Amorphous Alloys as a Promising Class of Functional Materials. Pt. 1: Manufacturing Methods, Structure, Physical and Mechanical Properties

The paper considers a special class of structural materials — amorphous alloys. Unlike crystalline alloys, there is no translation symmetry in the arrangement of atoms in amorphous alloys, which have only short-range atomic order. As demonstrated, the primary experimental techniques for confirming the formation of an amorphous structure are X-ray diffraction analysis (XRD) and differential scanning calorimetry (DSC). The effects of the manufacturing processes, structural relaxation, and solidification on the mechanical properties of amorphous alloys are discussed. The differences in the deformation processes between crystalline and amorphous alloys are considered. Deformation of crystalline alloys occurs due to dislocation sliding, whereas amorphous alloys are deformed due to the local rearrangement of atoms that requires significantly higher energies or stresses. As shown, three main types of crystallisation processes can occur, depending on the chemical composition of an amorphous alloy. The first one is polymorphic crystallization, when an amorphous alloy is transformed into a supersaturated solid solution, a metastable or stable crystalline phase without changing its composition. In the second case, two crystalline phases are formed simultaneously due to the eutectic reaction. The third type corresponds to primary crystallization, when stable or metastable phase is formed at the first stage.