How to break through the serious effect of hard and coarse primary Si on the properties of alloy matrix has become a major challenge for motivating the application of high-Si Al alloy piston in automobile lightweight. Herein, we proposed a novel in-situ Si reinforced Al-matrix functionally graded material with Si-rich◎Si-poor coating structure (Si-rich◎Si-poor FGM) by controlling the graded distribution of primary Si under rotating magnetic field. The results show that the segregation behaviors of primary Si and intermetallics (Mg₂Si, Al₉FeNi, Al₇Cu₄Ni) were directionally controlled during solidification of the multi-component Al–20Si alloy under electromagnetic stirring. The Si-rich◎Si-poor FGM has successfully combined the high tensile strength (296 MPa for Si-poor region) while meeting the gradient design of the mechanical properties (Vickers/Brinell hardness of Si-rich layer was 527%/86% higher than that of Si-poor region). The Si-rich◎Si-poor FGM shows the superior wear resistance when the temperature is less than 300 °C, which meets the limited operating temperature of automotive engine piston. More importantly, the Si-rich◎Si-poor FGM can be further fabricated into complex parts and constructed continuously, which give rise to the large-scale production of high-Si Al alloy piston in automobile lightweight.

如何突破初生硅坚硬粗大对合金基体性能的严重影响，成为推动高硅铝合金活塞在汽车轻量化上应用的重大挑战。在此，我们通过控制旋转磁场下初级硅的梯度分布，提出了一种具有富硅◎贫硅涂层结构（Si-rich◎Si-poor FGM）的新型原位Si增强铝基功能梯度材料。结果表明，初生 Si 和金属间化合物（Mg ₂ Si、Al ₉ FeNi、Al ₇ Cu ₄Ni) 在电磁搅拌下多组分 Al-20Si 合金凝固过程中受到定向控制。富硅◎贫硅FGM在满足力学性能梯度设计（富硅层维氏/布氏硬度527%/86%）的同时，成功结合了高抗拉强度（贫硅区为296 MPa）高于贫硅区）。富硅◎贫硅FGM在温度低于300℃时表现出优异的耐磨性，满足汽车发动机活塞的有限工作温度。更重要的是，富硅◎贫硅的FGM可以进一步制造成复杂的零件并连续构建，从而实现汽车轻量化高硅铝合金活塞的规模化生产。