Abstract
In the previous report (part I), the effect on the cast structure and grain refining character by addition of 39 lements to Al-Fe (0.5%) alloy was reported. In this second report, 12 elements (Ti, Ta, Zr, B, Nb, W, V, Mo, Be, Y, Li, Si) which showed the grain refining effect were added to Al. 99.99%, and furthermore 5 elements (Ti, Ta, Zr, Be, Y) were added to Al-Mg, Al-Cu and Al-Si alloys and their refining influences were investigated.
On the high purity Al-Ti alloy, supposing its grain refining mechanism with the result of microscopic observation, crystal nucleus substance was qualitatively analysed with electron micro-analyser.
The results of investigation were summerized as follows:
1. 12 elements (Ti-Si) showed cast grain refining character on Al. 99.99%, and the elements which refine the structure finer, reduce undercooling degree lower.
2. The results of addition of 5 elements to Al-Mg, Al-Cu and Al-Si alloys showed that Ti, Ta, Zr, which make peritectic reaction with Al, are effective for grain refining exept in case of Be and Y which react eutectically with Al. The relation between undercooling degree of primary α and grain size is almost same as in case of Al 99.99%.
3. Considering from the results obtained by adding Ti to Al-Si alloy, it can be said that the grain refining effect of Ti is only obtainable when the primary structure is in α solid solution in Al and this effect is increased with the increase of existing α
4. A phase which appears in the center of petal-shaped crystal of high purity Al-Ti alloy is to be considered as nucleus substance and which was revealed having Ti and Al constitution after qualitative analysis by electron micro-analyser. In respect on this point further report will follow.
