Abstract:Structural parameters as grain size, dendritic and cellular spacings, segregated products, porosity and other phases are strongly influenced by the thermal behavior of the metal/mold system during solidification, imposing a close correlation between this and the resulting microstructure. Several unidirectional solidification studies with the objective of characterizing cellular and dendritic spacings have been developed in large scale involving solidification in steady-state heat flow. The main objective of th… Show more
“…Previous studies focusing on the growth of monophasic cells demonstrated that 0.55 and 1.1 exponents are effective in representing the variation of cell spacing against solidification cooling rate and solidification velocity, respectively [36,37]. The exponents derived based on the present results are quite similar to those reported in the literature.…”
“…Previous studies focusing on the growth of monophasic cells demonstrated that 0.55 and 1.1 exponents are effective in representing the variation of cell spacing against solidification cooling rate and solidification velocity, respectively [36,37]. The exponents derived based on the present results are quite similar to those reported in the literature.…”
“…It can be seen that, for the downward solidification, the same power law represents the variation of primary spacings with tip cooling rate for the 5 and 15wt.%Pb alloys. Figure 2a shows also a comparison with the experimental laws obtained from the vertical upward directional solidification of these two alloys 11 . As can be seen, for a same cooling rate, the primary spacing is reduced (about 2 to 3 times) for conditions of downward vertical solidification.…”
Section: Resultsmentioning
confidence: 94%
“…The experiments were performed with Sn-Pb alloys (5, 15 and 20wt.%Pb) with melt superheats of 7 °C above the liquidus temperature, and under a thermal contact condition at the metal/mold interface corresponding to the heat-extracting surface being polished. The employed thermophysical properties of these alloys are those reported in a previous article 11 .…”
Section: Methodsmentioning
confidence: 99%
“…Although convection effects strongly influence on the development of solidification microstructure, the main theoretical dendritic models from the literature are based on purely diffusive transport mechanisms. In addition, recent articles on cellular 9,10 and primary dendritic 11 growth under unsteady-state solidification conditions have shown that the predictive theoretical models existing in the literature did not generate the experimental observations.…”
Microstructures are the strategic link between materials processing and materials behavior. A dendritic structure is the most frequently observed pattern of solidified alloys. The microstructural scales of dendrites, such as primary and secondary arm spacings, control the segregation profiles and the formation of secondary phases within interdendritic regions, determine the properties of cast structures. In this work, the influence of thermosolutal convection on dendrite arm spacings is experimentally examined in the downward vertical unsteady-state directional solidification of Sn-Pb hypoeutectic alloys. The experimental observations are compared not only with the main predictive theoretical models for dendritic spacings but also with experimental results obtained for Sn-Pb alloys solidified vertically upwards. Primary dendritic arm spacings have been affected by the direction of growth, decreasing in conditions of downward vertical solidification when compared with those grown vertically upwards. Further, the unsteady-state lambda1 predictive models did not generate the experimental observations
“…Vários pesquisadores têm proposto correlações entre microestrutura de solidificação e parâmetros térmicos para ligas de vários sistemas binários Rocha, 2002;Bouchard-Kirkaldy, 1997;Çardili e Gündüz, 2000;Cruz, 2008;Santos, 2001] utilizando-se da determinação experimental dos espaçamentos celulares ou dendríticos e dos parâmetros térmicos de solidificação. Esses parâmetros são velocidades da isoterma liquidus, gradientes de temperatura e taxas de resfriamento.…”
Section: Correlação Dos Parâmetros Microestruturais Com As Variáveis Térmicasunclassified
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