Transactions of The Indian Institute of Metals最新文献

Froth flotation is a widely used technique for the beneficiation of fine coals, specifically those whose size less than 0.5 mm. In this study, the flotation performance of Karma coal samples from Central Coalfields Limited (CCL) was analysed using the release analysis technique. The experimental samples had a size range of − 0.15 to + 0.074 mm. Various operational parameters such as collector dosage (kg/tonne), frother dosage (kg/tonne), and pulp density (%) were modified to assess their impact on flotation performance. Release curves were plotted to determine the cumulative product percentage and the product ash percentage for different operating parameters. The highest yield achieved was 92.33% with a combination of diesel oil and pine oil at dosages of 0.75 kg/tonne and 0.5 kg/tonne, respectively. This yield had an ash level of 30.65% at a pulp density of 15%. Conversely, the lowest yield of 53.26% was obtained using a single MIBC frother at a dosage of 0.15 kg/tonne.

In this study, the dissolution conditions and dissolution kinetics of copper from malachite in the presence of organic acid (C₄H₆O₆) as an organic leaching reagent were examined. The effects of particle size, acid concentration, time, solid/liquid ratio, temperature, and mixing speed on the dissolution process of copper were investigated. According to the test results, optimum dissolution conditions are as follows: particle size was 74 µm; organic acid concentration was 0.2 mol/L; duration was 60 min; solid/liquid ratio was 1/10; the temperature was determined as 25 °C and the stirring speed was 300 rpm; and the copper extraction value was obtained as 73.18% under optimum experimental conditions. Kinetic models were applied to the dissolution efficiencies obtained to determine the dissolution kinetics of copper in the presence of organic acid, and it was found that the dissolution process was controlled by the film diffusion model. In light of the data obtained, it can be said that organic acid, which is an economical and environmentally friendly leaching reagent, can be used in the dissolution of copper from malachite ((text{Cu}(text{OH}{)}_{2}{text{CuCO}}_{3})), as well as in the leaching of other precious metals such as copper, zinc, and cobalt from oxide and carbonate ores.

In this work, a new Double Rotating Shoulder (DRS) tool is designed to create a preheating effect and promote material flow in the shoulder-affected area during friction stir welding (FSW). A comparative study of the temperature field, strain field and material flow of AA 6061 aluminium alloy during FSW using a DRS tool and a conventional tool was carried out using numerical simulation. The model was verified according to the actual temperature field in both cases. Further, the macroscopic morphology and mechanical properties of both joints were investigated. The results showed that the simulated temperature field during FSW using a DRS tool has a good correlation with the actual temperature field. The DRS tool does lead to different macroscopic profiles but has almost no impact on mechanical properties.

In this work, the magnetic hysteresis loop of the polyvinyl alcohol@CoFe₂O₄ nanocomposite has been predicted and simulated using a deep artificial neural network (ANN) and Monte Carlo (MC) methods. To increase the capability of the traditional neural networks in modeling and forecasting problems, the proposed deep ANN has two hidden layers that benefit from deep learning techniques to overcome well-known issues such as overfitting and gradient vanishing. The deep ANN predicted results were compared with the simulated and experimental hysteresis loops of the synthesized polyvinyl alcohol@CoFe₂O₄ nanocomposites obtained from the vibrating sample magnetometer and MC method. The interaction between polymer and nanoparticles, their structure, and morphology were analyzed employing Fourier transform infrared spectroscopy, X-ray diffraction spectroscopy, and field emission scanning electron microscopy. Comparison between the hysteresis loops revealed that the deep ANN method that has been trained with the previous published data was successful in the prediction of the shape and coercive field of particles in a polymer matrix relative to the MC method, which considered only the uniaxial anisotropy and Zeeman energy of the nanoparticles. The coercivity and remanence magnetization measured with the accuracy of about 93.33% and 62.23% for deep ANN method and 80.76% and 66.66% for MC method, respectively.

A dissimilar TWIP/304L joint was produced using oscillation fiber laser welding with welding speeds of 80 mm/s and 120 mm/s, as well as different power levels. Tensile tests, hardness measurements, and SEM/EDS/EBSD analyses were conducted to reveal the characterization of dissimilar TWIP/304L steel joint. Oscillation of the laser beam resulted in layered marks in the fusion zone. These layered marks contain primary austenitic dendrites and inertinitic secondary austenite. Both steels exhibited narrow heat-affected zones. An interlayer of an unmixed zone was formed between the fusion zone and the heat-affected zone of 304L due to differences in their liquidus points. Some intergranular gaps were observed in the heat-affected zone of the TWIP steel. The maximum tensile strength, 561.3 MPa, was achieved at a laser power of 3600 W and a welding speed of 80 mm/s. All specimens failed from the fusion zone of the dissimilar joint due to high hardness difference and underfill induced notch effect. The hardness difference reached 51.4 Hv10 due to the heterogeneous composition of the fusion zone. This variation in the microstructure resulted in both ductile and brittle fractures.

Aluminum matrix composites incorporating titanium carbide (TiC) and nickel (Ni) were fabricated through the ultrasonic-assisted stir-casting technique. Micrographs revealed the uniform dispersion of TiC particles within the matrix, while Ni reacted with aluminum, forming the intermetallic compound Al₃Ni, dispersed along the grain boundaries. The incorporation of TiC and Ni resulted in a considerable decrease in grain size from ~ 130 to ~ 49 µm. Notably, the incorporation of 3 wt% TiC and 6 wt% Ni (sample S(3,6)) exhibited a substantial increase in yield strength (YS), ultimate tensile strength (UTS), and hardness by 51.11%, 32.57%, and 46.96%, respectively, compared to the unreinforced sample S(0,0). The observed improvements in these properties can be ascribed to a mix of factors, including grain refinement, Al₃Ni precipitate hardening, and dispersion hardening facilitated by the TiC particles. The increase in reinforcement weight percentage results in a decrease in the wear rate of reinforced composites, while wear rates for these composites exhibit a linear increase with a change in load from 10 to 20 N.

The reaction between MoAlB MAB phase and molten ZnCl₂ salt resulted in the formation of metastable Mo₂AlB₂ MAB phase. In our previous work, it was first discovered by us that the periodic layered structure (PLS) was formed at the solid (Cr, Fe)₂B/molten Al interface during hot-dip aluminizing and subsequent thermal diffusion treatment of Fe–Cr–B cast steel. The interaction between PLS form in situ, especially the Cr–Al–B MAB phase contained in the PLS, and molten ZnCl₂ salt was studied for the first time in this work. There were complex reactions between the PLS and molten ZnCl₂. Specially, the Zn²⁺ in the molten ZnCl₂ salt could partially occupy the positions of Al atoms in the Cr–Al–B MAB phase contained in the PLS through the A-site replacement reaction. The topochemical reaction was: Cr₃AlB₄(s) + ZnCl₂(l) → Cr₃(Al, Zn)B₄(s) + Zn(l) + AlCl₃(g).

Graphical Abstract

Arc welding of Al–Zn–Mg–Cu (7xxx) high-strength Al alloys is an urgent problem to be solved. In this study, tungsten inert gas (TIG) welding of 7075 Al alloy with newly developed 7075 Al alloy wire as filler is successfully carried out and the full-penetration and defect-free joint is formed. The fusion zone (FZ) is consisted of fine and equiaxed α-Al dendrites and a narrow transition zone (TZ) with columnar α-Al grains is formed between the heat-affected zone (HAZ) and FZ. The minimum hardness is obtained in FZ in 7075 Al alloy-welded joints and post-weld heat treatment (PWHT, solid solutioned at 480℃ for 1 h and then aging at 120℃ for 24 h) induces significant hardening in both FZ and HAZ due to the precipitation of GP zones and η' phase. The yield strength, ultimate tensile strength and ductility of as-welded joint are 223 MPa, 374 MPa and 4.6%, and they are improved to 435 MPa, 533 MPa and 7.8%, respectively, after PWHT. The high-strength coefficient for 7075 Al alloy TIG-welded joint can be attributed to the 7075Al alloy wire filler, optimized TIG welding parameters and PWHT.

This manuscript expounds the crystallization behavior of CaO–SiO₂–MgO–Al₂O₃ (CSMA) slags towards the smooth operation of the blast furnace, where a structure-oriented elucidation for viscous flow was highlighted for deeper understanding of the crystallization behavior. The CCT curves collected from confocal laser scanning microscopy showed that the initial crystallization temperatures decreased with lower CaO/SiO₂ mass ratios, and the primary crystal phases transformed from a merwinite phase (Ca₃MgSi₂O₈) with a stronger crystallization ability to a melilite solid solution (Ca₂Al₂SiO₇–Ca₂MgSi₂O₇) with a comparatively weaker crystallization ability, which correlates well with the variation of Mg/Al mole ratios in melilite and verifies the formation of Ca₂MgSi₂O₇ as one of the main reasons for the poor fluidity of the slag. Furthermore, a higher viscosity was observed for modified slags with CaO/SiO₂ mass ratios from 1.34 to 1.05, accompanied by the activation energy increased from 173.0 to 182.7 kJ/mol, which is consistent with the decreased NBO/Si value and the increased Q³/Q² ratio detected by Raman spectra. The crystal phase with melting point higher than the discharged temperature and the enhanced degree of polymerization of the slag structure will lead to the poor fluidity of the slag, which should be emphasized in the actual modification of the blast furnace slag.

The present study deals with the development of a harmonic structured commercially pure Ti using a novel and newly designed press-milling method to surface-deform the Ti powder particles and subsequent sintering. The harmonic structure is a bimodal distribution of fine and coarse grains where a continuous network of fine grains (shell) surrounds discrete clusters of coarse grains (core). A harmonic structured Ti featuring a shell with an average grain size of ~ 4.3 μm and a core with an average grain size of ~ 12 μm is obtained. The HCP crystal structure in the XRD patterns indicates the absence of any phase transformation due to press-milling. The hardness of the shell region improves ~ 2.5 times that of core regions. The compression studies also show an improved combination of strength and ductility in the harmonic structured Ti.