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EFFECT OF DISPERSOID-FORMING ADDITIONS ON THE RESPONSE TO HEAT TREATMENT OF
SPLAT-QUENCHED Al-Li-X ALLOYS
R. Pratt, P. Tsakiropoulos, H. Jones, R. Gardiner, J. Restall
To cite this version:
R. Pratt, P. Tsakiropoulos, H. Jones, R. Gardiner, J. Restall. EFFECT OF DISPERSOID-FORMING ADDITIONS ON THE RESPONSE TO HEAT TREATMENT OF SPLAT-QUENCHED Al-Li-X AL- LOYS. Journal de Physique Colloques, 1987, 48 (C3), pp.C3-341-C3-346. �10.1051/jphyscol:1987339�.
�jpa-00226570�
JOURNAL DE PHYSIQUE
C o l l o q u e C3, s u p p l e m e n t a u n 0 9 , Tome 48,
septembre
1987EFFECT OF DISPERSOID-FORMING ADDITIONS ON THE RESPONSE TO HEAT TREATMENT OF SPLAT-QUENCHED A1-Li-X ALLOYS
R.C.A.
P R A T T ( ~ ), P.
TSAKIROPOULOS( ),
H.JONES,
R.W.
GARDINER*and J.E.
R E S T A L L * "U n i v e r s i t y
of
S h e f f i e l d , D e p a r t m e n tof M e t a l l u r g y ,
G B - S h e f f i e l d , S1 3Jd, G r e a t - B r i t a i nateri rials and
S t r u c t u r e s D i v i s i o n , R o y a l A i r c r a f tE s t a b l i s h m e n t , G B - F a r n b o r o u g h - H a n t s , GU14 6 T D , G r e a t - B r i t a i n
*
P r o p u l s i o n D e p a r t m e n t , R o y a l A i r c r a f t E s t a b l i s h m e n t , P y e s t o c k , G B - F a r n b o r o u g h - H a n t s , G u 1 4 O L S , G r e a t - B r i t a i nA b s t r a c t
The paper r e p o r t s some r e s u l t s of a r e s e a r c h programme which i s d i r e c t e d towards i d e n t i f y i n g dispersoid-forming a d d i t i o n s , made p o s s i b l e v i a r a p i d s o l i d i - f i c a t i o n , t h a t a r e more e f f e c t i v e t h a n t h e 0 . 0 5 t o 0.25wt%Zr a d d i t i o n c u r r e n t l y made t o f i r s t - g e n e r a t i o n wrought-ingot aluminium a l l o y s c o n t a i n i n g l i t h i u m .
In t h e s t u d y 'b 2 ' v o l % of t r a n s i t i o n metal aluminides were d i s p e r s e d i n an A1-Li a l l o y m a t r i x u s i n g t h e two-piston splat-quenching t e c h n i q u e . The approach adopted f o r i n i t i a l s e l e c t i v i t y was t o a s c e r t a i n t h e s t a b i l i t y and r e l a t e d e f f e c t s of t h e aluminide d i s p e r s o i d s a t t h e (Al-Li) s o l u t i o n temperature o f 540°C f o r t r e a t m e n t s between 1 and 1000 h.
Hardness a s - s p l a t t e d i n c r e a s e d n o t a b l y a s a r e s u l t of t h e d i s p e r s o i d forming a d d i t i o n and incgeased f u r t h e r i n l h a t 540°c, d e c r e a s e s a f t e r more prolonged t r e a t m e n t a t 540 C b e i n g a t t r i b u t a b l e p a r t l y t o l o s s of l i t h i u m and p a r t l y t o m i c r o s t r u c t u r a l c o a r s e n i n g ,
S e l e c t e d c a n d i d a t e a l l o y systems-were s u b j e c t e d t o ageing h e a t t r e a t m e n t s a t 1 6 0 ~ ~ w i t h o r wlthout p r i o r s o l ~ t i o n ~ t r e a t m e n t a t 5 4 0 ~ ~ f o r 1 h . I n c r e a s e s i n microhardness, t y p i c a l l y by 40 k g / m h i g h e r t h a n f o r t h e corresponding b i n a r y A1-Li a l l o y , were o b t a i n e d a t e a c h - s t a g e of ageing. Al-4,lwt%
-
0.5wtY~o demon- s t r a t e d o u t s t a n d i n g b e h a v i o u r , b o t h i n s t a b i l i t y a t 5 4 0 ' ~ and i n response t o ageing t r e a t m e n t a t 160'~.~ n t r o d u c t i o n
The a d d i t i o n of L i t o aluminium a l l o y s , s i v i n r : r i s e t o reduced d e n s i t y simultaneously with i n c r e a s e d modulus o f e l a s t i c i t y , h a s been p r a c t i s e d s i n c e t h e 1 9 2 0 ' s ( 1 ) . Although t h e p r e s e n t emphasis worldwide i s t o develop A1-Li base a l l o y s by t h e wrought i n g o t r o u t e , a t l e a s t t h r e e p o s s i b l e r o l e s f o r r a p i d s o l i d i - f i c a t i o n (RS) have been i d e n t i f i e d i n r e s p e c t of p o s s i b l e developments of second generat i o n a l l o y s :
( i ) More uniform and r e f i n e d m i c r o s t r u c t u r e i n c l u d i n g e l i m i n a t i o n of i n g o t - d e r i v e d c o a r s e m e t a l l i c second phase t h a t may a c t a s s i t e s f o r c r a c k i n i t i a t i o n and c o r r o s i o n .
( i i ) I n c o r p o r a t i o n of d i s p e r s e d phases t h a t a r e more e f f e c t i v e i n homogenizing s l i p t h a n a r e phases i n c o r p o r a t e d by t h e i n g o t r o u t e , t h u s improving d u c t i l i t y and toughness.
( i i i ) F a b r i c a t i o n of a l l o y s with h i g h e r L i c o n t e n t s t h a n c a n be accommodated by t h e wrought i n g o t r o u t e , t h e r e b y f u r t h e r lowering d e n s i t y w h i l e f u r t h e r i n c r e a s i n g modulus and s t r e n g t h .
E a r l y r e p o r t s (2,3) of t h e a p p l i c a t i o n of RS t o A1-Li base a l l o y s were con- cerned with t h e e f f e c t s o f adding up t o 3wt%Li t o t h e wrought 2024 a l l o y composi- t i o n . There a r e now over 60 p u b l i c a t i o n s on the e f f e c t of RS on A1-Li b a s e a l l o y s ( 4 ) .
(')present address: Osprey Metals Ltd, GB-Neath, SAll 1NJ. West Glamorgan (GB).
(2)~resent address: Department Of Materials Science and Engineering. University of Surrey, GB-Guildford, GU2 5XH. Surrey (GB).
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1987339
JOURNAL
DE
PHYSIQUEDispersoid-forming a d d i t i o n s i n r a p i d l y - s o l i d i f i e d A1-Li base a l l o y s have i n c l u d e d ( i n wt$): 1 t o 7 S i , 0 . 2 T i , 0 . 4 C r , 0 . 2 t o 3 Mn, 0 . 5 Fe, 0 . 2 t o 1 Co, 0.04 Y and 0.2 t o 1 Zr ( 5 ) . Comparative s t u d i e s by Palmer e t a 1 ( 6 , 7 ) r e p o r t e d somewhat b e t t e r combinations of s t r e n g t h and d u c t i l i t y f o r Fe-containing r a t h e r t h a n Mn-containing d i s p e r s o i d s i n s p l a t - f l a k e e x t r u s i o n s . S i m i l a r i n v e s t i g a t i o n s (8) were concerned w i t h t h e e f f e c t s of 0 . 2 t o 0 . 6 w t % Mn, C r , Fe, Co, T i and Zr on. Al-3wt%Li. A l l t h e d i s p e r s o i d s i n c r e a s e d d u c t i l i t y a t t h e same s t r e n g t h l e v e l compared t o t h e b a s i c a l l o y without a d i s p e r s o i d former, a t t r i b u t a b l y t o d e l o c a l i s a - t i o n of s l i p when a d i s p e r s o i d i s p r e s e n t . Such l i m i t e d s t u d i e s , however, h a r d l y provide a b a s i s f o r s e l e c t i n g one d i s p e r s o i d r a t h e r t h a n a n o t h e r .
The paper r e p o r t s r e s u l t s from a programme aimed a t i d e n t i f y i n g d i s p e r s o i d - forming a d d i t i o n s , i n c o r p o r a t e d v i a RS, t h a t a r e more e f f e c t i v e t h a n t h e 0.05 t o 0.25wt%Zr a d d i t i o n c u r r e n t l y made t o f i r s t - g e n e r a t i o n wrought i n g o t A1-Li base a l l o y s .
Experiment a1
Relevant c h a r a c t e r i s t i c s of some p o t e n t i a l aluminide d i s p e r s o i d s with low e q u i l i b r i u m s o l i d s o l u b i l i t y a t t h e normal s o l u t i o n temperature (813 K) of A1-Li base a l l o y s a r e given i n T a b l e 1, t o g e t h e r w i t h l e v e l s of a d d i t i o n r e q u i r e d t o y i e l d 2 vol% s l ~ u n i n i d e i n an Al-based m a t r i x c o n t a i n i n g up t o 4wt%Li. The
r e s u l t i n g A1-Li-X a l l o y s were prepared under A r from b i n a r y master a l l o y s produced as i n g o t s 25 mm i n diameter and 150 mm l o n g by i n d u c t i o n m e l t i n g under A r and c h i l l c a s t i n g . For X = W , Nb, Mo, Ni/B t h e A1-Li-X m e l t s were s t i r r e d u s i n g a t u n g s t e n rod. A l l o t h e r m e l t s were s t i r r e d with a r e c r y s t a l l i z e d alumina t u b e . Fluxing was used t o minimise L i l o s s e s . For a l l m e l t s samples of between 0 . 5 g and 1 . 5 g were withdrawn by means of a p i p e t t e f i l l e r i n t o a r e c r y s t a l l i z e d alumina t u b e of bore 3 mm and l e n g t h 225 mm ( 9 ) . The e x t r a c t e d samples were c u t i n t o specimens %
70 mg i n weight f o r l e v i t a t i o n m e l t i n g and twin p i s t o n s p l a t quenching. The l e v i t a t i o n c o i l c o n s i s t e d of a 30° c o n i c a l lower s e c t i o n , t h e f i r s t two t u r n s being co-planar, t h e e x t e r n a l diameter i n c r e a s i n g i n f o u r t u r n s t o 65 mm and having two s t a b i l i s i n g r e v e r s e t u r n s of 40 mm e x t e r n a l diameter. The twin p i s t o n u n i t was o p e r a t e d under A r and t h e l e v i t a t e d d r o p l e t s were quenched on t o cqpper p i s t o n s u b s t r a t e s . S p l a t s of t h i c k n e s s % 50 ym and diameter 2 5 mm were produced. The s p l a t s were wrapped i n aluminium f o i l , s e a l e d under A r i n s i l i c a c a p s u l e s and s u b j e c t e d t o t r e a t m e n t s between 1 and 100 h r a t 813 K followed by a w a t e r quench.
Microhardness measurements were made on p o l i s h e d t r a n s v e r s e s e c t i o n s of t h e s p l a t s u s i n g a 1 5 g l o a d . The h a r d n e s s v a l u e s t o be quoted a r e each t h e averages of a t l e a s t 10 measurements. Thinning f o r e l e c t r o n microscopy was c a r r i e d o u t i n a twin j e t a p p a r a t u s w i t h an e l e c t r o l y t e of 10% p e r c h l o r i c a c i d i n e t h a n o l . The specimens were examined i n a P h i l i p s EM400T TEM. X-ray d i f f r a c t i o n was c a r r i e d o u t u s i n g Cu Ka r a d i a t i o n .
R e s u l t s and Discussion
Alloy compositions i n t h e a s - s p l a t t e d c o n d i t i o n a r e g i v e n i n T a b l e 2. The L i c o n t e n t of t h e s p l a t s v a r i e d from 2 . 5 t o 4 . 1 wtol, and was always lower by some 0 . 2 w t % t h a n t h e Li c o n t e n t of t h e i n i t i a l i n g o t . For t h e same a l l o y system i n t h e a s - s p l a t t e d c o n d i t i o n t h e L i c o n t e n t v a r i e d by
+
0.3 w t % . Table 2 shows t h a t , a s expected, Li l o s s e s o c c u r r e d d u r i n g s o l u t i o n t r e a t m e n t and t h e amount of l o s s i n c r e a s e d with time a t 813 K and a l o n g t h e s e r i e s X = Mo, Nb, W, Fe, Z r , Cr, N i , T i , V . I n g e n e r a l a l l o y s c o n t a i n i n g t h e f i r s t f i v e elements e x h i b i t e d a lower percentage of L i l o s s t h a n t h e b i n a r y a l l o y Al-2.6wt%Li. Hardness i n t h e a s - s p l a t t e d c o n d i t i o n i n every c a s e exceeded t h a t of t h e b i n a r y a l l o y , being almost doubled f o r X = Mo, W , Fe, N i . With t h e e x c e p t i o n of s p l a t s of t h e A1-Li-X(X = Cr,Fe,Ni) a l l o y systems, whose hardness decreased c o n t i n u o u s l y w i t h time a t 813 K , a l l t h e a l l o y s e x h i b i t e d peak hardness a f t e r 1 h r a t 813 K , t h e magnitude of peak hardness d e c r e a s i n g a l o n g t h e sequence X = Yo, W, Ni/B, Nb, Z r , T i and V.
The performance of A 1
-
4 . 1 Li-
0 . 5 Mo w a s q u i t e o u t s t a n d i n g , showing a 20 p e r c e n t i n c r e a s e i n hardness a f t e r 100 h a t 813 K, compared with d e c r e a s e s by 25% t o 67%f o r t h e o t h e r compositions s t u d i e d . T h i s i n c r e a s e i n hardness f o r Al-Li-lo o c c u r r e d i n s p i t e o f c o n s i d e r a b l e l o s s e s (from 4 . 1 t o 3.3wt%) of L i d u r i n g t h e extended t r e a t m e n t involved. The r e s u l t s i n d i c a t e t h e remarkable s t a b i l i t y o f
A1-Li-X (X = Mo,Nb,W) d u r i n g s o l u t i o n t r e a t m e n t comparing favourably
w i t h t h e s t a b i l i t y of t h e Al-Li-Zr a l l o y i n c l u d e d . The e f f e c t of added Nb, Mo and W on ageing of A1-Li a t 433 K w i t h o r without p r i o r s o l u t i o n t r e a t m e n t a t 813 K f o r 1 h i s i n d i c a t e d i n T a b l e 3 and F i g . 1. Again Al-Li-Mo showed t h e h i g h e s t hardness l e v e l s , t y p i c a l l y 40 kg/nun2 h a r d e r t h a n t h e b i n a r y A1-Li a l l o y a t each s t a g e o f ageing.
Binary a l l o y s w i t h high Li c o n t e n t (> 2wt%) form o n l y two s t a b l e s o l i d p h a s e s : t h e ~ ( f c c ) A1-Li s o l i d s o l u t i o n and 6 (bcc) AlLi
.
In a d d i t i o n , a m e t a s t a b l e phase6 ' ,
based on L12-type A13Li, can be p r e s e n t as-quenched from s o l u t i o n t r e a t - ments a t 813 K (10) a s w e l l a s a f t e r ageing f o r p e r i o d s up t o 100 h . T h i s 6 ' forms s p h e r i c a l coherent p r e c i p i t a t e s p o s s e s s i n g a cubic-cubic o r i e n t a t i o n r e l a t i o n s h i p w i t h t h e m a t r i x ( 1 1 ) . A s a consequence o f t h e Li-content of 6 ' , l a r g e volume f r a c t i o n s o f i t can be produced even a t r e l a t i v e l y low s u p e r s a t u r a t i o n s of t h e 0.phase. A l l t h e s e o b s e r v a t i o n s have been confirmed i n t h e p r e s e n t work by
examining TEM examination of samples t h i n n e d from A1-Li b i n a r y a l l o y s p l a t s both i n t h e i r s o l u t i o n t r e a t e d and/or aged c o n d i t i o n s .
D i s p e r s i o n s o f c o h e r e n t m e t a s t a b l e (L1,-type) A13Zr p a r t i c l e s i n r a p i d l y - s o l i d i f i e d Al-Li-Zr c o n t a i n i n g l w t % Z r have been r e p o r t e d (12) t o provide h e t e r o - geneous n u c l e a t i o n s i t e s f o r 6 ' . T h i s has s i n c e been confirmed i n c o n v e n t i o n a l ingot-processed a l l o y s (13). The r e d u c t i o n i n both s t r a i n and s u r f a c e energy a s s o c i a t e d w i t h n u c l e a t i o n of 6 ' a r e b e l i e v e d t o be r e s p o n s i b l e f o r t h e e f f e c t i v e - n e s s of t h e A13Zr p a r t i c l e s a s n u c l e a t i o n s i t e s . A n a l y s i s f o r L i i s d i f f i c u l t , however, u s i n g TEM t e c h n i q u e s and c o n f l i c t i n g r e s u l t s have been r e p o r t e d (14,15) concerning Li i n c o r p o r a t i n g i n t o A13Zr u s i n g E l e c t r o n Energy Loss Analysis (EELS).
R a p i d l y - s o l i d i f i e d A1-Li-X a l l o y s i n c o r p o r a t i n g d i s p e r s o i d s o t h e r t h a n Z r i n A1-Li m a t r i c e s have been i n v e s t i g a t e d (5-8). The r e s u l t i n g d i s p e r s o i d has been t a k e n t o be t h e corresponding A1-X i n t e r m e t a l l i c , a l t h o u g h it h a s been suggested (16) t h a t Li i n c o r p o r a t i o n may o c c u r i n some c a s e s .
P r e l i m i n a r y s t r u c t u r a l i n v e s t i g a t i o n s on s p l a t s o f t h e Al-Li-Mo a l l o y by X-ray d i f f r a c t i o n and e l e c t r o n microscopy/microanalysis s u g g e s t a r a t h e r complex
c o n s t i t u t i o n w i t h known A1-Li and A1-Mo based phases c o e x i s t i n g w i t h as-yet
un-
i d e n t i f i e d phases. I n t e r p r e t a t i o n is complicated by i n c o n s i s t e n c i e s concerning t h e i d e n t i t y and s t a t u s of aluminide phases r e p o r t e d t o o c c u r i n t h e A1-No b i n a r y system (17-20) and a d e a r t h of i n f o r m a t i o n on t h e c o n s t i t u t i o n ( o r any o t h e r a s p e c t s ) o f Al-Li-Mo a l l o y s . The hardening t h a t o c c u r s on ageing a t 433K appears t o r e s u l t ( F i g . 2 ) l a r g e l y from p r e c i p i t a t i o n o f 6' a s i n t h e A1-Li b i n a r y , F i g , 1 s u g g e s t i n g t h a t t Q e hardening increment a t t r i b u t a b l e t o Mo remains e s s e n t i a l l y c o n s t a n t a t-
45 kg/mma t l e a s t i n t h e f i r s t 100 h of t r e a t m e n t , Conclusions
1. Measurements of r e t a i n e d hardness a f t e r prolonged s o l u t i o n t r e a t m e n t a t 813 K and ageing a t 433 K i n d i c a t e remarkable s t a b i l i t y f o r t h e r a p i d l y - s o l i d i f i e d Al-4wt%Li-O.Bwt%Mo a l l o y compared w i t h e q u i v a l e n t a l l o y s i n which Mo i s r e p l a c e d by o t h e r t r a n s i t i o n m e t a l s o r by n i c k e l combined w i t h boron.
2. P r e l i m i n a r y s t r u c t u r a l i n v e s t i g a t i o n s o f s p l a t - c o o l e d Al-4wt%Li
-
0 . 5 w t m o i n d i c a t e t h e p r e s e n c e of p r e v i o u s l y known A1-Li and Al-lo based phases t o g e t h e r w i t h as-yet u n i d e n t i f i e d phases. Hardening d u r i n g a g e i n g a t 433K appears t o b e l a r g e l y a r e s u l t o f p r e c i p i t a t i o n of & ' a s i n t h e A1-Li b i n a r y .Acknowledgements
T h i s work was c a r r i e d o u t a t t h e U n i v e r s i t y o f S h e f f i e l d a s p a r t of Agreement No. 2031/0111 RAE(P) w i t h t h e M i n i s t r y o f Defence Procurement Executive,
Farnborough and Pyestock, UK.
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473.R. J . Gregson and H . I. Flower, J . fifater. S c i . L e t t . , 1984,
3,
829.W. Stimson, M. H . Tosten, P. R . Howell and D. B. W i l l i a m s , i n 'Al-Li Alloys 111; Eds. C. Baker e t a l . , I n s t . M e t a l s , London, 1986, p.329.
T. M a l i s , a s r e f . 1 4 , p.347.
S. M. L. S a s t r y and J . E . O'Neal, i n 'Al-Li Alloys 11: Eds. T . H. S a n d e r s , J r . , and E . A . S t a r k e , J r . , TMS-AIME, Warrendale, P a . , 1984, p.363.
F. Spencer, Z . Metallkunde, 1959,
50,
588.L. K . Walford, P h i l . Mag., 1964,
2,
513.L. Brewer and R. H . Lamoureux, Atom. En. Rev., Spec. I s s u e 7, 1980, p.195-356.
E. A . Guest, C. P. Chang, J . N . P r a t t and M. H. L o r e t t o , I n t e r n a t . J . Rapid S o l i d i f i c a t i o n , 1986,
2,
83.Table 1 - C h a r a c t e r i s t i c s of some Al-rich aluminide a d d i t i o n s t h a t a r e s t a b l e a t t h e A 1 - L i a l l o y s o l u t i o n t r e a t m e n t temperature o f 8 1 3 K . Aluminide Melting p o i n t Density of S o l u b i l i t y of W t % X t o g i v e
A1aXb of aluminide aluminide X i n ~1 A 1 2 ~ 0 1 % of
(K) kg a-3 wt% aluminide
A13Ti 1613 3310 0 . 2 4 1.14
A 1 l ~ V 943 2790 0 . 3 7 0 . 3 2
A 1 7 C r 1063 3180 0.85 0.53
A 1 3Fe 1433 3770 0.05 1.09
A 1 3 N i 1127 3800 0.05 1 . 1 7
A13Zr 1853 4110 0.23 1.42
A13Nb 1953 4520 0 . 0 7 1 . 7 7
Al12Mo 1373 3200 0.25 0 . 5 3
A112W 970 3880 0.15 1 . 0 3
Melting p o i n t and s o l i d s o l u b i l i t y d a t a from M. Hansen, C o n s t i t u t i o n of Binary A l l o y s , McGraw-Hill, 1958 and supplements, and from W. G. M o f f a t t , Handbook o f Binary Phase Diagrams, General E l e c t r i c , Schenectady, '1978 and supplements. Density d a t a from K . R. Van Horn, Aluminium, Vol. 1, Amer, Soc. f o r Metals, 1967 and W, B, Pearson, Handbook of L a t t i c e Spacings and S t r u c t u r e s of Metals and A l l o y s , Vole 2 , Pergamon, 1967.
Table 2
-
Microhardness of Li content of A1-Li-X splats as a function of duration of solution treatment at 813 K.Table 3
-
Microhardness and Li-content of A1-Li-Mo splats as a function of duration of ageing at 433 K following solution treated for lh at 813 K.As-splatted composition
(wt%)
A1-2.6Li-0.9Ti A1-3.7Li-0.2V A1-3.Li-0.7Cr A1-2.5Li-1.5Fe A1-2.6Li-1.1Ni A1-4.OLi-1.4Ni
-0.1B A1-2.7Li-1.5Zr A1-3.6Li-3.3Nb A1-4.1Li-0.5Mo A1-2.5Li-l.lW A1-2.6Li
2
Alloy Microhardness (kg/mm ) and Li-content (wt%, in parentheses) Microharduess (kg/mrn 2 ) and Li-content (wt%, in parentheses)
-
lOOOh at 813K
2623 (0.3) 2 3 ~ 3 (0.3) 2923 (1.1) 4023 (1.1) 2421 (0.5) 2 2 2 (1.8) 27+10 (1.1) 1921 (1.9) 6825 (2.1) 2528 (1.2) 2224 (1.0)
*
As-splatted
8 8 5 4 (2.6) 9423 (3.7) 9124 (3.1) 10622 (2.5) 1 0 0 ~ 4 (2.6) 1 1 6 5 2 (4.0) 7524 (2.7) 7822 (3.6) 1 0 4 ~ 8 (4.1) 1 0 3 9 (2.5) 5 7 5 (2.6)
lh at 813K
100210 (2.5) 9626 (3.5) 8125 (3.0) 7 5 9 (2.4) 9025 (2.5) 11827 (3.8) ' 1 0 5 ~ 6 (2.6) 11624 (3.4) 140225 (4.0) 1 2 2 7 (2.6) 6224 (2.4)
1Oh at 813K
6727 (1.8) 82211 (2.1) 6226 (2.9) 7022 (2.3) 6228 (3.6) 91-11 (3.1) 8725 (2.5) 8 8 5 7 (3.3) 1 2 0 9 (3.4) 7 6 3 (2.5) 5326 (2.5)
lOOh at 813K
4123 (1.1) 5626 (1.4) 5426 (2.9) 5323 (2.0) 4 5 5 (2.6) 3825 (2.1) 9 4 4 (2.0) 77+16
-
(2.7)12025 (3.3) 5223 (1.9) 4324 (1.6)
C3-346 JOURNAL
DE PHYSIQUE
F i g u r e 1 Microhardness of A1-Li-X s p l a t s a s a f u n c t i o n of d u r a t i o n of a g e i n g a t 433 K.
0
A1-3Li A1-3.6Li-3.3Nb0
A1-2.9Li-1.8WA
A1-4.1Li-0.5MoF i g u r e 2 T r a n s m i s s i o n e l e c t r o n n ~ i c r o g r a p h s of A1-4wt%Ll-O.S%Mo s p l a t t h i n n e d (a) a f t e r ' s o l u t i o n ' t r e a t m e n t f o r l h a t 813 K showing 6 i n a
m a t r i x o f aAl.
(b) a f t e r a g e i n g f o r 10h a t 433 K showing p r e c i p i t a t i o n o f 6' i n t h e aAl m a t r i x .
Micrographs s u p p l i e d by J. J u a r e z - I s l a s .
