Manufacturing Processes for Metallic Materials

1. Introduction and Scope

As the global manufacturing industry transitions toward high-value-added and low-carbon development, metal material manufacturing processes are undergoing systemic transformations. The explosive growth of new energy vehicles and the pursuit of superior performances in the aerospace field [1,2] have fostered the growth of a huge market for lightweight and high-strength metal components (such as aluminum alloys and magnesium alloys). These components often require a combination of complex topological structures, gradient functional characteristics, and ultra-high precision, which traditional metal manufacturing processes have struggled to achieve. In addition, as manufacturing systems impose strict requirements for the sustainable development of the whole life cycle of metal materials, resource efficiency and environmental pollution control have become prerequisites for process innovation.

Against this background, traditional processes have revealed their inherent limitations [3,4]. For instance, although the typical melt casting rolling process is mature and stable, it faces the dilemma of high energy consumption and low material utilization and often finds it difficult to form complex cavities. To address these challenges, researchers have integrated numerical simulations into manufacturing processes, enabling multi-physics field coupling simulations (thermal–mechanical–electrical–magnetic–fluidic) of the manufacturing process [5,6,7]. This makes it possible to predict the evolution of material microstructures (such as dynamic recrystallization and phase transformation kinetics) and key performance indicators before material manufacturing. Meanwhile, the precise control technology of microstructure is used to improve the performance of products from the perspective of material origin. For example, strategies such as grain refinement, interface strengthening, and in situ reaction layer design [8,9,10] optimize phase composition and defect distribution at the atomic scale, achieving a coordinated improvement in strength/toughness/corrosion resistance. Furthermore, additive manufacturing and hybrid processing technologies that have subverted traditional manufacturing logic are also utilized [11,12,13,14]. With layer-by-layer accumulation or in situ material synthesis as their core principles, these technologies break through the constraints of geometric complexity and open up new pathways for lightweight topological structures, functionally graded materials, and multi-material integration. In addition, systematic research on fatigue-resistant design and joining mechanisms has been conducted [15], which provides crucial theoretical support for the service reliability of products. Therefore, the chain of innovation in modern metal manufacturing process has been expanded from single equipment innovation to the full-dimensional collaboration of “basic theory—Numerical Simulation—process development—virtual verification—green assessment”.

2. Contributions

Numerical simulation and intelligent monitoring technology are reconfiguring the process design paradigm. This kind of technology not only avoids the high cost of the traditional trial-and-error method, but also lays the foundation for digital twin technology and virtual manufacturing.

Russo Spen (Contribution 1) proposed an efficient calibration-free method for predicting welding deformation. The welding thermal cycle data were obtained In Situ by infrared thermal imaging, and directly input into the forced Imposed Thermal Cycle (ITC) model for finite element simulation. This method avoids the destructive metallographic calibration required by the traditional Moving Heat Source (MHS) model. The experimental and numerical verification show that the predicted deformation error is less than 0.3%. The calculation time is significantly reduced by more than 85% compared with the classical method, which significantly improves the efficiency, although the error estimation is slightly increased by 0.03%. Based on the actual process data-driven simulation process, a virtual representation of this process can be realized, enabling the realization of future digital twin applications.

Dai (contribution 2) established an incremental coupling model, which effectively solved the problems of inaccurate coil temperature and nonlinear interactions between stress and deformation during the coiling process of hot-rolled steel strips. The model breaks through the limitations of the traditional method, and obtains the mechanical properties and radial elastic modulus of the strip steel by coupling the temperature and stress of the coil, and conducting tensile tests and laminated compression tests at different temperatures. Meanwhile, the effects of key process parameters such as strip thickness, coiling tension and initial mandrel temperature on the internal state of the coil core are analyzed. The results of the model were compared with the measured values and analytical solutions, which confirmed the effectiveness of the incremental coupling model, and provided a theoretical basis for optimizing and precisely controlling the hot strip coiling process.

Kendall (Contribution 3) investigated the key influence of surface geometry on the oxidation kinetics of conveying pipes. Based on the Stefan problem, the customized thermochemical database and the numerical solution of the diffusion equation, a prediction model for the oxide thickness of typical curved surface was developed. The critical effect of radial diffusion term on oxidation kinetics was quantitatively revealed for the first time when the radius of the curvature of pipe was ≤200 mm, and proved the necessity of the cylindrical coordinate system in the oxidation modeling of curved surfaces. The model provides a theoretical basis for the high-precision prediction of scale layer growth, the optimization of descaling processes and the reduction of tool damage.

Precise control of microstructure and interface engineering is the key to optimizing material performance.

Zou (Contribution 4) significantly improved the comprehensive properties of MIG welded joints of 5xxx series aluminum alloys by adding scandium (Sc) and erbium (Er) to the welding wire: the grain size was refined from 47 µm to 29 µm and 31 µm, respectively, which was attributed to the heterogeneous nucleation effect of submicron-sized coherent Al3Er and Al3Sc phases (L12 structure). The tensile strength, fracture elongation and microhardness of the welded joint were significantly improved due to refining and dispersion strengthening. In addition, the corrosion resistance of the joint was significantly enhanced, which showed that the corrosion current density decreased and the corrosion potential increased, which was attributed to the formation of a denser oxide film and the balance of the potential difference between the precipitates and matrix. The addition of Sc and Er elements have similar and significant effects on improving the properties of welded joints.

Sisodia (Contribution 5) innovatively used local electron beam-post-weld heat treatment (LEB-PWHT) to regulate the electron beam welded joint of 12 mm thick S960QL high-strength steel, and achieved accurate local energy input through a defocusing beam. The results show that LEB-PWHT significantly optimizes the joint performance: the hardness of the weld seam and heat-affected zone (HAZ) was reduced by 23% and 21%, respectively, the tensile strength was increased by 3% (reaching 1082 MPa), and the ductility was improved. However, attention should be paid to the decrease in the impact toughness of the weld metal at −40 °C (from 63 J to 27 J). Microstructure, LEB-PWHT promoted the transformation of martensite in the coarse-grain heat-affected zone (CGHAZ) into tempered martensite + carbide precipitation, and equiaxed grains and dispersed carbides were formed in the fine-grain heat-affected zone (FGHAZ). This reveals the directional control mechanism of local heat treatment on microstructure and properties. Local post weld heat treatment provides technical guidance for the precise control of micro zone properties for high-strength steel thick plate welding.

Wang (Contribution 6) developed a simple one-step method without additives or pre modification to directly prepare ZIF-8 films with strong adhesion on zinc substrates, revealing the dual-role mechanism of the ZnO interlayer. The ZnO interlayer is formed by the decomposition products of solvent and zinc ions. It not only serves as a sacrificial precursor to promote the nucleation and continuous growth of ZIF-8 crystal, but also acts as an anchoring site to significantly enhance the adhesion between the film and the substrate. This work provides a simple direct production process that can be applied to other metal substrates experimentally to further study the complete film formation mechanism, and will provide more comprehensive theoretical support for the preparation of metal substrate films.

At the same time, additive manufacturing (AM) technology has opened up new dimensions for the fabrication of complex metal components.

Cui (Contribution 7) successfully fabricated 22MnCrNiMo mooring chain steel with excellent comprehensive mechanical properties by utilizing the selective laser melting (SLM) additive manufacturing process and determining the combination of key process parameters (laser power: 200 W, scanning speed: 800 mm/s, layer thickness: 30 μm, scanning spacing: 110 μm) through experiments. The SLM-formed parts exhibit a microhardness of 513.2 HV0.5, a tensile strength of 1223 MPa, a yield strength of 1114 MPa, an elongation of 8.5%, and an impact energy of 127 J. The research findings reveal the microstructure evolution law and the strengthening–toughening mechanism of 22MnCrNiMo steel fabricated via SLM technology, providing a new method and technical basis for the direct fabrication of high-performance mooring chains

Gracheva (Contribution 8) systematically reviewed the current research findings on selective laser melting (SLM) technology for biodegradable metals (Mg, Fe, Zn), and quantified the key properties of three types of materials: Mg alloys fabricated via SLM achieve an elastic modulus matching that of bone (40–45 GPa) and a moderate degradation rate (1–3 mm/year); Fe-based metals exhibit excellent strength (400–600 MPa) but a relatively slow degradation rate (0.1–0.5 mm/year); Zn alloys offer moderate overall performance. Meanwhile, the design strategy of porous/lattice structure is proposed to enhance bone integrity and achieve performance gradients, and it is pointed out that the four core challenges in this field include controlling degradation kinetics, optimizing the SLM process for active metals, standardizing testing methods, and coordinating regulatory frameworks. This work provides systematic theoretical support and technical guidance for the development of the next generation of personalized biodegradable implants.

In the preparation process of metal materials, it is necessary to achieve collaborative optimization of design and process parameters to ensure that the materials possess sufficient fatigue resistance and reliable service life. Therefore, it is essential to study the failure mechanisms of materials under fatigue loads.

Meilinger (Contribution 9) addressed the lack of systematic high cycle fatigue (HCF) research on key aluminum/steel hybrid joints for lightweight vehicle structures. Through experiments, aluminum/steel hybrid joints were prepared using 5754-H22, 6082-T6 aluminum alloys and DP600 substrates, respectively, through resistance spot welding (RSW) and conventional clinching (CCL), and HCF testing was conducted. An HCF design curve with a 50% failure probability was established, and the study indicated a significant correlation between interface structure and fatigue life. The relative load bearing capacity of different joints under HCF was quantified (based on the steel/steel joint): the load bearing capacity of the aluminum/steel hybrid joint was significantly reduced (RSW was 48.7% and 73.0%, CCL was 35.0% and 38.7%), while that of the aluminum/aluminum joint was even lower (RSW was 39.9% and 50.4%, CCL was 31.7% and 35.0%). In addition, the study clearly shows that, with one exception, the load bearing capacity of CCL joints is better than that of RSW joints (156.1–108.3%). This study provides an important basis for the selection of lightweight vehicle bodies connection process.

Basak (Contribution 10) systematically reviewed the laws governing the performance of common non thermal mechanical connections (adhesive, bolted, clinched and riveted joints) under fatigue loads, mainly introducing the influencing factors of different connection types. For instance, the fatigue behavior of bonded connections was affected by the bond length, thickness, and the properties of different materials—increasing the bond length can improve its fatigue strength until a certain length is reached, while increasing the thickness of the laminate or adhesive reduces fatigue life unless the surface roughness is increased; the differences in mechanical properties of different laminated materials directly determine their fatigue performance. This review integrates the fatigue behavior of mechanical bonds and the effects of various internal and external parameters, providing a key theoretical basis for the selection of optimal parameters in product design.

3. Conclusions and Outlook

The contributions summarized above provide an overview of recent progress in the research on metal material manufacturing processes. Through theoretical research, numerical simulation and experimental verification, advanced manufacturing technologies are provided for the preparation of high-performance metal materials. Numerical simulation and intelligent detection have overcome the limitations of traditional manufacturing processes, while virtual manufacturing design has replaced the experience driven trial and error model. Studies on the microstructure and macroscopic properties of the materials further show the importance of reforming the manufacturing process. Meanwhile, emerging manufacturing technologies such as additive manufacturing show significant advantages in terms of their material forming limits. It is worth noting that the significance of material fatigue failure in actual service has been highlighted. As we look ahead, the manufacturing processes employed in the fabrication of metallic materials must further embrace intelligence, functional integration, and green development. It is essential to reduce energy consumption and resource usage in manufacturing to meet the higher standards required for sustainable industrial development while ensuring material performance.