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| 2. |
- Nosek, Brian A., et al.
(författare)
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National differences in gender-science stereotypes predict national sex differences in science and math achievement
- 2009
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 106:26, s. 10593-10597
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Tidskriftsartikel (refereegranskat)abstract
- About 70% of more than half a million Implicit Association Tests completed by citizens of 34 countries revealed expected implicit stereotypes associating science with males more than with females. We discovered that nation-level implicit stereotypes predicted nation-level sex differences in 8th-grade science and mathematics achievement. Self-reported stereotypes did not provide additional predictive validity of the achievement gap. We suggest that implicit stereotypes and sex differences in science participation and performance are mutually reinforcing, contributing to the persistent gender gap in science engagement.
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| 3. |
- Selin, Martin, 1979-, et al.
(författare)
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Comparison of material properties in as-cast and austempered cast irons with three different graphite morphologies
- 2008
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Ingår i: Giessereiforschung (International Foundry Research). - 0046-5933. ; 60:3, s. 20-25
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Tidskriftsartikel (refereegranskat)abstract
- Three cast irons with different graphite morphologies were austempered in order to investigate how some important material properties are affected. The cast irons had similar chemical compositions so valid comparisons could be made between morphologies and between as-cast and austempered samples. The cast irons were austenitized for 2h at 900°C and austempered at 350°C for five different times, resulting in coarse ferrite needles. Microstructure, hardness, scuffing resistance, ultimate tensile strength (UTS) in bending and thermal properties was investigated for both as-cast and austempered samples. The hardness increased by about 25% after 110 min austempering while the thermal conductivity dropped about 30%, for all three morphologies. Scuffing resistance increased significantly when austempering lamellar graphite cast iron but was slightly reduced for both the compacted and nodular graphite morphologies. After 110 min austempering, the ultimate tensile strength was reduced for the lamellar and compacted samples, but was slightly increased for the nodular morphology.
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| 4. |
- Selin, Martin, 1979-, et al.
(författare)
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Influence of alloying additions on microstructure and thermal properties in compact graphite irons
- 2009
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Ingår i: International Journal of Cast Metals Research. - Leeds : Maney Publishing. - 1364-0461 .- 1743-1336. ; 22:1-4, s. 283-285
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Tidskriftsartikel (refereegranskat)abstract
- Nineteen compacted graphite cast irons were investigated in order to determine how alloying additions affect the thermal transport properties and microstructure. All melts were based on one chemical composition and alloying elements were added to obtain melts with variation in magnesium, silicon, carbon, copper, tin, chromium and molybdenum. Increasing amounts of magnesium resulted in a further compaction of the graphite particles, reducing the thermal conductivity. Large amounts of silicon resulted in a fully ferritic metal matrix. Silicon also formed solid solution with iron which had a deteriorating effect on the thermal conductivity, i.e. the larger amount of silicon the lower the thermal conductivity. Copper and tin promoted formation of pearlite that had worse thermal properties compared to ferrite. Increasing amount of ferrite generally had a positive influence of the thermal conductivity. Chromium and molybdenum were carbide forming elements and carbides had a negative influence on the thermal conductivity.
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| 5. |
- Selin, Martin, 1979-
(författare)
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On the Microstructure and the Thermal Conductivity in Compacted Graphite Iron
- 2009
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Compacted graphite iron (CGI) is a cast iron material that has gained much attention due to its attractive material properties which are intermediate between those of grey and ductile cast iron. In the automotive industry compacted graphite iron has become an interesting alternative material to grey cast iron in components like cylinder blocks or cylinder heads. The reason for this interest is the higher strength found in CGI. However, one disadvantage is the lower thermal conductivity of CGI compared to grey cast iron. The aim of the present work is to investigate how chemical composition and cooling rate affects the microstructure in compacted graphite iron and trying to relate the microstructure to the thermal conductivity. The effect of an austempering heat treatment process on some material properties in CGI, grey and ductile cast iron is also investigated. The austempering heat treatment was shown to have a significant influence on many of the material properties investigated. The hardness was increased, while the thermal conductivity was reduced, for all three graphite morphologies observed. Scuffing resistance increased considerably for the austempered grey iron but was slightly reduced for the other two austempered morphologies. The ultimate tensile strength in bending was reduced in the austempered grey iron and CGI samples but slightly increased in the ductile iron sample. It was confirmed that alloying elements like magnesium increased nodularity, while copper and tin promoted formation of pearlite in CGI. Silicon had a ferrite promoting effect as well as an inoculating effect and chromium and molybdenum promoted formation of carbides. The thermal conductivity was highly affected by the fraction of ferrite as well as nodularity and addition of carbon and silicon. Based on these results a mathematical model was developed for calculation of the thermal conductivity at various temperatures.
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