Effect of Growth Rate on the Microstructure and Microhardness in a Directionally Solidified Al-Zn-Mg Alloy

The Al-5.5Zn-2.5Mg (wt pct) ternary alloy was prepared using a vacuum melting furnace and a casting furnace. Five samples were directionally solidified upwards at a constant temperature gradient ( G  = 5.5 K/mm) under different growth rates ( V  = 8.3–165 μ m/s) in a Bridgman-type directional solidi...

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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.3040-3051
Main Authors: Acer, Emine, Çadırlı, Emin, Erol, Harun, Gündüz, Mehmet
Format: Article
Language:English
Subjects:
Alloy solidification
Aluminum base alloys
Characterization and Evaluation of Materials
Chemistry and Materials Science
Constants
Dendritic structure
Directional solidification
Furnaces
Growth rate
Materials Science
Metallic Materials
Metallurgy
Microhardness
Microstructure
Nanotechnology
Physical metallurgy
Structural Materials
Surfaces and Interfaces
Thin Films
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Summary:The Al-5.5Zn-2.5Mg (wt pct) ternary alloy was prepared using a vacuum melting furnace and a casting furnace. Five samples were directionally solidified upwards at a constant temperature gradient ( G  = 5.5 K/mm) under different growth rates ( V  = 8.3–165 μ m/s) in a Bridgman-type directional solidification furnace. The primary dendrite arm spacing, λ 1 , secondary dendrite arm spacing, λ 2 , and microhardness, HV, of the samples were measured. The effects of V on λ 1 , λ 2 and HV properties of the Al-Zn-Mg alloy were studied by microstructure analysis and mechanical characterization. Microstructure characterization of the alloys was carried out using optical microscopy, scanning electron microscopy, wavelength-dispersive X-ray fluorescence spectrometry, and energy dispersive X-ray spectroscopy. From the experimental results, it is found that the λ 1 , λ 2 values decrease, but HV values increase with the increase in V , and HV values decrease with the increase in λ 1 and λ 2 . Dependencies of dendritic spacing and microhardness on the growth rate were determined using linear regression analysis. The growth rate, microstructure, and Hall–Petch-type relationships obtained in this work have been compared with the results of previous studies.
ISSN:1073-5623
1543-1940
DOI:10.1007/s11661-016-3484-9