Effect mechanism of in situ nano-intermetallic inoculation on the multilevel microstructure and mechanical properties of Al-13Si alloys

This experiment aimed to design a method to alter the multi-microstructure of Al-13Si-5Cu-0.6Mg alloys by in situ nano-intermetallics crystallized from Fe-B-Si metallic glasses. The results showed that for alloys inoculated by Fe2B and Fe3Si nano-intermetallics, the sizes of α-Al dendrites and eutectic Si were refined. In addition, the precipitates of β-Mg2Si and θ' phases were significantly refined and were evenly distributed in the matrix. The average sizes of the α-Al dendrites, the eutectic Si structure, and the θ' and β-Mg2Si precipitates were greatly reduced by 63.6%, 50.0%, 30.1% and 80.6%, respectively. In the refinement mechanism, the Fe2B and Fe3Si phases, which had excellent lattice mismatch with α-Al and Si, can be used as heterogeneous nucleation sites. Furthermore, the alloy inoculated by nano-intermetallics showed excellent strength and fracture strain at room and high temperatures, respectively. In particular, the treated alloy achieved an ultimate tensile strength (UTS) of 238 MPa at 250 °C, which is similar to the effect of Ni addition on high-temperature tensile properties. With this design, nano-intermetallics as refiners provide a new method for developing high-temperature lightweight alloys with high efficiency and low cost.