Effect of electrotransport on the solidification of Sn-Bi alloys
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was packed with g r a p h i t e wool to e l i m i n a t e convection i n s i d e the ftirnaCe. The s a m p l e tube was f i r s t e v a c u a t e d and b a c k f i l l e d with about -~ a t m , o f m e t h a n e and the f u r n a c e heated to 650~ Then a t a n t a l u m rod which n e a r l y filled the s m a l l tube wds p l a c e d all the way down to the bottom, so m o s t of the a l l o y was pushed up w h e r e the t e m p e r a t u r e Was h i g h e r . The s y s t e m was evacuated while the f u r n a c e continued to heat up to 725~ After -~ h at t e m p e r a t u r e the rod was r e m o v e d and a s m a l l t u n g s t e n
WATER OUTLET DC POWER CONNECTION
TO VACUUM OR GAS DRIVE MOTOR AND GEAR REDUCTION
TUBE
E X P E R I M E N T A L METHOD The p u r i t y of the s t a r t i n g m a t e r i a l s was g r e a t e r than 99.998 pct. M a s t e r alloys c o n t a i n i n g 50 to 100g Of t i n and b i s m u t h in the d e s i r e d r a t i o w e r e p r e p a r e d by m e l t i n g u n d e r v a c u u m at 400~ for 89 h. The alloys were quench c a s t into 5 m m ID P y r e x t u b e s b y a v a c uum f i l l i n g technique in o r d e r to avoid m a c r o s e g r e g a tion. Schematic d r a w i n g s of the e q u i p m e n t a r e given in F i g s . 1 and 2. The q u a r t z s a m p l e tube had a bottom s e c t i o n 2 m m ID and 3 m m OD, which had been fused to a top s e c t i o n 6 m m ID and 8 m m OD. The lower s e c t i o n was 15 c m long and the top s e c t i o n was 20 cm in length. A copper i n s e r t coated with a thin l a y e r of graphite which j u s t fitted i n s i d e the q u a r t z extended 5 e m up into the tube and s u p p o r t e d it at the b o t t o m . The upper s u p p o r t for the q u a r t z tube, Fig. 1, was e l e c t r i c a l l y floating, while the bottom was grounded. The s t e e l pipe s u r r o u n d i n g the s a m p l e tube, Fig. 2, J. C. WARNER, formerly with Ames Laboratory of the U. S. Atomic Energy Commission, Iowa State University, Ames, Iowa 50010, is now with Department of Metallurgy and Materials Science, CarnegieMellon University, Pittsburgh, Pa. 15213. J. D. VERHOEVEN is Senior Metallurgist,Ames Laboratory, U.S.A.E.C., and Professor, Dept. Metallurgy, Iowa State University, Ames, Iowa. Manuscript submitted September 25, 1972. METALLURGICALTRANSACTIONS
WIRES "/4---PROBE 1 W A T E R INLET
DRIVE SHAFT
FURNACE
SPLIT
TO VACUUM ,OR GAS
DC POWER CONNECTION
COOLING CHAMBER SUPPORT ROD
THERMOCOUPLE INLET GUIDE RODS
Fig. 1--Experimental apparatus for controlled solidification of alloys in an electric field. VOLUME 4, MAY 1973-1255
CURRENT PROBE
18CC
I
I
I
I
I
I
1600 ALLOY GRAPHITE
1400
WOOL
--FURNACE
I~00
STEEL PIPE I000
QUARTZ SAMPLE TUBE
~jw....../H,+.~,,l......... ? suPPORTPLATEI/
SOLID-LIQUID INTERFACE ] ~WATER SEAL / COPPER INSERT / B O T T O M VACUUM SEAL
WATER JACKET I / TOP P L A T E - ~
t - - WATER CHAMBER
FURNACE'
,,(__
=~ - - ~
SUPPORT ROD
Fig. 2--Sectional view through the sample and surroundings. w i r e was u s e d to r e m
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