This research was conducted to investigate the effect of different Pb levels (0.1-5 wt.%) on the microstructure, tensile properties, and machinability of Al–15 wt.% Mg2Si in-situ composite. The results depicted that not only the addition of Pb element (up to 1 wt.%) modifies the morphology of primary Mg2Si particles, but also it decreases the size of primary Mg2Si from about 40 µm to less than 15 µm. Although the further addition of Pb was not effective on reducing Mg2Si particle size, Mg2Pb and free Pb phases were identified in the microstructure. The results obtained from tensile testing showed that the optimum Pb amount is 1 wt.%. When different Pb contents were employed, similar trends were observed for both ultimate tensile strength (UTS) and elongation (El.%) values. During machining, a reducing trend was also seen in the cutting force of the composite, when higher levels of Pb were used. Increasing Pb up to 1 wt.% improved the finished surface of the Al composite owing to the presence of free Pb, and it is lubricating agent during machining
