| 1. |
- Laptev, Roman, et al.
(författare)
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Influence of beam current on microstructure of electron beam melted Ti-6Al-4V alloy
- 2019
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Ingår i: Progress in Natural Science. - : Elsevier BV. - 1002-0071 .- 1745-5391. ; 29:4, s. 440-446
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Tidskriftsartikel (refereegranskat)abstract
- The defect microstructure of the samples manufactured from Ti-6Al-4V powder was studied using electron beam melting (EBM) in the beam current range of 17 - 13 mA. The hybrid digital complex combined positron lifetime spectroscopy and coincidence Doppler broadening spectroscopy was used to characterize the defect structure of the materials. The microstructure and defects were also analyzed by transmission electron microscopy. It has been established that the main type of the defects in the EBM manufactured samples is dislocations. According to the conducted measurements and calculations, the dislocation density in the EBM manufactured samples exceeds by two orders the similar value for the cast Ti-6Al-4Valloy. Formation of Ti-Ti-Al nanoscale clusters has been found in the EBM manufactured samples.
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| 2. |
- Carlberg, Torbjorn, et al.
(författare)
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On vertical drag defects formation during direct chill (DC) casting of aluminum billets
- 2014
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Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science. - : Springer Science and Business Media LLC. - 1073-5615 .- 1543-1916. ; 45:1, s. 175-181
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Tidskriftsartikel (refereegranskat)abstract
- During air-slip direct chill casting of aluminum billets, one of the major defects occurring includes traces along the billet called vertical drags (VDs). If the VDs are too deep or too many, then they cause scraping of the billets. As in the subsequent extrusion process, the surface quality is known to impair both the productivity and quality of the profiles. In cast-house practice, many theories circulate about the causes of VD defects and how to avoid them, but in the literature, no thorough treatments have been made to explain this phenomenon. In the current study, the outer appearance, structure around, and compositions at the defects are analyzed. A theory for the formation of the defects, their cause, and how their appearance is coupled to different alloy types is presented. The segregation in the vicinity of the defects is discussed based on deformation of semisolid materials and coupled to Reynolds dilatancy ingranular materials. The theory can explain differences between 6063 and 6005 alloys.
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| 3. |
- Jaradeh, Majed, et al.
(författare)
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DTA and DSC Studies of Aluminium 3003 Alloys with Zn and Cu Additions
- 2007
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Ingår i: Metallurgical and Materials Transactions. A. - New York : Springer. - 1073-5623 .- 1543-1940. ; 38A, s. 2138-2147
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Tidskriftsartikel (refereegranskat)abstract
- The effect of Zn additions in the range of 0-5wt.% and Cu contents of 0.15-1.0 wt.%, on the solidification and precipitation behaviour of aluminium alloys of AA 3003 type was investigated with differential thermal analysis (DTA), differential scanning calorimetry (DSC), optical microscopy (OM), and scanning electron microscopy (SEM/EDX). The results show that the additions of varying Zn and Cu have significant effects on the crystallization process, phase precipitation and microstructure formation of the alloys. Phases formed have been identified and morphological differences have been discussed.
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| 4. |
- Jaradeh, Majed, et al.
(författare)
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Method Developed for Quantitative Assessment of Inclusions in Aluminium Billets
- 2007
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Ingår i: LIGHT METALS 2007. - : Minerals, Metals & Materials Society. - 9780873396592 ; , s. 679-684
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Konferensbidrag (refereegranskat)abstract
- A technique, based on sodium hydroxide hot macro etching, has been developed to deep etch non-metallic inclusions in a way that makes them visible on a macro scale. The distribution of inclusions in transverse sections along DC-cast aluminium billets could thus be studied. The technique has obvious advantages over other common analysis methods in giving a macroscopic spatial distribution of inclusions in a relatively simple way. The paper describes the development of the new technique and some applications. An analysis was made of how different inclusions behave during prolonged strong etching. Light optical microscopy, TEM and SEM/EDX have been used to identify specific inclusions.
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| 5. |
- Jaradeh, Majed, et al.
(författare)
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Solidification Studies of Automotive Heat Exchanger Materials
- 2006
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Ingår i: JOM. - : Springer Science and Business Media LLC. - 1047-4838 .- 1543-1851. ; 58:11, s. 56-61
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Tidskriftsartikel (refereegranskat)abstract
- Modifications of the aluminum alloy AA 3003 have been studied to improve and tailor its properties for applications in automotive heat exchangers. Laboratory techniques have been applied to simulate industrial direct-chill casting, and some basic solidification studies have been conducted. The results are coupled to structures observed in industrial-size ingots and discussed in terms of structure-property relations.
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| 6. |
- Koptyug, Andrey, 1956-, et al.
(författare)
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Electron Beam Melting: from Shape Freedom to Materials Properties Control at Macro- and Microscale
- 2021
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Ingår i: Proceedings of the THERMEC 2020, Graz, Austria. - : Trans Tech Publications. ; , s. 755-759
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Konferensbidrag (refereegranskat)abstract
- Electron beam melting (EBM) is one of the constantly developing powder bed fusion (PBF) additive manufacturing technologies (AM) offering advanced control over the manufacturing process. Freedom of component shapes is one of the AM competitive advantages already used at industrial and semi- industrial scale. Development of the additive manufacturing today is targeting both widening of the available materials classes, and introducing new enabling modalities. Present research is related to the new possibilities in tailoring different material properties within additively manufactured components effectively adding “fourth dimension to the 3D-printing”. Specific examples are given in relation to the electron beam melting, but majority of the conclusions are valid for the laser-based PBF techniques as well. Through manipulating beam energy deposition it is possible to tailor quite different material properties selectively within each manufactured component, including effective material density as well as thermal, mechanical, electrical and acoustic properties. It is also possible to acquire by choice both metal-metal composite and completely alloyed material, when blends of precursor powder are used together with the beam energy manipulation.
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| 7. |
- Koptyug, Andrey, 1956-, et al.
(författare)
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Steel-based functionally gradient materials obtained via Electron Beam Melting
- 2019
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Ingår i: Proc. Alloys for Additive Manufacturing Symposium AAMS2019.
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Konferensbidrag (refereegranskat)abstract
- Recent developments in metal Additive Manufacturing (AM) technologies have introduced great capabilities unparalleled by conventional manufacturing, not only in achieving freeform geometries, but also in opening new possibilities to tailor the microstructure/properties of materials by controlling process parameters. Electron Beam Melting (EBM) is one of the most important members of the Powder Bed Fusion(PBF) family; it uses a focused electron beam to melt metal powder in a layer by layer approach. One of the main challenges that EBM faces nowadays is the lack of commercially available materials (most of them are Ti-based or Ni-based alloys). Therefore, there is a strong interest to further develop the process for new materials, including steel-based ones. In this investigation two steel-based powders; stainless steel 316L and a tool steel developed by Uddeholm, were used to manufacture functionally graded materials. A special hardware setup using a single powder dispenser was installed in the EBM system, where powders were placed separately to manufacture 10x10x10 mm cubes. SEM images of the specimens’ polished cross sections show a gradual microstructural transition from characteristic 316L one on the bottom of the specimens to the tool steel towards the top. Nanoindentation experiments confirmed a consequent gradient in hardness and elastic modulus, which gradually increase towards top surface. These results show great possibilities to tailor microstructure and mechanical properties by combining different powders in the EBM technology. Potential applications include the tooling industry, where hard and wear-resistant materials are demanded on the surface whether tougher and more ductile behavior is desirable on the core of the tool.
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| 8. |
- Chudinova, Ekaterina, et al.
(författare)
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Additive manufactured Ti6Al4V scaffolds with the RF-magnetron sputter deposited hydroxyapatite coating
- 2016
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Ingår i: Journal of Physics: Conference Series. - : Institute of Physics Publishing (IOPP). - 1742-6588 .- 1742-6596.
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Konferensbidrag (refereegranskat)abstract
- Present paper reports on the results of surface modification of the additively manufactured porous Ti6Al4V scaffolds. Radio frequency (RF) magnetron sputtering was used to modify the surface of the alloy via deposition of the biocompatible hydroxyapatite (HA) coating. The surface morphology, chemical and phase composition of the HA-coated alloy were studied. It was revealed that RF magnetron sputtering allows preparing a homogeneous HA coating onto the entire surface of scaffolds.
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| 9. |
- Frisk, Karin, et al.
(författare)
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Characterisation of EBM-built shelled samples of Ti6Al4V compacted by HIP
- 2016
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Ingår i: World PM 2016 Congress and Exhibition. - : European Powder Metallurgy Association (EPMA). - 9781899072484
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Konferensbidrag (refereegranskat)abstract
- Compaction of additively manufactured Ti6Al4V components by Hot Isostatic Pressing (HIP) is often applied to eliminate porosity, producing fully dense material. In the present work shelled samples produced by Electron Beam Melting with the Arcam process (EBM) were compacted by HIP to produce fully dense samples. Cylindrical samples were studied. The walls of the cylinders were built with EBM, and the powder from the process was left uncompacted inside the cylinders. Samples with different wall thicknesses were produced. The samples were thereafter subjected to a HIP compaction. The critical wall thicknesses needed for compaction were evaluated, and the microstructures characterized. The results show that fully dense samples, with very fine microstructures, are possible.
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| 10. |
- Leicht, Alexander, 1987, et al.
(författare)
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As-HIP microstructure of EBM fabricated shell components
- 2016
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Ingår i: World PM 2016 Congress and Exhibition. - : European Powder Metallurgy Association (EPMA). - 9781899072484
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Konferensbidrag (refereegranskat)abstract
- Electron Beam Melting (EBM) was used to build Ti-6Al-4V cylindrical shell samples with different wall thickness filled with powder. Built shell samples were HIPed and the difference in microstructure between the EBM-built walls and densified powder inside the shell components was studied as well as the cohesion between these two regions. Components characterization utilizing LOM and SEM+EBSD indicates that columnar grain growth was consistent before and after HIP in the EBM-built part of the components (walls), whereas the densified material in the center of the component had a fine isotropic microstructure, characteristic for HIPed material. The combination of EBM and HIP is shown to be an attractive way of manufacturing complex-shape full density components for high performance applications, involving shortening of built time in the EBM-processing and lead time in capsule fabrication for HIP.
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