| 1. |
- Arshadi Rastabi, Shahrzad, et al.
(författare)
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Metallurgical investigation of aluminum anode behavior in water-in-salt electrolyte for aqueous aluminum batteries
- 2022
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Ingår i: Journal of Power Sources. - : Elsevier. - 0378-7753 .- 1873-2755. ; 523
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Tidskriftsartikel (refereegranskat)abstract
- Although ionic liquid electrolytes (ILs) are environmentally unfriendly, they are the most common electrolyte used in aluminum-ion batteries (AIB). Aqueous electrolytes offer a more sustainable alternative, but problem with oxide passivating barrier on Al surface becomes more profound. Recently, a new sub-class of aqueous electrolytes, water-in-salt (WIS) of (AlCl3·6H2O), has been considered, but experimental validation of the behavior of the Al electrode over cycling is required. This work investigates aluminum/graphitic cells using WIS electrolytes with a mass ratio of salt to water of 4, 8, and 12 and finds that they show similar trends in cycling performance. The degradation observed over cycling has been attributed to the formation of a detrimental solid electrolyte interphase (SEI) layer on the Al surface. It was found that WIS 4 increased Al corrosion, resulting in a slightly higher capacity and longer cycling life. Metallurgical observation showed that the Al matrix has a tendency to initiate corrosion around Al3Fe intermetallic phases in both WIS and ILs. This implies that the presence of Al3Fe particles allows the electrolyte to break the oxide barrier and access the bulk Al. These results suggests that metallurgical treatments are important to enhance the electrochemical performance of AIB.
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| 2. |
- Bayat, Nazlin, 1981-, et al.
(författare)
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On Liquid Metal Wetting of Casting Rings for DC Casting
- 2015
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Ingår i: TMS Light Metals. - Warrendale : Minerals, Metals & Materials Society. - 9781119082446 ; , s. 859-864, s. 855-863
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Konferensbidrag (refereegranskat)abstract
- During air–slip direct chill casting of aluminum alloys, uneven or low air pressure areas at the surface of the porous graphite ring mold, can cause the metal to stick to the graphite ring and produce traces along the billets called vertical drags (VD). To prevent this type of defect, it would be an advantage to decrease the wettability of the graphite ring. It has been shown that nanostructured surfaces can have hydrophobic properties, and a question is weather the same effect can be achieved for molten metals. A TiO2 nanowire structure is proposed to cover the casting ring, and the wetting behavior of such a structure has been studied, and compared to the wetting at a regular graphite ring surface by the dispensed sessile drop method. The results showed that the nanostructured surface very strongly dewetting metal droplets.
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| 3. |
- Carlberg, Torbjörn, 1951-
(författare)
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Silicon Particle Precipitation during DC Casting of Al-Si Clad Alloys
- 2010
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Ingår i: Materials Science Forum. - : Trans Tech Publications Inc.. - 9780878492909 ; , s. 307-313
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Konferensbidrag (refereegranskat)abstract
- The formation of polyhedral silicon crystals in aluminium 7-9% silicon alloys has been studied both in industrial ingots and in simulation experiments in a Bridgman furnace. It was found that the nucleation temperature and the cooling rate were important factors influencing the amount and size of the polyhedral crystals. To avoid large particles in the as cast material early nucleation have to be suppressed and the phosphorous content should be kept low. Modelling of diffusion-controlled growth of the silicon phase in this type of aluminium-silicon alloys shows how the nucleation temperature influences the morphology of the precipitated sili¬con.
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| 4. |
- Hellström, Lisbeth Maria, 1969-, et al.
(författare)
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A Study of Fracture processes in Wood Chipping
- 2008
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Ingår i: 6th Fundamental Mechanical Pulp Research Seminar. - Espoo : KCL Oy Keskuslaboratorio - Centrallaboratorium AB.
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Konferensbidrag (refereegranskat)
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| 5. |
- Razaz, Ghadir, et al.
(författare)
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Hot tearing susceptibility of AA3000 aluminum alloy containing Cu, Ti, and Zr
- 2019
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Ingår i: Metallurgical and Materials Transactions. A. - : Springer Science and Business Media LLC. - 1073-5623 .- 1543-1940. ; 50A:8, s. 3842-3854
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Tidskriftsartikel (refereegranskat)abstract
- Severe hot tearing has been observed during DC casting of modified AA3000 alloys with additions of Cu, Ti, and Zr, although these alloys are regarded as rather easy to cast. Extensive studies have been performed on both synthetic and industrial AA2000, AA6000, and AA7000 alloys, but less data are available for AA3000 alloys. This work was thus initiated to investigate the hot tearing susceptibility of AA3000 alloys with varying alloy element content using constrained rod casting molds. The results showed that the Cu and Fe content have a major impact on hot tearing resistance, while the effects of Zr and Ti are minor. Cu in a range from 0.3 to 1.2 wt pct significantly increased the hot tearing tendency. This is due to the existence of high eutectic fractions at low temperatures, as well as porosity formation associated with bad feeding at the end of solidification. A strong cracking tendency was observed below an Fe content 0.2 wt pct owing to decreased precipitation of the Al6(Mn, Fe) phase. It was found that primary Al6(Mn, Fe) phases lead to early bridging between the grains, which reinforces the alloy during the vulnerable temperature range for hot tearing. Zr and Ti additions weakly enhanced or reduced hot tearing severity, respectively.
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| 6. |
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| 7. |
- Razaz, Ghadir, et al.
(författare)
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Mold Design for More Accurate Chemical Composition Analysis of Aluminum Alloys
- 2021
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Ingår i: Light Metals 2021. - Cham : Springer. - 9783030653958 - 9783030653965 ; , s. 751-757
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Bokkapitel (refereegranskat)abstract
- Chemical composition analysis using sampling practices in as-cast aluminum alloys are not accurate enough. Optical emission spectrometry (OES) analyses of samples taken at specified milling depths do not match the desired nominal composition due to segregation phenomenon. Moreover, macrosegregation profiles within samples cast with current molds often exhibit significant variations. Various types of molds have been tested in the past to solve this problem, but none have had a satisfactory outcome. This paper presents research on a novel mold with an insulated periphery designed to yield more accurate sampling tests. The results from samples made with the insulated periphery mold show segregation profiles with good reproducibility. A value close to the nominal composition was observed at 6–7 mm milling depth. The reproducibility of segregation profiles is correlated to one-dimensional solidification, minimizing surface segregation areas, and melt convection.
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| 8. |
- Razaz, Ghadir, et al.
(författare)
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On the dissolution Process of Manganese and Iron in Molten Aluminum
- 2019
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Ingår i: Metallurgical and Materials Transactions. A. - : Springer. - 1073-5623 .- 1543-1940. ; 50:4, s. 1873-1887
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Tidskriftsartikel (refereegranskat)abstract
- The dissolution of Mn and Fe in liquid Al presents a challenge due to their high melting points and low diffusivity. A literature review reveals that the existing knowledge of the processes involved in the dissolution of both Fe and Mn in liquid Al is rather ambiguous. Thus, this work aimed to obtain more detailed insights into the dissolution behavior of Mn and Fe in various Al melts. The results of the Mn dissolution tests showed that three intermediate phases were involved in the dissolution process, all of which exhibited a smooth interface between Mn and the liquid. These three phases were identified as the γ2, Al11Mn4, and µ phases which grow slowly, penetrating the Mn particles. The results of the Fe dissolution tests showed that in pure Al, the Al5Fe2 phase dominates the dissolution process and penetrates the Fe particles. The addition of Ti into the molten Al alters the intermetallic compound formation by replacing Al5Fe2 by Al2Fe. The addition of Si significantly inhibited the Fe dissolution kinetics. A theoretical approach based on Ficks’ law was used to explain the experimentally obtained Mn and Fe dissolution rates. It showed that the surface area and shape of the additives significantly affected the dissolution processes.
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| 9. |
- Razaz, Ghadir
(författare)
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Problems in the Aluminium DC Casting Process Associated with Melt Treatment Operations
- 2019
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Konstnärligt arbete (övrigt vetenskapligt/konstnärligt)abstract
- The quality of DC cast Al alloys is highly dependent on melt batch composition and impurity level in the molten alloy. The chemical composition and cleanliness of a melt is controlled through the melt treatment operations, carried out while the melt is still in the furnace before casting starts. The present work has studied some of these operations and associated problems such as slow dissolution of alloying elements, non-reproducibility in chemical composition analysis and inclusions. The results of the dissolution of the alloy elements Mn and Fe showed different behaviors. For Mn three intermediate phases were involved, all of which exhibited a smooth interface between Mn and the liquid. These three phases were identified as the γ2, Al11Mn4, and µ phases, which grow slowly towards the dissolving Mn particles. The results from the Fe dissolution revealed that only one phase dominates the process, Al5Fe2, which penetrates the Fe particles with an irregular interface.The interaction between Mn and Ti additions to AA3003 alloys and consequences for the solidification and precipitation behavior was investigated. The study could map the limits for formation of an earlier unknown AlMnTi phase, which formed large particles, detrimental for subsequent rolling operations.Different sampling procedures for chemical composition analysis were studied, and a novel approach was proposed. A mould with an insulated periphery provided one-dimensional solidification, which gave compositions close to nominal. Inclusion distributions along as-cast billets were studied as a function of different holding times, and thus different grades of sedimentation. Holding times longer than 30 minutes did not show any improvements. It was also shown that if melt remaining in the furnace at end of casting is less than about 3000 kg, the sedimented inclusions are stirred into the bulk again, and can enter into the end of the billet.The impact on hot tearing susceptibility of different Cu and Fe contents for AA3000 alloys was studied. Cu contents in a range from 0.3 to 1.2 wt% significantly increase the hot tearing tendency, which was attributed to bad feeding at end of solidification. Decreasing of the Fe content below 0.2 wt%, gives a strong cracking tendency, owing to decreased precipitations of the Al6(Mn,Fe) phase, which contributes to early bridging and thus reinforcement between grains.
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| 10. |
- Razaz, Ghadir, et al.
(författare)
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Solidification studies of 3003 alloys with different Mn and Ti contents
- 2017
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Ingår i: Solidification processing 2017. - : bcast. - 9781908549297
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Konferensbidrag (refereegranskat)abstract
- Aluminum alloys of AA3003 are widely used in heat exchangers. This type of alloy mainly contains manganese as alloying element, but in recent developments there have been additions of both titanium and copper. The limits of Mn solubility in aluminum are influenced by these additions, which can cause the formation of large particles of an unwanted AlMnTi phase.This project was initiated to investigate the effects of Mn contents in combination with Ti additions on the solidification and precipitation behavior using both Bridgman directional solidification and DTA equipment. The results show that coarse AlMnTi particles start forming when Mn contents are over 1.5 wt% in alloys with 0.14 wt% Ti and that the amount significantly increases with increasing Mn content from this level. Large particles were also found for Mn contents slightly below 1.4 wt%. If the Ti additions were on the level of 0.25 wt%. The DTA experiments show that AlMnTi phases grow in a limited temperature interval, and can reach a size of 150 microns. Such large sized particles are detrimental for the material in the ensuing rolling operation and must be avoided, and it is, therefore, important to accurately control the combinations of Mn and Ti contents.
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