brittle-ductile TRANSITION IN DIAMOND CUTTING OF SILICON SINGLE CRYSTALS

Abstract

Silicon single crystals are not amenable to conventional machining operations because of their inherent low fracture toughness. This paper deals with an investigation of brittle-ductile transition in diamond cutting of silicon from the viewpoint of material response and tool geometry. Micro indentation and scribing tests were conducted in order to investigate the influence of applied loads on the deformation characteristics. The transition of material removal from brittle to ductile was observed by continuously changing the cutting depth. The effect of tool rake angle on the machined surface quality was studied by actual diamond turning. A mirror surface, with a roughness of 5 nm R _a, was produced using a tool with a −25° rake angle. The reason for the difference in the machined surface quality is discussed based on the analysis of stress distribution in the microcutting process.

Keywords:

• brittle-ductile transition
• Brittle materials
• Diamond cutting
• Hydrostatic stress
• Indentation
• Lateral crack
• Median crack
• Radial crack
• Rake angle
• Scribing test
• Silicon single crystals
• Silicon wafer
• Single crystal diamond
• Surface roughness
• Ultraprecision machining

5.0 ACKNOWLEDGMENT

This project is supported by the National Science and Technology Board of Singapore.