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Temperature-dependent stacking fault energy, deformation behavior, and tensile properties of a new high-entropy alloy
No full textThe stacking fault energy (SFE), deformation behavior, and tensile properties of a new high-entropy alloy (HEA), Fe35Mn35Co10Cr10Ni10 (in at. %), were investigated at room temperature (RT) and-100 degrees C. Deformation sub-structure evolution during tensile loading was studied using electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM). A transition in the slip configuration occurred from fully wavy to completely planar with the decrease in temperature from room temperature (RT) to-100 degrees C. The studied alloy revealed the onset of deformation twinning only during deformation at-100 degrees C and the same was absent during RT deformation. SFE of the studied alloy at-100 degrees C was-34.2 (+/- 4) mJ/m(2). SFE determination required the value of the distance between Shockley partial dislocations and the same was determined employing the transmission electron microscopy (TEM) based weak-beam dark field (WBDF) technique. SFE of the studied alloy could not be estimated at RT due to the presence of closely spaced partial dislocations (perhaps due to very high SFE) and therefore partial separation by the presently employed WBDF technique couldn't be achieved. The role of friction stress was limited and SFE was revealed as the main factor in defining the active slip mode in HEAs containing no apparent short-range ordering and similar shear moduli. Activation of planar slip-induced dislo-cation features such as Taylor lattices, microbands, and twinning at-100 degrees C provided greater work hardening resulting in improved tensile properties compared to RT
Life cycle assessment and thermophysical properties of a fly ash-based geopolymer containing drinking water treatment sludge-
No full textFly ash-based geopolymers have emerged as a sustainable alternative in construction, leveraging industrial by-products to mitigate CO2 emissions. This study investigates the novel incorporation of drinking water treatment sludge (DWTS) into fly ash-based geopolymers at varying proportions (5-40%). The authors' focus is to analyze the thermophysical properties and environmental implications, including a robust life cycle assessment case study conducted within the Moroccan context. The comprehensive analysis encompassed X-ray powder diffraction, apparent porosity, water absorption, scanning electron microscopy, hot disc, compressive strength, and a comparative assessment of fly ash-based geopolymer containing 20% of DWTS (GP-DWTS-20) and ordinary Portland cement (OPC). Notably, the results reveal that DWTS enhances thermal performance, with a remarkable 33% reduction in thermal conductivity observed in geopolymers containing 20% DWTS. This enhancement motivates the potential for innovative fly ash-based geopolymers. Moreover, the study contributes quantifiable evidence of a substantial 48% reduction in global warming potential for DWTS-based geopolymers compared to OPC. These findings underscore the environmental benefits of this alternative while emphasizing avenues for optimization in alkaline solution, curing, and renewable energy integration
Fe-Al core-shell structure as an efficient catalyst for dual hydrogen production and storage by thermochemical water splitting: A reactive molecular dynamic simulation
No full textCatalysts with dual functions in hydrogen production and storage are desired for the low-cost technology. In the preceding view, we used reactive force molecular dynamics to demonstrate how effective the Fe-Al core-shell structure is at breaking up water molecules and storing hydrogen free radicals via thermochemical water splitting. The results show that at T similar to 600 K, water molecules begin to dissociate in the presence of a Fe-Al catalyst, releasing OH and H free radicals. It is worth noting that the produced OH free radicals are bonded to the Al-shell, whereas the H free radicals move to the Fe-core and store via a chemical bond. Interestingly, at T 3000 K, the number of Fe -H bonds decreases while the number of H-H bonds increases, indicating that the stored H atom desorbs and forms an H2 molecule. Temperature can thus be used to monitor the ability of Fe-Al catalysts to dissociate water, store hydrogen, and produce hydrogen. This research shows that developing core-shell-type catalysts can provide an effective solution for hydrogen generation, storage, and transportation. (c) 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved
Elastic and transformation behavior of equiatomic NiTi shape memory alloys fabricated at different sintering temperatures
No full textThe growing demand for bulk Nitinol in ball and roller bearing applications is focused on in this article. The uniaxial compaction and sintering process is considered for the fabrication of the alloys where the sintering temperatures vary from 950 degrees C to 1150 degrees C. Better homogenization and diffusion are achievable except for the 950 degrees C sintered sample. The results of XRD of 950 degrees C and 1050 degrees C sintered samples show the presence of the Ni3Ti phase but in all the Samples sintered above 950 degrees C, NiTi is the major phase, unlike Ni3Ti in 950 degrees C. The TEM analysis shows a trace amount of TiO2 which comes from the impurity of the purged Ar gas. The O2 in the samples can be accommodated inside a few Ti2Ni phases to form Ni2Ti4O phases. Ni4Ti3 precipitates formed at higher temperatures help in precipitation strengthening. At room temperature, both austenitic B2 and martensitic B19 ' coexist. The DSC analysis shows that an increase in the sintering temperature increases the response time by consuming more energy. The elastic modulus and hardness have been increased up to 1100 degrees C and then decreased. Above Af temperature successful transformation of B2 to B19 ' takes place
Microstructure and Mechanical Property Characterization of Wire Arc Additively Manufactured SS308L Built Part: Study of Heat Interaction Phenomena
No full textIn the present work, CMT-based robotic MIG welding is carried out for wire arc additive manufacturing of SS308L part. Commercially available SS308L-T1 wire is used as feedstock material. Studies of direction-specific microstructure evolution and mechanical property characterization of as-built specimens are carried out. WAAMed SS308L exhibits a typical microstructure consisting of grain boundary δ ferrite with varied morphologies (vermicular/skeletal and lathy) within γ austenite dendrites. The amount of δ ferrite along with its morphology is observed to be varied from location to location, within the as-deposited specimen. Such variation diminishes after the heat treatment. The average ultimate tensile strength of horizontally cut specimens supersedes than that of vertically cut specimens. Heat treatment causes reduction in microhardness value of WAAMed SS308L. Additionally, temperature data as recorded by the thermocouple (tacked with the substrate plate) are utilized to understand various heat interaction phenomena during the WAAM process. Effect of post-deposition heat treatment is also studied
Petro-Mineralogical and Geochemical Evaluation of Glauconitic Rocks of the Ukra Member (Bhuj Formation), Kutch Basin, India
No full textGlauconites occurring within the Ukra Member of Kutch Basin have remained unexplored in terms of their economic significance. The present study aimed to present a detailed physicochemical characterization of glauconite occurring in the siliciclastic rocks of Guneri and Umarsar area of the Kutch district, Gujarat, India to explore their economic potential. The study involved an integrated petrographical, mineralogical, and geochemical investigation of glauconitic rocks to highlight the occurrence, nature, and maturity of glauconite. The characterization was carried out using X-ray diffraction (XRD), X-ray fluorescence (XRF), and electron probe microanalysis (EPMA) combined with energy dispersive X-ray (EDX), Field emission gun scanning electron microscopy (FEG-SEM), Fourier-transform infrared spectroscopy (FTIR), and inductively coupled plasma mass spectroscopy (ICP-MS). Petrographic and bulk XRD analysis revealed that the glauconite occurs as green pellets constituting similar to 30 and 40% of the glauconitic sandstone and shale, respectively. Whole-rock analysis showed that the value of K2O varies considerably from 3.93 wt.% (sandstone) to 5.63 wt.% (shale). Mineral chemistry indicated the distinctive chemical composition of glauconite pellets containing 7.4-8.4 wt.% of K2O. The parameters, such as the distance between the (001) and (020) peaks and the large K2O content (similar to 8 wt.%) of the glauconite fraction reflect an evolved to highly evolved stage of maturation. The morphological and spectral signatures further support the high degree of maturation in glauconites. Trace-element analysis implied that the glauconitic sandstone and shale contain elements such as Zn, Mn, Cu, Co, Mo, and Ni, which serve as essential micronutrients for plants. These data sets collectively constitute part of a preliminary study which is prerequisite to beneficiation, but further evaluation of its potential as a potash fertilizer also is needed
Mobility of metals and metalloids from SHOS coal ash and slag deposit: mineralogical and geochemical constraints
No full textDeposits remained after coal combustion are a well-known occurrence in the world; unfortunately, only a small percentage of such deposits are adequately regulated and, consequently, pose a serious threat to the local environment. Attenuation of negative consequences presupposes knowledge of a number of features, both of the deposit and the local environment as well the interaction with local biota. In this study, unregulated waste generated from decades of coal mining and combustion of superhigh-organic-sulfur Rasa coal, enriched in Se-U-Mo-V and located in a vulnerable karst region, was investigated. To assess the impact of landfill on the environment, in addition to its general geochemical and mineralogical features, the human health risk was assessed and the leaching of elements from the landfill, local soil, and the coal itself was investigated. For the latter, three extraction procedures, ASTM, EP, and TCLP (pH 4.93 and 2.9), were employed, mimicking different environmental conditions, including the sporadic occurrence of acid rains in the region. The soil around the landfill displayed enrichment in the majority of elements compared to expected values, with exception of Se, Mo, U, V, Sr, and Cu found at the highest levels in landfill samples. Mobility of elements was found to be controlled by both pH and mineralogy (carbonates and sulfates), whereby the overall highest relative mobility was observed in landfill samples for elements prevalently bound to sulfate phases. Calculated Hazard Quotient describes this landfill as a risk to the environment and human health through different pathways
Transduction Efficiency of a Magnetostrictive Sensor for the Generation of Guided Waves in Pipes Using Rapidly Quenched Amorphous Ribbons
No full textThe investigation addresses the magnetostrictive sensor (MsS) signal received from pipes of different materials using an amorphous alloy as a sensor element. This sensing system also acts as a transducer to generate ultrasonic waves which appear as echoes from pipe end and defect. The static magnetic field revealed different MsS signals from magnetically different pipes, viz., aluminum (nonmagnetic), galvanized iron (nonmagnetic coating), and mild steel (magnetic) pipes. Applied static field enhanced MsS signals in all the pipes. The extent of this enhancement is influenced by transduction efficiency of the MsS transducer. This efficiency varied with the magnetic nature of the pipe. Simulation through COMSOL Multiphysics elucidated the magnetic flux intensity patterns in these pipes and the consequent behavior of MsS transducer in inspection of pipes of different materials. The study indicated the role of static magnetic field in an MsS transducer for structural health monitoring (SHM) of pipes used prevalently in domestic and industrial sites
Effect of nitriding on mechanical and microstructural properties of Direct Metal Laser Sintered 17-4PH stainless steel
No full textIn this work, the effect of the nitriding process on microstructure and mechanical properties of additively manufactured (AM) 17-4PH stainless steel is investigated. The nitriding was performed at 530 degrees C, 560 degrees C, and 580 degrees C for 2 h. The nitriding process improves the hardness and surface roughness of the AM 17-4PH steel. Detailed microstructural characterizations of both as-built and nitride samples are performed using an optical microscope, scanning electron microscope (SEM) equipped with energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction technique. It reveals that the nitride layer thickness increases with nitriding temperature. A distinct transition layer between the substrate and nitride layer is observed in the 560 degrees C and 580 degrees C nitride samples. The nitriding process develops almost equiaxed grain microstructure with new secondary phase precipitates, whereas in the as-built material, the grains are primarily columnar along the AM process build direction. Specifically, the nitriding process introduces g-Fe4N, epsilon-Fe3N, CrN, and Ni3N precipitates. The increase in Ni- and Cu-rich precipitates with the nitriding temperature explains the observed improvement in the hardness and surface roughness. Furthermore, the nitriding process does not alter the substrate's initial weak crystallographic texture. (c) 2022 The Author(s). Published by Elsevier B.V. This is an open access article under the C
Influence of Hydrogen on Fatigue Crack Growth in 7075 Aluminum Alloy
No full textFatigue crack growth (FCG) behavior of 7075 T6 aluminum alloy was studied using constant stress intensity factor range (Delta K) envelopes in air and hydrogenating environments. The effects of loading frequency, stress ratio, and Delta K on FCG behavior were studied in the hydrogenating environment. The overall FCG rate was found to be significantly greater in hydrogenated specimens compared to that in air due to the hydrogen embrittlement effect which was observed through faceted surfaces, quasi-cleavage features, and secondary cracks. The influence of hydrogen observed through normalized crack growth rate revealed that crack growth was inversely proportional to Delta K. However, the frequency effect on FCG was found to be anomalous and ambiguous for hydrogenated specimens with no specific trend