The Atomic Structure of Some Metallic Glasses and the Influence of the Preparation Technique on the Amorphous State

Citation

Mehra, Madhav (1985) The Atomic Structure of Some Metallic Glasses and the Influence of the Preparation Technique on the Amorphous State. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/6twq-9080. https://resolver.caltech.edu/CaltechETD:etd-03272008-101236

Abstract

In this work the structure of some new transition metal-metalloid glasses is discussed. Based on the Ru-Zr-B and the Rh-Si-B alloy series, these glasses are unique in that they contain up to 52 atomic percent metalloids. Available dense random packing models are not successful in explaining the structure of these glasses. The presence of a peak in the reduced radial distribution functions, G(r), at a distance of √2 times the nearest-neighbour distance suggests the presence of octahedral coordination. This coordination, absent in the dense random packed models is explained by invoking a packing of trigonal prisms. With this proposed short range order the main features in the experimentally obtained G(r) have been reproduced.

Also presented is a study that compares the amorphous state obtained in the same alloy by two different techniques. Films of (Mo_0.6Ru_0.4)₈₂B₁₈ obtained by sputtering are found to be more disordered than their liquid quenched counterparts. This increased disorder is evidenced through measurements of the G(r) and superconducting properties. The films have a lower atomic density than liquid quenched films of the same composition. This lower density reflects the presence of more entrapped free volume.

Finally, the results of a study on wear resistant amorphous coatings is reported. It is found that, by coating a surface of 52100 bearing steel with a thin film of (W_0.6Re_0.4)₇₆B₂₄, the wear resistance of the steel is increased by three orders of magnitude. This encouraging result suggests that the technological hopes for amorphous materials may indeed be realised.

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