Modification of hypoeutectic Al-Si alloys

摘要: Modification of the Al-Si eutectic microstructure has been studied by using entrained droplet technique in a range hypoeutectic alloys doped with different levels phosphorus and sodium. Differential scanning calorimetry used to investigate kinetics silicon nucleation during solidification, transmission electron microscopy microchemistry. The can be modified from coarse-faceted particles nucleating at low undercooling clusters fine-scale high either increasing alloy purity, adding sodium, or cooling rate solidification. unmodified coarse are heterogeneously nucleated on pre-existing AIP particles. Increasing purity removes prevents formation AIP; sodium leads Na3P preference allows insufficient time for precipitation dissolved phosphorus. At ∼ 10 K min−1, transition an takes place when fall below 0.25–2 p.p.m., increase 80–850 p.p.m.