284 Prakt. Met. Sonderband 41 (2009) 
The modification process was carried out while overheating the metal bath to temperature 1003 K 
(730°C). The modifying additives included AITi5B1 and AlSr10 master alloys. They were applied 
separately and in combinations in total amounts of 0,2% and 0,3 %. The modification process lasted 
10 min. The modification conditions as well as the results of the experiments are presented in Table 
1. 
2.2 The results of the experiments 
The influence of the modification on the change of the structure of AlSi6Cu4 silumin is presented in 
Figure 1. It shows that the alloy in a non-modified state (Fig. 1a) reveals lamellar precipitation of 
eutectic silicon as well as considerable a-phase dendrites. The additives of the AITi5B1 master 
alloy in the amounts 0,2% (Fig. 1b) and 0,3% (Fig. 1c) caused refinement of the a-phase dendrites 
with no significant change in morphology of the eutectic silicon. The additives of the AlSr10 master 
alloy in the amounts 0,2% (Fig. 1d) and 0,3% (Fig. le) changed the morphology of the eutectic 
silicon in a very advantageous way, providing its fibrous form. It shows that the refinement of the 
eutectics with the AlSr10 as a modifying additive has been proven effective, particularly for 0,3% 
of the additive. Similar effects of the change of the structure have been achieved in the complex 
modification of the AlSi6Cu4 alloy with additives 0,2% AITi5B1 and 0.3% AISr10 (Fig. 1f) as well 
as with 0,3% AITi5B1 and 0.3% AISr10 (Fig. 1g).