Discontinuous twinning of titanium at 4.2 K
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d-Spacings, A hkl
o-phase*
A12a-Mnt
200 2] 1 022 400 431 222 422 6T1 253 453
4.775 3.242 2.490 2.388 2.100 2.004 1.621 1.497 1.407 1.253
2.396 2.258 1.957 1.555 2.045 -
Angle Between Planes82 Measured o-phase~ 4.747 3.833 3.403 2.363 2.226 2.693 1.924 1.514 2.011 1.608
0 47.24 90.00 0 28.40 65.19 47.24 19.82 72.87 58.35
A12a-Mn:~ 0 35.26 90.00 0 19.47 54.74 35.26 13.26 64.76 46.69
Measured 0 36 90 0 19.5 55 36 13.5 65.0 47.0
*Values calculated from the lattice parameters (a = 9.55,8,, c = 4.98A) reported in Ref. 3. t d-spacings are those given in ASTM card no. 8-363. $Calculated angles between (100) and various planes. 82 Planes (hi kill ) equal to (100) and (h2k212).
Fig. 4 - - M i c r o g r a p h s h o w i n g e n l a r g e m e n t of d i f f r a c t i o n p a t t e r n in Fig. 3(c). The solid lines a r e d r a w n t h r o u g h the m a t r i x s p o t s and the s t r o n g p r e c i p i t a t e s p o t s . The s t r u c t u r e r e p r e s e n t e d by both the s t r o n g and w e a k s p o t s is Ale ce -Mn. The r o t a t i o n b e t w e e n the two c r y s t a l o r i e n t a t i o n i s 19 deg.
f o r m . Since no second p h a s e s were o b s e r v e d following the higher t e m p e r a t u r e (1700~ anneal of the i r r a d i : ated s p e c i m e n it is concluded that any t r a n s m u t a t i o n products would be quite s m a l l . The p r e s e n t r e s u l t s also shows that the p r o p o s e d ~ - M n (WRes) phase goes into solution at a t e m p e r a t u r e no g r e a t e r than 1700~ An explanation for the i r r a d i a t i o n induced f o r m a t i o n of ~ - M n phase is not a v a i l a b l e at the p r e s e n t time. It is however quite p o s s i b l e that due to atom s i z e a n d / o r valence d i f f e r e n c e s between Re and W atoms that the atom d i s p l a c e m e n t s produced in the collision c a s c a d e regions would favor a Re atom r i c h c o r e which could be nucleation s i t e s for the ~ - M n phase. This work was p e r f o r m e d under the s p o n s o r s h i p of the United States Atomic Energy C o m m i s s i o n through Contract Number AT(11-1)-2093. METALLURGICAL TRANSACTIONS
1. G. G. Lessmarmand R. E. Gold: NASA SP-245, 26 June 1969, pp. 261-96. 2. J. M. Dickinson and L. S. Richardson: Trans. ASM, 1959, vol. 51, pp. 261-96. 3. P. Greenfield and P. A. Beck: Trans. AIME, 1956, vol. 206, pp. 265-76. 4. C. G. Wilson: Acta Cryst., 1963, vol. 16, pp. 724-30. 5. J. L. Kamphouse, R. L. Stuart, and J. Moteff: J. Nucl. Maters., 1971, vol. 39, pp. 1-17. 6. ASTM Card no. 8-363.
Discontinuous Twinning of Titanium at 4.2 K N. M. MADHAVA AND R. W. ARMSTRONG In a r e c e n t r e p o r t x on the d e f o r m a t i o n b e h a v i o r of s t e e l at 4.2 K, it was o b s e r v e d that c o n s i d e r a b l e p e r manent deformation was r e c o r d e d in c o m p r e s s i o n in the f o r m of discontinuous load d r o p s in the f o r c e - d i s p l a c e m e n t curve while in tension the m a t e r i a l failed b r i t t l e l y . The d e f o r m a t i o n and f r a
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