| 1. |
- Esmaily, Mohsen, 1987, et al.
(författare)
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A new semi-solid casting technique for fabricating SiC-reinforced Mg alloys matrix composites
- 2016
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Ingår i: Composites Part B: Engineering. - : Elsevier BV. - 1359-8368 .- 1879-1069. ; 94, s. 176-189
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Tidskriftsartikel (refereegranskat)abstract
- The capability of the newly developed rheocasting (RC) technique in combination with the RheoMetal process for producing SiC particulate-reinforced AM50 and AZ91D matrix composites (Mg-based MMCs) was investigated. The quality of the MMCs was studied by analyzing the fraction of casting pores, number density of SiC clusters and the uniformity of SiC particles. Solid fraction, particle size and oxidation of SiC particles had strong impacts on the overall quality of the MMCs. The MMCs produced by 40% solid fraction and oxidized micron-sized SiC particles exhibited an excellent casting quality. A low-quality MMC was obtained when non-oxidized sub-micron sized SiC particles were employed. The results showed the formation of various types intermetallic particles and carbides such as MgO, Mg2Si, Al2MgC2, Mg2C3, Al4C3 as the interfacial reaction products of SiC/Mg alloy's melts. Mg hydride (alpha-MgH2) was also identified in inter-dendritic regions of the MMCs for the first time.
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| 2. |
- Esmaily, Mohsen, 1987, et al.
(författare)
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Atmospheric Corrosion of Mg Alloy AZ91D Fabricated by aSemi-Solid Casting Technique: The Influence of Microstructure
- 2015
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 162:7, s. C311-C321
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Tidskriftsartikel (refereegranskat)abstract
- The atmospheric corrosion behavior of alloy AZ91D produced by a semi-solid metal (SSM) technique and by conventional high pressure die casting (HPDC) was investigated for up to 1176 hours in the laboratory. Alloy AZ91D in the SSM state was fabricated using a rheocasting (RC) technique in which the slurry was prepared by the RheoMetal process. Exposures were performed in 95% RH air at 22 and 4 degrees C. The RC alloy AZ91D exhibited significantly better corrosion resistance than the HPDC material at two temperatures studied. The effect of casting technology on corrosion is explained in terms of the microstructural differences between the materials. For example, the larger number density of cathodic beta phase particles in the HPDC material initially causes relatively rapid corrosion compared to the RC material. During later stages of corrosion, the more network-like beta phase particles in the RC alloy act as a corrosion barrier, further improving the relative corrosion resistance of the RC material.
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| 3. |
- Esmaily, Mohsen, 1987, et al.
(författare)
-
Effect of Rheocasting on Corrosion of AM50 Mg Alloy
- 2015
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 162:3, s. C85-C95
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Tidskriftsartikel (refereegranskat)abstract
- The corrosion behavior of magnesium-aluminum (Mg-Al) alloy AM50 produced by a rheocasting (RC) technique was examined in the presence and absence of CO2 at three temperatures -4, 4 and 22 degrees C. The slurry preparation in the RC material was performed with the newly developed RheoMetal process. For reference, 99.97% Mg was included in the corrosion exposures. The influence of the microstructure on the atmospheric corrosion of alloy AM50 produced by RC and high pressure die casting (HPDC) was investigated. The RC AM50 alloy showed better corrosion resistance than HPDC AM50 in all the exposure environments studied. For both materials, there was a strong positive correlation between temperature and the atmospheric corrosion rate. The superior atmospheric corrosion behavior of RC AM50 compared to HPDC AM50 is carefully discussed in relation to differences in the as-cast microstructure. This study demonstrates that producing the alloy AM50 by this type of RC technique opens the door to Mg-Al alloys as a promising candidate for various applications where corrosion resistance is of importance.
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| 4. |
- Esmaily, Mohsen, 1987, et al.
(författare)
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Microstructural characterization of the Mg-Al alloy AM50 produced by a newly developed rheo-casting process
- 2014
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Ingår i: Materials Characterization. - : Elsevier BV. - 1044-5803 .- 1873-4189. ; 95, s. 50-64
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Tidskriftsartikel (refereegranskat)abstract
- The microstructure of rheo-cast Mg-Al alloy AM50 produced by the RheoMetal process is investigated and compared with the same alloy produced by conventional high pressure die casting. The size and arrangement of microstructural constituents and pores are characterized quantitatively using image analyzing techniques. The nearest neighbor distribution of the intermetallic particles is determined. The area fraction of porosity in rheo-cast AM50 is about half that found in the high pressure die cast alloy. In rheo-cast material, the distribution of p phase (Mg17Al12) is relatively uniform throughout the cast. In contrast, the beta phase particles tend to form macroscopic agglomerates in high pressure die cast material. The externally solidified grains in the rheo-cast material exhibit a smaller aluminum gradient than in the high pressure die cast alloy. This indicates that the solidification of the rheo-cast material is closer to equilibrium.
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| 5. |
- Esmaily, Mohsen, 1987, et al.
(författare)
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On the microstructure and corrosion behavior of AZ91/SiC composites produced by rheocasting
- 2016
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Ingår i: Materials Chemistry and Physics. - : Elsevier BV. - 0254-0584 .- 1879-3312. ; 180, s. 29-37
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Tidskriftsartikel (refereegranskat)abstract
- The microstructure and atmospheric corrosion behavior of two types of SiC (10 vol%)-reinforced magnesium alloy metal matrix composites (Mg alloy AZ91D-based MMCs) produced by rheocasting (RC) were investigated and compared to the monolithic alloy. Micron-sized and nano-sized SiC particles were used for fabrication of the MMCs. Microstructural studies using a broad range of analytical techniques showed the formation Al carbides and MgO at the alpha-Mg/SiC interface. The higher corrosion rate of the MMCs than RC AZ91D was attributed to a lesser degree of connectivity of the beta phase, the high impurity level of SiC-reinforced MMCs and also the higher fraction of casting pores in the MMCs as compared to the RC alloy.
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| 6. |
- Johansson, Jan-Erik, et al.
(författare)
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Att skriva och lösa problem i grundskolans tre första årskurser
- 1997
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Under åren 1991-1992 deltog 77 barn i en förskoleverksamhet som arbetade enligt en fenomenografiskt inspirerad pedagogik vid sex förskolor, med tonvikt lagd på att utveckla barns tänkande och förståelse för olika fenomen omvärlden. När dessa barn slutade i förskolan följdes huvuddelen av dem in skolan genom ett projekt kallat "Att möta skolans värld", finansierat av Skolverket. Syftet med projektet var dels att beskriva och utvärdera barns möte med skolans värld, dels att studera hur barn som gått i en "traditionell", dvs den vanligast förekommande förskoleverksamheten respektive hur barn som deltagit i en fenomenografiskt inspirerad förskoleverksamhet klarar skolan. Barnen har följts genom observationer och intervjuer. I slutet av årskurs 1, årskurs 2 och årskurs 3 har barnen deltagit i ett flertal kunskapsprov. Genom kunskapsproven har man sökt ta reda på hur barnen som deltagit i den försöksverksamheten klarar några ämnen i skolan i jämförelse med sina klasskamrater som fungerar som kontrollgrupp. I detta bidrag kommer resultat från barnens färdigheter inom matematik och skrivning att redovisas och diskuteras. Inom området skrivning uppvisar flickorna bättre resultat än pojkarna både inom försöksgruppen och kontrollgruppen. Samma tendens kan observeras även inom de matematiska färdigheterna även om skillnaderna via en statisktisk prövning visar sig vara relativt små. I provresultaten från kunskapsproven i matematisk problemlösning i årskurs 1 och 2 uppvisar barnen från försöksverksamheten generellt bättre resultat än barnen från kontrollgruppen. I årskurs 3 har denna skillnad ebbat ut.
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