Abstract
The structure factor and the coordination numbers of liquid Al-Si alloys with different Si
content have been measured by a high temperature X-ray diffractometer. Radial distribution
functions (RDFs), the nearest atomic distance and the coordination numbers of eutectic Al-Si alloys
before and after being modified with Sr and Sb were studied. The RDFs of the liquid alloy were
decomposed by five Gaussian peaks. The results show that a Si-Si covalent bond exists in the liquid
of eutectic and hyper-eutectic alloys. Sr in the liquid Al-Si has a capability to weaken the
covalent bonds of Si-Si, suppressing the nucleation of the eutectic silicon phase. On the other
hand, Sb in the liquid Al-Si increases the order degree of Si atoms, decreasing the supercooling
degree of the nucleation and promoting the nucleation of eutectic
silicon. © 2001 Published by Elsevier Science Ltd.