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Journal ArticleDOI

Structural Integrity of an Electron Beam Melted Titanium Alloy.

14 Jun 2016-Materials (Materials (Basel))-Vol. 9, Iss: 6, pp 470
TL;DR: Support is provided in working towards development and validation strategies in order for advanced manufactured components to be safely implemented into future gas turbine applications by applying the small punch (SP) test to a series of Ti-6Al-4V variants.
Abstract: Advanced manufacturing encompasses the wide range of processes that consist of "3D printing" of metallic materials. One such method is Electron Beam Melting (EBM), a modern build technology that offers significant potential for lean manufacture and a capability to produce fully dense near-net shaped components. However, the manufacture of intricate geometries will result in variable thermal cycles and thus a transient microstructure throughout, leading to a highly textured structure. As such, successful implementation of these technologies requires a comprehensive assessment of the relationships of the key process variables, geometries, resultant microstructures and mechanical properties. The nature of this process suggests that it is often difficult to produce representative test specimens necessary to achieve a full mechanical property characterisation. Therefore, the use of small scale test techniques may be exploited, specifically the small punch (SP) test. The SP test offers a capability for sampling miniaturised test specimens from various discrete locations in a thin-walled component, allowing a full characterisation across a complex geometry. This paper provides support in working towards development and validation strategies in order for advanced manufactured components to be safely implemented into future gas turbine applications. This has been achieved by applying the SP test to a series of Ti-6Al-4V variants that have been manufactured through a variety of processing routes including EBM and investigating the structural integrity of each material and how this controls the mechanical response.

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Citations
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Journal ArticleDOI
TL;DR: To refine grains and obtain good mechanical properties, the effects of pulse frequency on the macrostructure, microstructure and tensile properties are investigated and results indicate that pulse frequency can result in the change of weld pool oscillations and cooling rate.
Abstract: Wire arc additive manufacturing (WAAM) offers a potential approach to fabricate large-scale magnesium alloy components with low cost and high efficiency, although this topic is yet to be reported in literature. In this study, WAAM is preliminarily applied to fabricate AZ31 magnesium. Fully dense AZ31 magnesium alloy components are successfully obtained. Meanwhile, to refine grains and obtain good mechanical properties, the effects of pulse frequency (1, 2, 5, 10, 100, and 500 Hz) on the macrostructure, microstructure and tensile properties are investigated. The results indicate that pulse frequency can result in the change of weld pool oscillations and cooling rate. This further leads to the change of the grain size, grain shape, as well as the tensile properties. Meanwhile, due to the resonance of the weld pool at 5 Hz and 10 Hz, the samples have poor geometry accuracy but contain finer equiaxed grains (21 μm) and exhibit higher ultimate tensile strength (260 MPa) and yield strength (102 MPa), which are similar to those of the forged AZ31 alloy. Moreover, the elongation of all samples is above 23%.

137 citations

Journal ArticleDOI
TL;DR: The most popular additive manufacturing (AM) technologies to produce titanium alloy parts are electron beam melting (EBM), selective laser melting (SLM) and directed energy deposition (DED) as discussed by the authors .
Abstract: The most popular additive manufacturing (AM) technologies to produce titanium alloy parts are electron beam melting (EBM), selective laser melting (SLM) and directed energy deposition (DED). This investigation explores mainly these three techniques and compares these three methods comprehensively in terms of microstructure, tensile properties, porosity, surface roughness and residual stress based on the information available in the literature. It was found that the microstructure is affected by the highest temperature generated and the cooling rate which can be tailored by the input variables of the AM processes. The parts produced from EBM have strength comparable to that of conventionally fabricated counterparts. SLM and DED yield superior strength, which can be up to 25% higher than traditionally manufactured products. Due to the presence of larger tensile residual stress, surface roughness and porosity, AM fabricated parts have lower fatigue life compared to those of from traditional methods. EBM parts have slightly lower fracture toughness (i.e., lower fatigue life) than conventionally produced parts while SLM and DED have significantly lower fracture toughness. Annealing, hot isostatic pressing, stress relief and additional machining processes improve the characteristics of parts produced from AM. Ti–6Al–4V alloy parts fabricated via AM may have limited applications despite the high demands in aerospace or biomedical engineering. Since rapid product development using 3D printers leads to significant cost reductions more recently, it is expected that more opportunities may soon be available for the AM of titanium alloys with newer AM processes such as cold spray additive manufacturing (CSAM) and additive friction stir deposition (AFSD).

81 citations

Journal ArticleDOI
TL;DR: In this paper, the microstructural features that were characterized are the α lath thickness, grain boundary α (GB-α) thickness, prior β grain size and α colony size.

60 citations

Proceedings ArticleDOI
26 Oct 2017
TL;DR: In this paper, the current status of the standard and highlights some of the changes with regard to the current CWA 15672 (2007) standard is described, as well as a machine readable format for representing and transferring test data.
Abstract: In the 1980s, studying the effect of neutron irradiation and temper embrittlement on structural materials for the fusion and fission programmes was a major challenge. In this context the development of small specimen test techniques began, allowing the characterization of structural materials for nuclear applications with small amounts of material. The small punch technique is of one these small specimen test approaches. It is widely used for the development and monitoring of structural materials, however there is currently no comprehensive international standard for small punch testing. An EN standard on small punch testing is currently being developed under the auspices of ECISS/TC101/WG1. Besides describing the apparatus, procedures, and specimens, it will include recommendations for the estimation of tensile, fracture and creep properties from small punch testing as well as machine readable formats for representing and transferring test data. This paper describes the current status of the standard and highlights some of the changes with regard to the current CWA 15672 (2007).

41 citations

Journal ArticleDOI
TL;DR: In this article, the authors discuss the development and implementation of a highly bespoke small-punch fatigue testing methodology that can accommodate alternative loading ratios and frequencies to mimic conventional fatigue data.
Abstract: Small scale mechanical test methods are now widely recognised as an established and quantifiable means of obtaining useful mechanical property information from limited material quantities. Much research has been gathered employing such approaches, but to date these methods have largely been restricted to characterising the creep, tensile and fracture characteristics of numerous materials and alloys through the small punch (SP) test. Clearly, a key element that is missing from this list of fundamental mechanical properties is understanding the cyclic response of the material, a significant form of damage that accounts for a large proportion of in-service failures in critical structural components. Therefore, in order to profit from the numerous benefits that SP testing has to offer, including a small sample size and hence reduced cost, a small scale fatigue testing methodology is now required to provide a holistic mechanical property evaluation. Such an innovative approach would provide real potential benefit to the engineering mechanical characterisation community. This paper will discuss the development and implementation of this highly bespoke SP fatigue testing methodology that can accommodate alternative loading ratios and frequencies to mimic conventional fatigue data. A number of novel experiments have been performed on the titanium alloy Ti-6Al-4V with accompanying analysis and fractography detailed. Numerical correlations to uniaxial fatigue data is also presented through the use of Finite Element Analysis.

40 citations

References
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Journal ArticleDOI
TL;DR: The state-of-the-art of additive manufacturing (AM) can be classified into three categories: direct digital manufacturing, free-form fabrication, or 3D printing as discussed by the authors.
Abstract: This paper reviews the state-of-the-art of an important, rapidly emerging, manufacturing technology that is alternatively called additive manufacturing (AM), direct digital manufacturing, free form fabrication, or 3D printing, etc. A broad contextual overview of metallic AM is provided. AM has the potential to revolutionize the global parts manufacturing and logistics landscape. It enables distributed manufacturing and the productions of parts-on-demand while offering the potential to reduce cost, energy consumption, and carbon footprint. This paper explores the material science, processes, and business consideration associated with achieving these performance gains. It is concluded that a paradigm shift is required in order to fully exploit AM potential.

4,055 citations

Journal ArticleDOI
TL;DR: There are many different rapid prototyping (RP) technologies available as discussed by the authors, and a taxonomy is also suggested, along with a preliminary guide to process selection based on the end use of the prototype.
Abstract: Until recently, prototypes had to be constructed by skilled model makers from 2D engineering drawings. This is a time-consuming and expensive process. With the advent of new layer manufacturing and CAD/CAM technologies, prototypes may now be rapidly produced from 3D computer models. There are many different rapid prototyping (RP) technologies available. This paper presents an overview of the current technologies and comments on their strengths and weaknesses. Data are given for common process parameters such as layer thickness, system accuracy and speed of operation. A taxonomy is also suggested, along with a preliminary guide to process selection based on the end use of the prototype.

865 citations


"Structural Integrity of an Electron..." refers methods in this paper

  • ...The process was initially used for rapid prototyping [1] and is now finding application towards the manufacture of near net shape structural parts [2], with significant potential cost benefit, short lead times and improved buy-to-fly-ratios [3]....

    [...]

Journal ArticleDOI
TL;DR: In this paper, a β-phase reconstruction from room temperature α-phase electron backscatter diffraction (EBSD) data, reveals a strong texture perpendicular to the build axis.
Abstract: An additive layer manufacture (ALM) technique, electron beam melting, has been used for the production of simple geometries, from prealloyed Ti-6Al-4V powder. Microstructure, texture, and mechanical properties achieved under standard operating conditions have been investigated. Three transitional regions are observed with a change in microstructural formation dependent on the thermal mass of deposited material. Prior β-phase reconstruction, from room temperature α-phase electron backscatter diffraction (EBSD) data, reveals a strong texture perpendicular to the build axis. Variation of build temperature within the processing window of 898 K to 973 K (625 °C to 700 °C) is seen to have a significant effect on the properties and microstructure of both as-deposited and hot isostatically pressed (HIP) samples.

653 citations


"Structural Integrity of an Electron..." refers background in this paper

  • ...This has been well documented in the literature [7] and is characterised by a columnar prior-β grain structure with epitaxial β <100> crystal growth parallel to the build direction (Figure 4c,d) due to primary thermal gradients that exist in the build direction (parallel and opposite to the principal direction of heat flow on cooling)....

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Journal ArticleDOI
TL;DR: In this paper, the effect of geometry on the variability in the grain structure and texture, seen in Tisingle bond6Al single bond4V alloy components produced by Selective Electron Beam Melting (SEBM), has been investigated.

570 citations


"Structural Integrity of an Electron..." refers background in this paper

  • ...[27] studied the prior β-grain texture of EBM components and found that the columnar structure exhibited strong texture of <001> β normal to the deposited powder layers....

    [...]

Journal ArticleDOI
TL;DR: In this paper, an exploratory characterization and comparison of electron-beam melted (EBM) or rapid manufacturing (RM) of Ti-6Al-4V components (from nominal 30mm diameter powder) with wrought products is presented.

502 citations