrix. Such a size of the diffusion zone indicates an anomalously high mass transfer during boriding of steel 20. Indeed, the calculated diffusion coefficient during boriding under induction conditions (about 1.35·10–9 m2/s) is two orders of magnitude higher than the diffusion coefficient in the classical boriding. X-ray studies showed that, under the considered conditions, Fe2B and FeB borides are synthesized, and a solid solution of boron in α­iron is also formed. An analysis of phase composition of the diffusion zone structural components indicates that, from the surface to the matrix, formation of boride phases occurs in the following sequence: FeB → Fe2B → (α­phase + B) → base metal. Microstructure of the diffusion zone consists of more or less pronounced layers consisting of FeB and Fe2B boride phases. On the whole, especially deep-ying regions of the diffusion zone are a composite material consisting of plastic α-phase and iron boride crystals. Crystals in FeB and Fe2B in the layer are oriented mainly perpendicular to the diffusion front. Perhaps, this is due to the rapid predominant growth of the boride phase under conditions of high diffusion mobility of boron atoms in one direction and hindered in others.

Penetration and microstructure of steel joints by ultrasonic-assisted gas metal arc welding

This work investigates the application of ultrasonic vibration to steel joints formed by gas metal arc welding. Welding is done using a metal active gas welding source with welding current of 120–160 A, 0.8 mm diameter welding wire and 10 l min−1 CO2 flow. The distance from the torch to the ultrasonic horn is 120 mm. Ultrasonic vibration most affects the weld when ultrasonic vibration position is 120 mm from torch and increases the penetration when welding speed is 190 (275) mm/min for a 5 mm thick (10 mm thick) plate. Moreover, weld width increases when welding speed is 190 mm min−1 for 10 mm thick plate. Although ultrasonic vibration does not affect the hardness of welding zones, it modifies the microstructure of the diffusion and welding-pool zones.

INVESTIGATION OF THE EFFECT OF NITROCARBURIZING TREATMENT ON TRIBOLOGICAL PROPERTIES OF AISI 1045 MEDIUM CARBON STEEL

In this paper, the effect of nitrocarburizing treatment on tribological properties of AISI 1045 steel was investigated. This medium carbon steel was used in automotive industry, especially in the manufacture of machine components due to the good mechanical properties and lower cost. Characterization of the surface layer of treated samples was made by optical microscopy (OM), Vickers microhardness test, scanning electron microscope (SEM), and pin-on-disk wear machine. Experimental results showed that the surface layers formed through nitrocarburizing processing at 580 °C (compound layer and diffusion zone) increased the microhardness. It was found also that the nitriding treatment reduced the friction coefficient and improved the wear resistance, where the specific wear rate were decreased to 1/9 was noticed after 10 hours of nitriding time.

Electric-Spark Alloying of Metal Surfaces with Graphite

The article reviews and analyses the current scientific research in the field of surface treatment of metal surfaces with concentrated energy fluxes (CEF) — the electric-spark (in the literature, known also as electrospark) alloying (ESA), which makes it possible to obtain surface structures with unique physical, mechanical and tribological properties at the nanoscale. The ESA method with a graphite electrode (electrospark carburizing — EC) is based on the process of diffusion (saturation of the surface layer of a part with carbon), and it is not accompanied by an increase in the size of the part. In this article, the influence of the EC parameters on the quality of the carburized layer is investigated. The microstructural analysis shows that the three characteristic zones could be distinguished in the structure: the carburized (‘white’) layer, the finely dispersed transition zone with fine grain, and the base metal zone. The analysis of the results of the durometric studies of the coatings is carried out. To achieve the required parameters of dimensional accuracy and roughness of the working surface of the part after the EC process, it is necessary to use the method of non-abrasive ultrasonic finishing (NAUF). In addition, because of applying the NAUF method, the surface roughness is decreased, the tensile stresses are changed to the compressive ones, and the fatigue strength is increased too. In addition, to reduce the roughness of the treated surface, it is proposed to apply the EC technology in stages, reducing the energy of the spark discharge at each subsequent stage. In order to increase the quality of the carburized layer obtained by the EC process, it is proposed to use a graphite powder, which is applied to the treated surface before alloying. The comparative analysis shows that, after the traditional EC process at Wp = 4.6 J, the surface roughness of steel 20 is Ra = 8.3–9.0 μm, and after the proposed technology, Ra = 3.2–4.8 μm. In this case, the continuity of the alloyed layer increases up to 100%; there increases the depth of the diffusion zone of carbon up to 80 μm as well as the microhardness of the ‘white’ layer and its thickness, which increase up to 9932 MPa and up to 230 μm, respectively. The local micro-x-ray spectral analysis of the obtained coatings shows that, at the EC process carried out in a traditional way, the applying Wp = 0.9, 2.6, 4.6 J provides the formation of the surface layers with high-carbon content depths of 70, 100, 120 μm, respectively, and with the use of a graphite powder, they are of 80, 120, 170 μm. While deepening, the amount of carbon is decreasing from 0.72–0.86% to the carbon content in the base metal — 0.17–0.24%. In the near-surface layer formed with the use of the new technology, the pores are filled with free graphite, which could be used as a solid lubricant to improve the operating characteristics of the friction-pairs parts processed thereby.

B-Cell NHL Subtype Risk Associated with Autoimmune Conditions and PRS.

A previous International Lymphoma Epidemiology (InterLymph) Consortium evaluation of joint associations between five immune gene variants and autoimmune conditions reported interactions between B-cell response-mediated autoimmune conditions and the rs1800629 genotype on risk of B-cell non-Hodgkin lymphoma (NHL) subtypes. Here, we extend that evaluation using NHL subtype-specific polygenic risk scores (PRS) constructed from loci identified in genome-wide association studies of three common B-cell NHL subtypes. In a pooled analysis of NHL cases and controls of Caucasian descent from 14 participating InterLymph studies, we evaluated joint associations between B-cell-mediated autoimmune conditions and tertile (T) of PRS for risk of diffuse large B-cell lymphoma (DLBCL; n = 1,914), follicular lymphoma (n = 1,733), and marginal zone lymphoma (MZL; n = 407), using unconditional logistic regression. We demonstrated a positive association of DLBCL PRS with DLBCL risk [T2 vs. T1: OR = 1.24; 95% confidence interval (CI), 1.08-1.43; T3 vs. T1: OR = 1.81; 95% CI, 1.59-2.07; P-trend (Ptrend) < 0.0001]. DLBCL risk also increased with increasing PRS tertile among those with an autoimmune condition, being highest for those with a B-cell-mediated autoimmune condition and a T3 PRS [OR = 6.46 vs. no autoimmune condition and a T1 PRS, Ptrend < 0.0001, P-interaction (Pinteraction) = 0.49]. Follicular lymphoma and MZL risk demonstrated no evidence of joint associations or significant Pinteraction. Our results suggest that PRS constructed from currently known subtype-specific loci may not necessarily capture biological pathways shared with autoimmune conditions. Targeted genetic (PRS) screening among population subsets with autoimmune conditions may offer opportunities for identifying those at highest risk for (and early detection from) DLBCL.

Chemical analysis of irradiated root dentin and its interaction with resin cements.

To investigate the chemical changes in root dentin submitted to ionizing radiation and how it affects the interaction with resin cements. Forty human premolars were randomly divided into two groups (n = 20): non-irradiated and irradiated. They were randomly subdivided according to the type of resin cement (n = 10): conventional (RelyX ARC, 3M ESPE) or self-adhesive (RelyX U200, 3M ESPE). After cementation of the fiberglass posts, the roots were sectioned to be analyzed by Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and confocal laser scanning microscopy (CLSM). The data obtained from FTIR and Raman were analyzed using two-way ANOVA followed Tukey's test (α = 0.05). For CLSM, a descriptive analysis was performed. In the FTIR, there was a significant difference between the non-irradiated and irradiated groups for phosphate (p = 0.011), carbonate (p < 0.001), amide III (p = 0.038), and carbonate/mineral ratio (p < 0.001). Regarding the root third, there was a difference for amide I (p = 0.002), mineral/matrix ratio (p = 0.001), and amide I/CH2 (p = 0.026) between the cervical and the others. Raman spectroscopy revealed no difference between groups for 961/1458cm-1 in the diffusion zone. CLSM showed a different interaction pattern for the two cements with the irradiated dentin from the cervical third. Ionizing radiation altered the chemical composition of root dentin, especially in the cervical third. The resin cements showed less interaction with the irradiated root dentin. As radiotherapy alters the chemical composition of root dentin, the interaction of resin cement with dentin can compromise the success of rehabilitation with fiberglass posts.

Spark plasma joining of HfB2-ZrB2 based Ultra High Temperature Ceramics using Ni interlayer

Real-life applications of ultra-high temperature ceramics (UHTCs) mandates the joining processes to realize the final complex shapes, often resulting in the compromised performance of metallic interlayer. In the present work, two pre-sintered HfB2-ZrB2 (HZ) and HfB2-ZrB2-SiC (HZS) composites were joined using interlayer of Ni powders via spark plasma sintering (1100 °C, 18 MPa). Solid-state diffusion of Ni into UHTCs has resulted in the formation of continuous and crack free interface in both HZ/Ni/HZ and HZS/Ni/HZS joints. Microstructure and phase analysis revealed the presence of nearly equal Ni-rich joint seam (∼100 μm) and diffusion zone width (∼150 μm) in HZ/Ni/HZ joint. However, prominent reaction of Ni with SiC in HZS composite has formed Ni2Si, while exhibiting wider diffusion zone (∼200 μm) and thinner Ni-rich joint seam (∼30 μm). Thus, microstructural inhomogeneity in HZ/Ni/HZ joint resulted in an overall reduction of ∼38% in hardness from parent HZ region (15.6 GPa) to Ni-rich joint (∼10 GPa), whereas for HZS, a uniform micro-hardness of ∼16 GPa was obtained in all the three regions owing to microstructural homogeneity across the interface. Damage tolerance of the joints has also been investigated by micro-scratch testing, revealing dominant abrasive wear in the parent UHTC region, whereas plastic deformation along with the tensile cracks is observed in the Ni-rich joint seam of HZ/Ni/HZ joint. In contrast, microstructural homogeneity in HZS/Ni/HZS joint has resulted in similar abrasive wear along with limited tensile cracks in all the regions, including that of Ni-joint seam, making it suitable for attaining superior structural integrity in joining complex shapes.

Active seismotectonics of the East Anatolian Fault

SUMMARYThe East Anatolian Fault (EAF) is a 700-km-long left-lateral transform fault located between the Anatolian and Arabian plates. The proximity of the Euler Pole to the Arabia–Anatolia Plate boundary leads to rapid changes in plate velocity along the boundary, which is manifested by the decreasing slip rates from east (10 mm yr–1) to west (∼1–4 mm yr–1). The EAF displays heterogeneous seismicity patterns with seismic gaps, localized clusters and broad diffuse zones. In this study, in order to understand the origin of these complexities and quantify the seismic hazard along the EAF, we present an improved seismicity catalogue with more than 26 000 earthquakes and 160 focal mechanisms from regional moment tensor inversion between 2007 and 2020. The focal mechanisms and seismicity show that the EAF dips towards north and forms a well-defined plate boundary in the east between Palu and Çelikhan with almost pure left-lateral motion. Further west, the boundary becomes broader with activity along subparallel faults. Focal mechanisms show heterogeneous stress orientations in consistence with geodetically determined strain rate field. The stress orientations show a transition from strike-slip to extension towards the west of Çelikhan. Amongst all segments of EAF, the Pütürge segment, which holds the near-repeating earthquakes in the vicinity of the nucleation of the 2020 Mw 6.8 earthquake, is distinguished with its steady and high rate of seismicity. Further east, the neighbouring Palu segment is characterized by several distinct moderate earthquakes. We do not observe any change in the seismicity rate on these segments of the EAF following large earthquakes. In order to quantify the seismic hazard along the EAF, we calculate the recurrence time and maximum magnitude for each segment by using an extended seismicity catalogue of 150 yr including the large historical earthquakes and the geodetic strain rate. The results show ∼150 yr recurrence time with Mmax∼6.7–7.0 along the seismically active Palu and Pütürge segments on the east, while relatively silent western segments yield longer recurrence times; 237–772 for Pazarcık and 414–917 for Amanos segments with slightly larger magnitudes (Mmax ∼7–7.4). We infer that the seismicity patterns and strain-rate field along the EAF are shaped by several factors such as strong geometrical irregularities, heterogeneous coupling and complex plate motion leading to rapid change of fault slip rate.

Investigation of the Diffusion Zone Formation Mechanisms during the Production of Functional Steel-Aluminium Compositions by Arc Processes

Interaction at the interface during the production of functional steel-aluminum compositions by arc processes has been investigated. Regularities and mechanisms of the diffusion zone formation have been proposed upon contact of a melt based on aluminum, alloyed with 11-13 wt% Si, with the steel substrate or Al-Fe system intermetallic compounds. It was found that the presence of Si in the composition of filler material leads to diffusion mobility of Al and Fe decreasing due to the replacement of Al, as well as the occupation of structural vacancies in double FexAly intermetallics and ternary intermetallic phases with different stoichiometric composition FexAlySiz formation. It was determined that during the arc cladding process using as substrate the steel with intermediate zinc coating, a diffusion zone with an average thickness of 7 μm is formed, while in the presence of an intermediate coating from aluminum deposited by the “cold metal transfer” process, its average thickness is 18 μm.

Features of Formation of a Diffusion Zone on Steel 20 Obtained by Boriding in an Induction Furnace

Features of Formation of a Diffusion Zone on Steel 20 Obtained by Boriding in an Induction Furnace

Grain boundary segregation in Si-doped B-based ceramics and its effect on grain boundary cohesion

Boron carbide and boron suboxide are attractive for their low densities and ultrahigh hardness values, yet they exhibit poor fracture resistance. Strategies to improve mechanical performance aim to control bulk microstructures and properties by incorporating Si-based additives. A related approach to toughen boron carbide is tailoring the phase-like states of grain boundaries by applying the concept of grain boundary complexion engineering. This work directly investigates the potential of grain boundary complexion engineering to improve fracture resistance by systematically evaluating grain boundary segregation behavior of a polycrystalline silicon hexaboride / boron carbide diffusion couple using aberration-corrected scanning transmission electron microscopy and ζ-factor microanalysis. A main result was that all grain boundaries in the diffusion couple exhibited Si segregation that, depending on the bulk Si concentration, approached up to 3 monolayers of coverage, thereby resulting in nanolayer complexions (oftentimes known as intergranular films). Furthermore, upon analyzing 110 distinct grain boundaries throughout the diffusion zone and an impurity boron suboxide region, free energies of Si segregation in boron carbide and boron suboxide were experimentally determined using the Brunauer, Emmett and Teller (BET) multilayer grain boundary segregation theory. Subsequently, changes in grain boundary energy due to Si segregation were quantified and a maximum energy reduction of 51% and 81% were observed in boron carbide and boron suboxide, respectively, which led to decreases in works of adhesion of 18% and 17%, respectively. In summary, this work uncovers grain boundary processing-structure-property relationships that can be used to improve the fracture resistance in icosahedral boron-based ceramics.