Electromagnetic Preparation and Wear Behavior of In Situ Si‐Reinforced Al–Matrix Gradient Self‐Lubricating Composites

Abstract

In this work, a novel Sn self‐lubricating Al–matrix composites with in situ Si‐reinforced gradient structure ([Sn×Si‐rich]⊚Al–matrix composites) is proposed. [Sn×Si‐rich]⊚Al–matrix composites is successfully prepared by controlling synergistic separation of primary Si and Sn under rotating magnetic field. In the results, it is shown that the wear‐resistant structure of “soft Sn surrounding hard Si” persists in [Sn5×Si‐rich] layer. [Sn5×Si‐rich]⊚Al–matrix composites with 5 wt% Sn addition is advised to balance self‐lubrication of Sn with its negative effects on hardness and tensile strength. The Vickers hardness of [Sn×Si‐rich] Al–matrix for [Sn5×Si‐rich]⊚Al–matrix composites reaches 1062 HV/120 HV, successfully achieving gradient design of mechanical properties. Meanwhile, tensile strength and average coefficient of friction (COF) value/wear rate are 263 MPa and 0.43/3.81 × 10−4 mm3 (N·m)−1, respectively. Furthermore, the average COF and wear rate of [Sn5×Si‐rich]⊚Al–matrix composites increase first, then decrease slightly, and finally increase, with increasing wear temperatures. And the lower COF/wear rate of 0.52/5.41 × 10−4 mm3 (N·m)−1 occurs at 300 °C as a turning point, because the soft Sn melts into liquid phase and can better spread over wear surface to form a self‐lubricating film to reduce wear. This study can accelerate the development and application of Sn self‐lubricating Al–matrix composites in high‐temperature industrial systems for automotive lightweight and aerospace.