Microstructural evolution during upward and downward transient directional solidification of hypomonotectic and monotectic Al–Bi alloys

Silva, Adrina P.; Spinelli, José Eduardo; Garcia, Amauri

doi:10.1016/j.jallcom.2009.01.105

Cited by 56 publications

(38 citation statements)

References 30 publications

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“…Such effects can be considered of prime importance since their presence can be observed in the majority of solidification industrial processes of monotectic alloys. The present authors have already examined the influence of natural convection on the transient solidification thermal parameters and the microstructural evolution of a monotectic Al-3.2 wt%Bi alloy solidified downwards and upwards [19]. The effect of convection on the interphase spacing was found to be negligible.…”

Section: Introductionmentioning

confidence: 83%

On the growth of the minority phase during downward transient directional solidification of hypomonotectic and monotectic Al–Pb alloys

et al. 2012

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Al-Pb alloys were solidified under non steady heat flow conditions using a casting assembly in order to promote vertical downward directional solidification. The downward configuration enables the effects of gravitydriven convection on the final microstructure to be evaluated since the collective movement of Pb-rich particles downwards is favored, due to density differences between the two coexisting liquid phases. Investigations have been made of the obtained solidification structures. Growth rates (v) and cooling rates (T Á ) of the Al-Pb alloys solidified downwards were experimentally determined by the cooling curves recorded along the casting length. The monotectic structure was characterized by metallography and a microstructural transition has been observed in all cases. The microstructure was characterized by well-distributed Pb-rich droplets in the aluminum-rich matrix from the casting cooled surface up to a certain position in the casting, followed by a mixture of fibers and strings of pearls from this point to the bottom of the casting. The increase in alloy lead content delays the formation of fibers for alloys solidified downwards, which occurs for v \ 0.48 mm/s and v \ 0.15 mm/s for Al-0.9 wt%Pb and Al-1.2 wt%Pb alloys, respectively. Experimental power laws relating the interphase spacing, k, to v and characterized by -2.0 and -6.5 exponents, were found to represent the growth of droplets and fibers, respectively, for both alloys solidified downwards.

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Section: Introductionmentioning

confidence: 83%

On the growth of the minority phase during downward transient directional solidification of hypomonotectic and monotectic Al–Pb alloys

et al. 2012

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“…Além do mais, ele não leva em consideração a falta de ajuste do modelo; ele poderá ser grande, mesmo que y e x estejam não linearmente relacionados (FONSECA;MARTINS, 1993;WONNACOTT;WONNACOTT, 1990). Dessa forma, vê-se que apesar de neste trabalho ter-se tomado como base de ajuste os valores de , sendo este amplamente aceito na literatura (FEITOSA, 2013;SANTOS et al, 2014;GARCIA;SPINELLI, 2013;SILVA, 2011), este não deve ser considerado sozinho, mas sempre aliado a outros diagnósticos do modelo.…”

Section: Procedimento Experimentalunclassified

“…As distintas morfologias dos sistemas monotéticos têm sido alvo de intensos estudos CALBERG;BERGMAN, 1985;DERBY;FAVIER, 1983;LOGRASSO;HELLAWELL, 1984;HELLAWELL, 1981;KAMIO et al, 1984;KAUKLER;ROSEMBERGER;CURRERI, 1997;OZAWA;MOTEGI, 2004;RATKE, 2005;RATKE;MULLER, 2005;GARCIA, 2009a, 2009b, SILVA et al, 2010YANG;LIU, 2001) durante as últimas décadas. Um dos parâmetros microestruturais normalmente investigados é o espaçamento interfásico, λ, sendo bastante comum a utilização da clássica relação para crescimento de sistemas eutéticos de Hunt e Jackson (GARCIA, 2007;STOCKER;RATKE, 1999): λ 2 v = C para representá-lo, ou ainda a relação de crescimento dendrítico proposta por Calberg e Bergman (1985), .…”

Section: Introductionunclassified

“…Não há uniformidade nos valores de C determinados experimentalmente nos diversos trabalhos que se propuseram a encontrar uma relação λ x v, nem há concordância quanto à validade dessas leis de crescimento para caracterizar o crescimento de sistemas monotéticos. A imensa maioria desses estudos é baseada na utilização de dispositivos de solidificação do tipo Bridgman que impõe um regime estacionário de extração de calor, com poucos avaliando processos de solidificação de ligas monotéticas em condições transitórias, levando em consideração os efeitos do escoamento das partículas ricas em soluto no volume líquido remanescente, e correlacionando os parâmetros térmicos de solidificação medidos com as estruturas monotéticas obtidas, o que tende a aproximar as experiências da realidade industrial (SILVA et al, 2012;GARCIA;SPINELLI, 2013). São também escassos os estudos que analisam a influência da direção de crescimento nos espaçamentos interfásicos e nas dimensões das partículas de bismuto, chumbo e índio.…”

Section: Introductionunclassified

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Lei de Crescimento em Função da Posição para Ligas do Sistema Monotético

Braga

Silva

Spinelli³

et al. 2016

Semina: Tech. Ex.

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ResumoLigas monotéticas apresentam aplicações promissoras em componentes automotivos resistentes ao desgaste. Muitos estudos têm sido realizados a fim de melhor compreender a reação monotética. Algumas pesquisas assumem que a evolução do espaçamento interfásico (λ) nas ligas monotéticas obedece à clássica relação utilizada para eutéticos: . . v G C λ = , ou ainda a relação de crescimento dendrítico , em que v é a velocidade de solidificação e C uma constante para ambos os casos, G é o gradiente de temperatura e a e b são constantes, entretanto, para alguns casos, as leis apresentadas não se mostraram válidas. No presente trabalho foram analisados os resultados desses experimentos de solidificação unidirecional em regime não estacionário, com as ligas hipomonotéticas Al-0,9%Pb e Al-5,5%In, com a liga monotética Al-1,2%Pb e com as ligas hipermonotéticas Al-5,0%Bi, Al-7,0%Bi e Al-2,1%Pb em configurações de extração de calor ascendente e descendente, a fim de propor nova lei de crescimento unicamente para sistemas monotéticos. Pôde-se estabelecer uma lei para crescimento de monotéticos em função da posição a partir da interface metal/molde, λ = k. (P) Monotectic alloys show promising applications in wear-resistant automotive components. Much research has been devoted in order to better comprehend monotectic reactions. Some researches assume that the interphase spacing evolution in monotectic alloys follows the classical relationship used for eutectics: λ2v = C, or the dendritic growth relationship , where v is the solidification velocity and C a constant value for both cases, G is the thermal gradient and a and b are constants. However, some studies reported that the aforementioned growth laws seem not to be valid for some cases. In the present study, the results of directional unsteady-state solidification experiments with hypomonotectic Al-0.9wt%Pb and Al-5.5wt%In, monotectic Al-1.2wt%Pb and hypermonotectic Al-5.0wt%Bi, Al-7.0wt%Bi and Al-2.1wt%Pb alloys, under different heat extracting configurations ( upward and downward) were taken into account to propose a new and exclusive growth law for monotectic systems. It was possible to establish a single monotectic growth law as a function of position from the metal/mold interface, λ = k.(P) 0,5.

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“…e globules of minority liquid phase were generated, and then they grew and migrated under a combined effect due to complex factors, including the Marangoni motion [8], Brownian motion [9], convective flow [10], gravity [11], wettability between the two liquid phases [12], and cooling rate [13]. Apparently, the seriously segregated microstructure of immiscible liquid alloys under normal ground conditions has greatly restricted their broad applications.…”

Section: Introductionmentioning

confidence: 99%

Liquid Phase Separation Mechanism of Cu‐40 wt.% Pb Hypermonotectic Alloys

Sun

Wei

et al. 2018

Advances in Materials Science and Engineering

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Solidification microstructures of Cu-40 wt.% Pb alloy were examined under different undercooling degrees. e liquid phase separation mechanism in the systems with stable miscibility gaps mainly involved Ostwald ripening, Brownian motion, Marangoni migration, and Stokes motion. Stokes had little influence on the liquid phase separation in the early phase and played a leading role in the later period. e liquid phase separation mechanism of Cu-40 wt.% Pb hypermonotectic alloy was illustrated in detail.

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Microstructural evolution during upward and downward transient directional solidification of hypomonotectic and monotectic Al–Bi alloys

Cited by 56 publications

References 30 publications

On the growth of the minority phase during downward transient directional solidification of hypomonotectic and monotectic Al–Pb alloys

On the growth of the minority phase during downward transient directional solidification of hypomonotectic and monotectic Al–Pb alloys

Lei de Crescimento em Função da Posição para Ligas do Sistema Monotético

Liquid Phase Separation Mechanism of Cu‐40 wt.% Pb Hypermonotectic Alloys

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