Heat-assisted metal spinning comprises incremental forming routes, conventional spinning, shear spinning and flow forming, performed at elevated temperature to increase formability. This review consolidates the main advances of the last fifteen years. It outlines spinning mechanics and the rationale for heating (higher ductility, lower forming forces and microstructure control), then compares global and local heating strategies (furnace, flame, induction, laser and hot-gas convection) in terms of temperature uniformity, industrial practicality, energy efficiency and cost. Key process parameters (spindle speed, feed rate and thickness reduction) are discussed with respect to defect formation, and representative windows for defect mitigation are reported. Progress in modeling is reviewed, including coupled thermo-mechanical finite element simulations, damage/formability prediction and emerging data-driven optimization. The review also summarizes microstructural evolution under heat-assisted conditions, phase transformation, dynamic recrystallisation and grain growth, and its impact on final properties. Across more than 100 studies, evidence shows that robust thermal management can roughly double achievable deformation before failure and enables property tailoring in difficult-to-form alloys (Ni-based alloys, high-strength steels, Al, Mg and Ti). Remaining challenges include reliable in situ temperature measurement/control and improved predictive fidelity of simulations. Future opportunities include digital twins, real-time sensing and adaptive, machine-learning-assisted control.

The slag from electric arc furnace (EAF) steelmaking has potential for various applications, but its safe use requires the assessment of heavy metals, such as chromium leaching, to meet environmental standards. This study investigates the microstructure of EAF slag cooled in a slag pot and its effect on Cr immobilization. Slag samples were collected at full scale using a representative sampling method, dividing the slag pot into six zones (internal and external, top to bottom). Microstructural analysis was performed using scanning electron microscopy coupled with energy dispersive spectroscopy and X-ray diffraction, followed by leaching tests on the milled samples. Thermodynamic calculations were performed using FactSage 8.4 to evaluate phase stability and composition. The results indicate that cooling conditions inferred from slag-pot location, spinel size, and spinel zoning are correlated with variations in Cr leaching under neutral conditions. Slower cooling is associated with the formation of large, reverse-zoned spinel phases that may contribute to Cr stabilization, whereas rapid cooling is associated with smaller, homogeneous spinel phases that may increase leaching risk. These findings provide insights for the environmentally safe utilization of EAF slags and inform strategies to minimize Cr release during slag valorization.

Wrinkle formation is a common defect in metal spinning, particularly during conventional spinning processes. This study investigates the use of a flanged-edge blank to prevent wrinkles by increasing the blank’s edge rigidity. The process forms an angled flange along the blank’s periphery with a spinning roller before performing the first pass of conventional spinning. Finite Element simulations were conducted to evaluate how flange geometry (angle and length) influences wrinkle initiation, and corresponding experiments compared flanged-edge blanks to flat blanks. Analytical calculations of the blank’s second moment of inertia indicate that adding a flange significantly increases bending stiffness. Larger flange angles and longer flanges redistribute material farther from the neutral axis, thereby elevating bending rigidity and raising the critical compressive stress threshold for buckling, which is consistent with classical plate buckling theory. Simulations and experiments confirmed that flanged-edge blanks with a 30° flange angle remained wrinkle-free, whereas flat blanks under identical conditions suffered severe wrinkling. The flange angle emerged as a key parameter in achieving the necessary rigidity and structural stability to suppress wrinkles. Overall, the results confirm that the spinning flanging technique is an effective method to improve conventional metal spinning processes, with significant potential for broader industrial applications.

Explicit dynamic finite element simulations are used to study wrinkle formation in metal spinning. Full three-dimensional models remain computationally demanding and therefore often require numerical acceleration. This work directly compares two acceleration routes in explicit solvers, loading-rate scaling and mass scaling, and systematically examines their influence on wrinkle prediction. An identical process definition and toolpath are implemented in two simulation environments, and predictions are validated against experiments. Quasi-static fidelity is quantified through the kinetic-to-internal energy ratio, while accuracy is evaluated using the axial force history and wrinkle-related axial displacement measures, including the displacement field at the final stroke position and the peak-to-valley amplitude Δ with peak count. Results show that moderate acceleration, up to a factor of 10 for the present setup, maintains a low kinetic contribution and reproduces the experimental force trend and final wrinkle pattern. In contrast, aggressive scaling at a factor of 50 increases inertial contributions, amplifies force deviations, and reduces reliability of wrinkle predictions. These findings indicate that force histories, interpreted with energy diagnostics and surface metrics, provide a basis for validation and for selecting acceleration levels in wrinkle-focused spinning simulations. Equal nominal scaling factors do not necessarily correspond to equivalent inertial content across mechanisms.

A 128 MT high-strength steel ingot was modelled using the finite element method. The thermal and thermomechanical behavior of the metal during solidification is considered in the simulations. The accuracy of the model was validated with experimental results of macrosegregation. Cases with a U-shape, V-shape, and H-shape ingate were investigated. The results for each case are analyzed to assess the influence of fluid flow and solute transport, during mold filling and solidification, on the macrosegregation profiles. The results of this study are used to determine an effective ingate design to improve the quality of the cast ingots. The analysis reveals and quantifies the impact of liquid metal flow field on macrosegregation. The influence of the opening angle of the ingate in limiting the well-known hump effect is demonstrated and the optimum angle determined. The longer solidification time, resulting from change in geometry, improved feeding and reduced both shrinkage and the risk of centerline porosity. The high velocity generated in the hot top region by the V-shape geometry promoted stronger residual flow and extended the isotherms further into the body of the ingot. Both the V-shape and H-shape designs demonstrated reduced macrosegregation in the upper section of the ingot.

Wrinkling remains a limiting defect in spinning processes because the unsupported rim is subjected to repeated circumferential compression, local bending, unloading, and partial recovery during roller contact. This study examines how the edge-preforming route affects pre-strain development, local strengthening, and pass-level wrinkle suppression during a subsequent spinning pass of AA5052-O blanks. Two edge-preforming routes are compared, namely edge forming by bending and edge forming by spinning. Although both routes produce a flanged edge, they impose different deformation histories near the flange root and curvature band. Controlled spinning experiments, Vickers microhardness mapping, and pass-resolved finite element analysis were combined to relate the inherited curvature-band condition to the subsequent wrinkling response. The results show that edge forming by spinning produces a broader prestrained region and a higher level of retained local strengthening than edge forming by bending. This inherited condition improves rim stability during the investigated pass by promoting a more recoverable hoop-strain response and reducing the severity of final circumferential waviness. Edge forming by bending gives an intermediate response, while the flat blank reaches the critical wrinkling condition earlier. The inclined-gap schedule delays late-stage instability for cases close to the wrinkling limit, but it does not change the route-dependent stability order established by edge preforming. The experimental results are therefore evidence of improved pass-level wrinkle suppression, not proof of complete multi-pass conventional-spinning formability. Further validation is required to assess inward material flow, diameter reduction, wall-thickness evolution, residual stress development, and final part accuracy over a complete forming route.

The integrity and corrosion resistance of 316L stainless steel weldments are critically influenced by the presence of oxygen in the backing gas during Gas Tungsten Arc Welding (GTAW). In this study, the effect of varying oxygen concentrations (50, 200, 500, and 5000 ppm) in the purging gas on weld root oxidation was systematically investigated through a combination of experimental and numerical approaches. Computational Fluid Dynamics (CFD) simulations were conducted to determine the spatial distribution of oxygen in the weld region, revealing localized zones of oxygen accumulation at specific angular positions along the weld line. Additionally, a Finite Element Model (FEM) was developed to calculate the temperature gradients in the Heat-Affected Zone (HAZ) and weld region. Thermodynamic analysis was employed to identify the dominant oxide phases. By integrating experimental findings with simulation results, it was possible to quantitatively predict oxide thickness evolution as a function of oxygen content in the backing gas, providing a quantitative link between backing gas purity and root-side oxidation behavior.

The effect of the Cr2O3 content of a synthetic CaO-Al2O3-SiO2-MgO base slag on MgO-C refractory corrosion was studied using controlled lab-scale experiments and thermodynamic modeling. A synthetic slag was designed to replicate a ladle furnace slag exhibiting high desulfurization capacity. The base slag was saturated with MgO to eliminate the thermodynamic driving force for MgO dissolution and to isolate the effect of Cr2O3 on slag penetration and refractory corrosion. Corrosion experiments were conducted at 1625 degrees C in a horizontal tube furnace in an Ar atmosphere, with slags containing 0, 5.0, and 10.0 wt% Cr2O3 for exposure times of 30, 60, and 90 min. Microstructural characterization using scanning electron microscopy coupled with energy dispersive spectroscopy revealed that increasing Cr2O3 content increased slag penetration depth and accelerated corrosion kinetics, primarily through the decarburization of Cr2O3 by reaction with the carbon matrix of the refractory and the dissolution of MgO. Effective penetration rate coefficients were determined for each slag composition, confirming the strong correlation between slag Cr2O3 content and refractory degradation. These findings provide mechanistic insights into the role of Cr2O3 in slag-refractory interactions and are directly relevant to stainless steelmaking and high-chromium alloy production, where Cr2O3-containing slags are prevalent and refractory performance is critical to process efficiency and lining life.

The influence of different prior austenite grain sizes (PAGS) on phase transformation during slow continuous cooling was investigated by high-resolution dilatometry in a medium-carbon low-alloy steel. The selection of different PAGS values was motivated by an industrial case study of a large steel block, in which significant grain size variation occurs between the center and the surface. PAGS of 101 mu m, 202 and 304 mu m, were achieved through austenitization at 1150 degrees C for 10 s, 10 and 35 min followed by continuous cooling with a rate of 0.05 degrees C/ s to room temperature, representative of the cooling of the large size steel block. Analysis of the dilatometry results combined with microstructure investigation using scanning electron microscopy revealed a two-stage phase transformation process. The first one occurred at high temperature and led to the formation of granular bainite and plate-like bainite. The second stage proceeded slowly over an extended duration, leading to the tempering of the bainite formed in the first stage and the formation of martensite from the residual austenite, accompanied by the auto-tempering. X-ray diffraction analysis indicated that, an increase in PAGS led to a rise in the volume fraction of retained austenite from 10% to 24.4%. Average microhardness values remained very similar despite variations in PAGS and volume fraction of phases. In contrast, nanohardness measurements revealed that bainitic ferrite in granular bainite exhibits the lowest hardness, whereas plate-like morphology shows intermediate hardness, and the (M-A) constituents display the highest hardness.

Deposition temperature is a known pivotal process parameter influencing the tribological and corrosion performance of physical vapour deposited ceramic coatings. Yet, the impact of the parameter remains highly system-specific, limiting generalization of observed trends across different coating-substrate systems. Therefore, this study investigates the effect of deposition temperature (350 - 450 degrees C; designated as T350 - T450) on the microstructural evolution, mechanical properties, wear, and corrosion behaviour of AlTiN/AlTiCrN coatings deposited on AISI A8 tool steel for woodworking applications. Coatings were characterized using scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, nanoindentation, scratch testing, ASTM G65 abrasive wear testing, and electrochemical analysis. Results showed that T350 exhibited the lowest wear rate (similar to 2 & times; 10(-4) mm(3)/Nm); 36 and 56 % lower than T400 and T450, respectively. This superior wear resistance was attributed to its higher adhesion (critical load similar to 11 N), thicker coating (2.8 mu m), smoother surface (R-a = 0.25 mu m), and higher H/E ratio (0.072), despite an intermediate hardness (31 GPa). Although maximum hardness (36 GPa) occurred at T400 due to finer crystallite (similar to 10.4 nm) and elevated microstrain (0.77 %), its higher macroparticle density (0.18 particle/mu m(2)) and roughness (R-a = 0.31 mu m) compromised performance. Additionally, corrosion resistance was superior at T350 and T450 (protective efficiency >45 % and porosity <0.70 %), attributed to denser structures, thicker coatings, coarser crystallites, and higher chromium content. Overall, these findings demonstrate that a deposition temperature of 350 degrees C provides an optimal balance of wear and corrosion resistance in AlTiN/AlTiCrN-coated A8 tool steels, offering valuable insights for tailoring PVD process parameters for woodworking applications.

Hybrid manufacturing routes combine additive manufacturing (AM) with conventional methods. They offer a potentially faster, more economical pathway to produce engineered components with performance that equals or exceeds that of wrought or cast counterparts. In these strategies, AM allows fabrication of preform geometries without the need for custom tooling or feedstock. Conventional post-processing mitigates AM-specific issues such as anisotropic mechanical properties, residual stresses, porosity, and the presence of large columnar grains with pronounced texture. This study focuses on a hybrid AM-forging approach, in which the hot deformation behaviour of wire arc additive manufacturing (WAAM) processed Inconel 718 preforms was evaluated using hot compression tests (HCT). Cylindrical samples from WAAM deposited walls were hot compressed in a Gleeble (R) 3800 physical simulator at 927-1100 degrees C and strain rates of 0.01-5 s(-1). The evolution of microstructural anisotropy and flow behavior under these conditions was examined using optical microscopy (OM), field emission scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS), and electron backscatter diffraction (EBSD). Dynamic recrystallization (DRX) was dominant in specimens deformed at 5 s(-1), while dynamic recovery (DRV) prevailed at 0.01s(-1). The size of recrystallized grains during hot deformation was predicted using a phenomenological model based on the Zener-Hollomon parameter. The results revealed that grain size varies as a function of strain, enabling the tailoring of the grain structure of components forged from AM preforms. Processing maps indicated a power dissipation efficiency (eta) of similar to 0.33 in a stable hot-working regime, consistent with DRX-dominated microstructural refinement.

Wear characterization is crucial for assessing material performance and guiding material selection for tribological applications, such as woodworking. This study investigates the wear behaviour of AISI W360 and two grades of modified A8 tool steels under coated and uncoated conditions, using the ASTM G65 dry sand rubber wheel (DSRW) and the ASTM G195 Taber abrasive tests. The wear performance of the uncoated steels varied with the tests, showing no correlation with the carbide properties. The resulting wear performance was the product of the competitive interplay between carbide properties, with uniform fine carbide distribution and average size being the most significant factors in the DSRW and Taber tests, respectively. The wear mechanism was predominantly microcutting, independent of the microstructure in the Taber test. However, the samples in the DSRW test exhibited microcutting and material pull-out, resulting in the formation of cavities, depending on the carbide volume fraction. On the other hand, the wear performance of the coated tool steels correlated with the coating thickness in the DSRW test, Macroparticle (MP) density, and roughness in the Taber test. The wear performance, despite being the product of the interaction between coating properties, was more impacted by the hardness and coating thickness in both tests. Additionally, the wear mechanism was independent of the coating properties in the DSRW test, whereas higher MP density and lower hardness resulted in adhesive coating failure and microgrooving, respectively, in the Taber test. Further mathematical modeling to facilitate the conversion of wear volumes between both tests revealed limited predictive accuracy. These findings underscore the complexity of the wear behaviour of coated and uncoated tool steels showing significant variation with the test method.

Large interfacial strains in particles are crucial for promoting bonding in cold spraying (CS), initiated either by adiabatic shear instability (ASI) due to softening prevailing over strain hardening or by hydrostatic plasticity, which is claimed to promote bonding even without ASI. A thorough microstructural analysis is vital to fully understand the bonding mechanisms at play during microparticle impacts and throughout the CS process. In this study, the HEA CoCrFeMnNi, known for its relatively high strain hardening and resistance to softening, was selected to investigate the microstructure characteristics and bonding mechanisms in CS. This study used characterization techniques covering a range of length scales, including electron channeling contrast imaging (ECCI), electron backscatter diffraction (EBSD), and high-resolution transmission microscopy (HR-TEM), to explore the microstructure characteristics of bonding and overall structure development of CoCrFeMnNi microparticles after impact in CS. HR-TEM lamellae were prepared using focused ion beam milling. Additionally, the effects of deformation field variables on microstructure development were determined through finite element modeling (FEM) of microparticle impacts. The ECCI, EBSD, and HR-TEM analyses revealed an interplay between dislocation-driven processes and twinning, leading to the development of four distinct deformation microstructures. Significant grain refinement occurs at the interface through continuous dynamic recrystallization (CDRX) due to high strain and temperature rise from adiabatic deformation, signs of softening, and ASI. Near the interface, a necklace-like structure of refined grains forms around grain boundaries, along with elongated grains, resulting from the coexistence of dynamic recovery and discontinuous dynamic recrystallization (DDRX) due to lower temperature rise and strain. Towards the particle or substrate interior, concurrent twinning and dislocation-mediated mechanisms refine the structure, forming straight, curved, and intersected twins. At the top of the particles, only deformed grains with a low dislocation density are observed. Our results showed that DRX induces microstructure softening in highly strained interface areas, facilitating atomic bonding in CoCrFeMnNi. HR-TEM investigation confirms the formation of atomic bonds between particles and substrate, with a gradual change in crystal lattice orientation from the particle to the substrate and the occurrence of some misfit dislocations and vacancies at the interface. Finally, the findings of this research suggest that softening and ASI, even in materials resistant to softening, are required to establish bonding in CS.

This study investigates the influence of substrate surface finish on the morphological, mechanical, and microstructural properties of AlTiN/AlTiCrN coatings on AISI A8 tool steel, and how this cascade of property changes collectively dictates the wear and corrosion behaviour of the coated tool steels. The wear resistance was evaluated as per the ASTM G65 test, while the corrosion performance was assessed using electrochemical impedance spectroscopy and potentiodynamic polarization techniques. Surface roughness was measured using profilometry, while the hardness (H) and elastic modulus (E) were determined via nanoindentation. Microstructural characterization was carried out using scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction techniques. The results showed that increasing the average substrate roughness by about 500-fold (from 0.003 to 1.7 µm) led to a relatively modest rise of about 22

The impact of prior austenite grain size (PAGS) on the kinetics of austenite formation with an initial martensite microstructure was investigated in a medium-carbon, low-alloy steel. Two distinct PAGS of 117 and 330 μm, representing the range of grain sizes encountered in industries, were considered. In this analysis, high-resolution dilatometry was used to study the formation of austenite during continuous heating experiments. The analysis of the dilatometry results revealed that grain refinement accelerated the rate of austenite formation without impacting its austenite formation temperature. Intermittent quenching tests were conducted to elucidate the nucleation and growth mechanisms of austenite formation using a combination of optical, scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD). The differences in austenite formation kinetics as a function of prior austenite grain size were quantified and modeled in the framework of diffusion-controlled nucleation and growth theories using the genetic algorithm optimization.

An Al-based functionally graded structure is fabricated, featuring a discrete compositional gradient of 48.1Al47.9Ti4.0V/73.7Al24.2Ti2.1V/89.5Al10.0Ti0.5V in atomic percentage. This structure is produced via dual-hybrid laser powder bed fusion and directed energy deposition combined with computer numerical control milling. Particularly remarkable is the high tensile strength, ranging from 0.5 to 1.7 GPa. This strength is attributable to three key factors: (1) rapid solidification during inert gas flow following high-energy laser irradiation, (2) the formation of γ-like intermetallic matrix phases along with γ′-like (α2-based in the composition of 48.1Al47.9Ti4.0V) intermetallic precipitate phases, and (3) the presence of segregates and precipitates with more V-based compounds at the grain boundaries, distinguishable by their sizes, shapes, and distributions across the microstructures. In addition, (4) large anisotropically lamellar precipitate phases, several hundreds of nanometers in diameter, are predominantly observed in the dendritic regions. Owing to these Al-based intermetallic compounds, each exhibiting low densities (2.9−3.7 g cm−3) and high thermal resistances (450−900 °C), the functionally graded structure is then employed in the topological optimization of a turbine blade system for a high-performance jet engine. This process involves identifying the stress-bearing regions, removing any stress-free areas, and applying a structural-stiffness-increasing mechanism through shape and geometric transformation.

The study herein presents the identification of the thermal boundary conditions during the air travel step before quenching by immersion under an industrial environment. The experimental characterization was done with quench probes instrumented with multiple in-body thermocouples and tested in situ to account for the uneven cooling during the air transfer. A fast-converging numerical approach using an exhaustive search algorithm was developed to solve the inverse heat transfer problem thus estimating the unknown thermal boundary conditions. The approach reconstructs the surface temperature based on the Hermite polynomials whose control points were determined as per the system movements and the underlying physics. The solver considers near-solution starting values obtained from converting the test data at subsurface locations into mathematical expressions, thereby bounding the solution domain. The proposed methodology minimizes the root mean square error (RMSE), it produces RMSE < 2 degrees C and peak max/min errors <3.5 degrees C confirming the accuracy of the procedure. Findings demonstrate the need to consider the heterogeneous conditions even for specimens that qualify for lumped capacitance analysis (Bi < 0.1). The irradiative effects can produce a difference in heat flux magnitude in the range of 10-35% between surfaces. This tendency has appeared for values of the Bi number between 0.05 and 0.08.

This study develops a machine learning (ML)-based decision-support model to assist in planning loading cycles for large-scale electric tempering furnaces in steel manufacturing. Addressing the limitations of experience-driven approaches, a data-driven framework was introduced using real-world production data from 1162 tempered forgings. The model uses eight input features covering dimensions, material grouping, and process parameters, and employs a multi-output Xtreme Gradient Boosting Regressor (XGBRegressor) algorithm. Cross-validation and test-set evaluations demonstrated strong predictive performance, with R2 scores of 0.74, 0.88, and 0.87 across three critical batch-level targets: Total Weight, Forging Count, and Total Length. Post-processing analyses, including feature importance rankings and Partial Dependence Plots (PDPs), highlighted the dominant influence of forging shape and width on loading configurations, while predefined process parameters such as temperature and holding duration showed limited impact. The model also identified interpretable thresholds in block dimensions, offering practical guidance for managing new or irregular loading scenarios. This framework enhances planning consistency, reduces reliance on subjective decision-making, and provides a foundation for integrating ML-driven support into industrial furnace operations without replacing technician expertise.

Additive manufacturing (AM) of H13 tool steel using the powder bed fusion (PBF) method is often limited by issues such as porosity (including lack of fusion, gas, and keyhole porosity), balling formation, and elemental segregation. These factors significantly impact the mechanical properties of the final product. This research investigates how volumetric energy density (VED) influences these issues and their subsequent effects on mechanical properties. VED affects the mechanical properties in multifaceted ways. An optimized VED prevents a lack of fusion and minimizes gas and keyhole porosities, especially near edges, ultimately reducing the material’s susceptibility to fracture under tensile load. Additionally, VED influences elemental segregation within a single laser track during the process; lower VED leads to less elemental segregation. This reduced segregation minimizes oxide formation, which are crack initiation sites after heat treatment, thereby enhancing mechanical strength. The study also identifies that an optimal VED minimizes balling formation, further reducing elemental segregation and improving mechanical properties. A VED range of 57–59 J/mm3 is found to be optimal for preventing a lack of fusion, minimizing segregation, and reducing near-surface defects. Furthermore, a relationship is established between these defects, the microhardness profile, and the mechanical properties, suggesting that microhardness can serve as a predictive tool for the mechanical properties of PBF-ed metal.