Foram feitos testes com o vidro óptico B270® através do torneamento com ferramenta de diamante. Foram aplicadas condições submicrométricas de corte, a fim de se gerar uma resposta dúctil, para o vidro, durante a usinagem. O perfil gerado pela remoção rápida da ponta da ferramenta da superfície usinada, analisado através de um Microscópio de Força Atômica, mostrou que a transição frágil-dúctil, nesse tipo difícil de usinagem, ocorre abaixo de alguns décimos de micrômetros. De acordo com os resultados da usinagem, a máxima taxa de avanço capaz de gerar, na usinagem, um comportamento dúctil é de 0.9 µm/rev. Além disso, ficou demonstrado que, para profundidades de corte menores do que 0.1 µm/rev., o mecanismo de remoção de material é totalmente dúctil. Não foram observados cavacos em forma de fitas durante a usinagem dúctil, como pode ser visto comumente durante a usinagem dúctil de cristais semicondutores. Nesse caso, os cavacos removidos têm formato de pequenas agulhas. O comportamento frágil desse material, durante a usinagem, pode estar relacionado com a alta densificação na interface ferramenta/peça com subsequente recuperação elástica.

Single point diamond turning tests were carried out on a B270 type glass. Submicrometer cutting conditions were applied in order to generate ductile response during single point machining. The profile generated by the rapid removal of the tool tip from the machined surface, analyzed by atomic force microscopy, showed that the brittle-to-ductile transition occurs at a few tenths of micrometers. According to the machining results, the maximum feed rate capable of generating a ductile mode machining behavior is of 0.9 micrometer/revolution. Furthermore, it was shown that with the cutting depth lower than 0.100 micrometer/revolution, the material removal mechanism is totally ductile. Ribbon-like chips were not observed when ductile machining was performed, as commonly seen during ductile machining of semiconductor crystals. The chips removed had a small needle-like shape. This material's fragile behavior during machining may be related to high densification during tool/material interaction with subsequent elastic recovery response.

Mechanical material removal during ultraprecision machining of semiconductors crystals normally induces surface damage. In this article, Raman micro-spectroscopy has been used to probe structural alteration as well as residual stresses in the machined surface generated by single point diamond turning. The damage found is characterized by an amorphous phase in the outmost surface layer. In addition, it is reported, for the first time, the results of in-situ re-crystallization annealing of micromachined silicon monitored by micro-Raman spectroscopy. It is also shown that the annealing heat treatment influenced surface roughness: results were Rmax equal to 24.2 nm and 47.3 nm for the non treated and for the annealed surfaces, respectively.

In this work, (100) oriented monocrystalline silicon samples were single point diamond turned under conditions that led to a ductile and brittle regime. Raman spectroscopy results showed that the ductile regime diamond turning of silicon surfaces induced amorphization and, on the contrary, in the brittle mode machining condition this amorphous layer does not exist. Ductile machined surface was found to be a mixture of crystalline and amorphous phases probed by (macro)-Raman spectroscopy. Transmission Electron Microscopy (TEM) analyses were then carried out in order to characterize the structural alteration in the machined surface and chips. The electron diffraction pattern of the machined surface detected a crystalline phase along with the amorphous silicon confirming the former results. The mechanism of material removal is widely discussed based upon the results presented here.

Some material aspects such as grain size, purity and anisotropy exert an important influence on surface quality, especially in single point diamond turning. The aim of this paper is to present and discuss some critical factors that can limit the accuracy of ultraprecision machining of non-ferrous metals and to identify the effects of them on the cutting mechanism with single point diamond tools. This will be carried out through observations of machined surfaces and chips produced using optical and scanning electron microscopy. Solutions to reduce the influence of some of these limiting factors related with the mechanism of generation of mirror-like surfaces will be discussed.