The effect of SiC particle distribution on the machining performance of a stir cast Al–SiC MMC

The significant mechanical and thermal properties of metal-matrix composites (MMCs) are among the main reasons for their use in the automotive and aerospace industries. The SiC-reinforced particles in the aluminium matrix can significantly increase mechanical strength, creep resistance at elevated temperatures and fatigue life without compromising ductility. However, their main drawback may be poor machinability. This leads to increased abrasive tool wear. This paper investigates the effects of the volume fraction and distribution of SiC particles on the machining performance of stir-cast Al–SiC, including apparent friction (the total of tool-chip and tool-workpiece friction), surface integrity, subsurface damage and wear mechanisms over a 25 mm cutting length, at different cutting speeds and with varying uncut chip thickness. An orthogonal cutting setup was used to investigate the effects of cutting parameters and tool geometry on machining performance. The measured cutting forces were directly proportional to the volume fraction of SiC particles. The apparent friction is the total friction between tool-chip and tool-workpiece contacts. At a 0° rake angle, friction was lower than at the 23° rake angle. The coefficient of friction of material O was greater by 1.2%–3.9% than that of material I at cutting speeds of 10 m/min, all depths of cut and both rake angles. As the depth of cut increased from 0.06 mm to 0.1 mm for both 0° and 23° rake-angle tools, the coefficient of friction decreased by 5%–7.2% and 12%–15%, respectively. Another observation was an increase in the coefficient of friction of the same material and depth of cut as the cutting speeds varied from 10 to 30 m/min. In addition, it was observed that the Al–SiC MMCs experienced various wear mechanisms, including two- and three-body abrasive wear.