Search Results (71)

Superplastic forming (SPF) of titanium alloys exhibits strong deformation path dependence because microstructural evolution, damage development, and material response are influenced by prior loading history. However, constitutive models for SPF are often evaluated primarily by fitting accuracy rather than their ability to represent deformation history. This review examines path-dependent constitutive modeling from a memory-architecture perspective. The relevant literature was identified through a structured review of titanium-alloy SPF studies, which were supplemented by selected high-temperature forming studies from other metallic systems when they provided transferable constitutive frameworks. Existing constitutive models were classified into four categories according to how deformation history is retained and represented: stateless models, implicit or projected memory models, reduced-order memory models, and high-dimensional or explicit memory models. The analysis shows that many conventional formulations achieve acceptable accuracy within calibrated monotonic regimes by strongly compressing deformation history, thereby limiting their ability to distinguish complex loading paths. Internal-state-variable models provide a practical balance between path representation, interpretability, and implementation, whereas high-dimensional memory models offer stronger sequence sensitivity at the cost of greater data and calibration requirements. This memory-architecture framework clarifies the limitations and applicability of existing constitutive models and provides guidance for model selection in SPF process simulation. Full article

The TC11 α + β dual-phase titanium alloy exhibits limited room-temperature ductility (3.3 × 10⁻⁴ s⁻¹: elongation 13.8%) but achieves significant superplasticity at 900 °C (3.3 × 10⁻⁴ s⁻¹: elongation 314%), which correlates strongly with the mechanical response of α/β interfaces. These interfaces, which often crack at room temperature, undergo extensive sliding while preserving structural integrity during superplastic deformation. Combining microstructural analysis with first principles calculations, this study reveals how the stability of the α/β interface is dominated by the redistribution of alloying elements, thereby leading to distinct mechanical behaviors. Energy-dispersive X-ray spectroscopy results and calculated solution energies demonstrate that Mo preferentially dissolves in the β phase, whereas Al exhibits comparable solubility in both phases with a slight preference for the α phase. During high-temperature deformation, the α→β transformation drives Mo redistribution away from the interface toward newly formed β phases. This redistribution of Mo lowers the interfacial energy, strengthens the interface, suppresses stress-induced cracking, and ensures macroscopic continuity. Our study provides a theoretical perspective for Ti alloy design through interfacial engineering. Full article

To elucidate the evolution of dynamic recrystallization (DRX) mechanisms in cold-worked Cr4Mo4Ni4V martensitic steel, tensile tests were conducted on a 50% cold-deformed material at 600–850 °C at a fixed strain rate of 0.001 s⁻¹, combined with systematic microstructural characterization. Under this specific strain rate, the results reveal a temperature-dependent transition from continuous dynamic recrystallization (CDRX) to discontinuous dynamic recrystallization (DDRX). At 600 °C, CDRX dominates, producing recrystallized grains with orientations close to the parent matrix and relatively strong texture. At 750 °C, CDRX and DDRX coexist, while DDRX is significantly enhanced, characterized by grain boundary nucleation and random orientations, leading to a marked reduction in texture intensity; simultaneously, the fraction of recrystallized grains and high-angle grain boundaries reaches a maximum. At 850 °C, DDRX becomes dominant. This transition in DRX mechanism governs the high-temperature plasticity, with optimal superplasticity achieved at 800 °C, corresponding to an elongation of 748%. Cavities are primarily initiated at carbide/matrix interfaces, and their growth and coalescence dominate the fracture process. These findings clarify the temperature-dependent DRX evolution and its role in regulating superplasticity, providing guidance for microstructure design and superplastic forming of martensitic steels. Full article

Achieving thickness uniformity is a critical challenge in superplastic forming (SPF) of hemispherical shells, as standard constant-thickness blanks suffer from excessive thinning at the pole. While the literature suggests using variable thickness blanks to mitigate this issue, existing solutions often rely on complex, non-linear profiles that are expensive and difficult to manufacture. This work proposes a cost-effective, truncated conical blank design (linearly variable thickness) to optimize material distribution. The approach combines Finite Element Method (FEM) analysis and experimental validation on AZ31 magnesium alloy. The study demonstrates that the optimized truncated conical profile (α = 0.2) yields superior structural quality, drastically reducing the thinning factor to 9%. This represents a significant improvement compared to the ~14% thinning observed with conical profile (α = 0) blanks and outperforms constant-thickness blanks (30%). These results demonstrate that a simplified, easily machinable blank geometry can effectively address the thinning problem, providing a practical solution for industrial SPF applications. Full article

This paper presents the design, manufacturing, instrumentation and validation by tests (ground and icing wind tunnel) of a full-scale Hybrid Laminar Flow Control (HLFC) leading-edge demonstrator based on Airbus A330 outer wing plan-form. The Ground-Based Demonstrator (GBD) was developed to reproduce a full-scale, realistic wing section integrating into the leading-edge three key systems: micro-perforated skin for the hybrid laminar flow control suction system (HLFC), the hot-air Wing Ice Protection System (WIPS) and a folding “bull nose” Krueger high-lift device. The demonstrator combines a superplastic-formed and diffusion-bonded (SPF/DB) perforated titanium skin mounted on aluminum ribs jointed with a carbon-fiber-reinforced polymer (CFRP) wing box. Titanium internal ducts were designed to ensure uniform hot-air distribution and structural compatibility with composite components. Manufacturing employed advanced aeronautical processes and precision assembly under INCAS coordination. Ground tests were performed using a dedicated hot-air and vacuum rig delivering up to 200 °C and 1.6 bar, thermocouples and pressure sensors. The results confirmed uniform heating (±2 °C deviation) and stable operation of the WIPS without structural distortion. Relevant tests were performed in the CIRA Icing Wind Tunnel facility, verifying the anti-ice protection system and Krueger device. The successful design, fabrication, testing and validation of this multifunctional leading edge—featuring integrated HLFC, WIPS and Krueger systems—demonstrates the readiness of the concept for subsequent aerodynamic testing. Full article

Biodegradable magnesium (Mg) alloys are promising materials for temporary orthopaedic implants, combining favourable mechanical properties and superplastic behaviour with in vivo resorption. This enables (i) prolonged implant duration, (ii) fabrication of complex-shaped prostheses via superplastic forming (SPF), (iii) elimination of removal surgery, and (iv) reduced risk of long-term complications. However, rapid corrosion under physiological conditions remains a major limitation, highlighting the need for surface treatments that slow degradation while preserving implant integrity. This study investigates the effects of hydrothermal surface treatment on MgAZ31-SPF alloys, focusing on immunomodulatory responses, antibacterial potential, and degradation behaviour. Hydrothermally treated MgAZ31-SPF (MgAZ31-SPF-HT) extracts released lower Mg²⁺ concentrations (29.2 mg/dL) compared to untreated MgAZ31-SPF (47.5 mg/dL) while maintaining slightly alkaline pH (7–8.7), indicating improved control of early degradation. In vitro assays with human peripheral blood mononuclear cells (hPBMCs) and normal human dermal cells (NHDCs) showed that MgAZ31-SPF-HT extracts maintained higher cell viability over 24–72 h. Gene expression analysis revealed significant downregulation of pro-inflammatory markers CTSE and TNF-α, while protein quantification via ELISA and BioPlex confirmed reduced secretion of TNF-α, TGF-β1, TGF-β2, IL-6, and IL-8, suggesting mitigation of early immune activation. Antibacterial assays demonstrated limited Staphylococcus aureus colonisation on both MgAZ31-SPF and MgAZ31-SPF-HT scaffolds, with CFU counts (~10⁵–10⁶) well below the threshold for mature biofilm formation (~10⁸), and SEM analysis confirmed sparse bacterial distribution without dense EPS-rich layers. Overall, hydrothermal treatment improves Mg alloy biocompatibility by controlling Mg²⁺ release, modulating early immune responses, and limiting bacterial adhesion, highlighting its potential to enhance clinical performance of Mg-based implants. Full article

The processing of bulk amorphous alloys is typically realized through superplastic deformation in the supercooled liquid region, and current research efforts predominantly focus on enhancing formability by optimizing processing parameters such as temperature and duration. However, excessive temperatures or prolonged exposure times can induce crystallization, which severely compromises the mechanical and functional properties of the alloy. This study presents the design of an ultrasonic vibration (UV)-assisted metal hot-forming apparatus that integrates an ultrasonic vibration field into the superplastic flow deformation of amorphous alloys. High-temperature compression experiments were conducted on Zr₅₅Cu₃₀Al₁₀Ni₅ amorphous alloy, and finite element simulations were performed to model the experimental process. Results show that ultrasonic vibration reduces the flow stress of the amorphous alloy, thereby enhancing its superplastic deformation capability. Simulation analysis reveals that surface effects arise from periodic interface separation between the pressure plate and the specimen caused by ultrasonic vibration, leading to a cyclic disappearance of friction forces, which manifest macroscopically as a reduction in effective friction. On the other hand, vibration introduces additional strain rates. Since the undercooled liquid of amorphous alloys exhibits non-Newtonian fluid behavior characterized by shear-thinning, ultrasonic vibration assistance can effectively reduce the apparent viscosity, thereby improving their filling capacity. Full article

Despite significant interest in their functional properties, the mechanical behavior of high-entropy oxides (HEOs) is not well studied, particularly at elevated temperatures. Bulk (Co,Cu,Mg,Ni,Zn)O (transition metal (TM)-HEO) samples were deformed under compression at applied stresses and temperatures ranging from 5 to 31 MPa and 600 to 850 °C, respectively. All of the deformation conditions result in creep stress exponents of n < 3, indicating that TM-HEO exhibits superplastic deformation. A transition from structural to solution-precipitation-based superplasticity is observed during deformation above 650 °C. Additionally, TM-HEO exhibits shear-thickening behavior when deformed at stresses above 9 MPa. The formation and behavior of a Cu-rich tenorite secondary phase during deformation is identified as a key factor underpinning the deformation mechanisms. The microstructure and phase state of TM-HEO before deformation also influenced the behavior, with finer grain sizes and increasing concentrations of Cu-rich tenorite, resulting in the increased prevalence of solution-precipitation deformation. While complex, the results of this study indicate that TM-HEO deforms through known superplastic deformation mechanisms. Superplasticity is a highly efficient manufacturing method and could prove to be a valuable strategy for forming HEO ceramics into complex geometries. Full article

A significant contradiction exists between the demand for standardized processes and the need for precise process parameter design in the rapid design of superplastic forming (SPF). To address this, an SPF process parameter design method integrating a knowledge graph and artificial intelligence is proposed. Firstly, based on process data analysis, the entity labels, relationship categories, and attributes are determined. On this basis, the knowledge graph for the SPF process is constructed, comprising the pattern layer and the data layer, which provides structured knowledge support for process generation. Secondly, the process parameter prediction model based on small samples and an improved back propagation (BP) neural network is constructed, with model convergence ensured through an adaptive maximum iteration strategy. Experimental results show that the improved BP model significantly outperforms support vector regression (SVR), random forest (RF), extreme gradient boosting (XGBoost), and standard BP models in prediction accuracy. Compared to the standard BP model, the improved model reduces the mean squared error (MSE), mean absolute error (MAE), and root mean squared error (RMSE) by 82.1% (to 0.0005), 46% (to 0.0188), and 57.1% (to 0.0229), respectively. Finally, the effectiveness, feasibility, and superiority of the method in the SPF process parameter design are verified by taking typical hemispherical parts as an example. Full article

Superplastic materials are characterised by extreme lightness and remarkable ductility. Instead of a punch, a gas is used to push the sheet into the die cavity, and it is precisely regulated to control the material’s strain rate. Forming a superplastic material while maintaining a high strain rate sensitivity index requires the forming gas to follow a precise pressure–time loading curve. This can be excellently predicted with the aid of the finite element method (FEM). Therefore, for the superplastic material to exhibit its best formability throughout the entire process, it is necessary to control the strain rate step by step to keep the maximum strain rate within the material’s optimal superplastic range. In this work, the results of a superplastic-forming process used to create a hemispherical shell are presented. This was carried out using both a circular blank of uniform thickness and a blank with a conical cross-section. The analysis was performed using finite element modelling. Specifically, the results obtained using 3D analysis were compared with those obtained using axisymmetric analysis for conditions of axial symmetry. Using the conical cross-section blank helped achieve a more uniform thickness distribution in the produced hemispherical shell. The success of the numerical activity was validated through results from appropriate experimental work conducted on the magnesium alloy AZ31. The results show that, by employing a blank characterised by a conical section profile, the thickness distribution appears more uniform than that of a constant-thickness blank. Full article

Optimizing superplastic forming (SPF) process parameters is vital for improving production efficiency and addressing the growing complexity of product requirements in high-end manufacturing fields. Current optimization of SPF process parameters focuses on meeting product requirements, often overlooking constraints related to quality indicators, process, and equipment limitations. This paper proposes an optimization approach that integrates SPF manufacturing process information using model-based systems engineering and simulation validation techniques to establish a continuous mapping between product requirements, process parameters, and equipment control parameters. First, SPF is modeled using the systems modeling language to describe the relationships between processes and equipment. Then, the process parameters are extracted via object flow analysis and categorized according to shape and performance control. The key process parameters and impact indicators for meeting customized product requirements are identified using the analytic hierarchy process. Finally, orthogonal experimental design and process simulation are employed to optimize the parameters, with the results mapped onto the physical model to guide the equipment control parameter design. A case study demonstrates its feasibility and effectiveness in meeting customized products. Full article

In this study, high toughness and superplastic deformability were achieved in Mg-9Li alloys through dual-phase microstructure optimization. Solid solution (SS) and equal channel angular pressing (ECAP) treatments were employed to refine the alloy’s microstructure. The effects of these treatments on room-temperature and low-temperature high-strain-rate superplasticity were systematically investigated under varying microstructural conditions. Results demonstrate that the SS-ECAP alloy exhibits outstanding superplasticity at room temperature and remarkable high-strain-rate deformation capability, achieving a maximum fracture elongation of 602.1%. Grain refinement and reduced dislocation density promote uniform void nucleation under high strain. Calculations of the strain rate sensitivity index (m-value) and activation energy (Q) reveal that the superplastic behavior in the SS-ECAP state is predominantly governed by grain boundary sliding facilitated by grain boundary diffusion. These findings provide critical insights into advancing the superplastic forming technology of Mg-9Li alloys. Full article

An Mg-based alloy device manufactured via a superplastic forming process (Mg-AZ31+SPF) and coated using a hydrothermal method (Mg AZ31+SPF+HT) was investigated as a method to increase mechanical and osteointegration capability. The cell viability and osteointegrative properties of alloy-derived Mg AZ31+SPF and Mg AZ31+SPF+HT extracts were investigated regarding their effect on human mesenchymal stem cells (hMSCs) (maintained in basal (BM) and osteogenic medium (OM)) after 7 and 14 days of treatment. The viability was analyzed through metabolic activity and double-strand DNA quantification, while the osteoinductive effects were evaluated through qRT-PCR, osteoimage, and BioPlex investigations. Finally, a preliminary liquid mass spectrometry analysis was conducted on the secretome of hMSCs. Biocompatibility analysis revealed no toxic effect on cells’ viability or proliferation during the experimental period. A modulation effect was observed on the osteoblast pre-commitment genes of hMSCs treated with Mg-AZ31+SPF+HT in OM, which was supported by mineralization nodule analysis. A preliminary mass spectrometry investigation highlighted the modulation of protein clusters involved in extracellular exosomes, Hippo, and the lipid metabolism process. In conclusion, our results revealed that the Mg AZ31+SPF+HT extracts can modulate the canonical and non-canonical osteogenic process in vitro, suggesting their possible application in bone tissue engineering. Full article

Superplastic forming is a process that enables the production of complex-shaped parts using metallic alloys. To design the optimal forming regimes and ensure the success of forming operations, it is essential to use mathematical models that accurately represent the superplastic deformation behavior. This paper is concerned with the study of the microstructure and superplastic deformation behavior, with the construction of a constitutive model, of Al-Mg-Zn-Cu-Zr aluminum alloys with varying Ni contents. The aluminum solid solution and coarse precipitates of the T(Mg₃₂(Al,Zn)₄₉ and Al₃Ni second phases were formed in the studied alloy and Cu dissolved in both second phases. The deformation behavior was investigated in the temperature range of 400–480 °C and the strain rate range of 10⁻³–10⁻¹ s⁻¹. Due to the fine Al₃Zr precipitates, the alloys exhibit a partially recrystallized grain structure before the onset of superplastic deformation. Coarse precipitates of the second phases facilitate dynamic recrystallization and enhance superplasticity at the strain rates and temperatures studied. The alloys with ~6–9% particles exhibit high-strain-rate superplasticity at temperatures of 440–480 °C and strain rates of 10⁻²–10⁻¹ s⁻¹. The presence of high fractions of ~9% Al₃(Ni,Cu) and ~3% T-phase precipitates provided high-strain-rate superplasticity with elongations of 700–800% at a low temperature of 400 °C. An Arrhenius-type constitutive model with good agreement between the predicted and experimental flow stresses was developed for the alloys with different Ni contents. Full article

In recent years, the excellent mechanical properties and lightweight characteristics of multi-layer hollow components have led to a surge in research focused on their forming processes. This growing interest has greatly advanced technological progress in aerospace and other related fields. In this paper, the metal flow behavior of TA15 titanium alloy at different temperatures from 840 °C to 940 °C and different strain rates from 0.001 s⁻¹ to 0.1 s⁻¹ was studied. Utilizing the finite element method, this study examined the local stress concentration, total strain distribution, thickness thinning characteristics, and pressure loading control during the superplastic forming process of the component. The integrated solid/hollow four-layer grid lightweight structural parts were successfully fabricated using the superplastic forming/diffusion bonding (SPF/DB) process. The quality of the components was evaluated using X-ray and ultrasonic C-scan detection methods. The results show that the maximum elongation of the alloy is 1340% at 900 °C/0.001 s⁻¹. When the temperature is too high, the grain size increases remarkably, and the elongation decreases. Based on the finite element simulation results, 900 °C is the best superplastic forming temperature. Under this temperature parameter, the maximum thinning rate of the core sheet is 39.7%, the SPF time is 10,000 s, the maximum thinning rate of the face sheet is 9.8%, and the SPF time is 2400 s. In addition, the solid block has a minimal effect on the thinning of the core sheet. The grid exhibits obvious stress concentration and thinning at its rounded corners, while the thickness distribution in other areas remains relatively uniform. The nondestructive testing results confirmed that the ribs of the component are fully formed, with no missing or broken ribs. The grid exhibits good geometry and high-quality diffusion bonding. The average thickness at key positions of the component is 1.84 mm, with the minimum thickness being 1.7 mm. As the size of the grid cavity decreases, the thickness of the component tends to increase gradually. The maximum error between the simulated and measured values is 4.47%, indicating good accuracy in the simulation. Additionally, the thickness distribution of the component is relatively uniform. Full article