Sllicide phases in some complex titanium alloys
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microstructure and the other mechanical properties of these a l l o y s , t l - m W h i l e t w o h e x a g o n a l s i l i c i d e s , S~ ( a = 0 . 7 8 0 n m , c = 0 . 5 4 4 n m ) a n d $2 ( a = 0 . 7 0 2 n m , c = 0.368 nm) with stoichiometries (TiZr)sSi3 and (TiZr)6Si3, r e s p e c t i v e l y , are f o u n d in silicon b e a r i n g a - a n d n e a r
Silicide Phases in Some Complex Titanium Alloys C. RAMACHANDRA Small titanium strength and also
and VAKIL
a - t y p e t i t a n i u m a l l o y s , T i - 5 Z r - l S i t6~ a n d T i - 6 A 1 - 5 Z r 0 . 5 M o - 0 . 2 5 S i , t8~ o n l y t h e $2 s i l i c i d e w a s f o u n d t o e x i s t o v e r t h e e n t i r e r a n g e o f a g i n g t e m p e r a t u r e i n ( a + /3) alloys like Ti-6A1-3Zr-3Sn-INb-0.5Mo-0.3Si I~~ and T i - 6 A I - 1 . 6 Z r - 3 . 3 M o - 0 . 3 S i fl21 a n d a l s o in a f u l l y / 3 a l l o y . [13]
SINGH
a d d i t i o n s o f silicon u p to a b o u t 0.5 m a s s pct to alloys to improve their high-tempera ture c re e p is w e l l e s t a b l i s h e d , tl-4~ S i l i c o n i n s o l i d s o l u t i o n i n t h e f o r m o f s i l i c i d e s is k n o w n t o a f f e c t t h e
H o w e v e r , A n t o n y , tSl w h i l e p o i n t i n g o u t a n u n s a t i s f a c t o r y match between certain measured and calculated interplanar spacings, has reported another hexagonal silicide ( h e r e a f t e r d e s i g n a t e d as S ' ) in the t~-titanium alloys T i - 6 A 1 - 3 S n - 3 Z r (silicon v a r y i n g f r o m 0.1 to 1.0 w t pct) w i t h l a t t i c e p a r a m e t e r s a --= 0 . 7 7 3 n m a n d c = 0 . 5 3 2 n m , c o n s i d e r a b l y d i f f e r e n t f r o m t h o s e o f $1 a n d $2. T h e p r e s ent communication deals with reanalysis of the X-ray
c . RAMACHANDRA, Lecturer, and VAKIL SINGH, Professor, are with the Department of Metallurgical Engineering, Centre of Advanced Study, Institute of Technology, Banaras Hindu University, Varanasi-221 005, India. Manuscript submitted April 30, 1991.
Table I. Comparison of the lnterplanar Spacings Determined by X-Ray Diffraction with the Calculated Values for the Silicides in Ti-6AI-3Sn-3Zr-0.5Si Titanium Alloy Silicide S] ~)
Experimental d Spacings
Silicide S~2b)
Matrix a_Titanium(d)
Silicide S , ( c )
d
d
(nm)
d
d
Values (nm)
hkil
Values (nm)
Ti-6AI-3Sn-3Zr-0.5Si (Antony[S])
Values (nm)
Values (nm)
hkil
-1120 --2020 1121 -0002 2130 -2131 3030 2022 -2240 2132 2241 ---. 4040 -2242 3230 --. 4042 0004 5030 . -----
0.6079 -0.3680 0.3510 . 0.3147 0.3039 . 0.2539 0.2342 0.2297 -. 0.2026 0.1948 . 0.1840 0.1774 0.1761 0.1755 . 0.1686 0.1629 0.1584 . 0.1532 0.1519 . 0.1436 0.1394 . . 0.1326 0.1303 0.1269 0.1243
. -. 0.350* . 0.312 0.303* . 0.252 0.232 0.228 0.222 . 0.201" 0.193 . 0.182 . . 0.174" 0.171 0.167 0.161" 0.157 . . 0.152" 0.146 0.143 . . 0.135 0.133" 0.130" . 0.124
. 0.3865 . 0.335
--
--
--
--
--
--
0.2544 0.233 -0.2234
0110 0002 -0111
-0.3904
--0.3381 0.3172 -0.2723 0.2555 -0.2306 0.2251 0.2121 -0.1952 0.1863 0.1838 ---. 0.1690 -0.1586 0.1551 --. 0.
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