Zone Melting Research Articles

Oxygen-rich combustion behaviors and mechanisms of a new Ni-Cr-based superalloy fabricated by selective laser melting

The mechanical and combustion behavior of a new Ni-Cr-based superalloy, fabricated by selective laser melting in an atmosphere with an oxygen concentration greater than 99.5 %, was investigated through the analysis of microstructural morphology, elements distribution and combustion kinetics. The results show that heat treatment eliminated the anisotropy of the as-built microstructures and improved the tensile strength. The studied superalloy can be ignited with a combustion threshold of about 2.5 MPa–3 MPa. The burning length and burning rate increase with the increase of pressure. The selective combustion of Al, Ti, Nb, Cr, Fe, Mo, and Cu elements occurred, resulting in the dissolution of γ′, γ", and δ precipitates and formation of holes at the grain boundaries in the heat-affected zone. The microstructures exhibit large elongated grains in the melting zone and column grains in the heat-affected zone along the heat dissipation direction. The combustion products are a mixture of oxides exhibiting dendritic structures in terms of selective combustion, density, and melting point. The findings from this study enhance our comprehension of the combustion process in nickel-based superalloys, offering valuable data and guidance for the advancement of new oxygen-rich combustion-resistant superalloys.

Cooling Air Velocity on Iron Ore Pellet Performance Based on Experiments and Simulations

During the pellet cooling process, cooling air velocity is crucial for optimizing the cooling rate, evaluating the utilization rate of cooling heat energy, and improving pellet performance. As the simulated cooling air velocity increased, the gas temperature at the cooling endpoint decreased from 87 °C to 51 °C, and the solid temperature decreased from 149 °C to 103 °C. The total enthalpy of the recovered gas initially reduced and then increased while the heat recovery rate gradually increased. During the experiment, the inhomogeneity of pellet quality gradually increased with the rise in cooling air velocity. The effect of cooling air velocity on pellet properties is primarily reflected in the formation of cracks and low-melting liquid phases (FeO and fayalite). As the cooling air velocity increases, the softening onset temperature of the pellet decreases significantly. The melting zone decreases from 193 °C to 105 °C, and the permeability of the adhesive zone increases.

Energy-efficient microwelding of copper by continuous-wave green laser: Insights into nanoparticle-assisted absorptivity enhancement

As a highly reflective material, copper has been difficult to weld with IR lasers. Short-wavelength (400–600 nm) lasers offer promising solutions to copper welding due to significant increases in absorptivity (to > 50 %). In this work, we present an experimental study on copper welding by CW green laser. We unveil that nanoparticles redeposited on the copper surface from the vaporized plume can strongly modify the surface condition and result in significant enhancement of the surface absorptivity. The absorptivity can be theoretically enhanced by nanoparticles up to 82 % compared to the polished copper surface. Assisted by this absorptivity enhancement, the threshold power density (critical laser intensity) for copper melting is reduced by more than 50 %, so that continuous and smooth conductive welding tracks can be generated in energy-efficient manner. In situ deposition of nanoparticles generated upon cooling and oxidation of the vapor plume in the vicinity of the melt zone has been identified as the key mechanism of absorptivity enhancement. XPS measurements of the nanoparticles indicated that Cu2O is the dominant species in the redeposited nanoparticles. This study provides novel insights into the fundamental mechanisms in highly-reflective material welding by short-wavelength lasers and offers an opportunity for energy-efficient high-quality welding of highly-reflective material thin films, which can find numerous applications in consumer electronics and electric vehicles, as well as battery industries. Moreover, it enables a new process-material-environment design route for laser additive manufacturing of nanoparticle-reinforced metal matrix composites.

The influences of nanoparticles on the microstructure evolution mechanism and mechanical properties of laser welded stainless steel/aluminum

In order to solve the problem of poor performance of welded joints of steel and aluminum dissimilar materials, this study proposes the use of ceramic particle-reinforced aluminum alloy as an alternative to traditional aluminum alloy for welding, effectively overcoming this problem. In this paper, the laser welding of stainless steel/6061 aluminum alloy (SA) and stainless steel/TiC–TiB2 duplex nanoparticle-reinforced 6061 aluminum alloy (SRA) was realized. The effect of ceramic nanoparticles on the microstructure and mechanical properties of SRA joint was systematically studied, and the strengthening mechanism of nanoparticles was revealed. Under the same process parameters, the melting zone of SRA joint is larger and the intermetallic compound (IMCs) layer is narrower. Moreover, the grain size of the brittle Fe–Al compound phase in the IMCs layer is significantly reduced, which effectively inhibits the initiation of cracks at the steel/aluminum interface. The study shows that ceramic particles have a pinning effect on the dislocations, limiting the grain growth, reducing the thickness of the intermetallic compound layer, and decreasing the content of the brittle FeAl3 phase. Moreover, ceramic nanoparticles promote the formation of Mg2Si strengthened phase at the grain boundary, further hinder the dislocation movement and improve the strength of the joint. Under the welding power of 3400 W and welding speed of 31 mm/s, SRA joint achieves the maximum tensile shear of 1718 N, which is 15% higher than the strength of SA joint.

Evaluation of melting front kinetics in cylindrical phase change materials module using infrared thermography and digital imaging

An experimental study examined buoyancy-driven convection in the unconstrained melting of PCM within a cylindrical module. Melting progress and PCM fraction were analyzed using IRT and digital imaging. Initial symmetric melting led to accelerated phase change at the bottom and a rippled PCM surface. Thermal stratification in the lower module was evident, with molten liquid displacing colder fluid. Observations underestimated bottom PCM waviness and melting. As the melt zone expanded, buoyancy-driven convection intensified, speeding up melting at the top while the bottom relied more on conduction. The study details transient front positions, temperature profiles, solid PCM amounts, and melting times. Unstable fluid layers near the bottom caused waviness due to chaotic fluctuations. Nucleation rates critically impacted PCM crystallization kinetics and properties.

The effect of laser surface melting on the microstructure, microsegregation and solidification path of service-aged ECY768 cobalt-based gas turbine nozzle

In this study, the laser surface melting of cobalt-based superalloy ECY768, which has been in service for 40,000 h at a temperature of 1000 °C, has been investigated. Subsequently, laser surface welding and post-welding heat treatment is performed on the samples. This study was conducted in order to restore the microstructure of the damaged service-aged gas turbine nozzle to as-cast state. The results showed that by performing laser surface remelting, the microstructure of as-cast state can be approached. Also, the results of this study have investigated the weldability, microsegregation and solidification path of this superalloy, and it can be used in the repairing this superalloy in the industry. Laser surface melting was performed using a continuous wave fiber laser at various speeds of 10, 12, 14, 20, 50, and 70 mm/s. The microstructure and phase characteristics of the samples were examined using optical and scanning electron microscopes. Upon analyzing the macrostructure of the weld metal, it was observed that the depth of the melt zone at the speed of 12 mm/s is 585 ± 40 μm. In the investigating the microstructure of the solidification modes, namely planar, cellular, columnar dendritic, and equiaxed dendritic, it was observed that microsegregation occurs during laser welding of the samples due to the presence of heavy elements such as tantalum and tungsten. The solidification distribution coefficient for tantalum was calculated to be 0.37, which increased to 0.60 after the solution annealing heat treatment, resulting in an improved segregation behavior. Characterizing the surface hardness profiles of laser-melted samples it was observed that the hardness in the melt zone significantly increased compared to the base metal. The results of the current research indicate that the weldability (resistance to various welding defects, especially hot cracks) of the cobalt-based superalloy ECY768 is acceptable, and this process can be used for rejuvenating service-aged ECY768 cobalt-based gas turbine nozzle.

Increasing the Efficacy of an Air Conditioning Unit by Utilizing Phase Change Material With Cylindrical Configuration

ABSTRACTThe goal of the current study is to determine how the SST and the standard turbulence models prediction on PCM with cylindrical configuration affect AC performance and PCM discharging when coupled with an AC unit. For simulation, 308.15 K and 318.15 K, the inflow air temperature has been considered with a fixed 33.6 L/s intake air flow rate. The low outside temperature charges the PCMs during the night. During the daytime, heated ambient air is cooled by the PCM heat exchanger before passing over the unit condenser. The present outcomes show that using the standard model, the cylindrical PCM has the lowest time of complete melting. The temperature contours demonstrate that turbulence occurs, particularly at higher temperatures, in the PCM melting zone within the solid region. This implies that there is increased convection in this area. The maximum improved percentage in COP increases as the rising input air temperature for both turbulence models increases. The average power saving of AC at 308.15 K of an input air temperature for 83.33 min is predicted by both the standard and the SST to be 14.0905 W and 14.1089 W, respectively.

Characteristics of structural defects of Cd0.9Zn0.1Te crystals grown by vertical zone melting

Large-size Cd0.9Zn0.1Te crystals were grown using high-pressure vertical zone melting. It has been found that Te inclusions ranging 70–150 μm with density 3.5·102 cm−2 are formed during crystal growth under conditions specified in this work. Optical spectra display the transmission of the CZT crystals in near- and medium infrared range, which is close to theoretical value and does not degrade despite presence of Te inclusions. Based on the obtained data on sizes and distribution of the inclusions, diffusion coefficient of tellurium in CZT was estimated for Te particles entrapped by growing interface. The calculated value (1.22–3.2)·10−8 cm2/s most probably indicates vacancy mechanism of diffusion. Density of in-grown dislocations revealed by chemical etching is 4·104 cm−2. Branched 3D dendrites are found in CZT crystals.

Regulation of dynamic recrystallization in p-type Bi2Te3-based compounds leads to high thermoelectric performance and robust mechanical properties

Bi2Te3-based bulk materials are the best commercially available thermoelectric materials for near room temperature applications. However, the poor mechanical properties of zone melting material and inferior thermoelectric performance of powder metallurgical material restrict their large scale deployment. In this study, p-type Bi₂Te₃-based materials were prepared using the hot extrusion technique, and the underlying mechanisms for microstructure evolution were revealed. The hot extrusion speed significantly impacts the strain rate, an indicator to modulate the dynamic recrystallization (DRX) and grain growth, thereby effectively regulating the microstructures of samples. For the sample extruded at a speed of 1.0 mm min−1, the refined grain with an average grain size of 1.53 μm and an orientation factor F(110) of 0.28 is achieved. This highly textured structure and high-density low-angle boundaries (LAGBs) maintain the high carrier mobility of 264 cm2 V−1 s−1, comparable with the zone melting sample. In contrast, increasing grain boundaries, dislocations, and inherent point defects intensifies the phonon scattering and suppresses the lattice thermal conductivity to 0.73 W m−1 K−1. All these contribute to a practical high ZT value of 1.1 at room temperature. Moreover, the fine grains and high-density dislocations ensure robust mechanic properties with a compressive strength of 189 MPa and a bending strength of 139 MPa, which is a guarantee for the successful cutting of microparticles with dimensions of 100 × 100 × 200 μm3. The fabrication of high-quality materials with both high thermoelectric performance and strong mechanical properties paves the way for the miniaturization of thermoelectric modules.

Unveiling crystallographic texture in laser floating zone melted Al2O3/YAG eutectic ceramic by seed-crystal inducing

This study demonstrated the unique crystallographic features in Al2O3/YAG eutectic by seed-crystal inducing in laser floating zone melting (LFZM) process for crystallographic orientation control. The as-fabricated eutectic ceramics induced by different single crystalline seeds were mainly composed of randomly oriented Al2O3 faceted particles and irregular eutectic, as a result of the initial uncoupled growth at the junction of seed and eutectic. Specifically, along the direction of directional solidification, the eutectic ceramics grew stably with a single crystallographic orientation relationship with low planar disregistry (2 %∼6 %). The stability of phase interface with minimum interfacial strain and better ionic charge balance in Al2O3/YAG eutectic has a greater effect on the regulation of the eutectic growth orientation than the constraint of the single crystalline seed.

Substantiation of the Monitoring Network of Talik Zones in Urbanized Permafrost Areas Based on GPR Profiling Data (Anadyr, Chukotka)

Modern climatic changes have an impact on the bearing capacity of permafrost soils at the base of the foundations of buildings and structures in the urbanized territories of the Arctic and Subarctic. The activation of cryogenic processes leads to the destruction of infrastructure and to social, economic, and environmental consequences for the population. Based on the results for the geothermy of frozen and thawing soil, and on the georadar profiling of the city of Anadyr, it was concluded that the main risks of permafrost degradation are associated with the spread of hydrogenic melting zones. Maps of the soil temperature in imaginary cross-sections with depths of 3, 5, and 10 m were compiled, along with maps of the capacity of thawing soils, the permafrost aquifer, and the dangerous spread zones for exogenous cryogenic processes. The total area of talik zones with a depth of 6 m or more in the urban area was 2.34 km2, or 67% of the built-up area. The system of permafrost monitoring in the territory of Anadyr was substantiated, and is based on monitoring the boundaries of talik zones. It consists of an automated network of observations of the ground temperature in 35 wells at the boundary and in the center of 20 zones of the dangerous development of exogenous cryogenic processes, as well as 12 control GPR profiles at the intersection of linear hydrogenic taliks.

Influence of discrete laser surface melting on hot cracking behavior and mechanical properties of Q235 steel

Modern industries demand higher mechanical properties from components. Traditional heat treatment methods often suffer from drawbacks such as high production costs, time-intensive processes, and labor-intensive procedures. The integration of bionic engineering with laser surface melting has given rise to Discrete Laser Surface Melting (DLSM) technology, effectively mitigating these shortcomings. Previous research has substantiated the capability of this technology to significantly enhance various metal properties. This study employed an Nd:YAG pulsed laser for the DLSM treatment of Q235 steel. The discrete laser surface melted (DLSMed) units were prepared on Q235 steel samples. Subsequent analysis utilized scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy-dispersive spectroscopy (EDS) to examine the microstructure and chemical composition of the DLSMed samples. Surface profilometry, hardness testing, and X-ray stress testing were conducted to measure surface roughness, microhardness, and residual stress, respectively. Mechanical properties were evaluated using tensile and impact testing machines. Experimental findings revealed that the DLSMed sample's surface could be divided into three regions: the melting zone, the heat-affected zone (HAZ), and the substrate. The microstructure of the melting zone consisted of refined martensite. The depth and width of the DLSMed units exhibited a certain regularity with variations in the defocus distance. Increasing the defocus distance positively impacted grain refinement and hardness but also led to an increase in surface roughness. Residual stress increased within a specific defocusing range, but beyond this range, its variation lost regularity. Hot cracking behavior within the DLSMed unit encompassed four stages: crack nucleation, propagation, healing, and decomposition. Different defocusing distances and the distribution of DLSMed units significantly affected the tensile strength and impact toughness of the samples. As the defocusing distance increased, the tensile and yield strength of DLSMed samples with transverse units gradually decreased. In contrast, samples with longitudinal units showed a trend of first decreasing and then increasing in tensile and yield strength. The distribution of DLSMed units played a significant role in improving the tensile properties of Q235 steel. The contribution of three factors to the impact performance of DLSMed samples was ranked from high to low as hardness, grain size, and yield strength ratio. The soft phase (substrate) could absorb impact energy and convert it into strain energy stored in the DLSMed sample. Only when the distribution of DLSMed units (hard phases) aligned with the tensile direction could they effectively limit the plastic deformation and enhance the mechanical properties of Q235 steel. However, an increase in defocusing distance led to increased brittleness, deteriorating the mechanical properties of the DLSMed samples. Finally, this study unveiled the strengthening mechanisms of DLSMed samples, providing valuable insights for future applications in enhancing the mechanical properties of metals.

Influence of discrete laser surface melting on scuffing resistance of W6Mo5Cr4V2 steel gear

The gear transmission system is advancing towards high-speed and heavy-duty applications. Among the main failure modes of the system, tooth surface scuffing due to increased tooth surface temperature has emerged as a prominent concern in mechanical transmission. Addressing the enhancement of gear scuffing resistance has thus become an urgent challenge in this field. This paper utilized discrete laser surface melting (DLSM) treatment to create discrete laser surface melted (DLSMed) units on the surface of W6Mo5Cr4V2 steel gears, resembling the radial ribs found on the surface of Limaria basilica. The paper investigated the size, hardness, residual austenite content, and residual stress of the DLSMed units at varying current intensities and laser frequencies. Microstructural observations were conducted on the DLSMed units, followed by gear scuffing experiments performed on the Forschungsstelle für Zahnräder und Getriebebau (FZG) testing machine. The experimental findings revealed that the change in laser frequency had a clearly weaker impact on the size of the DLSMed unit compared to current intensity. The DLSMed unit consisted of two parts: the melting zone (MZ) and the heat-affected zone (HAZ), with equiaxed and dendritic microstructures, respectively. Both zones exhibited refinement with increasing current intensity and laser frequency. Moreover, the microhardness of the DLSMed unit showed significant improvement compared to that of as-received gears. The scuffing resistance of DLSMed gears was found to be closely linked to their initial surface roughness. Residual stress formation in DLSMed gears was attributed to thermal stress and microstructural stress. The distribution pattern of DLSMed units had varying effects on the scuffing load-carrying capacity of DLSMed gears. Specifically, DLSMed gears with transverse distribution of DLSMed units demonstrated a 12.5% improvement in anti-scuffing performance compared to those with longitudinal distribution. Finally, this paper elucidated the mechanism through which DLSM enhances the scuffing resistance of W6Mo5Cr4V2 steel gears.

Up-conversion luminescence and thermal sensing properties of LuYO3: Er3+/Yb3+ phosphor

A series of LuYO3: Er3+/Yb3+ phosphors with different Yb3+ concentrations were prepared through a melting zone method with CO2 laser. The samples emit bright up-conversion luminescence (UCL) under a 980 nm laser. The UCL intensity and the luminescence color change significantly when Yb3+ concentration changes. Besides, when doped with 3 mol% Yb3+, the UCL intensity is maximal. The thermal sensing properties of LuYO3: Er3+(0.5 mol%)/Yb3+(3 mol%) were studied using the fluorescence intensity ratio (FIR) method from 298 K to 848 K. The maximum absolute and relative sensitivities are 0.0050 K−1 at 366 K and 0.0167 K−1 at 298 K, respectively. Thus, the LuYO3: Er3+(0.5 mol%)/Yb3+(3 mol%) fluorescent material is very suitable for thermal sensing because of the wide temperature range and the high sensitivity.

The effect of fibers addition on the microstructure and mechanical properties of ZrO2 fibers toughened Al2O3/ZrO2 (Y2O3) solidified ceramics

Fiber toughening is considered an effective way to strengthen the toughness of traditional sintered ceramics. Herein, ZrO2 fibers toughened Al2O3/ZrO2 (Y2O3) directionally solidified eutectic ceramics (DSECs) were prepared with the high-frequency induction heating zone melting (IHZM). The effects of ZrO2 fibers content on the phase composition, microstructure, and mechanical properties of the eutectic ceramics were studied. The findings revealed that DSEC consists of α-Al2O3 and ZrO2 phases, presents a typical colony microstructure. The phase spacing in the colony decreased with the addition of fibers, reaching a minimum value of 1.99 ± 0.25 μm at 20 wt%, which was nearly 40 % lower than that without the fiber’s addition. The hardness of DSEC increased gradually with the addition of fibers. Its highest value reaches 18.42 ± 0.55 GPa when the fiber content is 20 %. The fracture toughness of DSEC first increased and then decreased, reaching a maximum of 5.43 ± 0.22 MPa·m1/2 at 10 wt%, which was 1.5 times higher than that of the fibers-free eutectic ceramic. The improvement of fracture toughness was primarily due to the fibers toughening. In addition, the crack deflection, pinning, bridging, and branching had a significant inhibitory effect on the crack propagation.

Preparation, Deformation Behavior and Irradiation Damage of Refractory Metal Single Crystals for Nuclear Applications: A Review.

Refractory metal single crystals have been applied in key high-temperature structural components of advanced nuclear reactor power systems, due to their excellent high-temperature properties and outstanding compatibility with nuclear fuels. Although electron beam floating zone melting and plasma arc melting techniques can prepare large-size oriented refractory metals and their alloy single crystals, both have difficulty producing perfect defect-free single crystals because of the high-temperature gradient. The mechanical properties of refractory metal single crystals under different loads all exhibit strong temperature and crystal orientation dependence. Slip and twinning are the two basic deformation mechanisms of refractory metal single crystals, in which low temperatures or high strain rates are more likely to induce twinning. Recrystallization is always induced by the combined action of deformation and annealing, exhibiting a strong crystal orientation dependence. The irradiation hardening and neutron embrittlement appear after exposure to irradiation damage and degrade the material properties, attributed to vacancies, dislocation loops, precipitates, and other irradiation defects, hindering dislocation motion. This paper reviews the research progress of refractory metal single crystals from three aspects, preparation technology, deformation behavior, and irradiation damage, and highlights key directions for future research. Finally, future research directions are prospected to provide a reference for the design and development of refractory metal single crystals for nuclear applications.

Shock‐induced pervasive remelting of Fe sulfides in the basaltic shergottite Northwest Africa 14672: A benchmark for shock stages S6/S7 on Mars

AbstractNorthwest Africa (NWA) 14672, the most highly shocked Martian meteorite so far, has experienced >50% melting, compatible with peak pressure >~65 Gpa, at a transition stage 6/7. Despite these extreme shock conditions, the meteorite still preserves a population of “large” Fe sulfide blebs from the pre‐shock igneous assemblage. These primary blebs preserve characteristics of basaltic shergottites in term of modal abundance, preferential occurrence in interstitial pores along with late‐crystallized phases (ilmenite, merrillite), and Ni‐free pyrrhotite compositions. Primary sulfides underwent widespread shock‐induced remelting, as indicated by perfect spherical morphologies when embedded in fine‐grained silicate melt zones and a wealth of mineral/glass/vesicle inclusions. Extensive melting of Fe‐sulfides is consistent with the decompression path experienced by NWA 14672 after the peak shock pressure at ~70 GPa. Primary sulfides acted as preferential sites for nucleation of vesicles of all sizes which helped sulfur degassing during decompression, leading to partial resorption of Fe‐sulfide blebs and reequilibration of pyrrhotite metal/sulfur ratios (0.96–0.98) toward the low oxygen fugacity conditions indicated by Fe‐Ti oxides hosted in fine‐grained materials. The extreme shock intensity also provided suitable conditions for widespread in situ redistribution of igneous sulfur as micrometric globules concentrated in glassy portions of fine‐grained lithologies. These globules exsolved early on quenching, allowing dendritic skeletal Fe‐Ti oxide overgrowths to nucleate on sulfides.

IML-SSOD: Interconnected and multi-layer threshold learning for semi-supervised detection

While semi-supervised anchored detector of the R-CNN series has achieved remarkable success, semi-supervised anchor-free detector lacks the ability to generate high-quality flexible pseudo labels, resulting in serious inconsistencies in SSOD. In order to make the network learn more reliable and consistent label data to solve the problem of information bias, we propose an interconnected and multi-layer threshold learning for semi-supervised object detection (IML-SSOD). The Joint Guided Estimation (JGE) module uses the Core Zone refinement module to improve the position accuracy score of low semantic information, and combines the classification and the centerness score as evaluation criteria to predict stable labels. The multi-layer threshold filtering method selects more potential label samples for the student network ensuring the information used in training. Extensive experiments on MS COCO and PASCAL VOC datasets demonstrated the effectiveness of IML-SSOD. Compared with existing methods, our method on VOC achieved 81.9% AP50 and 57.89% AP50:95, which is highly competitive.

Mineralogy, ore genesis and zircon U[sbnd]Pb age characteristics of the Cerattepe Cu[sbnd]Au (±Zn) deposit (Artvin, NE Turkey)

The Cerattepe deposit is associated with bimodal felsic volcanics of the Kızılkaya Formation, which hosts the majority of VMS deposits in the Eastern Pontide Orogenic Belt. Pyrite, chalcopyrite, sphalerite, and bornite are the main sulfides, with minor galena, fahlores, marcasite, idaite, covellite, and chalcocite. Barite and quartz are the primary gangue minerals, with minor calcite and gypsum. Hematite, limonite, goethite, jarosite, and lepidocrocite are common oxide minerals. The sulfide ore is shaped by rapid cooling, zone refinement, replacement, and local deformation processes, which affect textural relationships and mineral paragenesis.Fluid inclusion studies have shown that the early stages of the ore were formed by boiling at temperatures of 250–355 °C and approximately 1900 m depth of sea water, while the later stages developed at temperatures as low as 148 °C. The Te temperatures imply that NaCl-dominated solutions with partial mixing of CaCl2 may be responsible for mineralization. The CO2 phase present in the early stages of the ore may have been derived from the interaction of hydrothermal solutions with the underlying carbonate rocks. Salinity values of 0.2–7.62 wt% NaCl equ., compatible with the average salinity of Kuroko type VMS deposits, indicate that the Cerattepe deposit was formed in a marine environment.The Co/Ni of pyrites (1–12, with an average of ∽2) and Zn/Cd of sphalerites (127–383) indicate an acidic source and magmatic source of acidic-andesitic for the ore-forming fluids, respectively. The δ34S values −4.4 ‰ – +9.63 ‰ indicate a magmatic sulfur source, with partial sulfate-reduced sulfur. A magmatic-related source is also inferred from δ18O values (+8.5 and + 9.5 ‰.) for the Cerattepe deposit. The leaching, zone refinement, and replacement processes, followed by remobilization and precipitation of the metals, resulted in gold enrichment in the oxide zone. The new zircon UPb dating constrains the formation age of the Cerattepe deposit into a time span from 79 ± 1–76.8 ± 1 Ma, a younger age compared to other VMS deposits in the eastern Pontide region.

Investigation of Creep Behavior of HDPE Pipe Butt Fusion Welded Joints Using a Stepped Isostress Method.

The utilization of high-density polyethylene (HDPE) pipes is prevalent in water transportation due to their exceptional durability, resistance to corrosion, and ease of installation. Traditionally, butt fusion welding has been employed to connect HDPE pipes. In this study, scanning electron microscopy (SEM) was utilized to examine the microstructure of butt fusion welded joints of HDPE pipes, while the stepped isostress method (SSM) was employed to investigate their creep behavior at 100 °C in ambient air. SEM results revealed a significant presence of craze or lamellae in the base material, whereas minimal occurrences of craze or lamellae were observed in the melt zone. The results obtained from the SSM indicated that the creep life of butt fusion welded joints of HDPE pipes was not adversely affected by the welding bead, and their creep life was no less than that of the base material when ductile creep failure occurred.