The structure of the oxide layer formed on Alloy 800 at 600°C in superheated steam markedly indicates the role of the grain boundaries as easy diffusion paths of Cr and Mn to the alloytoxide interface. Increasing the number of grain boundaries by lo-%% cold work leads to increasing Cr-and Mn-content in the scale and to decreasing oxide growth rates. Variation of the grain size by different annealing treatments leadssince the Cr-content in the scale is decreasing with the grain sizeto a linear relation of growth rate and grain size.The effect of cold work was also demonstrated on the protectiveness of the oxide scale towards carbon uptake and carburization of Alloy 800. After preoxidation of differently deformed specimens at 9OO"C, these were exposed to a CO-C02-H20-H2 mixture at 700°C for long time. The gas mixture was tagged with "C so that the C-ingress into the oxide scale and into the alloy could be sensitively monitored by autoradiography and (upon stepwise polishing) radioactivity measurements of the carbon penetration. The carbon uptake is effectively reduced with cold working; in contrast a non-deformed, electropolished and preoxidized specimen shows relatively high C-content after exposure.The investigations prove the highly favorable effect of mechanical pretreatment on the formation of the oxide scale on an austenitic Fe-Ni-Cr alloy. Cold work and other methods of surface deformation (grinding, polishing, sand blasting, shot peening) generate easy difision paths for fast Cr-diffusion to the surface and sufficient supply of Cr to form a protective oxide layer.Der Aufbau der Oxidschicht, die sich auf Alloy 800 bei 600°C in iiberbitztem Dampf bildet, zeigt deutlich die wichtige Rolle der Korngrenzen als schnelle Diffusionswege des Cr and Mn zur Grenzflache LegierunglOxid. Eine 1040% Kaltverformung fiihrt aufgrund der zunehmenden Zahl an Korngrenzen zu erhohtem Cr-und Mn-Gehalt der Oxidschichten und zu abnehmenden Oxidationsgeschwindigkeiten. Bei Veriinderungen der KorngraSe durch verschiedene Gluhbehandlungen erhalt manbei mit der Korngro6e abnehmendern Cr-Gehalteine lineare Beziehung zwischen Oxidationsgeschwindigkeit und KorngroBe.Die Auswirkung der Kaltverformung wurde ebenfalls fib die Schutzwirkung der Oxidschicht gegen das Eindringen von Kohlenstoff und die Aufkohlung von Alloy 800 gezeigt. Nach Voroxidation verschieden verformter Proben bei 900°C wurden diese liingere Zeit einer CO-COz-Hz-H20-Atmosphtire bei 700 O C ausgesetzt. Das Gasgemisch war mit I4C indiziert, SO da5 die C-Aufnahme in die Oxidschicht und in die Legierung durch Autoradiographie und Radioaktivitats-Messungen (unter schrittweisem Abpolieren) sehr empfindlich nachgewiesen werden koMte. Die C-Aufnalune wird mit zunehmendem Verformungsgrad wirksam vermindertim Gegensatz hierzu zeigt eine unverformte, elektropolierte und dann voroxidierte Probe relativ hohe C-Gehalte nach der Auslagerung.Diese Untersuchungen belegen die giinstige Auswirkung einer mechanischen Vorbehandlung auf die Bildung einer schiitzenden Oxidschicht auf einer aust...
Kindergarten children enjoy playing games, as games bring motivation and active learning. Many board and card games require mathematical competency and therefore, carefully selected board and card games could be used as meaningful learning tasks for mathematics education in early childhood. With this in mind, several games for fostering quantity-number competencies have been implemented in an intervention study. The study included 6 years old children and three conditions: training program (n = 110), play-based intervention (n = 89) and control (n = 125). For this article, videos involving 21 children in ten teams from one of the most widely played games in the play-based intervention were selected for in-depth analysis: the board game Shut the Box. This explorative analysis of children's mathematical behaviour and peer support whilst playing a board game allows researching in what way a specific game provides a meaningful learning task for early mathematics. The results show that children employ several mathematical skills while playing, depending on their individual quantity-number competencies. As the game can be easily repeated several times, the children practise and shape mathematical skills and monitor and support their co-player in order to increase their chances of winning the game. It is suggested, that the board game provides an adaptive and motivating setting, which can meet the learning needs of low as well as high achieving children.Keywords: quantity-number competencies, play-based early mathematics, early childhood education, play, video
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