Upward and downward unsteady-state directional solidification of a hypoeutectic Al-3wt.%Mg alloy

The aim of this research is to investigate the influence of solidification thermal parameters on the macrostructure of an Al-7wt%Si alloy during the horizontal directional solidification under unsteady-state heat flow conditions and its correlation with cutting temperatures. The solidification experiments were instrumented by thermocouples and an experimental approach was developed to quantitatively determine the solidification thermal parameters considered. The observation of the macrostructures has indicated that the columnar-to-equiaxed transition occurred in a sharp plane parallel to the chill wall and a higher average cutting temperature was obtained for the columnar structure.

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Dendritic Spacing and Macrosegregation Affecting Microhardness of an Al-Si-Mg Alloy Solidified Under Unsteady State Conditions

Materials Research ◽

10.1590/1980-5373-mr-2019-0390 ◽

2019 ◽

Vol 22 (suppl 1) ◽

Author(s):

Cássio da Silva ◽

Thiago Soares ◽

Noé Cheung ◽

Amauri Garcia ◽

Danieli A. P. Reis ◽

...

Keyword(s):

Mg Alloy ◽

Unsteady State ◽

Dendritic Spacing

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Correlation between dendrite arm spacing and microhardness during unsteady-state directional solidification of Al–Ni alloys

Philosophical Magazine Letters ◽

10.1080/09500839.2011.559911 ◽

2011 ◽

Vol 91 (5) ◽

pp. 337-343 ◽

Cited By ~ 17

Author(s):

Bismarck L. Silva ◽

Igor J.C. Araujo ◽

Wanderson S. Silva ◽

Pedro R. Goulart ◽

Amauri Garcia ◽

...

Keyword(s):

Directional Solidification ◽

Unsteady State ◽

Ni Alloys ◽

Dendrite Arm Spacing

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The Growth of Secondary Dendritic Arms in Directionally Solidified Al-Si-Cu Alloys: A Comparative Study with Binary Al-Si Alloys

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.719-720.102 ◽

2015 ◽

Vol 719-720 ◽

pp. 102-105 ◽

Cited By ~ 10

Author(s):

Laércio G. Gomes ◽

Daniel J. Moutinho ◽

Ivaldo L. Ferreira ◽

Otávio L. Rocha ◽

Amauri Garcia

Keyword(s):

Growth Rate ◽

Directional Solidification ◽

Dendritic Growth ◽

Ternary Alloys ◽

Unsteady State ◽

Directionally Solidified ◽

Cu Alloys ◽

Theoretical Predictions ◽

Growth Laws ◽

Experimental Scatter

Experiments of vertical unsteady-state directional solidification were carried out in order to permit the influence of copper alloying to Al-Si alloys on the scale of secondary dendritic arm (λ2) to be investigated. The microstructures of Al-nSi-3wt%Cu alloys, with “n” equal to 5.5wt%Si and 9.0wt%Si, were characterized and correlated with solidification thermal parameters: the growth rate (VL), the tip cooling rate (Ṫ) and the local solidification time (tSL). A comparative analysis between the present results and those from the literature related to the secondary dendrite growth during directional solidification of Al-nSi alloys is also conducted. It is shown that the addition of Cu to both Al-nSi alloys decreases λ2, and experimental growth laws relating λ2 to VL and ṪL are proposed for the ternary alloys examined. The experimental scatter of λ2 is also compared with the only theoretical dendritic growth model from the literature for multicomponent alloys, and it is shown that the theoretical predictions overestimate the present experimental results.

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The effect of back-melting on the continuity of crystallographic orientation and composition in HgZnTe

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100133114 ◽

1992 ◽

Vol 50 (2) ◽

pp. 1696-1697

Author(s):

H.J. Zuo ◽

M.W. Price ◽

R.D. Griffin ◽

R.A. Andrews ◽

G.M. Janowski

Keyword(s):

Directional Solidification ◽

Space Shuttle ◽

Solidification Process ◽

Space Experiment ◽

Infrared Detection ◽

Directionally Solidified ◽

Crystallographic Defects ◽

Semiconducting Alloys ◽

Uniform Composition ◽

Growth Experiments

The II-VI semiconducting alloys, such as mercury zinc telluride (MZT), have become the materials of choice for numerous infrared detection applications. However, compositional inhomogeneities and crystallographic imperfections adversly affect the performance of MZT infrared detectors. One source of imperfections in MZT is gravity-induced convection during directional solidification. Crystal growth experiments conducted in space should minimize gravity-induced convection and thereby the density of related crystallographic defects. The limited amount of time available during Space Shuttle experiments and the need for a sample of uniform composition requires the elimination of the initial composition transient which occurs in directionally solidified alloys. One method of eluding this initial transient involves directionally solidifying a portion of the sample and then quenching the remainder prior to the space experiment. During the space experiment, the MZT sample is back-melted to exactly the point at which directional solidification was stopped on earth. The directional solidification process then continues.

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