Defect distribution and microstructure heterogeneity effects on fracture resistance and fatigue behavior of EBM Ti–6Al–4V

Seifi, Mohsen; Salem, Ayman A.; Satko, Daniel P.; Shaffer, Joshua; Lewandowski, John J.

doi:10.1016/j.ijfatigue.2016.06.001

Cited by 208 publications

(115 citation statements)

References 42 publications

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“…HIP can significantly reduce the porosities, but still cannot result in 100% dense microstructure [70]. HIP reduces/eliminates the process-induced porosities [71], but might not close those gas-trapped pores since the trapped gas can still "prop up" the pores [72].…”

Section: Electron Beam Meltingmentioning

confidence: 99%

Additively Manufactured Inconel 718 : Microstructures and Mechanical Properties

Deng

2018

Linköping Studies in Science and Technology. Licentiate Thesis

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Linköping 2018Cover image: A fracture surface of EBM IN718 after tensile test at room temperature.During the course of research underlying this thesis, Dunyong Deng was enrolled in Agora Materiae, a multidiciplinary doctoral program at Linköping University, Sweden. Printed by LiU-Tryck 2018 © Dunyong Deng AbstractAdditive manufacturing (AM), also known as 3D printing, has gained significant interest in aerospace, energy, automotive and medical industries due to its capabilities of manufacturing components that are either prohibitively costly or impossible to manufacture by conventional processes. Among the various additive manufacturing processes for metallic components, electron beam melting (EBM) and selective laser melting (SLM) are two of the most widely used powder bed based processes, and have shown great potential for manufacturing high-end critical components, such as turbine blades and customized medical implants. The futures of the EBM and SLM are doubtlessly promising, but to fully realize their potentials there are still many challenges to overcome.Inconel 718 (IN718) is a nickel-base superalloy and has impressive combination of good mechanical properties and low cost. Though IN718 is being mostly used as a turbine disk material now, the initial introduction of IN718 was to overcome the poor weldability of superalloys in 1960s, since sluggish precipitation of strengthening phases γ ′ /γ ′′ enables good resistance to strain-age cracking during welding or post weld heat treatment. Given the similarity between AM and welding processes, IN718 has been widely applied to the metallic AM field to facilitate the understandings of process-microstructure-property relationships.The work presented in this licentiate thesis aims to better understand microstructures and mechanical properties EBM and SLM IN718, which have not been systematically investigated. Microstructures of EBM and SLM IN718 have been characterized with scanning electron microscopy (SEM), transmission electron microscopy (TEM) and correlated with the process conditions. Monotonic mechanical properties (e.g., Vickers microhardness and tensile properties) have also been measured and rationalized with regards to the microstructure evolutions before and after heat treatments.For EBM IN718, the results show the microstructure is not homogeneous but dependant on the location in the components, and the anisotropic mechanical properties are probably attributed to alignment of porosities rather than texture.iii Post heat treatment can slightly increase the mechanical strength compared to the as-manufactured condition but does not alter the anisotropy. SLM IN718 shows significantly different microstructure and mechanical properties to EBM IN718. The as-manufactured SLM IN718 has very fine dendritic microstructure and Laves phases in the interdendrites, and is "work-hardened" by the residual strains and dislocations present in the material. Mechanical properties are different between horizontally and vertically built samples, and heat treatment can m...

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Section: Electron Beam Meltingmentioning

confidence: 99%

Additively Manufactured Inconel 718 : Microstructures and Mechanical Properties

Deng

2018

Linköping Studies in Science and Technology. Licentiate Thesis

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“…These processes are subject to continuing challenges to devise the most efficient machine settings which generate a good surface of the artificial bone (implant), which ultimately lead to enhanced properties [6]. Though electron beam melting is a widely used additive manufacturing process for fabricating different complex shapes [7] in the biomedical industry, the challenge remains in dealing with the intrinsic changing surface roughness in between layers due to layer by layer deposition offering potential places for fatigue cracks to initiate [8,9]. Therefore, EDM is considered to be likely choice for machining as well as surface modification process due to having the potential to improve the mechanical properties, corrosion and fatigue resistance, improved surface hardness, fabricating the most favourable surface on bio-implant due to generation of carbon and oxygen-enriched surface [5,10,11].…”

Section: Introductionmentioning

confidence: 99%

On the Investigation of Surface Integrity of Ti6Al4V ELI Using Si-Mixed Electric Discharge Machining

et al. 2020

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Surface modification is given vital importance in the biomedical industry to cope with surface tissue growth problems. Conventionally, basic surface treatment methods are used which include physical and chemical deposition. The major drawbacks associated with these methods are excessive cost and poor adhesion of coating with implant material. To generate a bioactive surface on an implant, electric discharge machining (EDM) is a promising and emerging technology which simultaneously serves as machining and surface modification technique. Besides the surface topology, implant material plays a very important role in surgical applications. From various implant materials, titanium (Ti6Al4V ELI) alloy is the best choice for long-term hard body tissue replacement due to its superior engineering, excellent biocompatibility and antibacterial properties. In this research, EDM’s surface characteristics are explored using Si powder mixed in dielectric on Ti6Al4V ELI. The effect of powder concentration (5 g/L, 10 g/L and 20 g/L) along with pulse current and pulse on time is investigated on micro and nanoscale surface topography. Optimized process parameters having a 5 g/L powder concentration result in 2.76 μm surface roughness and 13.80 μm recast layer thickness. Furthermore, a nano-structured (50–200 nm) biocompatible surface is fabricated on the surface for better cell attachment and growth. A highly favourable carbon enriched surface is confirmed through EDS which increases adhesion and proliferation of human osteoblasts.

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“…The lack of melting (occurs between passes), together with columnar structure and texture, are the three main contributing factors to anisotropy seen in mechanical properties. [94,144] The reported fracture toughness values of SLM-produced alloys are shown in Figure 23. In a DED Ti-6Al-4V alloy, no significant anisotropy in tensile strength was observed [92] ; however, for a SLM Ti-6Al-4V specimen, the anisotropy in tensile strength and ductility is much greater, reaching 15.4% and 77.6%, respectively.…”

Section: Materials Propertiesmentioning

confidence: 99%

“…In horizontal specimens, cracks propagate through the columnar grains, whereas in the vertical orientation, cracks propagate along the columnar grain boundaries. [94,144] The reported fracture toughness values of SLM-produced alloys are shown in Figure 23. Heat treatment and stress relief increased the fracture toughness of Ti-6Al-4V whereas the fracture toughness decreased for Al-12Si specimens following a post-AM heat treatment.…”

Section: Materials Propertiesmentioning

confidence: 99%

Laser‐Based Additive Manufacturing Technologies for Aerospace Applications

2019

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Additive manufacturing (AM) is a transformative technology that has rapidly grown over the past decade. AM processes build parts layer by layer and have found applications in the aerospace, biomedical, and automotive fields. The technology holds particular promise for the aerospace industry due to the reduced process time, weight savings of parts, and opportunities for new material development. Herein, a review of laser-based AM processes, existing AM systems, and aerospace parts being fabricated is presented. It further explores the material properties and microstructure of printed samples with both powder bed fusion and direct energy deposition processes. The benefits and challenges associated with the widespread use of the technology are discussed with emphases on the aerospace sector. Finally, the steps required for parts produced by AM processes to become certified for use in aerospace applications are presented.

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Defect distribution and microstructure heterogeneity effects on fracture resistance and fatigue behavior of EBM Ti–6Al–4V

Cited by 208 publications

References 42 publications

Additively Manufactured Inconel 718 : Microstructures and Mechanical Properties

Additively Manufactured Inconel 718 : Microstructures and Mechanical Properties

On the Investigation of Surface Integrity of Ti6Al4V ELI Using Si-Mixed Electric Discharge Machining

Laser‐Based Additive Manufacturing Technologies for Aerospace Applications

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