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Processing-Microstructure-Property Correlation for Producing Stretch-Flangeable Grade Dual-Phase Steel
No full textContinuous annealing simulation experiment of a large sample (220 mm length and 110 mm width) is carried out for a better understanding of the role of annealing parameters on microstructure and mechanical properties so as to develop dual-phase steel with consistent quality. A typical complete annealing cycle used in industry for producing dual-phase structure was divided into several thermal stages to investigate various mechanisms at different thermal stages. A correlation among microstructure, process parameters and mechanical property is established by varying the important annealing process parameters. Based on the systematic study at each thermal stage, the annealing parameters that have greater influence on mechanical properties were identified. A modified complete thermal cycle, after control of these key parameters, produced a better distribution of fine martensite along the ferrite grain boundaries and thus enhanced mechanical properties. The study showed that higher amount and uniform distribution of fine martensite with granular morphology along the ferrite grain boundaries for a fixed composition of steel is essential for improved mechanical properties. The uniform distribution of fine martensite with required amount within the ferrite matrix not only enhanced strength-ductility balance but also improved stretch-flangeability
BOF Steel Slag: Critical Assessment and Integrated Approach for Utilization
No full textDuring steel production, the impurities in the hot metal react with the fluxes forming the steel slag. Chemical constituents of this steel slag (SS) are relevant to iron/steelmaking or blended cement manufacture. Harmful impurities present in it, however, limit its recycling to these applications. Japan, Europe, and the US consume a significant amount of their SS, but more than 50% end up in low-end applications such as aggregates, etc. Massive generation and limited usage have resulted in huge SS accumulation in China and India (the top two steel-producing countries). This paper takes a critical look at the developments toward steel slag recycling and utilization, leading to resource conservation and greenhouse emission control. Various approaches toward eliminating the inhibiting factors for recycling the SS in iron/steelmaking and blended cement manufacture are critically analyzed. Based on the analysis, the authors present a holistic approach toward steel slag utilization beyond the conventional application areas like aggregates, landfilling, etc. This approach involves heat recovery from the molten slag, optimal, and efficient materials recovery/recycling, and carbon capture. Energy recovery conserves fossil fuel consumption (with a consequent reduction in CO2 emission). The energy recovery processes inching toward commercial application yield a granulated glassy slag suitable for further recycling. Indirect benefits from these include a reduction in the environmental and ecological impacts of mining and related activities. Such endeavors will enable the steel industry to circumvent stringent environmental regulations and achieve energy efficiency
Evolution of microstructure during tensile creep deformation of nickel-based disk superalloy
No full textThe aim of the present investigation is to study the tensile creep behavior of nickel-based disk superalloy, which is widely used in the manufacturing of turbine disks for the aero engines. Tensile creep tests were performed over a wide range of stresses (100-900 MPa) and temperatures (625-850 degrees C) and rupture time varies from 93.1 to 9473 h. Furthermore, stress rupture strength was predicted using the time-temperature parameter at different temperatures for longer durations. The stress dependence of minimum creep rate for the alloy is found to follow the power law. The stress exponent (n) decreased from 31.2 to 7.8 with increase in the test temperature from 625 degrees C to 700 degrees C. Subsequently, the rate-controlling mechanism of creep is identified as dislocation climb by adopting the threshold stress analysis in the temperature range of 625-700 degrees C. At higher temperature, the n values are drastically reduced to 2.9, 2.7 and 2.2 at 750, 800 and 850 degrees C, respectively, due to dislocation annihilation and dissolution of precipitates. This indicates that the rate-controlling mechanism of creep changes from viscous glide to grain boundary sliding (n = 2.2). The activation energy for creep (Q(C)) has been determined by using the modified power law in the temperature range of 625-700 degrees C and is found to be 598 kJ/mol, whereas the obtained Q(C) is also decreased significantly to 435 kJ/mol at higher temperature range (750-850 degrees C). The calculated Q(C) values are found to be 52.5% and 34.7% higher than the activation energy for lattice self-diffusion of nickel (284 kJ/mol). Post creep microstructural examination using transmission electron microscopy (TEM) revealed extensive deformation in the microstructure is accommodated through the gamma' precipitates, formation of stacking faults and deformation twins within the larger gamma' precipitates. The major findings are well in strong agreement with the hardness characterization, where prominent increase in hardness within localized deformation is mainly due to extensive dislocation-interactions with the gamma' precipitates
Effect of dynamic strain aging on cyclic deformation in piping material SA333 Gr-6 steel
No full textIn piping structures, the low cycle fatigue loading arises from thermally induced strain cycles associated with start-up and shut-downs and fluctuation in loading conditions. SA333 Gr-6 steel is prone to dynamic strain aging (DSA) and the parameters that govern the DSA are temperature and strain rate. There are limited studies on DSA in the investigated steel. In the present investigation, fatigue experiments were conducted at a fixed strain amplitude of +/- 0.5 % with the variation of temperatures (RT to 400 degrees C) and strain rates (1 x 10(4) s(-1) to 1 x 10(-2) s(-1)). The results reveal that the cyclic deformation behavior depends on temperatures and strain rates. The steel shows cyclic hardening characteristics at elevated temperatures which indicates the occurrence of the DSA phenomenon. The negative strain rate sensitivity and temperature dependency of stress amplitude are the manifestations of DSA. The present study shows the deleterious effect of DSA on fatigue life. The DSA temperature regime found in the temperature 200-250 degrees C for 1 x 10(4) s(-1) strain rate, 250-300 degrees C for 1 x 10(-3) s(-1) strain rate, and 250-350 degrees C for 1 x 10(-2) s(-1) strain rate. The DSA regime gets shifted to a higher temperature with the increase in strain rate. Transmission electron microscopy investigations reveal that the fatigue failed specimen at the DSA regime shows severe dislocation activities and dislocation tangles, whereas minor dislocation activities and cell structures were observed at the non-DSA regime. The dislocation density calculated from the X-ray diffraction analysis was higher at DSA compared to the non-DSA regime
Study of the Effect of Two Separate Tilt Angles of Laser Scanning Lines on the Microstructure and Mechanical Properties in Direct Metal Laser Sintered AlSi10Mg Alloy
No full textThe scanning strategy has a measurable impact on the grain size and growth direction of the produced parts in powder bed fusion. Tilting of the laser scan lines by 67 degrees is a default procedure applicable to PBF machines for obtaining maximum variability in the direction of melt pools. In this work, AlSi10Mg parts were produced through direct metal laser sintering with two different scanning strategies. In the first strategy, the scanning lines were not tilted in between layers while in the second strategy, the scanning lines were tilted by 67 degrees. The microstructures of the as-deposited alloys for the two strategies were evaluated by state-of-art characterization methods like scanning electron microscopy, electron backscatter diffraction (EBSD), X-ray computed tomography (X-ray CT), and X-ray diffraction. Monotonic tensile tests were hence conducted in both categories. Greater tensile strength was demonstrated by the specimens with no tilting of the scan lines while the specimens produced with a 67 degrees tilt manifested greater elongation. Grain morphology characterized by EBSD studies suggested an inhomogeneity in grain size for the specimens with no tilting of the scan lines. This had primarily attributed to the early failure of the same. It was also found out that the preferred growth direction of grains in AlSi10Mg was hindered by tilting the scan lines by 67 degrees. X-Ray CT studies and Kocks-Mecking Analysis explained the deformation and hardening behavior of both the types in the view of porosity and structural defects
Discharge Profile and Its Correlation with Estimated Parametric Sensitivity and Electrical Contact Resistance Losses in Li-Ion Battery
No full textThe electrochemistry-based models contain a large number of parameters and their sensitivity estimation is essential to obtain an accurate Li-ion battery model. The mitigation of interfacial contact resistance and associated ohmic loss and/or power loss in the real time evaluation of a battery performance is an important issue in the energy management. A compact analytical model for cell voltage and the discharge profile of Li-ion battery has been developed to analyze the impact of parametric sensitivity and interfacial contact resistance loss. The cell voltage of the battery depends on the polarization effect due to the anodic and/or cathodic overpotential and the contact resistance of the electrode/current collector interface. The impact of parametric sensitivity and with/without contact resistance on cell voltage analysis for a discharge process have been investigated and verified with the available experimental literature data
Improved Interfacial Charge Transfer on Noble Metal-Free Biomimetic CdS-Based Tertiary Heterostructure @ 2D MoS2-CdS-Cu2O with Enhanced Photocatalytic Water Splitting
No full textHigh charge separation efficiency with a wide optical absorption window is the prime requirement for the scale up of a stable solar photocatalytic hydrogen generation process. A new noble metal-free heterostructure of 2D MoS2-CdS-Cu2O is designed by depositing cauliflower-shaped CdS and nanosized Cu2O on exfoliated 2D MoS2. Characterization by XPS, high-resolution transmission electron microscopy (HRTEM), and UV-visible spectra confirms the formation of nanosized Cu2O with desired interface formation with MoS2 sheet and CdS thus extending the optical absorption range up to 900 nm. Water splitting activity in the presence of lactic acid is found to be 7.89 and 11.53 mmol g(-1) h(-1) on MoS2-CdS and MoS2-CdS-Cu2O, respectively, with good repeatability under visible light. Efficient interfacial charge separation is manifested from demised photoluminescence (PL) intensity which supports the suppression of hole-electron recombination in the tertiary heterostructure. In addition, the formation of dual p-n junction as indicated from Mott-Schottky analysis further strengthen the faster electron and holes separation objective. Compared to the pure CdS, hydrogen efficiency is 20.96 times higher on a noble metal-free tertiary catalyst with an apparent quantum efficiency of 8.75%. Hopefully, the 2D material-based architecture of dual p-n junction with desired interface engineering will facilitate the catalyst design with increased water splitting activity under solar/visible light
Recovery of Rare Earth Metals (REMs) from Nickel Metal Hydride Batteries of Electric Vehicles
No full textNickel metal hydride (NiMH) batteries are extensively used in the manufacturing of portable electronic devices as well as electric vehicles due to their specific properties including high energy density, precise volume, resistance to overcharge, etc. These NiMH batteries contain significant amounts of rare earth metals (REMs) along with Co and Ni which are discarded due to illegal dumping and improper recycling practices. In view of their strategic, economic, and industrial importance, and to mitigate the demand and supply gap of REMs and the limited availability of
natural resources, it is necessary to explore secondary resources of REMs. Therefore, the present paper reports a feasible hydrometallurgical process flowsheet for the recovery of REMs and valuable metals from spent NiMH batteries. More than 90% dissolution of REMs (Nd, Ce and La) was achieved using 2 M H2SO4 at 75 C in 60 min in the presence of 10% H2O2 (v/v). From the obtained leach
liquor, the REMs, such as Nd and Ce, were recovered using 10% PC88A diluted in kerosene at eq. pH 1.5 and O/A ratio 1/1 in two stages of counter current extraction. La of 99% purity was selectively precipitated from the leach liquor in the pH range of 1.5 to 2.0, leaving Cu, Ni and Co in
the filtrate. Further, Cu and Ni were extracted with LIX 84 at equilibrium pH 2.5 and 5, leaving Co in the raffinate. The developed process flow sheet is feasible and has potential for industrial exploitation after scale-up/pilot trails
Phosphonomethyl iminodiacetic acid functionalized metal organic framework supported PAN composite beads for selective removal of La(III) from wastewater: Adsorptive performance and column separation studies
No full textThe rare earth elements being toxic in nature are being accumulated in water bodies as their industrial usage is growing exponentially, thus their efficient separation holds an immense significance. Herein, ligand functionalized metal organic framework (MOF), Phosphonomethyl iminodiacetic acid coordinated at Fe-BTC, was synthesized post-synthetically and incorporated subsequently in polyacrylonitrile polymer to prepare the composite beads via nonsolvent induced-phase-inversion technique for selective adsorption of La(III) from the wastewater in batch and dynamic column mode. XPS NMR, and FTIR were used to establish the interaction between functionalized ligand and unsaturated metal nodes of MOF. The adsorption capacity was 232.5 mg/g and 77.51 mg/g at 298 K of the functionalized MOF and composite beads respectively. Adsorption kinetics followed a pseudosecond order rate equation, and isotherm indicated the best fitting with Langmuir model. The dynamic behavior of the adsorption column packed with MOF/Polymer beads was fairly described by the Thomas model. The breakthrough time of 23.2 h could be attained with 12 cm of bed height and 10 ml/min of flow rate. These MOF/Polymer beads shown the selectivity of La over transitional metals were recycled over 5 times with about 15% loss of adsorption capacity. The findings provide suggestive insights of the potential use of functionalized MOF towards the separation of the rare earth element
Processing routes, resulting microstructures, and strain rate dependent deformation behaviour of advanced high strength steels for automotive applications
No full textAutomobile industry is continuously striving to obtain light body-in-white structures to meet tightened regulations on flue-gas emissions/crash-testing parameters. 'Advanced high strength steels (AHSS)' find increased applications in the automotive industry because of improved crashworthiness/formability at reasonably low costs. AHSS category mainly includes transformation induced plasticity (TRIP) steels, twinning induced plasticity (TWIP) steels, dual phase (DP) steels, complex-phase (CP) steels, and quenching-partitioning (Q&P) steels. AHSSs provide superior strength-ductility combination than conventional high-strength steels by virtue of their multi-phase microstructures. Mechanical properties of AHSSs are greatly influenced by processing routes/derived microstructures. Furthermore, mechanical properties/tensile deformation behavior are also strain rate dependent. During an automobile crash, deformation occurs at strain rates which are exceedingly higher than quasi-static conditions. So, investigation of AHSS properties under both quasi-static as well as high strain rates conditions is important to check applicability for superior crash-resistance. The present work critically reviews details of processing routes, room temperature microstructures, mechanical properties, and finally strain rate dependence of tensile deformation behaviour of AHSSs. Finally, main gaps in existing literature/scope for future research with regards to high strain rate deformation dependent properties of this steel category are presented