Browsing by Subject "Ti6Al4V"
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Item Comparison of Layerwise Preheating and Post-heating Laser Scan on The Microstructure and Mechanical Properties of L-PBF Ti6Al4V(University of Texas at Austin, 2023) Alptug Tanrikulu, Ahmet; Ganesh-Ram, Aditya; Farhang, Behzad; Amerinatanzi, AmirhesamThis study aimed to investigate the evolution of the microstructure and mechanical properties of asfabricated laser powder bed fusion (L-PBF) Ti-6Al-4V samples by introducing layerwise pre-heating or post-heating laser scans. Multiple laser scans, varying in scanning speed at constant power, were examined before the melting laser scan (pre-heating) or after it (post-heating). The analysis focused on microstructural features such as porosity, and α-phases lath structure, as well as the hardness response of the material. The results revealed the additional layerwise scans had a significant impact on reducing porosity by up to 98% when the additional scan was applied prior to or upon the melting scan. Additional laser scans decreased the microstructure and mechanical response variation along different orientations. Furthermore, these findings highlight the potential of layerwise heating strategies to improve the overall quality and performance of L-PBF Ti-6Al-4V components, thus paving the way for enhanced applications in various industries such as aerospace.Item Comparison of Surface Texture from Various Surface Morphology Techniques for Evaluating As-Built Ti6Al4V Laser Powder Bed Fusion(University of Texas at Austin, 2023) De La Cruz, Alex; Medina, Francisco; Arrieta, Edel; Weston, Luke; Benedict, Mark; Gibson, TheoAdditive manufacturing (AM) is capable of creating unique and complex geometries that conventional methods cannot achieve. The applications for AM have been rapidly increasing across a variety of sectors, particularly for biomedical and aerospace components, the relatively low production volumes and high demand for customizability in both sectors are especially amiable to AM. However, without post-processing, AM components contain a variety of flaws, such as surface roughness and porosity, that can partially be mitigated by process parameters like scan speed and laser power. Surface roughness is a flaw present for every as-built AM surface that serves as an array of sites for every mode of material failure to occur. Common surface roughness measurements involve the use of optical and contact stylus profilometry. However, xray Computed Tomography (xCT) is already the most widely used method of analyzing AM parts for porosity, inclusions, and various other flaws. In terms of resolution, xCT should be fully capable of analyzing surface roughness and is the only method of the three investigated that can inspect interior geometries. Therefore, evaluating xCT as a fully inclusive analysis method for AM parts is advantageous. In this study, we compared three surface characterization technologies, xCT, optical profilometry, and contact stylus profilometry. The comparison of these technologies is being done on as-built Laser Powder Bed Fusion (L-BPF) Ti6AI4V fourpoint bending fatigue samples. Further understanding the difference among each of the technologies will aid ongoing research on developing a standard for xCT surface characterization while also providing more knowledge and insight into each technique and what can be expected. Each of the samples was produced by varying scanning speed and laser power, resulting in different surface textures. Preliminary results show deviations of Sa _%, Sz _%, Sv _%, and Sku _% between the xCT and optical microscopy methods are comparable between these two methods.Item Design and Characterization of Orthotropic Re-Entrant Auxetic Structures Made via EBM Using Ti6Al4V and Pure Copper(University of Texas at Austin, 2011-08-17) Yang, L.; Harrysson, O.; West, H. II; Cormier, D.An orthotropic 3D re-entrant honeycomb structure that exhibits a negative Poisson’s ratio was designed and fabricated via the electron beam melting (EBM) process. The modeling work established the relationships between various structural parameters and the mechanical properties of the auxetic structures. Compressive tests were performed on the re-entrant honeycomb samples made with Ti6Al4V as well as pure copper. Results of the strength, modulus and energy absorption for the two materials were compared with the theoretical models in order to verify the theoretical predictions.Item Determination of the Optimum Joint Design for LENS Fabricated Ti6Al4V and Ti6Al4V/TiC Dual-Material Structures(University of Texas at Austin, 2010-09-23) Obielodan, J.O.; Stucker, B.E.Joints between dissimilar material systems made using laser metal deposition processes have been investigated. The fusion of materials with different physical properties and chemical compositions under high laser power often results in defects at the joints. Although some solutions have been suggested in previous work for defect-free fabrications, most of the joints studied have been characterized using qualitative techniques only. Quantitative study is imperative for predicting the mechanical behavior of fabricated structures for real life applications. In this work, tensile and flexural specimens made of different Ti6Al4V and Ti6Al4V/10%TiC dual-material transition joint designs were fabricated using laser engineered net shaping (LENS) and tested. It was found that transition joint design has a significant effect on the tensile strengths of dual-material structures.Item Effects of Powder Variation on the Microstructure and Tensile Strength of Ti6Al4V Parts Fabricated by Selective Laser Melting(University of Texas at Austin, 2014) Gu, Hengfeng; Gong, Haijun; Dilip, J.J.S.; Pal, DeepankarMetallic powders are used as raw materials in the Selective Laser Melting (SLM) process. These metal powders are typically available from more than one powder vendor. Even when powders have the same nominal chemical compositions, powders produced by different companies typically result in different powder particle size distributions and morphologies. These powder differences result in different powder bed thermophysical properties, which affect how the powder melts and solidifies. This paper studies the effect of powder variation on the microstructure and tensile strength of as-built SLM Ti6Al4V parts. Ti6Al4V powders from different vendors were used to fabricate parts via SLM. Powder characteristics, such as particle size distribution, morphology, and flowability, were obtained. Powder bed densities and thermal conductivities were measured and compared. The microstructures and tensile strengths were investigated by standard metallographic and tensile testing methods. Based on the experimental results, a correlation between the powder characteristics and part properties are discussed.Item Efficient Fabrication of Ti6Al4V Alloy by Means of Multi-Laser Beam Selective Laser Melting(University of Texas at Austin, 2017) Li, Fangzhi; Wang, Zemin; Zeng, XiaoyanA self-developed four-laser beam selective laser melting (SLM) system was used to fabricate Ti6Al4V alloy samples in this study. The relative density, micro-hardness and mechanical properties of all isolated processing areas were compared under optimized processing parameters to ensure the consistency of this system. Microstructures in overlap areas are dominated by columnar grains along the building direction and matensitic needles αˊ inclined at about ± 45° to the building direction, which are similar with those in isolated areas. Mechanical properties in overlap areas are also not inferior to those in isolated areas. The results prove the feasibility to fabricate large-scale components with a uniform microstructure and mechanical property by this SLM system. By the use of four lasers, this system can provide a high building rate of 80 cm3/h.Item Electropolishing of Ti6Al4V Parts Fabricated by Electron Beam Melting(University of Texas at Austin, 2016) Yang, L.; Wu, Yan; Lassell, Austin; Zhou, BinIn this study Ti6Al4V samples fabricated via electron beam melting were subjected to electropolishing under various polishing conditions using the re-designed in-house electropolishing device. The surface finish of the processed samples were characterized, and the tension-tension fatigue properties of the samples were evaluated via experimentation. The results provided preliminary information about the effect of electropolishing on surface crack initiation of the electron beam melted Ti6Al4V parts.Item Examination of the LPBF Process by Means of Thermal Imaging for the Development of a Geometric-Specific Process Control(University of Texas at Austin, 2019) Pichler, T.; Schleifenbaum, J.H.The development of process parameters for the Laser Powder Bed Fusion (LPBF) process is typically carried out by the manufacturing and metallurgical analysis of geometrically primitive test specimens (e.g. cubes). The process parameters identified in this way are used for the manufacturing of parts which are characterized by a high geometric complexity and a combination of solid and filigree component areas. Due to the discrepancy between the parameter development on primitive specimens and applications with complex parts, a geometric-specific process control is to be developed. In the context of this work different sample geometries are manufactured from Ti6Al4V by LPBF and the process is monitored by thermal imaging. The influence between component geometry and process parameters on the thermal behavior is shown.Item Fabrication and Characterization of Ti6Al4V by Selective Electron Beam and Laser Hybrid Melting(University of Texas at Austin, 2017) Zhou, Bin; Zhou, Jun; Li, Hongxin; Lin, FengA hybrid process, which combines electron beam selective melting(EBSM) and selective laser melting(SLM), is proposed in this study. Laser is led into the vacuum chamber through the lens so that laser can be used to fabricate the metal powder at the same time with electron beam. In this study, Laser is used to pre-preheat the metal powder in order to preventing powder spreading and laser is also used to fabricate the contour of the parts both inside and outside. Electron beam is used to preheat the metal powder to the specified temperature and to fabricate the interior of the parts. It can be sure that through the hybrid process we can fabricate the parts with both better surface quality, higher precision and higher efficiency. Ti6Al4V samples were fabricated by selective electron beam and laser hybrid melting. The surface roughness of the parts was measured, the microstructures of the contour and interior were characterized using scanning electron microscopy (SEM). The results are that as-fabricated parts have better surface quality than the parts fabricated only using EBM process.Item Further Study of the Electropolishing of Ti6Al4V Parts Made via Electron Beam Melting(University of Texas at Austin, 2015) Yang, Li; Lassell, Austin; Perez Vilhena Paiva, GustavoIn this study, the effect of various parameters including the voltage, current, polishing time, temperature and electrode spacing on the electropolishing quality of Ti6Al4V samples made via electron beam melting was investigated using specialty designed research setups. The relationships between these process parameters and the surface roughness of the parts were established experimentally.Item High Density Ti6Al4V via Slim Processing: Microstructure and Mechanical Properties(University of Texas at Austin, 2011-08-17) Kong, Chang-Jing; Tuck, Christopher J.; Ashcroft, Ian A.; Wildman, Ricky D.; Hague, RichardThis paper investigates a density improvement method for Ti6Al4V alloy processed by the selective laser melting method. A modified inert gas inlet baffle has been employed to develop improved mechanical properties for these materials. Comparisons of the top surface and cross-section porosities of solid blocks processed by the original and modified gas inlet baffles indicate that the modified baffle greatly increases the properties of the processing blocks. Results showed that the porosity of the Ti6Al4V alloy was lower than 0.1% by area. The microstructure of the SLM Ti6Al4V alloy exhibited martensitic α' phase. The UTS tensile strength was 920-960MPa and the elongation at the fracture was 3-5%. The fracture surfaces of the tensile samples demonstrated a mixture of ductile and brittle fracture.Item In-situ Reinforcement Processing for Laser Powder Bed Fused Ti64 Parts(University of Texas at Austin, 2023) Ganesh-Ram, A.; Tanrikulu, A.A.; Valdez Loya, O.; Davidson, P.; Ameri, A.The objective of this study was to investigate how the microstructure and mechanical properties of Ti-6Al-4V samples, fabricated using laser powder bed fusion (L-PBF), change when a predefined local double melting strategy is employed within each layer of the manufacturing process. The analysis primarily focused on evaluating microstructural aspects, defects, and grain size, along with the mechanical properties, specifically the Vickers hardness at various positions within the samples. The findings indicated that the integration of the predefined locally double melting scan in each layer had a significant influence on the microstructure, resulting in variations in grain size across different locations, as well as hardness values with variations of up to 10% across different areas. Moreover, these discoveries underscore the potential of employing the predefined locally double melting strategy in each layer to create fabricated components with distinctive behaviors, like composites, which could find applications in the aerospace industry.Item Increasing Process Speed in the Laser Melting Process of Ti6Al4V and the Reduction of Pores During Hot Isostatic Pressing(University of Texas at Austin, 2017) Ahlers, D.; Koppa, P.; Hengsbach, F.; Gloetter, P.; Altmann, A.; Schaper, M.; Tröster, T.Additive manufacturing of titanium alloys has gained intensive attraction from industry and academia. Moreover, for additively fabricated parts consisting of Ti6Al4V, hot isostatic pressing (HIP), is widely used as a post treatment in order to increase the relative density of the built parts. However, one aspect which has rarely been addressed so far, is the increase of process speed, accompanied by a reduced relative density in the as-built condition and a subsequent hot isostatic pressing process to achieve the desired dense material. The approach here is to use the standard process route as described, but intentionally increase the process speed and accept a certain value of porosity. The focal objective of this study is the identification of a parameter-set with the highest potential for an increase of process speed and subsequently reduce the internal defects during the hot isostatic pressing process to achieve completely dense components.Item Influence of Heat-Treatment of Selective Laser Melting Products - e.g. Ti6Al4V(University of Texas at Austin, 2012-08-22) Thöne, M.; Leuders, S.; Riemer, A.; Tröster, T.; Richard, H.A.Usually additive manufactured metal parts are showing a different mechanical behavior compared to conventionally produced parts used the same material. Apart from process-related macroscopic part imperfections (pores, surface roughness, etc.) the microstructure has a decisive influence on the mechanical properties of the materials. Thus, in order to optimize mechanical properties of metal parts a heat treatment for changing microstructures is routinely applied in most production lines to meet the product requirements. By means of the Titanium alloy Ti6Al4V the optimization of the static- and the fracture mechanical behavior by changing the microstructure with a heat treatment after the SLM process is discussed on the present work.Item Investigating the Relationship Between In-Process Quality Metrics and Mechanical Response in the L-PBF Process(2022) Sampson, Bradley J.; Morgan-Barnes, Courtney; Stokes, Ryan; Doude, Haley; Priddy, Matthew W.Laser powder bed fusion (L-PBF) additive manufacturing is a process that utilizes a high- powered laser to build near net-shaped parts in a layer-by-layer fashion using metal powder as the feedstock material. Traditionally, the analysis of L-PBF produced parts has relied solely on post- build characterization to understand the relationship between the printing process and the final mechanical properties. Recent developments of in-process quality assurance systems, such as Sigma Additive Solutions’ PrintRite3D, can measure in-process thermal signatures and melt pool disturbances in real-time. This research aims to examine the relationship between process parameters (e.g., scan strategy, scanning speed, and layer thickness) and in-process quality metrics (IPQMs) captured by the PrintRite3D system on a Renishaw AM400. The mechanical response of multiple part geometries (NIST residual stress bridges, single-arched bridges) and build materials (Ti6Al4V) includes residual stress deflection and hardness; the results are compared with the IPQMs.Item Microstructural and Mechanical Characterization of Ti6Al4V Cellular Struts Fabricated by Electron Beam Powder Bed Fusion Additive Manufacturing(University of Texas at Austin, 2018) Ewing, Cody; Wu, Yan; Yang, LiDespite the widespread use of the electron beam powder bed fusion (EB-PBF) additive manufacturing (AM) process in the fabrication of cellular structures, relatively little is known about the microstructural and mechanical properties of the individual cellular struts of different geometries fabricated by the EB-PBF. In this study, experimental investigation was carried out in the attempt to establish preliminary understanding of the material characteristics of the Ti6Al4V cellular struts using EB-PBF under various geometry design conditions (dimension and orientation angle). It was found that there exist significant geometry effects for the material characteristics of the Ti6Al4V cellular struts, which indicates that a non-uniform material model should be considered in the future design of these cellular structures.Item Numerical and Experimental Study on the Effect of Artificial Porosity in a Lattice Structure Manufactured by Laser Based Powder Bed Fusion(University of Texas at Austin, 2018) du Plessis, Anton; Yadroitsava, Ina; Kouprianoff, Dean; Yadroitsev, IgorAdditively manufactured lattice structures are used in various applications due to their unique properties, especially low weight with relatively good strength and stiffness. While lattices have been investigated widely, the effect of manufacturing flaws on the lattice performance was not yet analyzed in detail. One important type of manufacturing flaw which can be relatively easily analyzed numerically and experimentally is unwanted voids or porosity. In this work, using a simple cubic lattice structure as a test case, pores with varying sizes were induced in a single strut and compressive loading simulated. Ti6Al4V ELI (extra low interstitial) lattices produced by laser powder bed fusion, with and without induced pores, were subjected to mechanical compression tests. MicroCT images validated the presence and size of the induced voids in produced samples. The mechanical compression results show that even relatively large pores in individual loadbearing struts do not affect the ultimate compressive strength of these lattices, for these particular lattice shapes studied and for individual large pores.Item Observation and Numerical Simulation of Melt Pool Dynamic and Beam Powder Interaction During Selective Electron Beam Melting(University of Texas at Austin, 2012) Scharowsky, T.; Baureiβ, A.; Singer, R.F.; Körner, C.Selective electron beam melting (SEBM) is an additive manufacturing method used to produce complex parts in a layer-by-layer process utilizing Ti6Al4V powder. To improve the very good properties of built parts even more and to use the full capacity of the process, the fundamental understanding of the beam powder interaction is of essential relevance. Numerical simulations and observation with a high speed camera of powder melting show the strong melt pool dynamic and its lateral extent clearly. Furthermore, the immediate effect of beam parameters, e.g. beam current and velocity, on the melting behavior of the powder can be resolved in time steps of a few milliseconds.Item Prediction of Mechanical Properties of Electron Beam Melted Ti6Al4V Parts Using Dislocation Density Based Crystal Plasticity Framework(University of Texas at Austin, 2012-08-22) Pal, Deepankar; Patil, Nachiket; Stucker, Brent E.Parts produced using Electron Beam Melting (EBM) with Ti6Al4V powders are generally tested for two important mechanical properties, namely tensile strength and fatigue life. The optimization of the process input parameters, such as part orientation, initial powder size and hatch pattern, for the abovementioned mechanical properties has been attempted using two numerical finite element methods. First, the dislocation density based crystal plasticity framework (DDCP-FEM) has been used to evaluate the localized stress-strain evolution, dislocation density evolutions and non-local deformations as a function of loading, sample geometry, microstructural phase, grain size and shape. This analysis has been compared against simulations based on continuum plasticity based finite element techniques. Though the localized evolutions as a function of microstructural attributes are missing in the continuum analysis, the low computational costs involved makes this technique an ideal candidate for spatial homogenization of the DDCP-FEM framework. The simulations conducted in the current work only validate the mechanical properties for tensile and fatigue specimens fabricated with known process parameters. These simulations will form the basis for future modeling efforts to optimize these parameters for required mechanical properties in service.Item Surface Treatment of Ti6Al4V Parts Made By Powder Bed Fusion Additive Manufacturing Processes using Electropolishing(University of Texas at Austin, 2014) Yang, Li; Gu, Hengfeng; Lassell, AustinThis paper investigated the use of electropolishing on the surface treatment of the Ti6Al4V parts made by the powder bed fusion processes including direct metal laser sintering (DMLS) and electron beam melting (EBM). A non‐aqueous alcohol based electrolyte was used, and the relationship between the process and surface roughness was evaluated. Based on the results, the feasibility of electropolishing as a potential alternative post‐surface treatment for additive manufactured metal parts was discussed.