Ultra-mild wear in eutectic Al-Si alloys

No material removal was detected by mass loss measurements in either of the alloys after sliding to 2.2 × 103 m (105 cycles). Sliding occurred on the top of silicon particles at first. Evidence of both the sinking-in of silicon particles, and the pile-up of plastically deformed material around the sunken-in particles was observed. A contact stress analysis based on the Greenwood and Tripp model suggests that the applied normal pressure on the hard phases was approximately equal with the matrix hardness of the harder alloy, but exceeded the matrix strength of the softer alloy. This is consistent with the observation that the Al-11% Si with the higher matrix hardness suffered less surface damage - less significant amounts of particle sinking-in and aluminum piling up - when compared with the Al-12% Si with softer matrix.