Metallurgical Behavior Research Articles

Mechanical and Metallurgical behavior of Manual Metal Arc Welded P91 Ferritic Martensitic Steel Joints

In the nuclear power plant industry, Cr-Mo ferritic steels are indispensable due to their high-temperature tensile strength, creep strength, and resistance to stress corrosion cracking. This study evaluated and analyzed the mechanical properties and metallurgical behavior of indigenously developed filler (over matched with base metal) manual metal arc welded Cr-Mo ferritic steel (hereafter referred as P91 steel). The analysis revealed that the ultimate tensile properties of the weld joint exceed those of the unwelded metal, being 6% higher than the base metal. Consequently, the joint efficiency for the weld joint is 106%. However, the impact toughness of the weld pad is significantly lower compared to the unwelded metal, nearly 2.5 times less than the base metal. The weld metal region’s microstructure is characterized by untempered lath martensite pinned with dense dislocations, which is attributed to rapid cooling from the liquidus range. Furthermore, a distinct Heat-Affected Zone (HAZ) was identified adjacent to the weld metal region, which results from the elevated temperature experienced in this area.

Contributions of computing in geosciences: a case study of geometallurgical forecasting

Geometallurgical modeling has been improved over the years with the incorporation of mineralogical, chemical, and metallurgical information. However, the diversity of the database brings challenges since the information is not unified in procedures, sample support, or quantities. Characteristics such as nonlinearity and nonadditivity of the geometallurgical database impose even more difficulties. The objective of this article is to demonstrate the feasibility of geometallurgical models from multivariate techniques combined with computational tools. The algorithms used in this study were developed in Python programming language. The multivariate analysis and machine learning techniques allowed the grouping of transitional typological domains and the quantification of uncertainty; the selection and reduction of the dimensionality of the heterotopic database; and the prediction of metallurgical behavior from exhaustive primary variables using a transfer function. The results were verified and proved to be satisfactory. Other benefits of the computational structure were: reduction of subjectivity; automation; and dynamic updates of models using new data.

Influence of submerged arc welding process parameters and metallurgical behaviour in a thick carbon steel section for boiler application

AbstractThe aim of the research is to investigate the weldability of thick sections of carbon steel using submerged arc welding with varying process parameters. The experimental design for joining thick carbon steel involves manipulating input weld process parameters such as current (A), voltage (V), weld speed (mm/h), and weld electrode diameter (mm). The quality of the weld material is assessed based on transformations in microstructure, weld hardness measured by Brinell hardness number, and tensile strength (MPa). It is crucial to note that the grain structure and metallurgical behavior of other hard materials may differ significantly. The presence of carbon in the ferrite phase has led to the formation of bainite, martensite, and composites of martensite and austenite within the weld zone, as confirmed by high‐resolution microscopy. The weldment‘s hardness has increased from 242.5 HV 30 in the base metal to 316.4 HV 30 in the weldment due to metallurgical alterations in the microstructure. Weld energy input emerges as the primary factor influencing weld quality. With increasing weld current and voltage, there is a corresponding increase in the joined metal, resulting in improved characteristics in the weld structure, particularly at maximal energy input and welding speed. In the context of boiler applications, understanding the weldability of thick carbon steel sections is paramount for ensuring structural integrity and longevity under high‐temperature and high‐pressure conditions. The optimized welding parameters identified in this study can contribute to enhancing the reliability and performance of boilers, thereby promoting safety and efficiency in industrial settings.

Role of the Biogenic Carbon Physicochemical Properties in the Manufacturing and Industrial Transferability of Mill Scale-Based Self-Reducing Briquettes

The recovery of iron contained in mill scale rather than iron ore can be considered a promising valorization pathway for this waste, especially if carried out through reduction using biogenic carbon sources. Nevertheless, the physicochemical properties of the latter may hinder the industrial transferability of such a pathway. In this work, the mechanical and metallurgical behavior of self-reduced briquettes composed of mill scale and four biogenic carbons (with increasing ratios of fixed carbon to volatile matter and ash) was studied. Each sample achieved mechanical performance above the benchmarks established for their application in metallurgical furnaces, although the presence of alkali compounds in the ash negatively affected the water resistance of the briquettes. In terms of metallurgical performance, although agglomeration successfully exploited the reduction by volatiles from 750 °C, full iron recovery and slag separation required an amount of fixed carbon higher than 6.93% and a heat treatment temperature of 1400 °C. Finally, the presence of Ca-, Al-, and Si- compounds in the ash was essential for the creation of a slag compatible with steelmaking processes and capable of retaining both phosphorus and sulfur, hence protecting the recovered iron.

Tribological behavior of PDC-cutter including cemented carbide and polycrystalline diamond composites produced by HPHT for drilling applications

In this study, the tribological behavior of PDC-cutter including WC particles/Ta-20Nb binder composite as substrate and polycrystalline diamond composite as PCD layer produced by high pressure-high temperature (HPHT) for drilling applications was investigated. To examine the metallurgical behavior, phase analysis, hardness of substrate and PCD layer, and tribological behavior, scanning electron microscopy, X-ray diffraction, Vickers microhardness, and wear tests were used, respectively. Due to the HPHT of the manufacturing process, the high hardness of the interfaces, especially for the WC/Ta-20Nb was achieved, which had ∼28% higher hardness than the diamond grits/Ta-20Nb binder. Therefore, no obvious porosity was observed in the interfaces and the composites were completely densified because the particles had good retention strength. The wear results showed that the tribological behavior of PCD layer/granite or marble pairs was directly influenced by the binder content, with samples having a lower binder content showing superior wear performance. Additionally, worn surface investigations demonstrated that adhesive and abrasive wear mechanisms were present in all pairs, with their intensities being strongly correlated with the binder concentration.

Fluid Flow, Solidification and Solute Transport in Slab Continuous Casting with Different S-EMS Installation Positions

During continuous slab casting, strand electromagnetic stirring (S-EMS) has a significant effect on improving the slab quality. In the current work, a numerical model based on the practical slab continuous casting machine and coupled electromagnetic field, flow field, solidification, and solute transport was established to investigate and evaluate the effect of the S-EMS installation position with various current intensities on metallurgical behavior. The model was verified by magnetic field measurement, infrared camera, and nail shooting experiments. The results show that moving the S-EMS installation position to the solidification end reduces the stirring effect due to the skin effect and the increasing thickness of the slab shell. A higher installation position is beneficial for improving the equiaxed grain rate, while a lower one is beneficial for reducing carbon segregation. The maximum segregation index and range decrease from 1.26 to 1.2 and from 0.42 to 0.36 with the installation position being decreased from −3 m to −12.8 m, respectively. The industrial trials show that S-EMS installed at 3 m has a significant effect on expanding the equiaxed grain zone and a deteriorating effect on reducing carbon segregation.

Effect of friction time on the metallurgical behavior and mechanical properties of similar AA2024 and dissimilar AA2024/TA6V rotary friction welds

Effect of friction time on the metallurgical behavior and mechanical properties of similar AA2024 and dissimilar AA2024/TA6V rotary friction welds

Study of microstructure and mechanical properties of SA553/SA537 steels joints using multi-pass welding for pressure vessels application

In this study, gas metal arc welding (GMAW or MIG) process was investigated for similar and dissimilar joints of SA553 and SA537 steel plates in different thicknesses with E NiCrMo-3 filler metal and 0–3 panel joint design that joined pressure vessels body to manholes. In order to examine the metallurgical behavior of the weld, optical and scanning electron microscopies were used. The effect of cooling rate (∂T∂t) on microstructure, strength and impact energy (cryogenic fracture toughness) were examined. By doubling the thickness (6–12 mm), the heat transfer rate or cooling rate (∂T/∂t) increased 4 times. Therefore, the strength and impact energy for the similar welding joint SA553 increased by about 8 % and for the similar welding joint SA537 by about 5 %. For dissimilar weld joints with different thicknesses, strength and impact energy are caused by the type of base metals and the different cooling rates of each base metal. Due to the high elongation of the E NiCrMo-3 electrode (30 %), there was continuous plastic deformation during bending tests. Also, by carrying out radiographic tests, the absence of cracks in welding structures was confirmed.

Underwater wet welding of high-strength low-alloy steel using self-shielded flux-cored wire with highly exothermic Al/CuO mixture

Underwater wet welding processes with minimal energy consumption and high efficiency is the future goal for researchers in the field. Al/CuO exothermic mixtures in consumables for land welding process can improve welding process stability and decrease the electrical dependence of the welding process. To confirm the beneficial effects of Al/CuO thermite and gain a better understanding of metallurgical properties of the thermite welds in underwater environment, this study investigated underwater wet self-shielded flux-cored arc welding (FCAW-S) of high-strength low-alloy steel with highly exothermic Al/CuO mixture. The effects of Al/CuO thermite on arc stability, weld metallurgical behavior and melting characteristics of flux-cored wire were clarified. The ratio of chemical heat in the flux to the heat required to melt welding wire increased from 4.7% to 38.4% with the addition of Al/CuO, potentially accelerating the melting of flux-cored wires. The arc stability with thermite addition was superior to that without the addition of thermite. The presence of copper as a result of metallurgical reactions had a substantial impact on metallurgical behavior of underwater wet welds. The ferrite weld was a non-equilibrium Cu supersaturated solid solution, which increased the microhardness and tensile strength of wet welds. The measured cooling time proved that the incorporation of Al/CuO had the capacity to reduce cooling rate. The incorporation of 50 wt% thermite yielded a 7.8% increase in welding process efficiency compared to the base formulation. Current work provided an important direction for the development of a chemically self-heating flux-cored wire.

Depriving friction stir weld defects in dissimilar aluminum lap joints

The contemporary automotive industry increasingly incorporates composite materials and innovative joining techniques to meet customer demands for lightweight, high-strength alloys. This research explores the feasibility of using friction stir welding (FSW) methods to fabricate dissimilar aluminum nanocomposite lap joints, integrating Al2O3 nanoparticles into the weld nugget. Lap joints were prepared with varying tool rotation speeds (1000–1600 rpm) and the mechanical and metallurgical behaviors of AA6061–AA7075-T6/Al2O3 lap joints were examined. The inclusion of filler material in the weld joint resulted in an 18% increase in shear strength compared to joints without filler. Dynamic crystallization impeded grain boundaries and reduced grain size in the weld stir zone (SZ), with the most enhanced mechanical characteristics observed at a tool rotation speed of 1400 rpm. The shear strength at 1400 rpm was 5780 N, representing a 17% increase compared to joints prepared at 1000 rpm. Field emission scanning electron microscopic examination revealed evenly dispersed Al2O3 nanoparticles within the weld zone, supporting the lap shear test results. Notably, joints created at lower (1000 rpm) and higher tool rotational speeds (1600 rpm) exhibited brittle fracture behavior. The addition of Al2O3 significantly improved lap joint tensile strength due to its uniform dispersion in the SZ. Increasing the FSW tool rotational speed from 1000 to 1400 rpm facilitated nanoparticle dispersion, further enhancing lap joint strength.

Mechanical and Metallurgical behaviour of Aluminum/graphene nanocomposites in Fuselage applications

Mechanical and Metallurgical behaviour of Aluminum/graphene nanocomposites in Fuselage applications

Tribological, corrosion, mechanical, and metallurgical behavior of clay and Al2O3-reinforced aluminum-based composite material

Aluminum-based composite materials have garnered considerable attention in recent years owing to their outstanding mechanical and tribological properties. The integration of clay and Al2O3 into the aluminum matrix has notably elevated its tribological, corrosion, mechanical, and metallurgical characteristics. An examination of the metallurgical properties involved a thorough analysis of the material's microstructure and wettability. Notably, the composite material demonstrated enhanced wettability and a more uniformly distributed reinforcement, leading to improved mechanical attributes when incorporating 5% alumina and 5% clay particles. This composition resulted in heightened strength, improved hardness, and increased fatigue strength. Specifically, the addition of a mixture of ball-milled 5% alumina and 5% clay particles led to substantial improvements, with tensile strength, hardness, and fatigue strength increasing by approximately 40.49%, 44.11%, and 62.15%, respectively. However, this enhancement came at the cost of reduced toughness in aluminum, decreasing by about 46.66% following the addition of the ball-milled mixture. Tribological assessments, involving wear tests under varying loads and speeds, demonstrated that the inclusion of 5% clay and 5% Al2O3 substantially improved wear resistance. Furthermore, corrosion resistance was evaluated, revealing that the composite material exhibited enhanced corrosion resistance attributed to the passivation of the surface. Altogether, these findings underscore the promising potential of aluminum-based composite materials for various applications, particularly when tailored with specific ratios of alumina and clay particles.

Role of Ti and Cr on microstructure and hydrogen embrittlement of welded joint of low-alloy steel used for armor layer

Welded joints suffer from hydrogen embrittlement (HE) owing to the internal stress generated during welding. Alloying elements play a vital role in the metallurgical behavior of welded joints. In this study, the influence of chromium (Cr) and titanium (Ti) on the HE behavior of welded joints in low-alloy steel was investigated by examining the microstructural morphology, grain characteristics, precipitate particles, engineering stress–strain curves, and fracture modes. The experimental results indicated that, compared with the addition of Cr, the addition of Ti promoted the formation of acicular ferrite in the lower fusion zone (FZ) via Ti-bearing oxides, and refined the grains of the FZ. The strength and elongation of the Ti joint were superior to those of the Cr joint in both air- and hydrogen-containing environments. Furthermore, compared with the addition of Cr, the addition of Ti improved the HE sensitivity. The fracture modes of both the Cr and Ti welded joints changed from ductile to brittle when the prepared joints were exposed to an H-containing environment.

Study on Ce2Fe14B-based sintered magnets with Ce/RE> 80%

Up to now, the development of Ce/RE> 80% sintered permanent magnets still faces a challenge, owing to their seriously deteriorated microstructure. In this article, the Ce25.5∼31.5Nd0∼5Febal.B1.25M1.15 (wt.%) sintered magnets with Ce/RE > 80% were investigated, the roles of minor Nd substitution were explored. The typical island-like phase common existed in the grain-boundary (GB) regions of Ce2Fe14B-based SC alloys (which destroys the continuity of RE-rich GB phase), was confirmed as a tetragonal B-rich phase (fct-RE5Fe18B18), and probably generated by the peritectic reaction of “L + Ce2Fe14B → CeFe2 + B-rich” at 797 °C. It was found that: the deteriorated microstructures of high Ce sintered magnets were hardly improved (Nd element was not enriched in the main phase as it was expected), and the coercivity increments were far below expectations by directly adding 3–5% Nd in alloy designs. However, the GB phase distribution was more uniform and continuous, Nd-rich shells formed, and magnetic properties were remarkably promoted by blending 2% NdHx powders into the Ce27.5Nd3Febal.B1.25M1.15 (Ce27.5Nd3) magnet during JM milling, compared with the Ce25.5Nd5Febal.B1.25M1.15 (Ce25.5Nd5) magnet with similar composition. The good comprehensive magnetic properties of Hcj = 1.714 kOe, Br = 9.395 kG, and (BH)max = 11.16 MGOe have been reached in the Ce27.5Nd3+2% (NdHx) magnet (Ce accounted for 84.5 wt% of total rare earth). The present work deepens our understanding of metallurgical behavior, process/microstructure designing for Ce/RE> 80% sintered magnets, and shed a light on the large-scale utilization of Ce element in a permanent magnet.

Fabrication and characterization of Ni-TiO2 and Ni-V2O5 single-layer and double-layer coatings with the approach of improving the wear and corrosion properties

The main purpose of this study is to investigate the metallurgical behavior of Ni-TiO2 and Ni-V2O5 single-layer coatings and compare them with Ni-TiO2/Ni-V2O5 and Ni-V2O5/Ni-TiO2 double-layer coatings. The general attitude is the optimal choice of coatings in terms of wear and corrosion properties. The dimensions of TiO2 and V2O5 ceramic powders were 20 nm and 500 nm, respectively, and their morphology was also different. The presence of the submicron V2O5 particles was more than the TiO2 nanoparticles in the nickel matrix deposit. Also, with double layering the coatings (Ni-TiO2/Ni-V2O5 and Ni-V2O5/Ni-TiO2), the presence of ceramic particles in the upper layer had increased compared to the same single-layer coatings. Therefore, the increase in the hardness of the deposits was directly related to the percentage of ceramic powders in the coating. The surface morphology of the Ni-TiO2 layers was formed as a cauliflower shape while the Ni-V2O5 deposits had a smooth morphology. Increasing participation of TiO2 particles in the Ni-TiO2 layer had made the morphology rougher. Also, by applying the Ni-TiO2 layer under the Ni-V2O5 deposit, the surface morphology of the Ni-V2O5 layer became smooth, which can be due to the increase in the V2O5 content in this layer. The lowest amount of fluctuation appeared in the roughness profiles related to the Ni-V2O5 layers, and the large fluctuation range in the Ni-TiO2 layers was due to the smooth and cauliflower structure, respectively. The crystallite size in double-layer coatings was smaller than the single-layer coatings due to the higher nucleation and growth rate of nickel deposition in the nickel matrix upper layers. According to the presented results, the Ni-V2O5 and Ni-V2O5/Ni-TiO2 coatings were the most wear resistant coatings. Also, the Ni-V2O5/Ni-TiO2 and Ni-TiO2/Ni-V2O5 double-layer coatings were suitable candidates for corrosion resistance and to consider both properties, Ni-V2O5/Ni-TiO2 was very suitable. Hardness, surface morphology, roughness, preferred planar texture, and ceramics powder participation were important parameters in determining the wear and corrosion properties of coatings. Also, it seems that the effect of the double layering of nickel matrix deposits on the metallurgical properties was greater than the dimensions of the ceramic particles participating in the coating.

Predictive insights for copper recovery: A synergistic approach integrating variability data and machine learning in the geometallurgical study of the Tizert deposit, Morocco

This work involved the application of machine learning (ML) to predict copper recovery through variability data in the context of the geometallurgical study of the Tizert deposit in Morocco. For this purpose, geological and metallurgical variability investigations were conducted on drilling samples from Tizert ore, leading to the consolidation of a robust database for ML algorithms. The dataset comprised 345 observations across seven variables, namely GPS coordinates, geological units, lithological facies, the main copper deportment, and metallurgical responses from flotation tests, as well as the copper grade and the oxidation rate. The geological and mineralogical variability revealed two geological units: The Basal Series and Tamjout Dolomite unit, hosting copper mineralization dominated by chalcocite and malachite. Besides, the metallurgical evaluation demonstrated recovery variability, primarily influenced by oxidized copper. Copper oxides exhibit less efficient flotation than sulfides, with recovery decreasing as the oxidation rate increases. The prediction of copper recovery was performed using the variability data through the XGBoost algorithm. The resulting model showed good performance on the test dataset, with a coefficient of determination R2 of 0.83 and a RMSE of 2.47, improving the accuracy of copper recovery predictions. In addition, the model elucidated the most significant variables impacting Tizert ore behavior, notably the casing, copper-bearing mineral, and oxidation rate. These variables were considered key factors for advancing Tizert ore valuation and geometallurgical model development. Overall, metallurgical modeling based on the ML approach provided an innovative way to integrate variables into mine planning and processing. The use of such a predictive model gave valuable insights for improving efficiency, understanding the metallurgical behavior, optimizing production, and reducing costs along the value chain of the Tizert deposit. Further data processing efforts are underway, to improve the assessment of copper recovery quality for the Tizert ore and the development of a complete geometallurgical model on a plant scale.

The Effect of Niobium Addition on the Operational and Metallurgical Behavior of Fe-Cr-C Hardfacing Deposited by Shielded Metal Arc Welding

Hardfacing is commonly used in parts recovery and in obtaining surfaces with improved properties. Within this field, it is important to analyze the effect of alloying elements on the properties of the deposited layers. One of the critical parameters affecting alloying performances in SMAW is improper arc length. This article examines the effect of the addition of niobium in different quantities (0, 2, 4, 6, and 8% by weight) to the electrode coating in Fe-Cr-C shielded metal arc welding (SMAW), with short and long arc lengths, on the operational process efficiency, dilution, arc energy, microstructure, and microhardness of the deposited layers. A decrease in operational process efficiency and dilution was found with increases in niobium content. On the other hand, it was found that adding niobium leads to a refinement in chromium carbide sizes, directly affecting the hardness of the obtained deposits. There is a direct relationship between the arc energy, with both short and long arc lengths, leading to a tendency to decrease the dilution in the obtained hardfacing.

Finite element modeling of machining-induced microstructure evolution of IN625 superalloy fabricated by laser-based powder bed fusion

The surface quality of components fabricated via laser-based powder bed fusion (L-PBF) is highly dependent on the post-machining technique. This study aims to investigate the microstructure evolution of the turning-affected subsurface layer of the IN625 superalloy manufactured by L-PBF with the assistance of the finite element analysis (FEA). A finite element model with integrated user-defined subroutine VUSDFLD was created for numerical modeling of the dislocation density and grain size evolution due to turning operation. The simulation results regarding grain size and the depth of the affected layer were validated against the experiments. This study shed some light on the metallurgical behavior evolution when turning of L-PBF of nickel-based superalloy based on the proposed material microstructure model.

Effect of Heat Input on the Metallurgical Behavior of Underwater Wet Welding Using FCAW-S Process

Resumen La soldadura subacuática mojada utilizando el proceso con alambre tubular autoprotegido ha sido foco de estudio en los últimos años debido principalmente a su mayor productividad en comparación con el proceso de soldadura manual con electrodo revestido. En la presente investigación se evalúa el efecto del aumento del aporte térmico sobre las características geométricas y microestructurales de cordones de soldadura desarrollados sobre placas de acero ASTM A36. Para este propósito, fueron realizadas tres soldaduras experimentales con diferentes velocidades de avance resultando en tres niveles diferentes de aportación térmica. Las características geométricas evaluadas fueron la penetración, el refuerzo y el ancho de la zona afectada por el calor (ZAC), además, se llevó a cabo el análisis de la porosidad interna y de la microestructura en la sección transversal de cada cordón. Los principales resultados mostraron que el aumento de aporte térmico incrementa el refuerzo, la penetración y el ancho de la ZAC. Por otra parte, la microestructura de la zona de fusión consistió básicamente de ferrita y bainita, mientras que en la ZAC se detectó presencia de martensita. El análisis general de los resultados indicó que es posible obtener soldaduras clase B según el código de soldadura AWS D3.6.

Metallurgical Behaviour and Characterization on Polymer Metal with HCHCr Tool by using Friction Stir Welding Adopting L27 Taguchi Technique

Friction stir welding is a technique of combining harmless for the environment because it doesn’t use flux or any other shield gas and doesn’t produce hazardous gas. To study the FSW process on composite material this work offers an experimental enquiry and optimisation technique. In this investigated how input process operating factors like tool rotational speed, feed rate and depth of cut affect an output parameter like hardness of welded connections and Ultimate Tensile Strength (UTS), Microstructure and metallurgical on the metal. To achieve this L27 Taguchi approach orthogonal array used to optimise design tests on friction stir welding parameters and also HCHCr tool used to improve the good weld ability and to increase the heat input. The experimental setup is run with several combinations of process parameters such as 900, 1000, and 1200 rpm of Tool rotational speed 20 mm, 25 and 30 mm as feed rate by adjusting the depth of cut values of 5.4 mm, 5.6 mm and 5.8 mm respectively. Additionally, utilising the regression analysis equations (ANOVA) used to identify the significant input parameters how it effects for the output metal structure. Finally, by achieved effective evaluation of the metallurgical and microstructure on the nylon 6A metal by various analysis and Testing.