Titanium Aluminum Alloy Research Articles

Effects of conventional interweaving and secondary deposition on the microstructure and properties of Ti6Al4V/AA2024 alloy component fabricated by laser-directed energy deposition

The connection of dissimilar materials has always been a great challenge, especially titanium alloy and aluminum alloy, which have broad application prospects in the aerospace industry. In this work, the Ti6Al4V/AA2024 alloy component was prepared by laser-directed energy deposition (L-DED) technology based on a conventional interweaving structure, and the microstructure of four typical position interfaces was analyzed. Aiming at the problem of poor forming quality of titanium alloy in the second interweaving layer caused by high laser reflectivity of aluminum alloy, a secondary deposition process was proposed. The microstructure and mechanical properties of Ti6Al4V/AA2024 alloy component fabricated by two different processes were characterized and tested. The problems of discontinuity and penetrating cracks at the Ti6Al4V layer in the second interweaving layer are effectively tackled by secondary deposition. As a result, the mechanical property of the deposited structure can be effectively improved, of which the average compressive shear strength is 8% higher than that of the conventional interweaving Ti6Al4V/AA2024 alloy component. The stress at the Ti6Al4V/AA2024 interface presents a zig-zag distribution because of the interweaving structure, which avoids the generation of continuous stress bands and effectively inhibits the interface crack propagation.

Evolving trends and advanced applications of engineering materials in contemporary aircraft: a review

This review article discusses the engineering materials used in aircraft, with a focus on aluminum alloys, titanium alloys and composite materials, including where and why they are most used in aircraft. There are many research papers that deal in detail with materials such as aluminum alloys, titanium alloys and composites used in an aircraft, including theoretical and experimental results. However, the author felt that a review of aircraft materials was necessary, both for himself and to help others interested in similar topics. In addition, the author felt the need of thinking back to the past on what materials used to be prevalent and what materials have superseded them. One such example written in this study is the case of Aluminum that used to be the predominant material in aircraft structural components, has been increasingly supplanted by polymer composites in recent years due to their advantageous properties. It is hoped that from this review article the reader will be able to understand the general trend of recent developments in aeronautical engineering materials and be able to choose which path to follow and which area to focus on in their future research.

Study on Multi-Objective Optimization of Milling Process of Powder Metallurgy Titanium Aluminum Alloys

Study on Multi-Objective Optimization of Milling Process of Powder Metallurgy Titanium Aluminum Alloys

Numerical Simulation of Electromagnetic-Thermal-Fluid Coupling for the Deformation Behavior of Titanium-Aluminum Alloy under Electromagnetic Levitation.

Electromagnetic levitation (EML) is a good method for high-temperature processing of reactive materials such as titanium-aluminum (Ti-Al) alloys. In this study, the oscillation and deformation processes of Ti-48Al-2Cr alloy specimens at different high-frequency currents during the EML process were simulated using the Finite Element Method and Arbitrary Lagrangian-Eulerian (ALE) methods. The data of oscillation, stabilization time, deformation, and distribution of electromagnetic-thermal-fluid fields were finally obtained. The accuracy of the simulation results was verified by EML experiments. The results show the following: the strength and distribution of the induced magnetic field inside the molten droplet are determined by the high-frequency current; under the coupling effect of the electromagnetic field, thermal field, and fluid field, the temperature rise of electromagnetic heating is rapid, and accompanied by strong stirring, resulting in a uniform distribution of the internal temperature and a small temperature difference. Under the joint action of gravity and Lorentz force, the molten droplets are first within a damped oscillation and then tend to stabilize with time, and finally maintain the "near rhombus" shape.

Application and performance analysis of advanced materials in engine lightweight

This paper discusses the application and performance analysis of advanced materials in engine lightening. Firstly, we analyze the properties of high performance aluminum alloy, titanium alloy and composite materials, including their composition, mechanical properties and high temperature resistance. Then, the practical application effects of these materials in key components such as automobile and aero-engine are analyzed through concrete cases. For example, the introduction of micronutrient and improvements in heat treatment processes have significantly increased the strength and corrosion resistance of high-performance aluminium alloys. Titanium alloy is widely used in the key parts of aero-engine because of its high strength and light weight, which greatly improves the performance of engine. The low density and high strength of the composite make it an ideal choice for reducing engine weight. Finally, we discuss the current challenges and future directions, and explore solutions to reduce costs, improve processing efficiency and develop new alloys, in order to provide guidance and reference for the further development of engine lightweight technology.

The study on interaction mechanisms between Ti48Al2Cr2Nb alloy and Y2O3 ceramic crucibles with good thermal shock resistance: Assessing a novel, cost-effective approach to the preparation of high-performance TiAl alloys

Enhancing the thermal shock resistance of Y2O3 ceramic crucibles, coupled with advancements in melting and casting technologies to reduce the adverse influence of interfacial reactions, is essential for producing low-energy consumption, high-quality titanium-aluminum (TiAl) alloys. In this study, the Y2O3 ceramic crucible with good thermal shock resistance was developed through the optimization of particle size distribution and sintering holding time. The interaction mechanisms between Y2O3 ceramics and TiAl alloys under extreme conditions were investigated, and strategies for enhancing the mechanical properties of TiAl alloys through the integration of Y2O3 crucibles with centrifugal casting were discussed. The results indicated that introducing large particles of 1–3 mm under sintering conditions of 2023 K and 6 h effectively enhances the thermal shock resistance of Y2O3 crucible. The interaction between Y2O3 and TiAl alloys primarily involved physical erosion (spalling/dispersion), dissolution of separated particles, and surface modification of interface layer particles (reaction). Physical erosion played an important role in this dynamic interaction, with the extent of erosion intensifying through continuous use of the crucible, while electromagnetic forces ensured the uniform distribution of inclusions within the TiAl alloy matrix. Moreover, the application of centrifugal casting technology substantially refines the grain size and reduces the inclusion count, thereby significantly enhancing the mechanical properties of TiAl alloy.

The influence of building parameters on residual stress, interfacial structure, and cracking control of laser powder bed fusion processed Ti6Al4V/AlMgScZr multi-material parts

With the growing demand for lightweight and high-performance components applied in extreme aerospace environments, there is a prospective interest in producing the integrated multi-material components consisting of titanium alloy and aluminum alloy. Laser powder bed fusion (LPBF), as a laser powder bed based additive manufacturing process with a high production flexibility, shows a promising potential in creating multi-material components. However, due to the possibility of the generation of various intermetallic compounds (IMCs) at the interface, it has been a significant challenge to fabricate reliable Ti/Al alloy multi-material components without any crack formation by LPBF. In this study, the Ti6Al4V/AlMgScZr multi-material parts were fabricated by LPBF and the effects of building parameters of AlMgScZr on the residual stress and crack control of Ti6Al4V/AlMgScZr multi-material parts were investigated. The evolution mechanisms of IMC phases at the interface under laser interaction were further revealed. Due to the change of elemental compositions and difference in Gibbs free energies of IMCs, a gradient ordered transition zone with a width of about 450 μm consisting of Al3Ti, TiAl, and Ti3Al was formed from AlMgScZr to Ti6Al4V. A finite element model was established to explain the effects of process parameters on residual stress evolution, cracking formation and its control. As the scan speed increased from 500 to 1100 mm/s and the attendant building height of AlMgScZr increased to 60 layers, the residual stress of laser processed Ti6Al4V decreased from 439 to 364 MPa, but the residual stress of AlMgScZr increased from 195 to 303 MPa. As the applied scan speed was enhanced to process AlMgScZr, the element diffusion was mitigated, thereby reducing the formation of IMCs and stress concentration. This study shows the possibility of in-situ control of IMCs and residual stress by process optimization during LPBF preparation of titanium alloy/aluminum multi-material parts without crack formation.

Изотермическое прессование в конической матрице релаксирующего материала

The relations for calculating the deformation mode and force conditions of isothermal extrusion of blanks made of high-strength metallic alloys are proposed. Under isothermal deformation, the material is hardened and softened, which is associated with the manifestation of the viscous properties of the material (creep). In this regard, the state of viscoplasticity is taken on. The deformation state is accompanied by stress relaxation, which is greater the lower the speed (longer duration) of the operation. Based on the mechanics of deformation, the dependence of moulding conditions (deformation, force, damage to the work material) is expressed by analytical relations. The power balance of activity of forces results in a pressure estimation for isothermal exposure. In this case, a discontinuous field of path velocities is used, which consists of a block of deformations and rigid blocks. The blocks are separated by slip surfaces. Deformations occur in the deformation block and on slip surfaces. Since pressing leads to the occurrence of micro-damages, the damage rate of the coating material was estimated. In this case, the criteria of fracture kinetics are used: energy and deformation equations. The damage rate of the material depends on the speed and degree of deformation, or solely on the degree of deformation. For a number of materials, reducing the speed helps to reduce damage and, consequently, the possibility of increasing the degree of shaping of the primary blank. The relations for stiffness analysis of the stress pattern are given, on which the damage also depends. Calculations of the pressure and damage of the material under compaction for blanks made of titanium and high-strength aluminum alloys have been performed. It is shown that at low operation speeds on the appropriate hydraulic forging equipment, the exposure pressure decreases significantly. The aluminum alloy damaging is also reduced, and for titanium it depends only on the degree of forming.

Wear mechanism of diamond-cutting tool in nano-cutting polycrystalline γ-TiAl alloy based on molecular dynamics simulation

The machining of γ-TiAl is susceptible to tool wear, and investigations into tool-wear mechanisms can contribute to enhancing machining efficiency and optimizing the surface integrity of workpieces. In this study, a molecular-dynamics method is employed to simulate the cutting process of polycrystalline titanium–aluminum alloys using a single-crystal diamond tool. The findings suggest that tool wear is induced by cutting forces and plastic deformation, with amorphization and diffusive wear as the primary mechanisms. Plastic deformation within the matrix facilitates interactions between internal dislocations in the grains, thus resulting in work hardening at the surface layer, increased cutting forces, and heightened susceptibility of the cutting edge to wear due to plastic deformation. Moreover, elevated temperatures and pressures in the cutting contact area induce atomic amorphization, which reduces both the strength and hardness of the tool while triggering structural phase transitions for certain atoms. Consequently, lattice distortion occurs within this region, thus causing matrix atoms to diffuse into the tool. The combined effect of amorphization and diffusion significantly exacerbates tool wear. This investigation provides valuable insights into wear mechanisms and guidance for enhancing the quality of γ-TiAl alloy.

Material Selection Using Hybrid Grey Relation Analysis Approach Based on Weighted Entropy for Ranking: The Case of Helicopter Rotor Blade

Engineering design relies highly on the selection of suitable materials. Because there are many engineering materials, selecting a suitable material for a product requires a systematic selection approach. This paper provides a hybrid strategy for choosing the best material for an engineering design to give the best performance at the lowest cost based on Ashby's performance indices. Then, it ranks the result by the grey relational approach integrated with the Weighted Entropy Method to choose the optimum material for the main rotor blade of a helicopter. Different materials used for manufacturing rotor blades, such as Aluminium alloys, titanium alloys, steel, composites, and wood, have been discussed. The performance indices chosen are stiffness, strength, and fracture toughness. The performance indices proved that the composite material has excellent structural strength, stiffness, and toughness. The result shows that CFRP is the best material for manufacturing helicopter rotors, while wood and steel were the best and cheapest when the design had to be economical.

Pin penetration depths in the neurocranium using a three-pin head fixation device

In estimated 10–15% of neurosurgical interventions employing a conventional three-pin head fixation device (HFD) the patient’s head loses position due to slippage. At present no scientifically based stability criterion exists to potentially prevent the intraoperative loss of head position or skull fractures. Here, data on the skull penetration depth both on the single and two-pin side of a three-pin HFD are presented, providing scientific evidence for a stability criterion for the invasive three-pin head fixation. Eight fresh, chemically untreated human cadaveric heads were sequentially pinned 90 times in total in a noncommercially calibrated clamp screw applying a predefined force of 270 N (approximately 60 lbf) throughout. Three head positions were pinned each in standardized manner for the following approaches: prone, middle fossa, pterional. Titanium-aluminum alloy pins were used, varying the pin-cone angle on the single-pin side from 36° to 55° and on the two-pin side from 25° to 36°. The bone-penetration depths were directly measured by a dial gauge on neurocranium. The penetration depths on the single-pin side ranged from 0.00 mm (i.e., no penetration) to 6.17 mm. The penetration depths on the two-pin side ranged from 0.00 mm (no penetration) to 4.48 mm. We measured a significantly higher penetration depth for the anterior pin in comparison to the posterior pin on the two-pin side in prone position. One pin configuration (50°/25°) resulted in a quasi-homogenous pin depth distribution between the single- and the two-pin side. Emanating from the physical principle that pin depths behave proportionate to pin pressure distribution, a quasi-homogenous pin penetration depth may result in higher resilience against external shear forces or torque, thus reducing potential complications such as slippage and depressed skull fractures. The authors propose that the pin configuration of 50°/25° may be superior to the currently used uniform pin-cone angle distribution in common clinical practice (36°/36°). However, future research may identify additional influencing factors to improve head fixation stability.

Double side friction stir Z shape butt lap welding of dissimilar titanium aluminum alloys

Achieving excellent mechanical performance of medium-thick Ti/Al dissimilar joints is important in many industrial applications. However, due to the inherent heat generation mode associated with conventional friction stir welding (FSW), it is impossible to achieve sound medium-thick Ti/Al dissimilar joints. Although double side friction stir welding (DS-FSW) has been reported to solve the problems of conventional FSW. The inherent problems of forming hook structure and interface cracking in the center of the DS-FSW joints significantly weaken the joint performance. Therefore, an innovative double-side friction stir Z shape butt-lap welding (DS-FSZW) process was proposed to eliminate the inherent problems of conventional DS-FSW. The research objective of this work was to reveal the physical mechanisms of the novel DS-FSZW by the combination of numerical simulation and experimental characterization for optimizing the welding parameters. The influence of tool shoulder diameter on the heat generation, heat transfer, plastic material flow, microstructure evolution and mechanical properties of medium-thick dissimilar Ti/Al DS-FSZW joint has been systematically studied. The results indicate that the innovative DS-FSZW process lowers the axial force compared to the conventional DS-FSW, and the centerlines of the first and the second sides welds are staggered. Those are beneficial to inhibiting the cracking of the first-side weld at the interface. In addition, the DS-FSZW method eliminates the hook structures and cracks at the center of the conventional DS-FSW joint and also adds a lap joining interface, which significantly enhances the tensile strength of the joint from 150.7 MPa to 262.5 MPa, which is increased by 74%. Optimization of the shoulder diameter of DS-FSZW from 18 mm to 12 mm reduces the welding heat input and significantly thins the thickness of the IMCs layers at the Ti/Al interface. This helps to suppress the cracking at the Ti/Al lap interface and refine the grains. As a result, thus the tensile strength of the DS-FSZW joint increases from 262.5 MPa to 312.5 MPa, which is increased by 19%. The medium-thick Ti/Al dissimilar DS-FSZW joint at the tool shoulder diameter of 12 mm fracture at the SZ. It proves that the novel DS-FSZW is a suitable welding method for joining medium-thick dissimilar Ti to Al alloys.

Approaching theoretical strength in aluminum alloys via directional heterogeneous nanostructured design

Strengthening a material to its theoretical limit is the unremitting pursuit in the field of materials science and engineering. However, it remains extremely difficult for polycrystalline alloys to reach the theoretical limit using conventional strengthening methods. Here, we propose a directional heterogeneous nanostructured strategy (DHNS) to develop super-strong metallic materials. Based on the microstructural strategy, an aluminum-titanium alloy was developed with a yield strength up to ∼3.9 GPa approaching the theoretical limit (G/τY∼22) and a record-breaking specific strength (∼1219 KNm/kg) among metals and alloys. Microstructural characterizations showed that the DHNS alloy mainly consists of directional nanoscale columnar fcc-Al crystals surrounded by nanosized stripe amorphous phases. The columnar crystals are shown to be in hard orientation and defect free, behaving crystalline whisker-like properties. The synergistic effect of hard-orientation nano-colunmar crystals and strong nanoscale amorphous phases renders the initiation of plastic flow difficult, eventually leading to the ultrahigh yield strength of the alloy. The DHNS strategy provides a facile and effective method for developing strong metallic materials especially for fcc-type alloys where slip systems are easy to be activated.

Fabrication, sintering behavior and mechanical properties of calcium oxide doped yttrium oxide refractory via aqueous gel casting method

Yttrium oxide is an ideal choice for titanium aluminum alloy melting and casting, its wider use is hindered by sintering challenges and low thermal shock resistance. To address this, we propose a gel casting method for calcium oxide-doped yttrium oxide production. We pretreated yttrium oxide with phosphoric acid to prevented hydrolysis and adjusted the isoelectric point of yttrium oxide to match calcium carbonate's. Anions from calcium carbonate increased slurry solid content (up to 58 vol%) while maintaining low viscosity (57.78 mPa·s at 40 s−1 shear rate). After sintering at 1650 °C for 2 h, the material showed a flexural strength of 78 MPa, with a 90% retention rate after thermal shock test. The introduction of calcium oxide induced lattice distortion, improving mechanical properties by aiding sintering and grain boundary diffusion. XPS and STEM analysis confirmed random replacement of Y3+ by Ca2+ at the C2 position with 1 wt% doping.

ESTIMATION OF FATIGUE CURVES USING ORTHOGONAL POLYNOMIALS

The article proposes a methodology for processing fatigue tests carried out to assess the fatigue curve of materials and structural elements, the most important design characteristic of the endurance, service life and reliability of aircraft products, transport engineering and other structures operating under conditions of both regular and irregular loading. The task of estimating the parameters of the fatigue curve is often complicated by the limited scope of fatigue tests, significant scattering of cyclic durability, uneven duplication of experiments at a given level of alternating stress amplitudes, the presence of censoring, especially at low levels, and other factors. which necessitates the use of the weighted least squares method. These circumstances lead to the violation of the conditions for using standard methods of regression analysis and the least squares method. This is especially true for the confidence assessment of the fatigue curve, the accuracy of which significantly depends on these factors. For this purpose, the article proposes to apply the procedure of orthogonalization of factor characteristics to estimate the parameters of the fatigue curve, which reduces the errors arising from standard approaches and makes it possible to obtain accurate confidence intervals for durability. A special feature of the technique is the use of orthogonal polynomials in statistical procedures, which makes it possible to modify the covariance matrix of estimates by converting it to a diagonal form, regardless of the spread of the weight parameters of the original data. These transformations make it possible to perform statistical procedures for point and confidence estimation when processing the results of fatigue tests. To test the methodology, a statistical analysis of a large volume (about 200 samples) of fatigue tests of samples with varying degrees of stress concentration from titanium alloy VT3-1 and aluminum alloy V-95 was performed, algorithms and computer programs were developed in the public domain.

A method for preparing alloy coating on the aluminum alloy substrate via laser cladding technology to prevent the galvanic corrosion of TC4/5083 couple

The Cu-Ni-Cr alloy coating was prepared on 5083 aluminum alloy substrate using laser cladding technology. The microstructure of the coating and its galvanic corrosion resistance in contact with TC4 alloy were studied. The results indicate that the Cu-Ni-Cr alloy coating primarily consists of Al-rich dendrite phase and Cu-rich matrix phase. The shear strength of the Cu-Ni-Cr alloy coating is 154.68 MPa, which is greater than that of the aluminum alloy substrate. The galvanic current density of the TC4/Cu-Ni-Cr couple is 0.05 μA·cm−2. The neutral salt spray corrosion test results demonstrate that the Cu-Ni-Cr alloy coating exhibits excellent resistance to galvanic corrosion. The coating can attenuate the galvanic corrosion effect when it is in contact with the TC4 titanium alloy, offering new solutions to address the galvanic corrosion challenges between titanium alloy and aluminum alloy in marine environments.

Synergistic in-situ reinforcement of lignin and adhesive for high-performance aligned bamboo fibers composites

To replace plastics with bamboo, it is necessary to develop renewable, lightweight, high-strength, damping, and vibration-reducing bamboo structural materials that can be applied in buildings, transportation, and mechanical engineering applications. Here, a low-cost and high-efficiency top-down method was designed for processing natural bamboo into a lightweight and high-strength aligned bamboo fiber composite. This composite used oriented bamboo fibers that had their lignin and hemicellulose removed, which were used as continuous reinforcement materials, and phenolic resin was used as the adhesive, followed by hot pressing. A highly-interwoven structure was formed by the penetration of the adhesive and the combination of strong hydrogen bonds and chemical bonds formed during hot pressing. This resulted in the high performance of the composite, which exhibited a tensile strength of 421.5 MPa, a bending strength of 211.19 MPa, and an impact toughness of 26.7 J/cm2, which were respectively 2.50, 2.09, and 5.7 times higher than those of natural bamboo. Due to its low density (1.08 g/cm3) and specific tensile strength of 390 MPa g−1 cm3, it was superior to commonly used engineering structural materials such as aluminum alloy, steel, and titanium alloy. It also exhibited excellent damping and vibration reduction performance (with the first three damping ratios of 0.75 %, 0.68 %, and 1.75 %) and dimensional stability (with a 24-h water absorption thickness expansion rate of 7.75 %). Due to its excellent mechanical properties and dimensional stability under wet and hot conditions, this composite is expected to replace nonrenewable synthetic materials as a green and sustainable engineering structural material. It may find applications in drone wings, wind turbine blades, and automotive manufacturing.

Advances in ultrasonic welding of lightweight alloys: A review

Abstract The lightweight alloy sheet materials have been widely used in industries such as automobiles, aviation, and aerospace. However, there are huge challenges in the structural joining process. Likewise, industries are probing new technologies and are rapidly adapting to more complex light alloy materials. The ultrasonic metal welding is a reliable solid-phase joining technology, which has incomparable development prospects in the high-strength joining of lightweight alloy sheet materials. This article summarizes the research progress of ultrasonic welding of aluminum alloy, magnesium alloy, and titanium alloy thin plates in recent years. The key features of this review article are the ultrasonic welding process, advantages, applications, and limitations. It introduces the welding process parameters to explore the breakthroughs for straightforward direction. Furthermore, to strengthen the phenomena, the current state of the ultrasonic welding of lightweight alloys and their future perspectives are also reflected.

Microstructural and Eddy Current Evaluation of Ball-Milled Nanostructured Aluminum–Titanium Alloys

Microstructural and Eddy Current Evaluation of Ball-Milled Nanostructured Aluminum–Titanium Alloys

Preparation of titanium powder using a combined method of aluminothermic reduction and molten salt electrolysis

In this study, aluminothermic reduction and molten salt electrolysis were combined to prepare titanium powder. In this combined method, titanium dioxide was first deoxidized to produce titanium–aluminum alloy through an aluminothermic reduction reaction, and then the titanium–aluminum alloy was separated through chloride molten salt electrolysis to generate titanium powder. The obtained titanium powder, titanium aluminum alloy and slag was analyzed using several techniques, including X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy. A mass ratio of 2:3 of titanium dioxide and aluminum was suitable for the production of titanium–aluminum alloys. A large amount of alumina generated through the aluminothermic reduction reaction was separated into slag phases using cryolite. Then, the phases were electrolyzed into aluminum and cryolite, which were reused as raw materials. The final titanium–aluminum alloy product was electrolyzed in a chloride molten salt system to separate titanium and aluminum and produce titanium powder. Therefore, the combination of thermal reduction and molten salt electrolysis is efficient and has great potential for producing high-purity titanium powder.