Effect of antimony on the phase equilibrium of binary AlSi alloys

Small additions of antimony to eutectic AlSi alloys cause an increase in eutectic undercooling. The undercooling results in a eutectic with primary αAl in its microstructure. The metastable AlSi phase diagram is constructed in order to explain the undercooling and the existence of αAl in the microstructure. A method of calculating the undercooling, ΔT, from fα, the volume fraction of αAl in the microstructure, is given. The ternary AlSiSb phase diagram is calculated. From the ternary system it is possible to predict overmodification of AlSi alloys is caused by the formation of the compound AlSb.