| 1. |
- Åkerfeldt, Pia, et al.
(author)
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Electron backscatter diffraction characterization of fatigue crack growth in laser metal wire deposited Ti-6Al-4V
- 2018
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In: Materials Characterization. - : Elsevier BV. - 1044-5803 .- 1873-4189. ; 135, s. 245-256
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Journal article (peer-reviewed)abstract
- By additive manufacturing (AM) there is a feasibility of producing near net shape components in basically one step from 3D CAD model to final product. The interest for AM is high and during the past decade a lot of research has been carried out in order to understand the influence from process parameters on the microstructure and furthermore on the mechanical properties. In the present study laser metal wire deposition of Ti-6Al-4V has been studied in detail with regard to its fatigue crack propagation characteristics. Two specimen orientations, parallel and perpendicular to the deposition direction, have been evaluated at room temperature and at 250 °C. No difference in the fatigue crack growth rate could be confirmed for the two specimen orientations. However, in the fractographic study it was observed that the tortuosity varied between certain regions on the fracture surface. The local crack path characteristic could be related to the alpha colony size and/or the crystallographic orientation. Moreover, large areas exhibiting similar crystallographic orientation were observed along the prior beta grain boundaries, which were attributed to the wide alpha colonies frequently observed along the prior beta grain boundaries. © 2017 Elsevier Inc.
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| 2. |
- André, Alann, et al.
(author)
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Finite element delamination study of a notched composite plate under flexural loads
- 2009
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In: ICCM-17, 17th International Conference on Composite Materials, Edinburgh, UK. - London : IOM Communications.
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Conference paper (peer-reviewed)abstract
- The delamination process in notched composite plates under flexural loading has been investigated using finite element analysis. Cohesive elements implemented in the commercial finite element package ABAQUS have been used in the region around the drilled-hole, and positioned between layers where delamination was observed during experiments presented in an accompanying paper. The delamination initiation and subsequent propagation was studied between the layers at the tension side separately and simultaneously. For all FE models, the load displacement curve was in good agreement with the one from experiments. However, the amount of damage reported from the fractography study was more extensive than that predicted by the models. Finally, it was shown that the models with only one cohesive layer show significantly different results to that of the model with four cohesive layers in terms of size of the degradation area.
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| 3. |
- Andersson, Anton, et al.
(author)
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Ground granulated iron silicate slag as supplementary cementitious material: Effect of prolonged grinding and granulation temperature
- 2023
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In: Cleaner Materials. - : Elsevier. - 2772-3976. ; 10
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Journal article (peer-reviewed)abstract
- The metallurgical and cement industries contribute significantly to anthropogenic carbon dioxide emissions. Utilizing oxidic by-products from the metallurgical industry as supplementary cementitious materials (SCMs) can improve resource efficiency and reduce emissions from cement production. Iron silicate copper slags have been studied as SCMs, but mainly in systems where Portland cement is used as an activator. There is limited research on the inherent reactivity of the slag under changing processing conditions. The present study offers insight into the effect of granulation temperature and grinding on the inherent reactivity of an industrially produced iron silicate copper slag. The results showed that granulation temperature had an insignificant effect on reactivity, while grinding generated substantial improvements. The latter effect was concluded to stem from the increased specific surface area, increased number of sites for nucleation and growth of hydrates, and changes in the inherent reactivity owing to structural changes induced by the grinding.
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| 4. |
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| 5. |
- Hedström, Peter, et al.
(author)
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Load partitioning between single bulk grains in a two-phase duplex stainless steel during tensile loading
- 2010
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In: Acta Materialia. - : Elsevier BV. - 1359-6454 .- 1873-2453. ; 58:2, s. 734-744
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Journal article (peer-reviewed)abstract
- The lattice strain tensor evolution for single bulk grains of austenite and ferrite in a duplex stainless steel during tensile loading to 0.02 applied strain has been investigated using in situ high-energy X-ray measurements and finite-element modeling. Single-grain X-ray diffraction lattice strain data for the eight austenite and seven ferrite grains measured show a large variation of residual lattice strains, which evolves upon deformation to the point where some grains with comparable crystallographic orientations have lattice strains different by 1.5 x 10(-3), corresponding to a stress of similar to 300 MPa. The finite-element simulations of the 15 measured grains in three different spatial arrangements confirmed the complex deformation constraint and importance of local grain environment.
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| 6. |
- Åkerfeldt, Pia, et al.
(author)
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The effect of crystallographic orientation on solid metal induced embrittlement of Ti-6Al-1Mo-1V in contact with copper
- 2013
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In: IOP Conference Series: Materials Science and Engineering. - : IOP Publishing Ltd. - 1757-8981 .- 1757-899X. ; 48:1, s. 012011-
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Conference paper (peer-reviewed)abstract
- Solid metal induced embrittlement (SMIE) occurs when a metal experiences tensilestress and is in contact with another metal with lower melting temperature. SMIE is believed tobe a combined action of surface self-diffusion of the embrittling species to the crack tip andadsorption of the embrittling species at the crack tip, which weakens the crack tip region. In thepresent study, both SMIE of the near alpha alloy Ti-8Al-1Mo-1V in contact with copper and itsinfluence by crystallographic orientation have been studied. U-bend specimens coated withcopper were heat treated at 480°C for 8 hours. One of the cracks was examined in detail usingelectron backscatter diffraction technique. A preferable crack path was found along high anglegrain boundaries with grains oriented close to [0001] in the crack direction; this indicates thatthere is a connection between the SMIE crack characteristics and the crystallographicorientation.
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| 7. |
- Mellin, Pelle, 1985-, et al.
(author)
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Nano-sized by-products from metal 3D printing, composite manufacturing and fabric production
- 2016
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In: Journal of Cleaner Production. - Sweden : Elsevier. - 0959-6526 .- 1879-1786. ; 139, s. 1224-1233
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Journal article (peer-reviewed)abstract
- Recently, the health and environmental perspective of nano-materials has gained attention. Most previous work focused on Engineered Nanoparticles (ENP). This paper examines some recently introduced production routes in terms of generated nano-sized by-products. A discussion on the hazards of emitting such particles and fibers is included. Fine by-products were found in recycled metal powder after 3D printing by Selective Laser Melting (SLM). The process somehow generated small round metal particles (~1e2 mm) that are possibly carcinogenic and respirable, but not small enough to enter by skin-absorption. With preventive measures like closed handling and masks, any health related effects can be prevented. The composite manufacturing in particular generated ceramic and carbonaceous particles that are very small and respirable but do not appear to be intrinsically toxic. The smallest features in agglomerates were about 30 nm. Small particles and fibers that were not attached in agglomerates were found in a wide range of sizes, from 1 μm and upwards. Preventive measures like closed handling and masks are strongly recommended. In contrast, the more traditional production route of fabric production is investigated. Here, brushing residue and recycled wool from fabric production contained few nano-sized by-products.
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| 8. |
- Zhang, Hanzhu, 1991-, et al.
(author)
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A high-entropy B4(HfMo2TaTi)C and SiC ceramic composite
- 2019
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In: Dalton Transactions. - : Royal Society of Medicine Press. - 1477-9226 .- 1477-9234. ; 48:16, s. 5161-5167
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Journal article (peer-reviewed)abstract
- A multicomponent composite of refractory carbides, B4C, HfC, Mo2C, TaC, TiC and SiC, of rhombohedral, face-centered cubic (FCC) and hexagonal crystal structures is reported to form a single phase B4(HfMo2TaTi)C ceramic with SiC. The independent diffusion of the metal and nonmetal atoms led to a unique hexagonal lattice structure of the B4(HfMo2TaTi)C ceramic with alternating layers of metal atoms and C/B atoms. In addition, the classical differences in the crystal structures and lattice parameters among the utilized carbides were overcome. Electron microscopy, X-ray diffraction and calculations using density functional theory (DFT) confirmed the formation of a single phase B4(HfMo2TaTi)C ceramic with a hexagonal close-packed (HCP) crystal structure. The DFT based crystal structure prediction suggests that the metal atoms of Hf, Mo, Ta and Ti are distributed on the (0001) plane in the HCP lattice, while the carbon/boron atoms form hexagonal 2D grids on the (0002) plane in the HCP unit cell. The nanoindentation of the high-entropy phase showed hardness values of 35 GPa compared to the theoretical hardness value estimated based on the rule of mixtures (23 GPa). The higher hardness was contributed by the solid solution strengthening effect in the multicomponent hexagonal structure. The addition of SiC as the secondary phase in the sintered material tailored the microstructure of the composite and offered oxidation resistance to the high-entropy ceramic composite at high temperatures.
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| 9. |
- Akhtar, Farid, et al.
(author)
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Thin zeolite laminates for rapid and energy-efficient carbon capture
- 2017
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In: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 7
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Journal article (peer-reviewed)abstract
- Thin, binder-less zeolite NaX laminates, with thicknesses ranging between 310 to 750 μm and widths exceeding 50 mm and biaxial tensile strength in excess of 3 MPa, were produced by pulsed current processing. The NaX laminates displayed a high CO2 adsorption capacity and high binary CO2-over-N2 and CO2-over-CH4 selectivity, suitable for CO2 capture from flue gas and upgrading of raw biogas. The thin laminates displayed a rapid CO2 uptake; NaX laminates with a thickness of 310 μm were saturated to 40% of their CO2 capacity within 24 seconds. The structured laminates of 310 μm thickness and 50 mm thickness would offer low pressure drop and efficient carbon capture performance in a laminate-based swing adsorption technology.
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| 10. |
- Alkebro, Jesper, et al.
(author)
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Modeling high-energy ball milling in the alumina-yttria system
- 2002
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In: Journal of Solid State Chemistry. - : Elsevier BV. - 0022-4596 .- 1095-726X. ; 164:1, s. 88-97
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Journal article (peer-reviewed)abstract
- Experimental results from high-energy ball milling of alumina-yttria powder mixtures have been analyzed with models collected from the literature. Depending on the milling conditions, either there is formation of an intermediate phase in the alumina-yttria system (yttrium aluminum perovskite, YAP), or the sample becomes mostly amorphous. Variations due to milling tool material can be accounted for by local models based on the Hertzian theory of elastic bodies, but the effects of changing mills are poorly accounted for by published models. Therefore, the concept of an impact frequency distribution over the energy spectrum is introduced as a tool for studying the characteristics of the mills. The pressure on the powder trapped between two colliding bodies has been found to be the factor deciding the outcome of the process. The threshold behavior of the system yields an amorphous structure for low pressures, and formation of YAP when impact pressures exceed the threshold value.
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