Microstructure evolution and interface structure of Al-40 wt% Si composites produced by high-energy ball milling

Abstract High silicon content Al-Si composites with a composition of Al-40 wt% Si were fabricated via a high-energy ball milling method. The microstructure evolution of Al-40 wt% Si milled powders and sintered composites has been thoroughly studied by scanning electron microscopy, X-ray diffraction, energy-dispersive spectrometry and high-resolution transmission electron microscopy. The mechanism of ball milling Al-40 wt% Si powders has been disclosed in detail: fracture mechanism dominating in the early stages, followed by the agglomeration mechanism, finally reaching the balance between the fragments and the agglomerates. It has been found that the average particle sizes of mixed Al-Si powders can be refined to the nanoscale, and the crystallite sizes of Al and Si have been reduced to 10 nm and 62 nm upon milling for 2 h–50 h, respectively. The finally formed Al-Si interfaces after ball milling for 50 h are well-cohesive. A dense and homogenous Al-40 wt% Si composite have been achieved by solid-state sintering at 550 °C. The results thus provide an effective support for producing bulk nanostructured Al-Si composites.