Thermal Parameters and Microstructural Development in Directionally Solidified Zn-Rich Zn-Mg Alloys

Transient directional solidification experiments have been carried out with Zn-Mg hypoeutectic alloys under an extensive range of cooling rates with a view to analyzing the evolution of microstructure. It is shown that the microstructure is formed by a Zn-rich matrix of different morphologies and co...

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Bibliographic Details
Published in:Metallurgical and materials transactions. A, Physical metallurgy and materials science Physical metallurgy and materials science, 2016-06, Vol.47 (6), p.3052-3064
Main Authors: Vida, Talita A., Freitas, Emmanuelle S., Brito, Crystopher, Cheung, Noé, Arenas, Maria A., Conde, Ana, De Damborenea, Juan, Garcia, Amauri
Format: Article
Language:English
Subjects:
Alloy solidification
Alloys
Characterization and Evaluation of Materials
Chemistry and Materials Science
Cooling rate
Directional solidification
Magnesium base alloys
Materials Science
Metallic Materials
Metallurgy
Microstructure
Nanotechnology
Structural Materials
Surfaces and Interfaces
Thermal properties
Thermodynamics
Thin Films
Zinc
Zinc base alloys
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Summary:Transient directional solidification experiments have been carried out with Zn-Mg hypoeutectic alloys under an extensive range of cooling rates with a view to analyzing the evolution of microstructure. It is shown that the microstructure is formed by a Zn-rich matrix of different morphologies and competitive eutectic mixtures (Zn-Zn 11 Mg 2 and Zn-Zn 2 Mg). For 0.3 wt-pct Mg and 0.5 wt-pct Mg alloys, the Zn-rich matrix is shown to be characterized by high-cooling rates plate-like cells (cooling rates >9.5 and 24 K/s, respectively), followed by a granular–dendritic morphological transition for lower cooling rates. In contrast, a directionally solidified Zn1.2 wt-pct Mg alloy casting is shown to have the Zn-rich matrix formed only by dendritic equiaxed grains. Experimental growth laws are proposed relating the plate-like cellular interphase, the secondary dendritic arm spacing, and the eutectic interphase spacings to solidification thermal parameters, i.e ., cooling rate and growth rate. The experimental law for the growth of secondary dendritic spacings under unsteady-state solidifications is also shown to encompass results of hypoeutectic Zn-Mg alloys subjected to steady-state Bridgman growth.
ISSN:1073-5623
1543-1940
DOI:10.1007/s11661-016-3494-7