Influence of Na and Sb on Modification Effect of Hypolutectic Al-Si Alloy

After holding temperature time for 1～5 hours and rewelting for 1～3 times, the microstructures and mechanical properties of AlSi hypolutectic alloy are investigated and compared by adding respectively alterants of Na or Sb into the alloy. The experimental results show that with the prolonging of static holding temperature time the lengths of two kinds of modificated eutectic silicon in the alloy increased,and both the tensile strength and extensive ratio decreased,but the length of eutectic silicon modificated by Na is much larger than by Sb,and the mechanical properties of the alloy modificated by Sb are higher than by Na;with the increase of the times of rewelting,the length of eutectic silicon and the mechanical properties of the alloy after modification of Na remain no change,whereas the length of eutectic silicon modificated by Sb increased and the mechanical properties decreased,but the length of eutectic silicon is far shorter than that modificated by Na and mechanical properties are better than that modificated by Na.This indicates that the degradation of Sb modification is slower than others,and Sb has good rewelting property.