|
|
THE MODIFICATION OF Al-Si EUTECTIC ALLOYS WITH RARE-EARTH ELEMENTS |
Zhang Qiyun; Zheng Chaogui and Han Wanshu (Beijing University) |
|
Cite this article:
Zhang Qiyun; Zheng Chaogui and Han Wanshu (Beijing University). THE MODIFICATION OF Al-Si EUTECTIC ALLOYS WITH RARE-EARTH ELEMENTS. Acta Metall Sin, 1981, 17(2): 130-241.
|
Abstract A systematic study has been made of the modification of Al-Si alloys with eleven individual rare-earth elements (La, Ce, Pr, Nd, Sin, Eu, Gd, Tb, Ho, Er and Y) and also mischmetal at a cooling rate of 70—80℃/min. The modifier was added into the alloys by the methods of both reciprocal reaction and electrolysis of corresponding binary molten salts of rare-earth chloride and KCl. From the metallographic observation, it was shown that Eu possesses the greatest modification ability, and La the next, and both of them are permanent modifiers. The modification ability of Ce, Pr, Nd and mischmetal are even weaker than that of La. It was also found that modification ability of rare-earth elements decreases rapidly with the decreasing of their atomic radii. The greatest modification ability of Eu may be referred to the leap of its atomic radius. Owing to the similar reason, Yb (not investigated) would be expected to be the another element possessing strong modification ability in the lanthanide. In the consequence of lanthanide, from Sm to Ho the modification ability is negligible. Finally, under the conditions mentioned above, Er and Y did not show any modification effect on Al-Si eutectic alloy at all. According to the information that the atomic radius of Ac (2.03(?)) is somewhat greater than that of La (2.02A) and the modification ability may become greater in the order Y-La-Ac of the periodic table, it is deduced that the radioactive element Ac may have even greater modification ability than that of Eu. Thus the strongest modifiers would be elements La, Sr and Ac set on an oblique straight line in the periodic table. Therefore, it is assumed that the modification ability of a modifier may be the result of a certain combination of the valence electron charge number, the atomic number and the atomic radius of the modifier.
|
Received: 18 February 1981
|
[1] Pacz, D., U. S. Pat. 1, 387, 900, 1921. [2] Mondolfo, L. F., Aluminum Alloys: Structure and Properties, Butterworth, London, 1976, p. 677. [3] Pillai, N. R. and Anantharaman, T. R., Trans. AIME, 242 (1968) , 2025. [4] Day, M. G.and Hellawell, A., Proc. Roy. Soc., A 305 (1968) , 473. [5] Sharan, R. and Saksena, N. P., Int. Cast Met. J., 3 (1978) , 29. [6] #12 [7] Levin, E. M., Phase Diagrams for Ceramists, Fig. 1275, 1276, Amer. Cer. Soc., 2nd ed., 1969. [8] #12 [9] Barin, L and Knacke, O., Thermochemical Properties of Inorganic Substances, Berlin, Springer-Verlag,1973,pp.11,19, 392, 394. [10] #1 |
No Suggested Reading articles found! |
|
|
Viewed |
|
|
|
Full text
|
|
|
|
|
Abstract
|
|
|
|
|
Cited |
|
|
|
|
|
Shared |
|
|
|
|
|
Discussed |
|
|
|
|