Transient directional solidification of a eutectic Al–Si–Ni alloy: Macrostructure, microstructure, dendritic growth and hardness

Kakitani, Rafael; Cruz, Clarissa; Lima, Thiago S.; Brito, Crystopher; Garcia, Amauri; Cheung, Noé

doi:10.1016/j.mtla.2019.100358

Cited by 29 publications

(20 citation statements)

References 46 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The microstructure of the eutectic Al-Si-Ni alloy has been reported in previous studies to be composed exclusively of α-Al, Si, and Al 3 Ni phases. [29][30][31] The α-Al phase grows both as dendrites and within the eutectic at cooling rates above 1 C s À1 , with Si and the Al 3 Ni IMCs having a plate-like morphology. In this study, it has been observed that the sizes of Si and Al 3 Ni particles decrease with an increase inṪ or V. Moreover, aṡ T and V decrease, the Al 3 Ni IMCs exhibit a morphological transition, starting at the position P ¼ 15 mm from the water-cooled bottom of the DS Al-Si-Ni casting.…”

Section: Resultsmentioning

confidence: 99%

“…By controlling the electrical resistances, the device superheated the molten alloy above the eutectic temperature ( T E = 568 °C for the Al–11 wt% Si–5 wt% Ni alloy) or above the liquidus one ( T L = 588 °C for the Al–11 wt% Si alloy). [ 29 ] When the thermocouple closest to the bottom of the mold indicated 10% of melt superheating, the resistances were switched off and the water flow was established at the bottom steel sheet, promoting upward unidirectional solidification. More details about the experimental procedure can be found in a previous article.…”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Morphology of Intermetallics Tailoring Tensile Properties and Quality Index of a Eutectic Al–Si–Ni Alloy

2020

Self Cite

View full text Add to dashboard Cite

The Al-Si-Ni alloy system is a source of multicomponent piston alloys, which combine good castability and wear resistance of Al-Si alloys with great thermal stability and corrosion resistance of Al-Ni alloys. [1-3] The inherent high piston temperature during engine functioning is one of the limiting factors for the application of Al-Si-based alloys. [4] On the other hand, alloys containing Al-Ni-based intermetallic compounds (IMCs) are mainly used for high-temperature structural products, which also demand wear resistance, such as aircraft engines, turbine vanes, and guide vanes of industrial steam turbines. [5,6] The formation of Ni-rich IMCs occurs even for low Ni concentrations, [7] as Ni is almost insoluble in aluminum, with a solubility of about 0.05 wt% at 640 ºC and less than 0.005 wt% at 450 ºC. [8] Thus, the addition of Ni to Al─Si alloys can potentially improve their wear resistance at elevated temperatures. Once the second phases are responsible for these characteristics, the modification of the microstructure, regarding its refinement, usually improves the properties and extends the lifetime of the component. Apart from the formation of different IMCs, the addition of new alloying elements can promote modification of other phases, mainly on Si. Kaya and Aker [9] studied ternary Al-12.6 wt% Si-2 wt% X alloys, where X was Cu, Co, Ni, Sb, or Bi. They verified that the addition of Co promotes a better distribution of Si flakes (i.e., smallest interflake spacings) and, consequently, highest hardness and tensile strength are achieved. Although the addition of Cu induced the least efficient refinement effect, the Al-12.6 wt% Si-2 wt% Cu alloy showed the second highest tensile properties. This occurred probably due to the formation of a supersaturated solid solution and hard Al 2 Cu particles. As Al 2 Cu and Al 9 Co 2 have similar hardness (588 [10] and 568 HV, [11] respectively), and Co is restricted to the formation of Al 9 Co 2 , the refinement of Si seems to have a major effect on mechanical properties. The aforementioned alloying elements are not modifiers of the eutectic Si morphology, but they just decrease the interflake spacing. Sr is a strong modifier, which is capable of transforming the acicular Si in welldistributed fibers with only a few hundred parts per million. In an Al-10 wt% Si alloy, 240 ppm of Sr has the same effect as 520 ppm of Ti-B grain refiner in terms of tensile properties. [12] Another Si modifier, Sc, also decreases the secondary dendritic arm spacing and refines the grain size; however, it requires an amount 20 times greater than that of Sr to improve the mechanical properties at the same level. [13] In secondary aluminum, Mn, [14,15] Cr, [16,17] Ni, [18,19] and other alloying elements are added to suppress the precipitation of harmful β-AlFeSi, aiming at the formation of α-AlFeSi, which has a Chinese-script morphology. Even though modification is, in general, desirable, excessive addition can lead to overmodification. Riestra et al. [20] observed in Al-11 wt% Mg 2 Si alloys, in ...

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Morphology of Intermetallics Tailoring Tensile Properties and Quality Index of a Eutectic Al–Si–Ni Alloy

2020

Self Cite

View full text Add to dashboard Cite

show abstract

“…De maneira geral, pode-se notar a tendência de elevação da microdureza com a diminuição dos valores tanto de  1 como de  2 . Os valores de microdureza encontrados neste trabalho são relativamente próximos aqueles encontrados por KAKITANI et al [4]. Todavia, enquanto KAKITANI et al [4] adotaram um valor médio de microdureza (48 HV) para a liga Al-11%Si, o presente trabalho propõe equações matemáticas para descrever a variação da microdureza HV em função de  1 e de  2 .…”

Section: Avaliação Estruturalunclassified

“…Os valores de microdureza encontrados neste trabalho são relativamente próximos aqueles encontrados por KAKITANI et al [4]. Todavia, enquanto KAKITANI et al [4] adotaram um valor médio de microdureza (48 HV) para a liga Al-11%Si, o presente trabalho propõe equações matemáticas para descrever a variação da microdureza HV em função de  1 e de  2 . Observa-se que equações experimentais do tipo potência podem ser aplicadas para representar HV = f ( 1 ) bem como HV = f( 2 ) tendo em vista que para todos os casos foram encontrados R 2 > 0,7.…”

Section: Avaliação Estruturalunclassified

“…Em geral, as ligas desse sistema possuem uma faixa larga de acréscimo de silício, sendo de 5 a 7% para processos com baixas taxas de resfriamento (areia, gesso, por exemplo), de 7 a 9% para moldes permanentes e de 8 a 12% em peso para fundição sob pressão [3]. De modo particular, nos estudos recentemente desenvolvidos por KAKITANI et al [4,5], são apresentadas equações matemáticas que relacionam variáveis térmicas de solidificação com parâmetros microestruturais da liga Al-11%Si durante a solidificação direcional vertical ascendente, incluindo ainda a adição de Ni como terceiro elemento. Entretanto, a caracterização da liga Al-11%Si processada em sistemas de solidificação nos quais fluxos convectivos térmicos e solutais tendem a ser mais intensos ainda permanece como um campo aberto para pesquisa.…”

Section: Introductionunclassified

See 1 more Smart Citation

Liga hipoeutética Al-11%Si: coeficiente de transferência de calor interfacial, variáveis térmicas, parâmetros microestruturais e microdureza

Rodrigues¹,

Júnior²,

Barros³

et al. 2021

Matéria (Rio J.)

View full text Add to dashboard Cite

RESUMO Este artigo apresenta um estudo teórico-experimental com o objetivo de determinar o coeficiente de transferência de calor interfacial, as variáveis térmicas de solidificação, os espaçamentos dendríticos primários e secundários bem como a microdureza Vickers da liga Al-11%Si solidificada direcionalmente, sob condições transientes de fluxo de calor, em um dispositivo de configuração horizontal refrigerado a água. Para o monitoramento dos perfis de temperatura utilizou-se um conjunto de termopares tipo K localizados em diferentes posições a partir da interface metal-molde, considerando a linha central correspondente ao eixo longitudinal do lingote. Uma técnica numérica, que compara perfis térmicos teóricos e experimentais, foi utilizada no cálculo do coeficiente de transferência de calor na interface metal/molde durante a solidificação cuja condição transiente é representada por uma equação analítica na forma de potência. Foram aplicadas técnicas experimentais para o cálculo das variáveis térmicas de solidificação, ou seja, deslocamento da frente de solidificação, velocidade da isoterma liquidus e taxa de resfriamento. Os resultados experimentais e simulados apresentaram uma concordância muito boa e possibilitaram estabelecer correlações analíticas entre tais variáveis térmicas e os espaçamentos dendríticos primários e secundários obtidos, por meio de equações na forma de potência representadas por expoentes característicos. Finalmente, são também apresentadas expressões experimentais capazes de correlacionar os valores dos espaçamentos dendríticos estudados com o comportamento da microdureza Vickers da referida liga.

show abstract

Anomalous Mitigation in Phase Evolution Impacting Thermal Stability in a Rapidly Solidified AA5182 Al–Mg Alloy via Continuous Thin‐Strip Casting

Pouraliakbar,

Howells,

Gallerneault

et al. 2023

Adv Eng Mater

View full text Add to dashboard Cite

This study, for the first time, reports an anomalous phase evolution and its impact on the thermal and oxidation behavior of rapidly solidified AA5182 Al–Mg alloy strip fabricated using a novel thin‐strip (TS) continuous casting technique. The microstructural analysis reveals a through‐thickness gradient microstructure of distinct types, morphology, and fractions of nonequilibrium Al–Mn–Fe intermetallic and Al–Mg eutectic phases. The rapid solidification experienced in TS casting effectively mitigates the formation of phases, particularly with the Al–Mg (β‐Al3Mg2) eutectic, being nearly absent from the near‐surface regions. The total fraction of formed phases is considerably lower than that in the slowly cooled direct‐chill counterpart. The solute macrosegregation also shows an inverse Mg segregation profile toward the strip surface primarily due to a higher degree of matrix supersaturation closer to the strip surface. Modeling of solidification successfully predicts the influence of cooling rate on the fractions of the nonequilibrium eutectic phase, agreeing well with the experimental data obtained from image analysis. Heat treating the samples over a broad temperature range unveiled unexpected improvements in oxidation resistance and excellent thermal stability, attributed to the absence of the eutectic β‐phase in subsurface regions. The research findings have practical implications for improving the properties of sheet Al–Mg alloys.

show abstract

Transient directional solidification of a eutectic Al–Si–Ni alloy: Macrostructure, microstructure, dendritic growth and hardness

Cited by 29 publications

References 46 publications

Morphology of Intermetallics Tailoring Tensile Properties and Quality Index of a Eutectic Al–Si–Ni Alloy

Morphology of Intermetallics Tailoring Tensile Properties and Quality Index of a Eutectic Al–Si–Ni Alloy

Liga hipoeutética Al-11%Si: coeficiente de transferência de calor interfacial, variáveis térmicas, parâmetros microestruturais e microdureza

Anomalous Mitigation in Phase Evolution Impacting Thermal Stability in a Rapidly Solidified AA5182 Al–Mg Alloy via Continuous Thin‐Strip Casting

Contact Info

Product

Resources

About