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The article presents the results of studies of the process of obtaining granular materials from high-strength aluminum alloys of the Al - Zn - Mg - Cu system by centrifugation of the melt with ultra-high cooling rates of granules. The concept of a «steam jacket» is introduced, namely, a steam layer that occurs between the granule body and the cooling liquid, which prevents the intensity of heat removal and is an obstacle to increasing the crystallization rate due to the lower thermal conductivity of water vapor. It is established that the formation of a vapor layer always occurs due to the heating of the cooling liquid in contact with the melt drop to boiling temperatures and the transition of the cooler from the liquid phase to steam. The technology of increasing the rate of crystallization of granules due to the constant removal of the vapor layer is proposed. The removal (knocking down) of the vapor shell that occurs around the drop occurs due to the high speed of the drop movement in the cooling medium. Fundamentally important in the industrial implementation of this technology is not so much the design of the device for obtaining pellets by centrifugation of the melt, namely, the high required rotation speed of the spraying crucible of the device under consideration. The results of experimental data are presented to determine the necessary rotation speed of the perforated cup, which ensures the creation of a sufficient initial velocity of the drop movement, leading to a constant churning of the «steam jacket». It is determined that an increase in the rates of heat removal from the crystallized granules and, as a result, an increase in the crystallization rate leads to an increase in the strength characteristics of granular aluminum alloys of the Al-Zn-Mg-Cu system. In particular, in the production of pressed semi-finished products from alloys of the Al-Zn-Mg-Cu system, such as B95, B96c. the increase in the strength characteristics of the material of the press products is up to 15 % compared to the same granular materials obtained by traditional methods with industrial crystallization rates of melt droplets. It is established that this method, based on the removal of the vapor layer around the formed granule, is the only possible one for further increasing the cooling rate and, as a result, the crystallization rate. Reducing the size of granules to the size of powders leads to serious technological problems in the further consolidation of granules and, in fact, is a dead end branch of the further development of granulation methods.

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This paper presents results of research of influence of extra high speeds of aluminum alloys grain solidification on the increase of mechanical strength characteristics of produced grains and semifinished products, which are made of grains by pressing. During the research it was determined that the most influential factor on metal grain and alloys solidification speed is the vapor film forming around the graining drop of liquid alloy. The vapor film forms due to transformation of the boundary layer into vapor state. The term ‘vapor barrier’ around graining object is implemented for the first time. The article offers the methods of removing the vapor barrier with an aim of a considerable increase of heat rejection intensity and, as a result, increase of grain solidification speed. It is determined that the only effective method of vapor barrier removal is a considerable increase of initial drop movement speed in the cooling liquid during the spinning of metal liquid alloy. The conducted experiment proved theoretical suppositions. The received semifinished products of grained aluminum alloys had a considerable upgrade of metal strength characteristics.