Journal of Manufacturing Innovations
Volume:1 Issue: 2, Spring 2023

Third-generation advanced high-strength steels serve as advanced engineering materials in various industries, including land, air, rail, and maritime transportation, with expanding applications. In the present study, a sample of low-alloy steel with medium carbon content (0.529 wt%) and high silicon content (1.670 wt%) was selected and subjected to one-step quenching and partitioning heat treatment at temperatures of 140 and 180 oC for different partitioning times (isothermal holding for redistribution of carbon element between initial martnsite and untransformed austenite). Phase transformations and microstructural investigations were conducted using dilatometry, laser microscopy, and Electron Backscatter Diffraction (EBSD) analysis. Dilatometry results indicated that the formation of initial martensite occurs at a temperature of 275 oC, and during a holding time of 3600 s, only carbon partitioning into retained austenite takes place at temperatures of 140 and 180 oC, yet martensite formation occurs during the final cooling. Additionally, considering the changes in specimen width during isothermal holding, tempering of the initial martensite can be anticipated. Microstructural examinations also confirmed the formation of microphasic structures, including initial martensite, retained austenite, and final martensite.

The kinetic assessments for calcination reaction (dehydration reaction) of the bauxite sample was studied in this article under non-isothermal condition. After crushing and grinding the bauxite sample, the chemical analysis of the sample was obtained using x-ray fluorescence (XRF) method. The X-ray diffraction (XRD) patterns identified boehmite, hematite, and silica (silicon oxide) as the primary phases in the bauxite sample. The calcination reaction of the bauxite sample was evaluated using simultaneous thermal analysis (STA). The results of STA analysis indicated that the calcination reaction occurred at approximately 537 °C, with the final mass loss reaching about 13%. When the bauxite sample was heated to 600 °C in an air atmosphere for one hour, the boehmite phase decomposed, but the aluminum oxide phase did not fully crystallize. Kinetic evaluations were conducted using thermogravimetric analysis (TGA) data (STA analysis) under non-isothermal conditions, employing the Coats-Redfern method. The kinetic assessments revealed that the activation energy for the calcination reaction of the bauxite sample containing the mineral boehmite is approximately 198 kJ/mol, and the reaction follows the Crank equation of the diffusion models.

In this research, the Smoothed Particle Hydrodynamics (SPH) method has been used to model the dynamic behavior of solids under large deformation. In this regard, a set of combined equations for linear momentum, deformation gradient tensor, volume mapping, and area mapping (the co-factor of the deformation gradient tensor) is derived in form of first-order conservation laws. Subsequently, the corrected SPH method has been employed for spatial discretization within the solution domain. To reduce computational costs, explicit temporal discretization is considered using the third-order Runge-Kutta method. In the SPH meshless method, neighboring point information is utilized for computations. The primary objective of employing these equations in Updated Lagrangian description, where neighboring points may change at each time step, is enabling the simulation of severe deformation, which poses challenges for mesh-based approaches. Hence, the modeling capability of the proposed numerical method is examined by simulating the behavior of materials undergoing severe plastic deformation in the forging process. The simulation of the necking example demonstrates the model's capability to predict plastic behavior accompanied by large deformations. Additionally, simulation in the forging process accompanied by very large and complex deformations showed that the proposed meshless model can simulate such deformations without the need for ALE formulation or remeshing.

The microstructural characteristics of the CMSX-4 single crystal produced by the Bridgman method at a withdrawal rate of 2 mm/min, was investigated through experimental measurements as a function of the distance from chill plate in the present study. The single crystal examined in this research was fabricated using a vertical Bridgman device equipped with a radiation baffle. The microstructural characteristics of the primary dendrite arm spacing (λ₁) and the secondary dendrite arm spacing (λ₂) have been calculated from transverse and longitudinal sections at different distances from the chill plate, using software analysis of images prepared with an optical microscope (OM). The comparison of the obtained values for the microstructural characteristics λ₁ and λ₂ reveals that both variables increase with increasing distance from the chill plate by 19.6% and 18.8%, respectively, in the single crystal. Additionally, the thermal gradient has been calculated based on the primary and secondary dendrite arm spacing and the result obtained from the primary dendrite arm spacing was found to be more reasonable due to its better alignment with experimental values.

The integrity of steel pipes is crucial for their application in petrochemical industries and refineries. Given the corrosive nature of the working environment containing sour gasses, the pipes must possess the ability to withstand pressure and temperature, resist corrosion, endure fatigue and comply to safety and environmental regulations. A significant challenge in steelmaking of distinctive steel products, especially high-strength low-alloy steels, is the segregation of carbon, sulfur, manganese, and other elements within the slab's core. Additionally, the solidification process in the slab could leads to the concentration and buildup of shrinkage cavities in the middle thickness of the slab. The Baumann test is a crucial examination in steelmaking process for manufacturing of the pipes and pressure vessels since it verifies the quality of the products. Mannesmann pipes are categorized differently according to this test. In the current research, the microstructure, location and type of defects, has been investigated and the degree of segregation and the shrinkage holes in the slab's cross-section have been studied. The results obtained revealed that the aggregation of alumina and manganese sulfide inclusions were the primary factors contributing to the rejection of Baumann test. The investigations have been revealed that by simultaneously controlling the alumina impurity and using the best practice of secondary cooling, and employing the soft reduction technology, the problem mentioned above could be entirely resolved.

The conventional techniques of pyrometallurgy and hydrometallurgy used to produce copper involve high energy consumption, substantial costs, and pose environmental challenges. Leaching in biocompatible solvents such as deep eutectic solvents (DESs) can be considered a suitable alternative to conventional production methods. In this study, Sungun copper concentrate (SCC), with the primary phases of chalcopyrite, and pyrite, was used to evaluate the leaching of copper, and iron in various DESs with a solid-to-liquid ratio of 20 g/L, at a temperature of 100 °C, and a time of 24 h. Three-component DES based on choline chloride (ChCl) as hydrogen acceptor, and p-toluene sulfonic acid (PTSA), and various third phases as hydrogen donors were used as solvents. The third components are oxalic acid (OA), ethylene glycol (EG), sucrose (S), malonic acid (MOA), fructose (F), urea (U), maleic acid (MA), citric acid (CA), glucose (G). According to the results of the leaching of copper, and iron, selective dissolution wasn’t achieved in any of the ternary DESs. Among these DESs, the ChCl:PTSA:MOA with a leaching efficiency of 89% of copper had the highest leaching efficiency, and at the same time, it dissolved less iron. By adding a small amount of water to sugar-based DES (i.e., ChCl:PTSA:S, ChCl:PTSA:F, and ChCl:PTSA:G), the synthesis was successfully performed by changing the physical, and chemical properties, but the dissolution of chalcopyrite in sugar-based DES was significantly reduced.