Amorphous alloys production methods

The thickness of amorphous alloys is dependent upon production methods. Rapid quenching from the liquid state, which is the most widely used method, produces generally thin amorphous alloy sheets of 10-30 tm thickness. This has been called melt spinning or the rotating wheel method. Amorphous alloy powder and wire are also produced by modifications of the melt spinning method. The corrosion behaviour of amorphous alloys has been studied mostly using melt-spun specimens. 

The formation enthalpy AHf of amorphous alloys is less negative than that of crystalline materials of similar composition, which means that the former alloys are metastable. As a function of temperature and time the amorphous alloys will therefore transform into the stable crystalline phases. This transformation can conveniently be studied by means of diffraction methods. As will be discussed later on, no sharp diffraction lines occur in the diffraction diagrams of amorphous alloys. The transformation into the crystalline state is generally accompanied by the occurrence of sharp diffraction peaks. In some cases the stable crystalline phases are not reached directly. First one or more metastable crystalline phases may be formed which transform into the stable end products at a later stage of the crystalUzation process. 

The mechanisms and products of crystallization of amorphous alloys are influenced by both inherent (e.g. composition, oxygen) and extraneous (e.g. preparation method, pressure, etc) factors. 

During the searching for strong glass-forming alloys, the effect of composition on the crystallization behavior has been extensively studied in a variety of amorphous alloys, despite of the preparation methods (Suryanarayana Inoue, 2011). Two examples are listed in this section to show how the chemical compositions of amorphous alloys influence the crystallization mechanism and crystallization products. 

Silicomanganese, 15 556 low carbon, 15 555—556 world production of, 15 550—551t Silicomanganese, 22 519 Silicomanganese furnace, 15 553, 555 Silicomanganese production, 15 555—556 Silicon (Si), 9 731-733, 22 480-501, 502-511. See also Doped silicon re-type (negative) silicon p-type (positive) silicon Ribbon silicon Sheet silicon Amorphous silicon (a-Si) Si-hybrid sealants Silica entries analytical methods for, 22 498—499 in aluminum alloys, 22 508, 509, 510 applications of, 22 499, 508—509 atomic force microscopy of etching, 3 333-337... 

Fig. 10. Production of amorphous wires by quenching a jet of a molten alloy ejected from a nozzle into water that rotates with the turning wheel. On the left side a sample of a 100 p.m diameter wire obtained with this method. (From Baltzer and Kiinzi, 1987.)...

A. Inoue, T. Zhang, T. Masumoto Production of 1.90 amorphous cylinder and sheet of La55Al25Ni2o alloy by a metallic mold casting method, JIM 31, 425 1.91... 

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