An investigation of the influence of phases' removal ways on surface quality in micro milling SiCp/Al composites

SiC particle-reinforced aluminum matrix (SiCp/Al) composites are widely employed due to their outstanding performance. However, since they are composed of brittle SiC and ductile aluminum, the different removal mechanisms of the two phases may affect the surface quality in micro milling. In this paper, an experimental investigation of micro milling a kind of 45% SiCp/Al composites is presented. Using different values of the feed rate, the changes of the removal ways of the two phases are shown by 3D surface roughness and surface morphology. The results indicate that the surface roughness decreases firstly and increases later with the feed rate growing, which may be caused by the change of the removal way of the particle. A criterion for that is built. SEM pictures show that the surface is significantly coated by aluminum matrix when the feed rate is small; as the feed rate increases, the coating effect of the matrix weakens, and the removal ways of the particle changes from ductile regime machining to brittle fracture. Smaller feed rate may lead to the incompletely removing (plowing) of the Al and make the soft matrix coat the surface, while larger feed rate may result in the particle fracture, producing large numbers of cracks and damaging the surface integrity. Using suitable feed rate, the Al matrix can be removed efficiently and the SiC particle can be cut in its ductile regime. The unit of the suitable removal ways of Al matrix and SiC particle in machining process can produce a better surface. (C) 2018 The Authors. Published by Elsevier Ltd.