George, Joy (1955)
Optical studies of some metals and alloys. A. Examination of hardness test indentation. B. Study of cathode glow etching.
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In Part A of the thesis, the concept of hardness and its measurements are briefly reviewed at the beginning. Micro-hardness and its relation to crystal properties is also discussed. Micro-hardness test indentations with the double cone made on the (0001) plane of cleaved single crystals of zinc are measured and the variation of hardness with direction is studied. The value of hardness repeats itself for every 60 degrees due to the six fold symmetry of the basal plane. The observations are not in conformity with theory. The distortion around the impressions is studied by multiple-beam interferometry using the microflat technique. Kink traces on a microscopic scale are very clearly shown by phase contrast microscopy. The extent of the region of kink traces belonging to different kink systems, with the different positions of the indenter is revealed and discussed. Micro-twins are observed at the tips of the impression for certain positions only. An X-ray study of the disordered region around the impression was also made and is discussed. Clear evidence for the process of polygonization is seen after annealing at 380°C for 2 hours. In Part B, the equilibrium diagrams of binary alloys is briefly reviewed. The different theories of cathode sputtering are discussed. This technique of etching by the bombardment of positive ions using the metal to be etched as the cathode in a glow discharge, is described. Tin and tin-indium alloys of low indium percentages are etched after different heat treatments and a metallographic study is made. The different phases observed are discussed. The results do not agree with the equilibrium diagram determined by Rhines, Urquhart and Hoge. Many interesting features are observed during the course of the microscopic examination and these are discussed. An optical method for determining the rate of etching is given.
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Institution: University of London, Royal Holloway College (United Kingdom).