Papers by Keyword: Ti-6Al-4V

Abstract: Additively manufactured titanium alloys such as Ti-6Al-4V have been used as functional components in industry due to their excellent mechanical properties. However, the machining of these alloys is a challenge due to their enhanced tensile/yield strength, low elastic modulus, poor thermal conductivity, and microstructural anisotropy. Thermal assisted machining (TAM), as a hybrid manufacturing technology, can improve the machinability of additively manufactured alloys. The main aim of this paper is to investigate the effect of temperature buildup on the machinability of additively manufactured Ti alloy with different build directions in the TAM process. It was found that the surface integrity was notably enhanced by preheating, and it was the best at 90° build orientation. Serrated chips were generated at room temperature, and curlier chips were formed in high-preheating machining environment. By analyzing the surface quality, the influence of the build-up orientation on the surface quality at different temperatures was evaluated.

Abstract: This study explores the additive manufacturing of porous Ti-6Al-4V reticular structures using Powder Bed Fusion Laser Beam, with a focus on their morphological and mechanical properties for biomedical implant applications. Three triply periodic minimal surface (TPMS) designs—diamond, primitive, and split-P—were fabricated with both constant and radial density gradients, and subjected to electropolishing and chemical etching to enhance surface quality. The results showed that split-P structures exhibited the highest yield strength (274.93–288.95 MPa) and a moderate Young’s modulus (7.16–7.76 GPa), making them strong candidates for load-bearing implants due to their mechanical behavior closely resembling that of trabecular bone. Diamond structures had the highest stiffness (6.95–8.65 GPa) but showed brittle behavior, while primitive structures presented the lowest modulus and strength, offering ductility suitable for flexible applications. The findings underscore the potential of optimized TPMS lattices to improve mechanical compatibility and reduce stress shielding in next-generation orthopedic implants.

Abstract: Solution quenching and aging are used to thermally treat Ti-6Al-4V, an α+β titanium alloy. Three Ti-6Al-4V alloy plates were subjected to high temperatures and quenched in water, 5% HCL, and 15% HCl in this investigation. As a comparison, a fourth untreated sample was employed. When compared to the untreated samples, the microstructure and strength of the quenched plates revealed an increase in elongation and a decrease in yield strength. An equiaxed increase of α+β was recorded in all post-quenched samples.

Abstract: Selective Laser Melting (SLM) is a promising technique for fabricating intricate metal components. The scanning strategy is a critical parameter that can be optimized to improve the quality of the final parts, as different strategies produce temperature distribution variations. It can impact on the melt pool dynamics and the mechanical properties of the fabricated components. In this study, four scanning strategies were investigated: uni-directional scanning, altered-sequence uni-directional scanning, bi-directional scanning, and altered-sequence bi-directional scanning. Their effects on localized temperature distribution, melt pool morphology, and surface roughness (Ra) during the SLM process of Ti-6Al-4V across five tracks were evaluated using numerical simulation. The simulations were performed using FLOW-3D AM. This simulation integrates the Discrete Element Method (DEM) with Computational Fluid Dynamics (CFD) model. The simulation results demonstrated that the scanning sequence and scanning direction directly effects on the localized temperature distribution. Heat accumulation is more diffusely distributed over the last three scanned tracks in bi-directional scanning and altered sequences of bi-directional scanning. The scanning sequence significantly affects melt pool depth. A symmetric depth profiles of the five tracks were formed at altered sequences of uni-directional scanning and altered sequences of bi-directional scanning cases. Conversely, the left-skewed profiles, where melt pool depth gradually increases with each additional track, peaking at the last one, were generated at uni-directional scanning and bi-directional scanning cases. This trend is primarily attributed to heat accumulation from preceding solidified tracks. In addition, both scanning direction and scanning sequence are significantly impact on the surface roughness by changing from uni-directional scanning to bi-directional scanning showed 27.38% of Ra reduction and changing from uni-directional scanning to altered sequences of uni-directional showed 14.29% of Ra reduction.

Abstract: Surface coatings are crucial for improving the thickness distribution by reducing the interfacial friction between the component and forming die during superplastic forming process. In addition, these coatings act as an oxygen barrier to minimise the formation of alpha case. In this paper, the effect of friction was studied with a single-sheet superplastic forming component using finite-element (FE) analysis and validated through experimental trials. Tensile tests of Ti-6Al-4V were conducted at 900° C according to ASTM E2448 standard, and time-hardening creep power law was used to estimate the material parameters for FE simulation. Herein, two cases were studied. Firstly, a uniform friction condition (one frictional constant) for the whole die surface was studied and a pressure cycle using a strain rate control algorithm was derived using Abaqus. Four different friction constants were studied using the pressure cycle. Low, medium and high fiction coefficients were analysed, along with frictionless conditions. A comparison of FE and experimental results indicated that combining a new coating variant and Boron nitride (BN) achieved similar results to that observed with FE simulation with low friction constant, while results with Boron nitride coating correlated with FE simulation with a medium friction constant. Secondly, a varying friction approach was studied wherein the die surface geometry was segmented and assigned heterogeneous coefficient of friction (COF) values. The obtained FE results suggest that varying friction can introduce slight improvement in the thickness distribution for the selected component geometry.

Abstract: Tailored machined blanks are sheets that feature heterogeneous thicknesses, allowing different areas of the final part to withstand distinct structural loads effectively. Conventional methods of tailoring the thickness of the final part, like chemical machining, are labour intensive processes that requires pre-masking and post cleaning of complex industrial component. The proposed method provides a cost-effective solution to manufacture light-weight components by simplifying the material removal compared to shaping intricate 3D parts. In fact, machining a flat blank is simpler than removing the material from complex 3D geometries. In this study, the feasibility of superplastically formed Ti-6Al-4V tailored machined blanks was analysed. Three industrial relevant design examples were developed for components forming with initial dissimilar thickness distributions. The results were examined through Finite Element (FE) simulation and experimentation. The FE simulations guided the design of these blanks. Two examples aimed to address the excessive thinning issue typically encountered with standard homogeneous thickness approaches, where specific regions in the part undergo maximum deformation. The blank designs were preserved with higher thicknesses in regions where maximum deformation was expected. The third example explored forming a structured pattern thickness distribution, incorporating thicker stiffeners covering the sheet in two perpendicular directions. Although the approaches differed, the goal of all three designs was to reduce the total weight of the part. The tailored blanks were manufactured via CNC machining from a 2.6 mm thick Ti-6Al-4V sheet, introducing variable thickness profiles. Subsequently, the blanks were superplastically formed in an SPF press. The successful forming of the parts demonstrated the feasibility of the tailored thickness blank approach that can enable the reduction in component weight. Also, this approach can help the industry to phase out chemical milling for the purpose of light-weighting and removing of excess material from post formed component. Importantly, the experimental trials showed good correlation with the FE simulations, emphasizing the crucial role of the FE tool in designing such components.

Abstract: In the aerospace industry, hot forming processes, using materials like Ti-6Al-4V titanium, are known for their complexity and cost. Senior Aerospace Thermal Engineering (SATE) has traditionally relied on a trial-and-error approach for new product introductions (NPIs), which, while effective, has led to significant time and resource expenditures. This paper examines the transition of SATE's NPI processes to a more efficient digital approach using AutoForm Forming simulation software. By doing so, SATE has been able to accurately predict forming outcomes, optimize tooling designs, and significantly reduce both the number of physical tryouts and the overall project costs. Two case studies are presented to demonstrate the practical applications of this digitalization, highlighting how important engineering decisions were taken. The paper concludes with an assessment of the impact on SATE's operations, noting improvements in development time, feasibility assessments, and overall production efficiency.

Abstract: The exceptional corrosion resistance, low weight, and high strength of titanium (Ti) make it an excellent choice for components in proton exchange membrane fuel cells (PEMFC). However, during PEMFC operation, Ti undergoes passivation, which diminishes the bipolar plates' (BP) ability to transport electrons between cells. Applying titanium nitride (TiN) coatings, known for their good conductive properties, can resolve this issue and enhance corrosion resistance. Additionally, using additive manufacturing (AM) to produce BP offers numerous benefits in terms of structural control for more intricate designs. This study examines the impact of TiN coating via gas nitriding on Ti-6Al-4V open structures created by powder bed fusion-electron beam/metal (PBF-EB/M) or PM routes, focusing on the surface characteristics such as composition and interfacial contact resistance (ICR).

Abstract: Titanium alloys are widely used in aerospace applications due to their excellent strength-to-weight ratio, corrosion resistance, and high temperature performance. However, including nanoparticles as reinforcement in titanium alloys can further improve their mechanical properties, making them even more suitable for demanding aerospace applications. Titanium matrix composites (TMC) are titanium alloys typically reinforced with micron-sized ceramic particles. These reinforcements improve some properties, such as strength, but deteriorate others. However, reducing the size of reinforcements to the nanometer range allows for larger reinforcement effects to be obtained with much smaller volumetric fractions of reinforcement, which is less detrimental to fatigue, toughness, ductility, etc. This work focuses on the study of simple and safe manufacturing routes for nanoreinforced Ti alloys that increase the strength of the base material with a low negative effect on ductility. The selection of the compositions and treatment temperatures was carried out using binary phase diagrams and experimental results.

Abstract: The Selective Laser Melting (SLM) process involves directing a laser beam onto a powder bed to create intricate metal parts. However, the as-built quality is strongly influenced by several process parameters, especially, laser power, scanning speed, layer thickness, and hatch spacing. Therefore, this study explored the impact of varying scanning speed (800 to 1,400 mm/s) on the temperature distribution and morphology of the melt pool using Ti-6Al-4V material with a high layer thickness of 80 μm and constant laser power of 170 W using numerical simulation. The temperature distribution, assessed from the top view and at the cross-sectional plane, showed that a lower scanning speed (v) or higher Linear Energy Density (LED) results in a wider hot zone. The effect of scanning speed on melt pool morphology and dimensions is demonstrated through the classification of molten pools based on the width-to-depth ratio of the melt track. The higher scanning speeds resulted in a transition mode, while low scanning speeds led to the formation of a keyhole mode. The findings indicate that under these specified conditions of laser power and powder layer thickness for Ti-6Al-4V, a scanning speed of 1000 mm/s is optimal, as it produces a weld with a w/d ratio that avoids the problematic keyhole mode while maintaining good weld morphology and quality.