Tool rake angle selection in micro-machining of 45 vol.%SiCp/2024Al based on its brittle-plastic properties

Abstract

The influence of brittle and plastic properties of 45% volume fraction silicon carbide particle reinforced aluminum matrix composites (45 vol.% SiCp/2024Al) on machining are first taken into account in this work. Considering the coexistence of brittle and plastic properties, a novel micro-machining process is specially proposed for this material to suppress the shedding of SiC particles with a polycrystalline diamond tool, which requires a suitable negative rake angle. As expected, the unwanted materials accumulate ahead of tool cutting edge to form the chips and are finally removed under the compressive stress. In this case, the SiC particles are frequently pressed into the machined surface, so the number of shedding particles reduces considerably. As a result, the finished surface roughness is improved, and the tool wear is also suppressed effectively. However, a larger negative rake angle induces an excessive cutting force but decreases the stability of machine system, which in return speeds up tool wear and produces a higher surface roughness Sa. Turning experiments show that the smallest surface roughness Sa is achieved when tool rake angle is −30°. Moreover, the wear volume of the −30° rake angle tool is only 1/22 times the 0° rake angle tool.