| 1. |
- Diószegi, Attila, 1962-, et al.
(författare)
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Austenite Dendrite Morphology in Lamellar Cast Iron
- 2014
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Ingår i: The 10<sup>th</sup> International Symposium on the Science and Processing of Cast Iron, SPCI10, November, Mar del Plata, Argentina, 2014. - : The Institute for Research in Materials Science and Technology (INTEMA).
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Konferensbidrag (refereegranskat)abstract
- Primary austenite has been underestimated in general when the theories of nucleation, solidification, microstructure formation and mechanical properties was established for cast iron and particularly for lamellar cast iron. After extensive use of colour etching during the last two decades it has been found that primary austenite dendrites can be characterized using general morphology parameters like those used for other technical cast alloys with dendritic structure. The present work aims to investigate the primary austenite morphology of as-cast samples of a hypoeutectic lamellar cast iron produced with different cooling rates. Morphological parameters as the area fraction primary austenite, the secondary dendrite arm spacing, the dendrite envelope surface, the coarseness of the primary dendrite expressed as the relation between the volume of the dendrite and its envelope surface and the coarseness of the interdendritic space also known as the hydraulic diameter are measured. Furthermore the role of the size of investigation area is revealed be sequential investigation. A strong relation between all measured morphological parameters and the solidification time have been established excepting the volume fraction of primary austenite which is constant for all cooling conditions.
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| 2. |
- Diószegi, Attila, 1962-, et al.
(författare)
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Dynamic Coarsening of Austenite Dendrite in Lamellar Cast Iron Part 1 – Investigation based on interrupted solidification
- 2014
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Ingår i: Materials Science Forum. - : Trans Tech Publications. - 0255-5476 .- 1662-9752. ; 790-791, s. 205-210, s. 205-210
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Tidskriftsartikel (refereegranskat)abstract
- Dynamic coarsening of austenite dendrite in lamellar cast iron has been studied for a hypoeutectic alloy. The common morphological parameter to characterize dynamic coarsening, secondary dendrite arm space has been replaced by the Modulus of primary dendrite (MPD) and the Hydraulic diameter of the interdendritic space (DHydIP) to interpret the dynamic coarsening with respect to the local solidification time. The obtained results demonstrate the coarsening process of both the solid and liquid phase. The interdendritic space is increasing as the contact time between the solid and liquid phase increases. The ratio between the DHydIP/MPD is strongly dependent on the precipitated fraction primary austenite indicating clearly the morphology variation during coarsening. The interrupted solidification method demonstrate that the observed coarsening process is not only a combination of the increasing fraction precipitated solid phase and the rearrangement of the solid - liquid interphase curvature but the volume change due to density variation is also contribute to the coarsening process.
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| 3. |
- Fourlakidis, Vasilios, et al.
(författare)
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Dynamic Coarsening of Austenite Dendrite in Lamellar Cast Iron Part 2 – The influence of carbon composition
- 2014
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Ingår i: Materials Science Forum. - : Trans Tech Publications. - 0255-5476 .- 1662-9752. ; 790-791, s. 211-216, s. 211-216
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Tidskriftsartikel (refereegranskat)abstract
- Investigation of dynamic coarsening in lamellar cast iron is extended over a wide interval ranging from hypoeutectic to eutectic composition. The dendrite morphology is defined on as-cast samples produced under various cooling rates. The as-cast morphology is considered being close to the one at the end of solidification. The obtained relations describing the coarsening process as a function of local solidification time and fraction austenite are compared to results obtained from interrupted solidification experiments. By using the Modulus of primary dendrite (MPD) and the Hydraulic diameter of the interdendritic space (DHyd IP) become possible to characterize the coarseness of a wide range of lamellar cast irons solidified under various cooling rates.
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| 4. |
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| 5. |
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| 6. |
- Lora, Ruben, et al.
(författare)
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Dynamic coarsening of 3.3C–1.9Si gray cast iron
- 2012
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Ingår i: Metallurgical and Materials Transactions. A. - : Springer. - 1073-5623 .- 1543-1940. ; 43:13, s. 5165-5172
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Tidskriftsartikel (refereegranskat)abstract
- The dynamic coarsening of primary austenite has been investigated by means of interrupted solidification in a hypoeutectic gray cast iron at three different cooling rates. The fundamental characteristic of the coarsening phenomenon, which is the reduction of the total interfacial area (i.e., the primary austenite surface) over time, has been investigated along the solidification interval for the first time in gray cast iron. The primary austenite surface is confirmed to decrease with increasing solidification time. The relation between primary austenite surface reduction and the secondary dendrite arm spacing is reported as well as the time dependence of the inverse surface area of the primary phase per unit volume. The primary austenite surface has been determined via a stereological approach. The secondary dendrite arm spacing is observed to increase throughout the whole solidification range. A novel stereological relation, the modulus of primary dendrite, has been implemented on the calculation of the primary austenite surface. The size scale of the interdendritic phase has been determined by the hydraulic diameter of the interdendritic phase. The linear relations between secondary arm spacing and eutectic cells size and between secondary arm spacing and solidification time have been found to exist during solidification independently of cooling rate. The cooling rate dependence of the secondary dendrite arm spacing and the eutectic cells size is confirmed.
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| 7. |
- Lora, Ruben, et al.
(författare)
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Solidification Study of Gray Cast Iron in a Resistance Furnace
- 2011
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Ingår i: Key Engineering Materials. - : Trans Tech Publications. - 1013-9826. ; 457, s. 108-113
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Tidskriftsartikel (refereegranskat)abstract
- Solidification of hypoeutectic gray cast iron has been investigated in a resistance furnace. A cylindrical shaped sample with three thermocouples, two inside and one in the surrounding, was solidified and compared to samples quenched at different stages during the solidification interval. An additional sample in the series has been produced to reveal the primary grain structure using Direct Austempering After Solidification (DAAS) treatment. The present paper collect for the first time under the same experimental procedure the solidification of a hypoeutectic gray cast iron where both the growth of the primary and eutectic phase are observed. An increase of the secondary dendrite arm spacing (SDAS) was observed until the end of the solidification interval. A comparison of the measured solidified fractions of the phases with those predicted using Fourier Thermal Analyses evidenced the quenching effectiveness. The eutectic cell size is in agreement with the literature. The method presents good consistency.
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| 8. |
- Lora, Ruben, et al.
(författare)
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Solidification Study of Gray Cast Iron in a Resistance Furnace
- 2010
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Ingår i: Science and Processing of Cast Iron IX. - Switzerland : Trans Tech Publications Ltd.. - 9780878492275 ; , s. 108-113
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Konferensbidrag (refereegranskat)abstract
- Solidification of hypoeutectic gray cast iron has been investigated in a resistance furnace. A cylindrical shaped sample with three thermocouples, two inside and one in the surrounding, was solidified and compared to samples quenched at different stages during the solidification interval. An additional sample in the series has been produced to reveal the primary grain structure using Direct Austempering After Solidification (DAAS) treatment. The present paper collect for the first time under the same experimental procedure the solidification of a hypoeutectic gray cast iron where both the growth of the primary and eutectic phase are observed. An increase of the secondary dendrite arm spacing (SDAS) was observed until the end of the solidification interval. A comparison of the measured solidified fractions of the phases with those predicted using Fourier Thermal Analyses evidenced the quenching effectiveness. The eutectic cell size is in agreement with the literature. The method presents good consistency.
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| 9. |
- Lora, Ruben
(författare)
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Study of microstructure development in hypoeutectic grey cast iron
- 2011
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The avoidance of shrinkage porosity and metal expansion penetration defects as well as the control of the size and number of eutectic colonies and the tensile properties of the casting are issues of major importance in the production of lamellar cast iron. These defects, characteristics and properties are related to the microstructure that develops during solidification. An improved control of this features derive from our understanding of how the microstructure changes until its final state and our capacity to accurately measure such changes. The aim of this work is to enhance such understanding in hypoeutectic grey cast iron and provide experimental and analytical techniques to facilitate a deeper investigation of the solidification phenomena. Interrupted solidification, natural solidification, direct austempering after solidification treatment, cooling curve analysis, Fourier thermal analysis, different etching reagents, non-standard image processing techniques and stereological relations are combined for the first time to study the development of the microstructure from the beginning of the solidification to the as-cast state.Stereological relations are successfully combined with bi-dimensional observations to approximate tri-dimensional parameters of the microstructure in single or multiple sections analysis. The fundamental phenomenon of the coarsening of the primary phase (reduction of the primary austenite surface) and the increase of the secondary dendrite arm spacing are observed to occur prior, during and after the eutectic solidification in different cooling conditions. The validity of the secondary dendrite arm spacing as a measure of coarsening is assessed. The ease of flow for the interdendritic melt is characterized in terms of the hydraulic diameter of the interdendritic phase, which captures the improved flow conditions during the eutectic phase. The change of and interdependence between the inverse surface area per unit volume, secondary dendrite arm spacing, the cube root of time, solidification time, eutectic colony diameter and cooling rate as well as the change of fraction of primary austenite is presented. A tri-dimensional solid reconstruction of the microstructure of grey cast iron is attempted for the first time.
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| 10. |
- Sayers, Dave, et al.
(författare)
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The Dawn of the Human-Machine Era : A forecast of new and emerging language technologies
- 2021
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- New language technologies are coming, thanks to the huge and competing private investment fuelling rapid progress; we can either understand and foresee their effects, or be taken by surprise and spend our time trying to catch up. This report scketches out some transformative new technologies that are likely to fundamentally change our use of language. Some of these may feel unrealistically futuristic or far-fetched, but a central purpose of this report - and the wider LITHME network - is to illustrate that these are mostly just the logical development and maturation of technologies currently in prototype. But will everyone benefit from all these shiny new gadgets? Throughout this report we emphasise a range of groups who will be disadvantaged and issues of inequality. Important issues of security and privacy will accompany new language technologies. A further caution is to re-emphasise the current limitations of AI. Looking ahead, we see many intriguing opportunities and new capabilities, but a range of other uncertainties and inequalities. New devices will enable new ways to talk, to translate, to remember, and to learn. But advances in technology will reproduce existing inequalities among those who cannot afford these devices, among the world’s smaller languages, and especially for sign language. Debates over privacy and security will flare and crackle with every new immersive gadget. We will move together into this curious new world with a mix of excitement and apprehension - reacting, debating, sharing and disagreeing as we always do. Plug in, as the human-machine era dawns.
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