Abstract
Recent studies showed that structural changes in amorphous alloys under high pressure torsion (HPT) are determined by their chemical composition and processing regimes. For example, HPT treatment of some amorphous alloys leads to their nanocrystallization; in other alloys, nanocrystallization was not observed, but structural transformations of the amorphous phase were revealed. HPT processing resulted in its modification by introducing interfaces due to the formation of shear bands. In this case, the alloys after HPT processing remained amorphous, but a cluster-type structure was formed. The origin of the observed changes in the structure and properties of amorphous alloys is associated with the chemical separation and evolution of free volume in the amorphous phase due to the formation of a high density of interfaces as a result of HPT processing. Amorphous metal alloys with a nanocluster structure and nanoscale inhomogeneities, representatives of which are nanoglasses, significantly differ in their physical and mechanical properties from conventional amorphous materials. The results presented in this review show that the severe plastic deformation (SPD) processing can be one of the efficient ways for producing a nanocluster structure and improving the properties of amorphous alloys.
Highlights
Amorphous alloys are one of the most attractive areas of modern materials science [1,2,3,4,5,6,7].Amorphous metals and alloys are usually produced by melt quenching at typical rates of ≥106К/s down to temperatures of 0.2–0.3 Тmelt (Тmelt is the melting temperature), at which diffusion and crystallization processes are suppressed [1,2,3,4]
The value of ∆V = 0.44% obtained by XRD for bulk metallic glasses” (BMGs) after high pressure torsion (HPT) at room temperature is less than the value of ∆V = 0.74% for samples treated with HPT at 150 ◦ C, i.e., processing at a higher temperature leads to a more expressed formation of free volume
Recent studies have shown that severe plastic deformation (SPD) significantly affects the atomic structure and properties of amorphous alloys
Summary
Amorphous alloys are one of the most attractive areas of modern materials science [1,2,3,4,5,6,7]. We should note that the author Valiev is a pioneer in the research areas on SPD processing, including HPT processing, of metallic materials for producing a nanocrystalline state [15,37,38], and a leading expert in this field. He and Gunderov, together with other co-authors, conducted one of the first studies on the effect of HPT processing on amorphous alloys [39,40,41,42,43,44,45,46,47,48], and since they have performed quite many studies in this area. The aim of this review is to present and analyze the effect of SPD processing on the atomic structure of amorphous alloys, their properties, internal energy, and the relaxation processes during heating, as well as the crystallization kinetics of amorphous alloys during subsequent annealing
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