Ductile regime machining of metal matrix composites

This paper presents research results on ultraprecision machining of metal matrix composites (MMCs) reinforced with either SiC or Al(2)0(3) particles. Ductile-regime machining of both SiC and aluminum was applied to improve the surface integrity of the composite. Both polycrystalline diamond (PCD) and single crystalline diamond (SCD) tools were used to ultraprecision machine the composites at the depth of cut ranging from nearly 0 to 1.0 mu m. A SCD tool removed the MMC as chips while a PCD simply smeared the surface. The critical depths of cut were found to be 1 mu m and 0.2 mu m for MMCs reinforced with Al(2)0(3) and SiC, respectively. Both depth of cut and crystallographic direction of the ceramic particle were the sufficient conditions for ductile-regime machining. Because of the random orientation of the reinforcing particles, some were fractured due to the cutting action while others were machined in ductile mode at the same depth of cut. A measured surface finish, therefore, varied significantly depending on the measured areas.