Surface engineering: Amorphous Alloys and Nanocrystallinity

This work encapsulates the production and properties of metallic amorphous and nanocrystalline alloys. Laser surface engineering has been proven to be a viable production method for developing thick amorphous coatings and their properties are shown to include high hardness, low friction and good wear resistance to both dry-sliding wear and, in the case of nanostructured coatings, abrasive wear. Various mechanical tests have all been found to induce shear band formation, a characteristic feature of plastic deformation in amorphous alloys, and investigations have delved in to the further understanding of shear band formation in amorphous metallic alloys. Fundamental analysis of the volume of material involved in shear band formation and fracture of amorphous metallic alloys – the so-called liquid-like-layer – has been investigated by combined electron microscopy techniques to address some of the discrepancies in published data regarding this layer. A comparative study between the experimental value and theoretical value shows that theoretical analysis makes a gross overestimate of this layer since several assumptions do not hold true. Fracture does not take place instantaneously at the moment when the liquid like layer is at its maximum thickness and not all of the liquid like layer volume produces the characteristic veins associated with fracture of amorphous metallic alloys.