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

In this work, a novel Sn self-lubricating Al-matrix composites with in situ Si-reinforced gradient structure ([SnxSi-rich](sic)Al-matrix composites) is proposed. [SnxSi-rich](sic)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 [Sn(5)xSi-rich] layer. [Sn(5)xSi-rich](sic)Al-matrix composites with 5wt% Sn addition is advised to balance self-lubrication of Sn with its negative effects on hardness and tensile strength. The Vickers hardness of [SnxSi-rich] Al-matrix for [Sn(5)xSi-rich](sic)Al-matrix composites reaches 1062HV/120HV, successfully achieving gradient design of mechanical properties. Meanwhile, tensile strength and average coefficient of friction (COF) value/wear rate are 263MPa and 0.43/3.81x10(-4)mm(3)(N center dot m)(-1), respectively. Furthermore, the average COF and wear rate of [Sn(5)xSi-rich](sic)Al-matrix composites increase first, then decrease slightly, and finally increase, with increasing wear temperatures. And the lower COF/wear rate of 0.52/5.41x10(-4) mm(3)(N center dot m)(-1) occurs at 300 degrees 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.