Abstract
The results of an investigation into the influence of micro crack formation on the machinability of metals are described. The number, the distribution, and the behaviour of microcracks in the deformation zone of three work materials were examined using electron microscopy and machining tests. It was found that microcrack formation in machining is restricted to materials of two or more phases. The number of microcracks in the deformation zone depends on both material composition and cutting condition. Metallurgical examination of several chip roots showed that not only is the distribution of microcracks non-uniform throughout the deformation zone but their dynamic behaviour also varies, depending on their location in the deformation zone. Results obtained from machining tests indicated that the formation of microcracks influences machining characteristics in many aspects including material flow stress and chip formation. The role of microcracks in the formation of a continuous chip with a built-up edge and a quasi-discontinuous chip is discussed in detail.
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