Ti6Al4V Components Research Articles

Ti6Al4V Implants with Dense-Trabecular Bilayer Morphology for Bone Ingrowth: Synergy of Green Net Shaping and Sacrificial Templating.

Stress shielding in dental and orthopedic implants is a long-standing hurdle, and trabecular porous architecture to improve bone ingrowth is deemed to be a potential solution. Fabricating Ti6Al4V components with dense-porous bilayer structures is complicated with limited lab-scale and commercial success. Here, a green dough-forming technique with metal powders is successfully explored to develop heterogeneous structures with a monolith-like dense-porous interface. The porous region achieved 70% porosity with a 25 MPa compressive strength comparable to human cancellous bone. Due to its simplicity and versatility, this process is a promising solution for developing and mass-manufacturing customized designs for bone-related implants with improved bone ingrowth and osseointegration.

Influence of Process Parameters on Selected Properties of Ti6Al4V Manufacturing via L-PBF Process.

This study investigates the microstructural effects of process parameters on Ti6Al4V alloy produced via powder bed fusion (PBF) using laser beam melting (LB/M) technology. The research focuses on how variations in laser power, exposure velocity, and hatching distance influence the final material's porosity, microhardness, and microstructure. To better understand the relationships between process parameters, energy density, and porosity, a simple mathematical model was developed. The microstructure of the alloy was analyzed in the YZ plane using a confocal microscope. The study identified optimal parameters-302.5 W laser power, 990 mm/s exposure velocity, and 0.14 mm hatching distance-yielding the lowest porosity index of 0.005%. The material's average hardness was measured at 434 ± 18 HV0.5. These findings offer valuable insights for optimizing printing parameters to produce high-quality Ti6Al4V components using PBF-LB/M technology, shedding light on the critical relationship between process parameters and the resulting microstructure.

Microstructure and mechanical properties of large Ti6Al4V components by electron beam powder bed fusion

Electron beam powder bed fusion (EB-PBF)-built Ti–6Al–4V(Ti6Al4V) has increasingly shown great potential for orthopedic implant and aerospace applications in recent years. Large components prepared by additive manufacturing (AM) have heterogeneous microstructures, defect size, and residual stress in the building direction due to the high temperature gradient. The samples with a height of 170 mm ware prepare via EB-PBF. The microstructure, mechanical properties, defect size, and residual stress along the building direction have been systematically study in this work. The grains epitaxial growth along the build direction as coarse prior β columnar grains. The residual compressive stress increases from the sample bottom to top. The max void size increases from 23.8 μm at the bottom to 108 μm at the top, and the mechanical properties gradually deteriorate along the building direction, which is related to the temperature gradient on the building direction of the sample. It is found that the ultimate tensile strength decreases from 916 ± 9 MPa at the bottom to 876 ± 7 MPa at the top, and the elongation to failure decreases from 9.13 ± 0.61 % to 6.49 ± 0.34 %. Meanwhile, the hardening ability is also weakened along the building direction. This study reveals the evolution process of the sample's microstructure, mechanical properties, and defects, providing data support for further control of material defects.

Build Orientation Effect on Bending Fatigue Performance and Impact Toughness of Laser Powder Bed Fusion Manufactured Ti6Al4V Without Heat Treatment

Titanium alloys are highly valued in various industries due to their exceptional qualities. This study examines how the build orientation affects the mechanical and fatigue properties of Laser Powder Bed Fusion (PBF-LB) produced Ti6Al4V, without heat treatment. The research shows mechanical properties vary based on build orientation with vertically oriented specimens exhibiting the highest yield and tensile strengths, while vertical orientation excels in ductility, measured through elongation at break. Impact toughness sees variations with horizontal orientation performing the best. However, build orientation has minimal influence on flexural bending fatigue performance. Both diagonal and vertical orientations show similar fatigue limits at around 40 MPa. Dry electropolishing proves to be an effective technique, significantly enhancing fatigue performance with limits stabilizing at about 150 MPa. This study underscores the importance of considering build orientation in PBF-LB manufacturing for specific mechanical and impact properties and the potential of dry electropolishing in improving the fatigue performance of Ti6Al4V components. These findings offer valuable insights for the additive manufacturing industry, aiding in the optimization of Ti6Al4V component production.

Preparation and mechanical performance analysis of porous Ti6Al4V scaffold fabricated by direct ink writing

In order to mitigate the stress-shielding effect resulting from the stiffness disparity between titanium alloy and bone, the use of additive manufacturing to create porous Ti6Al4V components shows promise for orthopedic implant applications. In this study, a novel hot-melt–quick-frozen polyvinyl alcohol hydrogel was developed for direct ink writing to create porous titanium structures using Ti6Al4V powders with an irregular morphology. The rheological and sintering properties of inks with varying solid phase contents were examined to assess their molding quality. Furthermore, the effect of porosity on the morphology, shrinkage, and mechanical properties of the scaffolds was thoroughly investigated. The results of the experiments show that inks loaded with 65 vol. % Ti6Al4V particles exhibit the highest printing performance. Furthermore, the analysis revealed a positive correlation between the total porosity of the scaffold and its mechanical performance. In particular, the strength of the scaffold with a porosity of 54.8% exceeded that of human bone, and it also exhibited matched stiffness. Upon analyzing the final microstructure and mechanical properties, it is evident that these scaffolds meet the necessary criteria for use as orthopedic implants.

Quasi-static tensile properties of DMLS TI6AL4V(ELI) specimens exposed to two different heat treatment processes and tested at different elevated temperatures

The use of Ti6Al4V components in the aerospace industry has increased in the past years s. Jet engine components made of Ti6Al4V such as compressor blades and exhaust ducts, as well as landing gear, hydraulic systems, and many airframe parts, are exposed to different temperatures while in service, which may affect their mechanical properties. Compressor blades are exposed to temperatures up to 400 °C, exhaust ducts up to 300 °C, and hydraulic systems in the range of −50 °C–135 °C, while landing gears and many airframe structures are exposed to temperatures in the range of −50 °C–70 °C. Therefore, it is of great importance to determine their stability at different temperatures. The results of a study aimed at investigating the effect of elevated temperatures on the mechanical properties and microstructures of DMLS Ti6Al4V(ELI) alloy are presented and discussed in this paper. A DMLS EOSINT M290 machine was used to manufacture test specimens, which were then machined to comply with ASTM E8 for tensile tests. Thereafter, tensile tests were carried out at different test temperatures till fracture. Fractography was then used to study the characteristics of the fracture surfaces. The results obtained in this work showed that temperatures between 175 °C and 325 °C have a significant effect on the mechanical properties and microstructures of the alloy.

Effect of constraint on fracture performance of Ti6Al4V alloy fabricated by laser powder bed fusion

Laser powder bed fusion (LPBF) is increasingly being used as an alternative to traditional manufacturing in the aerospace and biomedical industries. The effect of constraint on fracture performance is a crucial issue in assessing the integrity of engineering applications. This paper aims to better understand the fracture performance of Ti6Al4V components with different constraint levels produced by LPBF. Fracture toughness tests were performed on compact tensile (CT) specimens with varying crack length and specimen thickness. The results show that the fracture toughness decreases with increasing crack length, while the fracture toughness shows a large fluctuation with specimen thickness because of LPBF manufacturing defects. Both in-plane and out-of-plane constraint effects of a crack subjected to mode-I loading are analyzed by three-parameter K-T11-T33 method. A correlation line between fracture toughness and normalized T11 stress is established, which can be used to transform fracture properties of specimens with different constraint levels.

Combined effect of random porosity and surface defect on fatigue lifetime of additively manufactured micro-sized Ti6Al4V components: An investigation based on numerical analysis and machine learning approach

Surface defects and internal porosities resulting from the additive manufacturing process contribute to a scatter in fatigue lifetime, increasing uncertainty in applications such as aerospace engineering. This study proposes a combined approach of machine learning and finite element modelling to explore the interaction between random porosity distribution and high surface roughness on the fatigue lifetime of micro-sized additively manufactured parts. To achieve this, a high-fidelity finite element model is constructed with randomly distributed porosities and surface defects. A fatigue lifetime estimation model, developed using a combination of continuum damage mechanics and the theory of critical distance, is then applied to predict lifetime using effective stress extracted from simulations. A total of 1200 simulations are conducted using these models to examine the interaction effects of subsurface porosity and surface defects on localized stress distribution and fatigue lifetime. Subsequently, two machine learning algorithms, Support Vector Regression and Kernel Ridge Regression, are employed to estimate fatigue lifetime, accounting for the effects of randomly distributed subsurface porosities and surface defects. Eighty percent of the developed finite element models are employed to construct an input dataset, incorporating geometrical features of pores, and to train the algorithms, while the remaining 20% are reserved for verification purposes. The observed results demonstrate that the combined effect of random porosity and surface defects increases fatigue scatter behaviour, leading to greater uncertainty in lifetime prediction. Furthermore, the machine learning algorithms exhibit promising prediction performance.

Microstructure and properties nonuniformity of Ti6Al4V component fabricated by high-power laser melting deposition

High-power laser melting deposition provides an efficient solution for the fabrication of large-sized titanium alloy components. In this study, Ti6Al4V blocks with well-formed structures were prepared using a 7 kW laser power, and their internal defect distribution, microstructure along the deposition direction, tensile properties, and fatigue performance were investigated. The results showed that the density of the as-deposited Ti6Al4V blocks could reach 99.94%, and the main internal defects were cavities, primarily spherical and dispersed, with a maximum diameter of 326.7 μm. Among them, 65.53% of cavities had a diameter smaller than 100 μm, and 92.76% had a diameter smaller than 200 μm. The microstructure at the top region of the specimen consisted of a needle-shaped α phase, the middle region had a mixture of needle-shaped and lamellar α-phase, and the bottom region showed a lamellar α-phase structure. With an increase in deposition height, the aspect ratio of α-phase increased, and the average width decreased from 3.22 μm to 0.88 μm. The internal structure was mainly composed of a basket-weave structure, with a small amount of Widmanstätten structure present at grain boundaries. Hardness and tensile properties exhibited significant non-uniformity along the deposition height. The tensile strength and yield strength at the top region were approximately 50 MPa higher than those in the middle and bottom regions, while the elongation was about 2% lower. The top region's tensile fracture surface displayed a sawtooth pattern, whereas the middle and bottom regions exhibited fractures along the 45° direction of the principal stress. The length of α-bundles and the interface density within the bundles were crucial factors affecting crack propagation. In the top region, α bundles were the longest, and the interface density was the highest. During crack propagation, when the crack extended perpendicular to the α bundles, it encountered high resistance, and when it extended non-perpendicular, it rapidly propagated along the bundle boundaries, exhibiting high strength and low plasticity. The fatigue performance of the Ti6Al4V specimens fabricated by high-power laser melting deposition showed significant dispersion, with cracks originating from subsurface lack of fusion defects. At different stages of fatigue crack propagation, the role of α phase laths varied: during the fatigue source region, cracks primarily propagated along the boundaries of α laths, displaying significant cleavage fracture characteristics. In the fatigue propagation region, crack propagation velocity was mainly influenced by the direction of the laths, and in the fatigue final rupture region, ductile fracture was predominant. Α laths parallel to the tensile direction exhibited the best plasticity, promoting the formation of large dimples and high tear ridges.

In-situ synchrotron X-ray diffraction investigation of martensite decomposition in Laser Powder Bed Fusion (L-PBF) processed Ti–6Al–4V

Laser powder bed fusion (L-PBF) processed Ti–6Al–4V components present two substantial challenges: the presence of tensile residual stress and brittleness of the as-fabricated component due to the formation of the martensite (α′) phase. Industrially, post-heat treatment is performed to improve the quasi-static mechanical properties of the Ti–6Al–4V component through martensite (α′) decomposition and residual stress relaxation. However, detailed insights into the martensite decomposition and stress relaxation mechanisms are still lacking. To address this, in-situ high-energy synchrotron x-ray diffraction (HEXRD) was employed to simultaneously track: (I) martensite (α′) decomposition into a mixture of hexagonal α and body-centered cubic β phases, (II) residual stress relaxation process during heating. Rietveld refinement of 2D diffraction patterns recorded over a temperature range spanning from 25 to 1000°C revealed a three-stage evolution in the α′ unit cell parameters. Unit cell parameter analysis combined with the phase fraction analysis based on the diffraction patterns and the chemical composition profiles predicted by Thermocalc simulation gave detailed insight into the martensite (α′) decomposition process. In Stage 1 (until 375°C), the α′ phase unit cell exhibited linear expansion without indications of any phase transformation or stress relaxation. Upon commencement of stage II at 375°C, an increased expansion rate of the martensite (α′) unit cell was observed, attributed to the enhanced outward diffusion of vanadium (V), succeeded by β phase nucleation at 575°C. Simultaneously, during stage II, residual stress relaxation was observed at both macro and micro scale, culminating in a stress-free state achieved at approximately 750–800°C. Lastly, α-to-β phase transformation was observed in stage 3. The thermal evolution of the hexagonal unit cell dimensions was compared between martensitic and mill-annealed α+β microstructures. This comparison unraveled the link between the initial microstructure and the thermal expansion behavior of the hexagonal α′ and α phase.

Process parameter optimization for laser directed energy deposition (LDED) of Ti6Al4V using single-track experiments with small laser spot size

Single-track experiments are routinely used in the optimization of process parameters in additive manufacturing processes. Most of the process parameter optimization studies use a laser spot size of 1 mm or more. Since laser spot size affects the input energy density and in turn the efficiency of the deposition process, it is important to develop process maps every time a laser of different spot sizes is used. In this work, we determine the process maps for a laser of 0.6 mm spot size. By combining the process maps and the metallographic inspection, we estimate the optimum process parameters (laser power, scan speed, powder feed rate) for building Ti6Al4V components using powder-based laser-directed energy deposition(LDED). Single-tracks corresponding to 64 different parameter combinations are deposited. After eliminating the process parameter combinations resulting in defective tracks, the optimum process parameters of 300 W laser power and 720 mm min−1 scan speed is established by considering the relationship between the process parameters and the geometrical features of the deposit. The experimental results are then used to calibrate the modeling parameters of a three-dimensional finite element model for simulating the deposition process.

Yield strength evaluation of 3D-printed Ti–6Al–4V components based on non-contact eddy-current measurement

The demand for metal additive manufacturing (AM), also known as three-dimensional (3D) printing, is increasing owing to its ability to produce components with complex shapes, heterogeneous material properties, low material waste, etc. However, for broader acceptance of metal AM, quality assurance of mechanical properties, such as elastic (Young's) modulus, Poisson's ratio, and ductility, is becoming critical in additively manufactured components. This study proposes a non-contact, non-destructive and automated eddy-current technique for yield strength estimation of additively manufactured Ti–6Al–4V components with the potential for online operation during metal AM. After conducting the eddy-current measurement at a specific inspection point within the Ti–6Al–4V component, the relationship between the eddy-current phase value and electrical conductivity is established. Subsequently, the yield strength of the Ti–6Al–4V component is estimated by utilizing the analytical relationship between yield strength and electrical conductivity, which is based on Andrew's research and the Hall–Petch relationship. For experimental validation, Ti–6Al–4V test specimens with different electrical conductivities (yield strengths) were fabricated by adjusting the cooling rate during metal direct energy deposition AM. Then, the yield strengths estimated using the proposed technique were compared with those obtained using conventional destructive tensile tests. The results show that the proposed technique can estimate the yield strength with an error rate of less than 8%. The uniqueness of this study lies in (1) the theoretical derivation of the relationship between the eddy-current phase value and yield strength, (2) non-destructive, non-contact, and automated estimation of the yield strength using eddy-current measurements, and (3) performance evaluation using additively manufactured Ti–6Al–4V specimens with different yield strengths.

Process parameters for three-dimensional specimens made of Ti6Al4V materials using additive manufacturing: A review

The Ti6Al4V alloy is highly mechanical, corrosion-resistant, low-specific weight, and biocompatible. Several high-performance applications are ideal for technical uses in the auto, aerospace, and medical sectors. The recent process parameters for Ti6Al4V, manufactured using additive manufacturing methods, are reviewed in this article for the past 20 years. It is possible to link processing parameters with fundamental information. This review finds that the process parameters in additive manufacturing are laser power, scanning speed, layer thickness, and hatch distance. In addition, this reviewed the presence of processes in the additive manufacturing of Ti6Al4V components and their impact on mechanical performance and microstructure analysis. In the additive manufacturing process, the reviewed parameter is the additive manufacturing component that has reduced the defects of microstructural evaluation, residual stress, porosity, compression, and corrosion behaviour of the study.

Influence of laser printing mode on thermal behaviors, forming characteristics, and microstructure evolutions of additive manufactured Ti6Al4V alloy

Ti6Al4V parts fabricated by laser powder bed fusion (LPBF) technology have been widely used in such fields as aerospace, automotive and medical implants. This study investigates the effect of laser scanning modes on thermal behaviors, forming characteristics, and microstructural evolutions of LPBF-fabricated Ti6Al4V parts. The numerical simulations on the temperature field provide a theoretical explanation of various surface morphologies, surface roughness values and relative densities of samples. The rotation between adjacent layers diminishes the large directional thermal stress generated by X scanning or Y scanning, the Ti6Al4V samples using XY scanning and Island scanning present smooth surface and higher relative density (> 99.0%). The observed staggered martensite within the columnar β grains is due to the epitaxial solidification across the deposited layers with 90° or 37° rotation. The martensite growth of LPBF-processed Ti6Al4V components using X scanning has a similar inclination along the building direction and presents anisotropic characteristics. These findings provide new inspirations for achieving high-performance titanium alloy components with specific microstructure by LPBF technique using a proper laser scanning mode.

Novel Heat Stamping of Ti6Al4V panels with high drawability and low springback

Conventional commonly used titanium stamping techniques like hot forming and superplastic forming each have distinct disadvantages. Hot forming usually leads to limited formability and significant springback, whilst superplastic forming often results in long cycle times, high energy use, and costly tooling. A novel, energy-efficient, and cost-effective Heat Stamping process emerges as a promising solution. Two types of Ti6Al4V components, cup-shaped and U-shaped, were produced using the novel Heat Stamping process, and their properties were examined. A defect-free cup-shaped component achieving a considerably high draw ratio of up to 1.8, was successfully fabricated. A moderate enhancement in the hardness of the component indicated a superior post-form strength achieved by Heat Stamping. Further analysis of the U-shaped components shows that the one produced using the novel method demonstrated a notable reduction in springback angle, from 4.8° to 0.7°, highlighting the potential of H eat Stamping in achieving high shape accuracy for near-net-shape forming.

Simultaneous improvement of strength and ductility of laser additively produced Ti6Al4V by adding tantalum

Laser additive manufacturing (LAM) technique can efficiently fabricate Ti6Al4V components of complex shapes, but often show poor mechanical properties. In this study, tantalum (Ta) was added into Ti6Al4V as an alloying element to improve the overall mechanical performance using a laser cladding system. It was found that Ti6Al4V–4Ta (corresponding to 4 wt% Ta) exhibited excellent mechanical performance with the yield stress of 956 MPa, ultimate tensile strength of 1042 MPa and the elongation of 10.8 %, meeting the ISO 7209 requirements for titanium and titanium alloys. The synergistic improvement of strength-ductility of Ti6Al4V–4Ta was attributed to the microstructure refinement, weakened α-variants selection, Ta solid solution, modified dislocation density and β phase content. Further quantitative analysis demonstrated that the strength increase was mainly contributed from the additional grain boundary, solid solution and dislocation induced by Ta elemental alloying. This study established Ta elemental alloying as an effective method to simultaneously enhance the strength and ductility of Ti6Al4V alloy using LAM technology.

Microstructure evolution and fracture behavior of Ti–6Al–4V fabricated by WAAM-LDM additive manufacturing

WAAM and LDM are two typical DED technologies. WAAM-LDM additive manufacturing technology can achieve the purpose of producing large and complex Ti–6Al–4V components, improving processing efficiency and precision. However, there is a lack of in-depth research on the microstructure evolution mechanism and the fracture behavior of WAAM-LDM samples. Therefore, horizontal and vertical WAAM samples were invoked as the substrate for LDM processes in this study, and the mechanical properties and tensile fracture behavior under different load directions were evaluated. The results show that the samples fabricated by WAAM-LDM manufacturing consist of four zones: WAAM zone, heat affected zone (HAZ), remelting zone (RZ) and LDM zone. WAAM zone mainly composed of coarse colony structure, HAZ and RZ are dominated by α colonies and fine basketweave structure, respectively, and LDM zone consists of acicular α phases and fine basketweave structure. The thickness of α laths shows a trend of ‘WAAM > HAZ > LDM > RZ’. The strengths are greatly improved at the interfaces due to the good metallurgical bonding and finer microstructure. All the fractures locate at WAAM zone during tensile test and propagate along the basketweave structure. These strengths of WAAM-LDM samples under the action of horizontal loading are higher than that of WAAM samples, and all the elongations of WAAM-LDM samples are higher than 10 %.

Production of a Ti6Al4V Automobile’s Lower Control Arm with EBM

Lattice structures and Topology Optimization are two of the main routes to design lightweight high resistance components. These design techniques often lead to complex geometries not obtainable by traditional manufacturing. In this work we show how Additive Manufacturing (AM) of metals can be a successful way to reach that result. At first, we studied Ti6Al4V samples produced by Electron Beam Melting (EBM) to determine the mechanical properties of the base material. Hot Isostatic Pressing (HIP) was performed on a part of these samples to understand the impact of this process on defects and material properties. The results we obtained showed that the properties of Ti6Al4V produced by EBM are comparable to the one of the conventionally produced one. Given these results we redesigned an automobile’s lower control arm to reduce its mass: considering both Topology Optimization (TO) and lattice structures. Ti6Al4V components with different lattice structures were successfully manufactured by EBM.

Microstructure quality assessment for hybrid additive manufactured Ti6Al4V components via ultrasonics

Metal components with functionally organized microstructures for specific applications are emerging thanks to hybrid additive manufacturing (AM). The customization of these high value components accentuates the need for nondestructive methods to characterize their microstructural functional patterns. Nondestructive evaluation (NDE) methods that are economical, fast, energy efficient, and easy to integrate into routine component inspections are preferred. Most importantly, NDE methods must be sensitive to changes in the microstructure such that regions that do not satisfy the design requirements (i.e. out-of-spec regions) can be detected. In this work, ultrasonic NDE methods grounded in diffuse backscatter modeling were used to detect and quantify spatial property variations resulting from a hybrid AM process. The manufacturing process coupled directed energy deposition (DED) with milling in a cyclical manner. These methods were successfully implemented to evaluate the microstructural uniformity of Ti6Al4V samples as well as to make comparisons across an ensemble of samples manufactured with identical parameters. Out-of-spec regions were mapped with respect to the sample geometry on a layer-by-layer basis. The results of this work are expected to inform future NDE strategies for both research and practitioner contexts, and limitations are discussed.

Microstructure and microhardness of electron beam melted Ti–6Al–4V components with differential thickness in initial deposition layers

Electron beam powder bed fusion (EB-PBF) is a process to additively manufacture Ti–6Al–4V. Along with process induced defects, the unique microstructure of EB-PBF Ti–6Al–4V leads to anisotropic properties, and therefore an understanding of how the microstructure evolves as layers are added is required. This experimental study presents the microstructural evolution of Ti–6Al–4V during the deposition of initial layers in EB-PBF process. Two geometries of specimens, ramp and step, were fabricated from 0.1 mm thickness (2 layers) to 0.7 mm (14 layers), and 0.2 mm (4 layers) to 1.4 mm (28 layers). The evolution of the microstructure was investigated through optical and electron microscopy, spatial microhardness mapping, and detailed microstructural characterization. Up to the deposition of seven layers, the microstructure comprised of α+β phases with partially retained α′ phase from rapid solidification cooling that resulted in higher microhardness. A unique microstructural gradient composed of three distinct regions (Region I, II, III) appears along the build direction from the deposition of 10 layers until 28 layers. Region I showed a finer α+β microstructure in irregular prior β grain with partial martensitic α’ phase and displayed greater microhardness. Region II showed coarser α+β microstructure and lower microhardness than both Region I and III. The average α-lath thickness and α-volume fraction increased as new layers were deposited. Perpendicular to the build direction, the hardness distribution was observed to be uniform along the longitudinal x-y direction.