Effects of boron addition on the morphology of silicon phases in Al-Si casting alloys

The influence of B elements on the morphology of Si phases in Al-11Si and Al-14Si alloys has been investigated employing Optical Microscope, Scanning Electron Microscopy, Transmission Electron Microscopy and Differential Scanning Calorimetry. In Al-11Si alloy, the addition of B element not only refines the primary Al dendrites, but also reduces the length of eutectic Si plates. In Al-14Si alloys, the addition of B element promotes the nucleation temperature of primary Si phases, but shows weak influence on the nucleation temperature of eutectics. The effects of B element on the morphologies of both primary Si particle and eutectics can be attributed to the interaction between B and Si elements during the solidification process. •The influence of boron on Si phase was studied.•Boron addition reduces the length of eutectic Si plates in Al-11Si alloys.•Boron addition promotes the nucleation temperature of primary Si phases in Al-14Si alloys.•Boron addition increases the twin density in the ⟨112⟩Si growth direction of eutectic Si in Al-11Si and Al-14Si alloys.