Transactions of The Indian Institute of Metals最新文献

The recovery of Fe from an oversized sample in a spiral classifier upgrades a 55% Fe to 59% Fe output in a size range (− 3 mm + 150 μm). The output was subjected to fine grinding making it suitable for pellet plant. The ground fine ore was subjected to 2 processing routes: gravity concentration followed by magnetic separation. The tailing after gravity separation was subjected to magnetic separation with varying Gauss. One set of Fe enrichment was achieved in the concentrate after gravity separation and in the mag part of magnetic separator. The overall concentrate was 61.38% Fe, 4.53% SiO₂, and 2.97% Al₂O₃, with an yield of 83.45%. The Fe recovery was 86.27%. Alternately, fine ore was directly subjected to magnetic separation at 8000 Gauss, enriching the ore to 65.12%Fe with 48.15% yield which corresponds to 52.81% Fe. Thus, gravity concentration followed by magnetic separation gave higher grade, yield and Fe recovery.

Graphical Abstract

The performance of coke could significantly impact the permeability of a deadman in a blast furnace (BF). The poor permeability of the deadman would increase the flow rate of molten iron near the carbon brick and increase the temperature of the carbon brick. In this paper, the relationship between the production parameters of a 3200 m³ BF and the lining temperature in a hearth was studied based on the Pearson correlation coefficient. The research results indicated that the main factor affecting the lining temperature in the hearth was the proportions of dry quenched coke (DQC) to wet quenched coke used. When the proportion of DQC used increased, the lining temperature decreased after approximately 95 to 120 days. The results could be used to expand our understanding of the mechanisms by which the lining temperature of BF hearth could be reduced and the BF service life could be prolonged.

The utilization of uniformly deposited metal droplets has attracted significant attention for diverse applications, such as rapid prototyping and manufacturing. Achieving flawless aluminum structures through droplet-based liquid metal 3D printing (LM3DP) is critical in aerospace and electronics. However, challenges persist in eliminating defects during deposition due to constrained temperature ranges and complex impact dynamics. This study introduces a 3D computational model using a volume of fluid technique to analyze the consecutive deposition of molten aluminum droplets on a heated substrate, protected by nitrogen gas. Simulations reproduce droplet shapes in agreement with experimental results. Molten aluminum droplets solidify layer by layer continuously in an upward direction due to high thermal conductivity, forming surface ripples. L-shaped ripples emerge on neighboring droplets due to combined effects of solidification and oscillation, which involve alternating spreading and recoiling of the droplets leading to defects like cold laps, whereas bottom-hole defects occur due to inadequate metal filling with the substrate. This investigation systematically explores shape, defect formation, temperature, solid fraction, and velocity evolution during continuous deposition. Insights establish a fundamental basis for LM3DP technology.

This study investigates how welding travel speed and spindle speed influence the quality of welds in 270 mm diameter AISI 316L stainless steel pipes joined through friction stir welding (FSW). The FSW process was performed with spindle speeds of 250 rpm and 300 rpm, and travel speeds of 50 mm/min and 100 mm/min, utilizing a PCBN-coated W–Re tool in position control mode. Axial force, spindle torque and penetration depth were evaluated. The microstructure was analyzed using an optical microscope to understand the effects of spindle and travel speeds. High-resolution microscopy was employed to identify variable grain sizes across different weld zones. Vickers micro-hardness tests showed higher hardness in the stir zone and adjacent thermo-mechanically affected regions. The joint welded at 300 rpm and 100 mm/min displayed the highest hardness in the stir zone at 254 HV, indicating grain refinement confirmed by microstructural evaluation.

The effect of evolved heat-affected zone (HAZ) during metal inert gas (MIG) and cold metal transfer (CMT)–MIG welding of two IS2062 structural-steels, i.e. E250 and E410, was studied. The comparison of mechanical properties such as yield strength, ultimate tensile strength, tensile ductility being represented by %elongation, impact toughness at room temperature, and microhardness was done. Conventional optical and field-emission scanning electron microscopy were used for detailed examination of microstructural evolution across weldments. CMT–MIG in comparison to MIG mode was observed to produce a well-refined microstructure for both E250 and E410. Various HAZ subzones comprised of fully formed pearlite colonies in coarse-grain HAZ, pearlite in patched form in fine-grain HAZ, partially distributed pearlite in inter-critical HAZ, and fine Widmanstätten and acicular ferrite in deposited weld-metal of ER-70S6. Such microstructural manifestations particularly in HAZ subzones exhibited a positive effect leading to improved mechanical performance.

This study focused on the synthesis of Ti36-Al16-V16-Fe16-Cr16 high-entropy alloys (HEAs) through spark plasma sintering to ascertain their corrosion resistance performance. Varied sintering temperatures, ranging from 700 to 1100 °C were employed to discern their impact on the alloy's characteristics. The fabricated HEAs underwent characterization using scanning electron microscopy and X-ray diffraction. A potentiodynamic polarization measurement was employed to compare the electrochemical properties of HEAs sintered at different temperatures in sulfuric and chloride aggressive media. The study outcomes indicate that the HEA sintered at 1000 °C exhibited superior corrosion resistance compared to other HEAs at other temperatures. This study contributes valuable insights into the nuanced relationship between sintering temperature, microstructure, and corrosion resistance of Ti36-Al16-V16-Fe16-Cr16 HEAs.

ZrB₂ stands out among ultra-high-temperature ceramics due to its exceptional thermal resistance, chemical stability, high hardness, high electrical and thermal conductivity, and low density. In this work, the Al₂O₃–ZrB₂ nanocomposite was fabricated using mechanically activated self-propagating high-temperature synthesis. The effect of mechanical activation, using three different milling times (i.e., 0, 3, and 5 h), and addition of Al₂O₃ as a reaction diluent on Al₂O₃–ZrB₂ nanocomposite properties were investigated. The combustion behavior of different powder mixtures was evaluated using DSC. The phase analysis and microstructure of synthesized samples were investigated by X-ray diffraction (XRD) and scanning electron microscopy. Results indicated that 5 h ball milling of initial powder mixture synthesis caused the combustion reaction to start at about 650 °C which was lower than that of the unmilled sample (1140 °C). The microstructure of pre-milled samples contained a uniform distribution of ZrB₂ particles in the Al₂O₃ matrix. The addition of Al₂O₃ to the initial mixture (up to a 6 wt.%) increased the amount of heat energy released upon heating the sample. The DSC and XRD results showed that the sample milled for 3 h, in which 6 wt.% Al₂O₃ was added to the mixtures had the most tendency to combustion and the most purity of the final microstructure. Further addition of Al₂O₃ up to 10 wt.% reduced the system’s ability to perform self-propagating high-temperature synthesis.

Unique characteristics such as biocompatibility, degradation capability, and mechanical properties have positioned magnesium alloys as highly favorable choices for use in various medical devices and implants. However, their rapid degradation and associated challenges have limited their widespread use. This study conducts a thorough analysis into the corrosion behavior of magnesium alloys when open to various coatings, using both in vitro and in vivo environments. The review focuses on understanding the degradation mechanisms, factors influencing corrosion, and the resulting consequences. Additionally, it explores the composition of coatings and metals as effective means to control degradation, along with surface treatment and corrosion management methods. To enhance the degrading behavior, bioactivity, and biocompatibility of magnesium alloys, a multistep approach involving coating techniques such as HA coating, LDH, CaP, and titanium dioxide coating is recommended. These coatings have shown significant potential in improving the exterior properties of Mg alloys. Furthermore, using multifunctional coatings is extremely effective in creating secure and bioactive substrates for the application of biodegradable implants, demonstrating significant potential in the field of biomedical engineering.

The analysis of the small punch test is based on the force on the moving punch and the deflection data acquired at a single point of the specimen bottom. However, the spatial distribution of stress and strain at any given instant is non-uniform and its variations with increase in punch penetration are quite complex. In this work, the digital image correlation (DIC) technique is integrated with small punch test for in-situ full field strain measurement in the bottom surface of the specimen. The DIC results reveal that with the progression of deformation, the peak equivalent plastic strain at the bottom surface shifts from the center of the specimen to a characteristic radial location, where the strain rapidly builds up and concentrates leading to instability and cracking. Combining DIC-based strain results with finite element model-based stress estimation at the characteristic radial location, a methodology for determining the stress–strain curve from small punch test is formulated and the outcomes are compared with tensile test results for four different metallic alloys.

We present the synthesis (solid-state reaction) and characterization of an iron-modified lanthanum silver manganate ceramic, La_0.85Ag_0.15Mn_0.8Fe_0.2O₃. XRD investigation at room temperature using Rietveld refinement indicates rhombohedral crystal symmetry (#R (overline{3}) c) with a crystallite size of 30 nm. Scanning electron micrographs demonstrate a homogeneous distribution of well-grown grains with defined grain boundaries, which is critical for understanding the conductivity mechanism. The compactness of the grains verifies the creation of a dense sample, which could be one of the factors contributing to the observed physical attributes. The purity and uniform distribution of all constituent elements were confirmed using the energy-dispersive X-ray analysis spectrum and color mapping, respectively. The Maxwell–Wagner polarization effect is observable at low frequencies. The analysis of impedance and modulus plots indicates the existence of a negative temperature coefficient of resistance and a non-Debye relaxation process, respectively. The existence of a thermally activated conduction mechanism in the investigated sample is supported by the analysis of AC conductivity as a function of temperature and frequency. The semiconducting nature is supported by the existence of semicircular arcs in both the Nyquist’s and Cole–Cole plots, suggesting that they would be good candidates for energy storage devices. The presence of NTC thermistor character for temperature sensor applications is suggested by the resistance versus temperature investigation.