Abstract
The article deals with the state of production of bulk amorphous and nanocrystalline materials. Conditions for the preservation of the “X-ray” amorphous state in compact materials obtained by explosive pressing of amorphous alloy powders are formulated. The two-front Stefan problem is solved and it is shown that the cooling rate of liquid layers on the contact surfaces of powder particles under explosive loading corresponds to the critical quenching rate of the formation of amorphous structures in metal alloys.
Highlights
Amorphous metals are a relatively new class of metallic materials, which were of great interest in the middle and end of the last century and have an extensive bibliography [1,2,3,4,5,6,7]
Obtaining the amorphous state of metals in the solid phase is associated with the achievement of very high cooling rates, which is achievable in cross sections up to several tens of micrometers
One of the ways to obtain nanocrystalline structures is controlled crystallization of amorphous alloys [19,20,21,22,23,24], so it seems relevant to discuss the issues of preserving the amorphous state of compacts of amorphous alloy powders during shock-wave processing
Summary
Amorphous metals are a relatively new class of metallic materials, which were of great interest in the middle and end of the last century and have an extensive bibliography [1,2,3,4,5,6,7]. Obtaining the amorphous state of metals in the solid phase is associated with the achievement of very high cooling rates (on average 106 K/s), which is achievable in cross sections up to several tens of micrometers. The main form of obtaining amorphous metals is thin tapes, powders or microwires. One of the ways to obtain nanocrystalline structures is controlled crystallization of amorphous alloys [19,20,21,22,23,24], so it seems relevant to discuss the issues of preserving the amorphous state of compacts of amorphous alloy powders during shock-wave processing. Based on the "X-ray" amorphous state of the alloy, it can be assumed that the main thermal processes of shock compression are concentrated on the contact surfaces of the particles, the connection of which is carried out by the mechanism of setting in the solid phase and through the formation of liquid layers. The melt cooling rate and the temperature distribution in the melt and the solid amorphous substrate can be estimated using the instantaneous source approximation, taking into account the heat release at the phase front [25]
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