This manuscript intends to carry out a comprehensive study on the microstructural evolution, mechanical properties and performance of DP780 dual-phase steel joints under the influence of the post-weld cooling rates during Shielded Metal Arc Welding (SMAW). DP780 has already been used for thin-gauge automotive components; in this study we evaluate the suitability of the 6 mm thick plates in high-pressure industrial applications requiring weight reduction. The cooling mode was set to three different modes including water quench (rapid), still air (moderate), and thermal insulation blankets (gradual). Specific microstructural characterization of the Fusion Zone (FZ) and Heat Affected Zone (HAZ) indicated that rapid cooling leads to a large volume fraction of lath martensite with a maximum microhardness of 350 HV and ultimate tensile strength (UTS) of 728 MPa. In comparison, moderate cooling enables a balanced phase distribution of bainite and polygonal ferrite, resulting in considerable tensile strength versus ductility trade-off, attaining a yield strength of 624 MPa. The observed gradual cooling leads to the development of a coarser ferritic-pearlitic structure, which reduces the hardness and load-bearing capacity considerably. Tensile testing also revealed high dependence upon the phase transformations due to cooling at the FZ/HAZ interface. This reinforces the importance of accurate thermal control for high-strength steel joint safety due to peak loading conditions.
This study used a solvent extraction technique with AcorgaOPT5510 extractant in kerosene to examine the extraction of copper ions from the actual leach solution produced after leaching malachite ore in sulfuric acid solutions. On the Cu/Fe separation factor and the effectiveness of copper extraction, the impacts of significant parameters, including stirring speed, contact duration, extractant concentration, beginning solution pH, and temperature, were examined. The following values were chosen as the optimal ones: 1:1, 1.5, 12%, 20 °C, 10 min, 10 min, and 500 rpm for maximum Cu2+ extraction from the aqueous-phase, aqueous/organic phase ratio, equilibrium pH of the aqueous phase, extractant concentration, temperature, contact time, settling time, and stirring speed. Under these conditions, 94% of the copper in the leach solution was removed, yielding about 40.09 Cu/Fe separation factor. A McCabe-Thiele plot was revealed, and it was shown that a two-step extraction procedure would yield the best results. Furthermore, employing a sulfuric acid concentration of 4 mol·L-1 for 10 minutes, the loaded organic phase was stripped and recovered 91% copper.
Laser-induced breakdown spectroscopy (LIBS) shows great promise for the rapid chemical characterization of materials. However, quantitative analysis of elements remains challenging due to strong matrix effects and the predominance of emission lines. In the present study, a machine learning–assisted LIBS model (LIBS-ML pipeline) was employed to analyze carbon, medium-alloy, and high-alloy steels. A total of 900 spectra from 18 reference specimens were used to train Random Forest (RF), Gradient Boosting (GB), and Extremely Randomized Trees (ET) ensemble models, while five independent steel specimens were reserved for prediction evaluation. The ET model demonstrated the best training performance (MSE = 0.1551; R² = 0.9435), while the RF model exhibited greater stability during independent validation. Low prediction errors were obtained for carbon steels, with mean absolute error (MAE) values as low as 0.0142 wt% for C and 0.0178 wt% for Mn. In medium-alloy steel, the predicted values of Cr and Ni remained close to the nominal compositions. Higher deviations were observed in high-alloy steel, with MAE reaching 1.1191 wt% for Ni and 1.0919 wt% for Mo, reflecting the increased complexity of the matrix. The obtained results confirmed the LIBS–ML pipeline applicability for quantitative steel analysis and highlight its potential as a rapid tool for metallurgical monitoring and alloy characterization.
This year marks the 138th anniversary of the beginning of modern Hydrometallurgy. This milestone began in 1887 with the publication of the cyanidation patent by McArthur and the Forrester brothers, which represented a decisive step forward in the recovery of gold from gold-bearing ores. New technologies, such as gold adsorption on activated carbon, have made cyanidation the established basis of gold Hydrometallurgy. On the other hand, in the 21st century, the concept of urban mining and recycling has made the recovery of gold from waste materials a necessity. This work combines the basic concepts of gold Hydrometallurgy with new developments in this technology when applied to both primary and secondary materials.
The use of carbon-fiber-reinforced polymers (CFRPs) is common in high-performance engineering because it has a high strength-to-weight ratio and mechanical characteristics. Nevertheless, micro-holes of CFRP laminates are difficult to obtain in high-quality because of the destruction created by drilling, especially delamination. In this research, micro-drilling tests were performed on CFRP laminates in a vertical machining center, taking into account the spindle speed, feed rate and drill treatment conditions. The performance of drilling was assessed in terms of thrust force and entry delamination factor. An experimental design was conducted with the help of a Taguchi L9 orthogonal array, and signal-to-noise (S/N) ratio and Analysis of variance (ANOVA) were used to analyze the results. The analysis indicated that the most influential factor is the drill condition, which contributed about 66% to the variation, then the spindle speed, and the feed rate had little influence. The cryogenically treated drill greatly enhanced performance, minimizing the thrust force to at least 1.6 N and delamination factor to 0.32 in experimental conditions. The optimum drilling parameters were confirmed thus it indicated that the responses predicted were in good agreement with confirmation results. The results indicate that statistical optimization of the tool surface modification is extremely useful in reducing the damaging effects of drilling, which offers viable advice on the high-precision production of micro-holes in CFRP.
