Experimental investigation and mechanism of material removal in nano finishing of MMCs using abrasive flow finishing (AFF) process

Aluminum alloy and its composites appear to have a good future as a candidate material for engineering and structural components. Finishing of these materials is a big challenge as they are heterogeneous in nature having abrasive particles randomly distributed and oriented in the matrix material. Metal matrix composite (MMC-aluminum alloy and its reinforcement with SiC) workpieces were initially ground to a surface roughness value in the range of 0.6 +/- 0.1 mu m, and later were finished to the R-a value of 0.25 +/- 0.05 mu m by using Abrasive Flow Finishing (AFF) process. The effects of different process parameters, such as extrusion pressure, number of cycles and viscosity of the medium were studied on a change in average surface roughness (Delta R-a) and material removal. The relationship between extrusion pressure and Delta R-a shows an optimum at about 6 MPa. In the same way, the relationship between weight percentage of processing oil (plasticizer) and Delta R-a also shows an optimum at 10wt%. Further, an increase in workpiece hardness requires more number of cycles to achieve the same level of improvement in Delta R-a. Material removal also increases with an increase in extrusion pressure and number of cycles while it decreases with an increase in processing oil content in the medium. It is also concluded that the mechanism of finishing and material removal in case of alloys is different from that in case of MMC. (C) 2008 Elsevier B.V. All rights reserved.