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ArticleName Understanding the Effect of Intensified Heat Dissipation during Crystallization of High-Strength Aluminium Alloys of the Al – Zn – Mg – Cu System
DOI 10.17580/tsm.2022.03.09
ArticleAuthor Zharov M. V.

Moscow Aviation Institute (National Research University), Moscow, Russia:

M. V. Zharov, Associate Professor at the Department of Computer-Aided Design of Metallurgical Processes, Candidate of Technical Sciences, e-mail:


This paper describes the results of a study that looked at granulated materials produced from high-strength aluminium alloys of the Al – Zn – Mg – Cu system by meltspinning. The concept of Steam Jacket is introduced, which stands for a layer of vapour that forms between the particle and the coolant and inhibits heat dissipation while also hindering the crystallization rate due to lower heat conductivity of water vapour. It was established that the vapour layer forms when the coolant comes in contact with the melt and heats up to the boiling point resulting in its transition from liquid phase to vapour. This paper describes how the particle crystallization rate can be increased by the vapour layer being constantly removed. The steam jacket that forms around a droplet gets removed due to a high speed with which the droplet travels through the coolant. What is crucial for industrial implementation of this process is not so much the design of the meltspinning unit but the velocity of the spray crucible. The paper describes the results of theoretical calculations, as well as proven experimental data, which can help determine what velocity a perforated cup should have to ensure sufficient initial speed of the droplet and constant removal of the steam jacket. It was established that by rising the rate of heat dissipation from solidified granules and, consequently, the crystallization rate one can enhance the strength of the resulting granulated aluminium alloys of the Al – Zn – Mg – Cu system. Thus, when dealing with Al – Zn – Mg – Cu alloys (such as ‘B95’, ‘В96ц’) with additional zirconium doping up to 0.5% for making pressed semi-finished products, the resultant material can have an up to 15% higher strength compared with similar granulated materials that are made using conventional processes and industrial solidification rates. It is pointed out that the technique that involves removal of the vapour layer around a forming granule is the only possible way to further raise the cooling rate and, consequently, the solidification rate. Bringing the granule size to the size of little powder particles can disrupt the following granule consolidation process meaning that it is not a feasible technique that could enhance the granulation process.

keywords Granules, granulation techniques, crystallization of aluminium alloys, melt solidification rate, coolant, vapour layer, steam jacket, heat dissipation rate, granule diameter, particle size distribution, dendritic structure, degassing, granule briquetting, pressing of granular materials, strength of granular materials

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