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THE FUSION WELDING OF Al-Li-Cu-Mg (8090) ALLOY
M. Edwards, V. Stoneham
To cite this version:
M. Edwards, V. Stoneham. THE FUSION WELDING OF Al-Li-Cu-Mg (8090) ALLOY. Journal de Physique Colloques, 1987, 48 (C3), pp.C3-293-C3-299. �10.1051/jphyscol:1987333�. �jpa-00226564�
JOURNAL DE PHYSIQUE
Colloque C3, suppl6ment au n09, Tome 4 8 , septembre 1987
THE FUSION WELDING OF Al-Li-CU-Mg (8090) ALLOY
M.R. EDWARDS and V.E. STONEHAM
Materials Technology Group School of Mechanical, Materials and Civil Engineering, Royal Military College of Science,
Shrivenham, GB-Swindon SN6 8LA, Wilts., Great-Britain
ABSTRACT
S u c c e s s f u l TIG welds have been made i n t h e A1-Li-CU-Mg a l l o y 8090-T6. Weld zone p o r o s i t y a s s o c i a t e d w i t h t h e a d s o r p t i o n o f water vapour by o x i d e formed d u r i n g s o l u t i o n t r e a t m e n t o r h o t r o l l i n g can be l a r g e l y e l i m i n a t e d by machining p r i o r t o welding. S u s c e p t i b i l i t y t o weld c r a c k i n g a s measured by bead-on-plate t e s t s is s i m i l a r t o t h a t o f 2014-T6, i n d i c a t i n g t h e l i k e l i h o o d o f s u c c e s s f u l welding e x c e p t where t h e r e is s e v e r e r e s t r a i n t . Using a n 8090 f i l l e r p r o d u c e s s p e c i f i c weld s t r e n g t h s comparable t o t h o s e o f t h e s t r o n g e s t commercial weldable aluminium a l l o y s . D u c t i l i t y is lower and f r a c t u r e s a r e i n t e r g r a n u l a r . T r a n s g r a n u l a r f r a c t u r e s occur when A1-5Mg f i l l e r i s used, b u t t h e s t r e n g t h a c h i e v e d is lower. Post-weld (-T6) h e a t t r e a t m e n t i n c r e a s e s t h e s t r e n g t h o f t h e welds b u t t h e g r a i n boundary s t r u c t u r e and composition, with which t h e b r i t t l e n e s s o f t h e welds is a s s o c i a t e d , r e s t r i c t s t h e improvement o f mechanical p r o p e r t i e s .
I n t r o d u c t i o n
The r e c e n t l y developed t e r n a r y and q u a t e r n a r y A1-Li a l l o y s were n o t d e s i g n e d with w e l d a b i l i t y i n mind. I n v e s t i g a t i o n s of t h e w e l d a b i l i t y o f e a r l i e r a l l o y s , n o t a b l y 01420 ( ~ 1 - 5 . 5 ~ g - 2 ~ i - 0 . 3 M n ) , have been reviewed by P i c k e n s ( 1 ) . Work on t h e more modern 2090 (A1-2.4Li-1.2Cu-O.,7Mg-O.l2Zr) a l l o y by S k i l l i n g b e r g ( 2 ) h a s i n d i c a t e d t h a t t h i s a l l o y can be s u c c e s s f u l l y f u s i o n welded w i t h s p e c i f i c s t r e n g t h s g r e a t e r t h a n most commercially a v a i l a b l e weldable aluminium a l l o y s . However, c e r t a i n welding d i f f i c u l t i e s have been r e p o r t e d , n o t a b l y t h e p r e s e n c e o f weld zone g a s p o r o s i t y i n 01420 (3-5) and i n t e r g r a n u l a r f r a c t u r e with consequent low d u c t i l i t y i n 8090 (2).
The aim o f t h e p r e s e n t work, which forms p a r t o f a l a r g e r programme l o o k i n g a t both f u s i o n and s o l i d - s t a t e welding o f 8090, is t o i n v e s t i g a t e t h e TIG welding o f 8090, u s i n g v a r i o u s f i l l e r s and post-weld h e a t t r e a t m e n t s .
Experimental
The 8090 a l l o y used i n t h e TIG welding was i n t h e form o f 6mm t h i c k h o t r o l l e d p l a t e . I t s composition was A1-2.41 Li-1.18 Cu-0.7 Mg-0.12 Zr-0.6 Fe-0.07 S i , w i t h a hydrogen c o n t e n t o f 16ppm by weight. Hydrogen was a n a l y s e d by m e l t i n g t h e a l l o y i n vacuum, and measuring t h e volume o f g a s absorbed by a palladium thimble.
TIG welding was c a r r i e d o u t on 5mm t h i c k s h e e t specimens, which had been s o l u t i o n t r e a t e d a t 530°C f o r 30min and aged a t 1900C f o r 16h ( - ~ 6 temper). The welding p a r a m e t e r s u2ed were an a c c u r r e n t o f l l O A a t 1 5 V , w i t h welding s p e e d s i n t h e range o f 1-4mm s- . Welding took p l a c e a t r i g h t a n g l e s t o t h e r o l l i n g d i r e c t i o n and t e n s i l e t e s t p i e c e s were c u t p a r a l l e l t o t h e r o l l i n g d i r e c t i o n . S u r p l u s weld m e t a l was machined o f f p r i o r t o t e n s i l e t e s t i n g . The gauge l e n g t h used was 25mm.
S u s c e p t i b i l i t y t o weld c r a c k i n g was measured u s i n g a t e s t p i e c e ( F i g 1) (61, based on t h e H o u l d c r o f t s l o t t e d p l a t e geometry (7). I n o r d e r t o p r o v i d e s u f f i c i e n t r e s t r a i n t t o produce c r a c k i n g , i t was n e c e s s a r y t o reduce t h e p l a t e t h i c k n e s s t o 1.6mm.
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1987333
JOURNAL DE PHYSIQUE
length of toe crack length of centre crack
1 - 1 2
0 d
dimensions in rnrn
F i g 1 T e s t p i e c e t o e v a l u a t e h o t c r a c k i n g tendency ( 6 )
E l e c t r o n beam welds were performed on 5mm t h i c k p l a t e , composition A1-2.32 Li-1.37 Cu-0.8 Mg-0.12 Zr, which was given a -T6 temper b e f o r e welding. No f i l l e r r o d was used and t h e welding p a r a m e t e r s were an a c c e l e r a t i n g v o l t a g e o f 140kV, l a c k i n g c u r r e n t o f 5mA, welding c u r r e n t o f 30mA and welding s p e e d o f 1 750mm min-
.
Thep l a t e was machined p r i o r t o welding t o reduce p o r o s i t y . R e s u l t s
Weld m e t a l p o r o s i t y , a s shown i n am and 2, a p p e a r s t o be a s s o c i a t e d with specimens t h a t have been s o l u t i o n t r e a t e d and t h e n l e f t a t room t e m p e r a t u r e f o r some hours. I f t h e s u r f a c e l a y e r is removed a s h o r t time b e f o r e welding, t h e weld m e t a l p o r o s i t y i s s u b s t a n t i a l l y removed.
Weld c r a c k i n g t e s t s showed t h a t t h e c r a c k i n g index f o r 8090 ( F i g 1 ) was 62.5%, compared w i t h 66% f o r 2014-T6 and 83% f o r both 7017-T6 and 7079-T6. I t s h o u l d be noted t h a t 7017-T6 i s normally welded w i t h an A1-5Mg f i l l e r and 2014-T6 with an A1-6Cu f i l l e r , i n o r d e r t o reduce weld c r a c k i n g
R e s u l t s o f t e n s i l e t e s t i n g o f welded specimens u s i n g d i f f e r e n t f i l l e r a l l o y s a r e i n T a b l e 3. Maximun s t r e n a t h s a r e a s s o c i a t e d with t h e u s e o f ~ a r e n t - m e t a l 180901 f i l l e r rods.
The e f f e c t of post-weld s o l u t i o n t r e a t m e n t and a g e i n g on t h e t e n s i l e behaviour o f 8090 weldments i s summarised i n T a b l e 4. There i s some i n c r e a s e i n s t r e n g t h on h e a t t r e a t m e n t , b u t s t r e n g t h s o f unwelded specimens given an i d e n t i c a l h e a t t r e a t m e n t remain much h i g h e r .
O p t i c a l micrographs a r e shown i n F i g 2. I n t h e as-welded c o n d i t i o n t h e weld m e t a l u s i n g 8090 f i l l e r ( F i g 2 a ) is made up of l a r g e equiaxed g r a i n s w i t h p r e c i p i t a t i o n w i t h i n t h e g r a i n s . For t h e A1-5Mg f i l l e r ( F i g 2b) t h e r e is a p r e c i p i t a t e o f B ( ~ g , A l , ) a l o n g t h e g r a i n boundaries. The weld p o o l o f t h e electron-beam welded specimen ( F i g 2 c ) h a s much f i n e r g r a i n s t h a n t h e c o r r e s p o n d i n g TIG welds ( F i g 2 a ) , w h i l e c l o s e t o t h e f u s i o n l i n e t h e r e i s an a r e a o f s t i l l f i n e r g r a i n s ( F i g 2 d ) . When s o l u t i o n - t r e a t e d and aged, g r a i n boundary p r e c i p i t a t i o n i n t h e A1-5Mg weld m e t a l becomes more c o n t i n u o u s ( F i g 3 a ) , w h i l e r e c r y s t a l l i z a t i o n and g r a i n growth a d j a c e n t t o t h e f u s i o n l i n e occur i n t h e e l e c t r o n beam welded specimens ( F i g 3b).
The l a t t e r i s due t o t h e r e s i d u a l s t r e s s e s s e t up d u r i n g welding.
R e s u l t s o f scanning e l e c t r o n microscopy o f f r a c t u r e d specimens a r e shown i n F i g s 4 and 5. I n t h e as-welded c o n d i t i o n , TIG welds u s i n g 8090 f i l l e r ( F i g 4 a ) f a i l i n a b r i t t l e i n t e r g r a n u l a r manner, a s do t h e EB welds which f a i l i n t h e f i n e - g r a i n e d r e g i o n n e a r t h e f u s i o n l i n e ( F i g 4b). Welds u s i n g A1-5Si f i l l e r e x h i b i t b r i t t l e f r a c t u r e with t h e f r a c t u r e p a t h f o l l o w i n g t h e c o a r s e s i l i c o n p l a t e s . In. c o n t r a s t , as-welded specimens with both A 1 and A1-5Mg f i l l e r s ( F i g 4 c ) f a i l i n a d u c t i l e t r a n s g r a n u l a r manner. A f t e r a -T6 temper, f r a c t u r e s i n specimens w i t h 8090 ( F i g 5 a ) and A1-5Mg ( F i g 5b) f i l l e r s both f a i l i n t e r g r a n u l a r l y , a s does t h e €8 welded specimen ( F i g 5 c ) . Compared t o t h e as-welded i n t e r g r a n u l a r f r a c t u r e s ( F i g s 4 a and 4 b ) , t h e r e a p p e a r s t o be more g r a i n boundary d u c t i l i t y p r e s e n t i n t h e -T6 h e a t t r e a t e d specimens. Transmission e l e c t r o n microscopy confirmed t h e absence of S ( A ~ , c u M ~ ) p r e c i p i t a t e s i n t h e weld m e t a l a f t e r post-weld h e a t t r e a t m e n t . T h i s is t o be e x p e c t e d s i n c e t h e r e was no s t r e t c h i n g between s o l u t i o n t r e a t m e n t and ageing.
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C3-296 JOURNAL DE PHYSIQUE
F i g 5 SEM f r a c t o g r a p h s of post-weld h e a t t r e a t e d (-T61 specimens with ( a ) 8090 f i l l e r , ( b ) A1-5Mg f i l l e r and ( c ) EB weld, no f i l l e r .
D i s c u s s i o n
As shown i n T a b l e 2, welding immediately a f t e r s o l u t i o n t r e a t m e n t d o e s n o t produce e x t e n s i v e p o r o s i t y . I t i s n e c e s s a r y t o a l l o w time a f t e r s o l u t i o n t r e a t m e n t i n o r d e r t o a d s o r b m o i s t u r e from t h e a i r , b e f o r e p o r o s i t y becomes a problem. S i n c e t h i s p o r o s i t y o c c u r s i n both A1-Mg-Li (3-5) and Al-Li-Cu ( 2 ) a l l o y s , it must be a s ~ o c i a t e d with t h e l i t h i u m - c o n t a i n i n g o x i d e s produced d u r i n g s o l u t i o n t r e a t m e n t o r h o t r o l l i n g , r a t h e r t h a n t h e magnesium o x i d e ( 8 , 9 ) which is a l s o p r e s e n t i n t h e oxide s c a l e o f A1-Li a l l o y s c o n t a i n i n g magnesium. Table 1 a l s o s u g g e s t s t h a t , i f t h e o x i d e l a y e r formed a t high t e m p e r a t u r e is removed by machining and t h e p l a t e s l e f t i n l a b o r a t o r y a i r f o r more t h a n 96h, t h e n t h e r e i s s u f f i c i e n t m o i s t u r e adsorbed on t h e o x i d e s c a l e formed a t room t e m p e r a t u r e t o i n c r e a s e t h e p o r o s i t y l e v e l somewhat. T h i s was p r e v i o u s l y n o t e d by Kainova and Malinkina (10) with 01420.
However, Table 2 i n d i c a t e s t h a t t h i s e f f e c t produces l e s s p o r o s i t y t h a n does t h e omission o f t h e machining s t a g e .
The occurence o f weld zone c r a c k i n g i n aluminium a l l o y s c o n t a i n i n g copper, magnesium and/or s i l i c o n i s most l i k e l y when t h e composition is i n one o f t h e
f o l l o w i n g r a n g e s ( 1 1 ) :
( a ) copper (0-5%) and s i l i c o n (0.5-1.5%)
( b ) magnesium (0.5-2.5%) and i r o n p l u s s i l i c o n (0.05-1%) ( c ) magnesium (0.5-2%) and copper (0.5-2.5%)
( d ) magnesium (0.5-2.7%) and manganese (0-0.5%)
T h i s would i n d i c a t e t h a t , assuming t h a t l i t h i u m e f f e c t s do n o t s u p e r s e d e t h o s e o f copper and magnesiun, an a l l o y o f 8090 composition c o n t a i n i n g 1.3% copper and 0.7%
magnesiun is n o t l i k e l y t o be r e a d i l y weldable, a s i s t h e A1-CU a l l o y 2219. The c r a c k i n g t e s t r e s u l t s showed t h a t , f o r a t e s t under s e v e r e r e s t r a i n t and w i t h o u t s e p a r a t e f i l l e r r o d s , t h e r e s i s t a n c e t o c r a c k i n g was s i m i l a r t o t h a t o f 2014-T6.
T e s t s w i t h 5mm t h i c k p l a t e s o f 8090, where t h e r e s t r a i n t was l e s s , showed no s i g n o f c r a c k i n g . These r e s u l t s show t h a t 8090 is c a p a b l e of b e i n g welded w i t h l i t t l e r i s k o f c r a c k i n g , p r o v i d e d t h a t t h e r e s t r a i n t p r e s e n t i s n o t t o o high. By analogy w i t h t h e A1-CU a l l o y s , i t would be expected t h a t c r a c k i n g would be reduced with lower r e s i d u a l i r o n c o n t e n t s ( 1 2 ) . V a r e s t r a i n t t e s t i n g of high p u r i t y b i n a r y A1-Li a l l o y s by Cross et a 1 ( 1 3 ) showed t h a t t h e maximum s u s c e p t i b i l i t y t o h o t t e a r i n g o c c u r r e d a t a l i t h i u m c o n t e n t o f 2.6wt%. Even t h i s maximum l e v e l o f h o t t e a r i n g was l e s s t h a n t h a t f o r t h e weldable A1-Mg-Mn a l l o y 5083. They assumed t h a t t h e high r e s i s t a n c e t o h o t t e a r i n g o f t h e b i n a r y A 1 - L i a l l o y s was due t o t h e absence o f low-melting e u t e c t i c s i n t h e system. T h i s may n o t be s o t r u e f o r commercial t e r n a r y and q u a r t e r n a r y A1-Li a l l o y s .
T e n s i l e t e s t i n g ( T a b l e 3 ) shows t h a t welds u s i n g A1-5Mg f i l l e r s a r e l e s s s t r o n g than t h o s e u s i n g p a r e n t p l a t e f i l l e r s , a l t h o u g h t h e f r a c t u r e ( F i g 4 c ) i s much more d u c t i l e t h a n t h a t o f t h e weld with t h e 8090 f i l l e r ( F i g 4 a ) . T h i s confirms t h e r e s u l t s o f S k i l l i n g b e r g ( 2 ) and would i n d i c a t e a g r e a t e r weld m e t a l toughness f o r t h e Al-5Mg f i l l e r , compared t o 8090 f i l l e r . When comparing s p e c i f i c s t r e n g t h s ( T a b l e 5 ) with commercially a v a i l a b l e weldable aluminium a l l o y s , t h e formula ( 1 4 ) , r e l a t i n g d e n s i t y and chemical composition:
where t h e chemical symbols r e p r e s e n t weight %, h a s been used.
T a b l e 5 s u g g e s t s t h a t t h e s p e c i f i c s t r e n g t h s a v a i l a b l e u s i n g 8090 with a f i l l e r t h a t g i v e s a t r a n s g r a n u l a r f r a c t u r e a r e n o t up t o t h e l e v e l o f t h e h i g h e r s t r e n g t h commercially a v a i l a b l e A1-Zn-Mg a l l o y s . To a c h i e v e a s p e c i f i c t e n s i l e s t r e n g t h comparable t o t h a t a v a i l a b l e i n 7017-T6, n a t u r a l l y aged f o r 30 days, it is n e c e s s a r y t o u s e a n 8090 f i l l e r which g i v e s low d u c t i l i t y and a b r i t t l e i n t e r g r a n u l a r f r a c t u r e . S p e c i f i c p r o o f s t r e n g t h o f t h e welds with 8090 f i l l e r s a r e s u b s t a n t i a l l y h i g h e r t h a n t h o s e o f 7017-T6. Comparison with S k i l l i n g b e r g ( 2 ) shows t h a t MIG welds o f 8090 w i t h A 1 and A1-5Mg f i l l e r s a l s o have t r a n s g r a n u l a r d u c t i l e f r a c t u r e s , w h i l e MIG welds w i t h 2319 f i l l e r and T I G welds with 8090 f i l l e r e x h i b i t i n t e r g r a n u l a r f r a c t u r e , low d u c t i l i t y and low impact toughness. The Al-Li-Cu 2090 a l l o y shows d u c t i l e f r a c t u r e ( 2 ) whether welded w i t h A1-5Mg o r 2090 f i l l e r s , a l t h o u g h t h e s t r e n g t h s a r e lower t h a n c o r r e s p o n d i n g v a l u e s f o r t h e 8090 a l l o y .
Post-weld h e a t t r e a t m e n t w i l l t e n d t o i n c r e a s e t h e s t r e n g t h o f weldments, a s s o l u t e e l e m e n t s a r e brought back i n t o s o l u t i o n and p r e c i p i t a t e d o u t d u r i n g ageing.
I n t h e c a s e where an A1-5Mg f i l l e r was used, t h e l i t h i u m c o n t e n t o f t h e weld metal was 0.69% compared with 2.41% i n t h e p a r e n t p l a t e , showing t h e e f f e c t s o f d i l u t i o n and l i t h i u m l o s s , and t h e p r o o f s t r e n g t h o f t h e weldment was only r a i s e d from
176 MPa t o 245 MPa. When a n 8090 f i l l e r was used, t h e l i t h i u m c o n t e n t o f t h e weld m e t a l was 2.34%, i n d i c a t i n g l i t t l e l i t h i u m l o s s d u r i n g welding. T h i s s u g g e s t s t h a t t h e r e l a t i v e l y low proof s t r e n g t h o f t h e weld (315 M P ~ ) is due t o t h e g r a i n boundary s t r u c t u r e and a s - c a s t g r a i n s t r u c t u r e , r a t h e r t h a n a l o s s i n s t r e n g t h e n i n g 6, (A1,Li) w i t h i n t h e g r a i n s .
The i n c i d e n c e o f i n t e r g r a n u l a r d u c t i l e - f r a c t u r e i n p r e c i p i t a t i o n - h a r d e n e d aluminium a l l o y s has been reviewed by Vasudevan and Ooherty (15). The p r i n c i p a l p r o c e s s involved a p p e a r s t o be t h e growth o f microvoids a t g r a i n boundary p r e c i p i t a t e s . S t r a i n l o c a l i s a t i o n i n t h e s o f t p r e c i p i t a t e - f r e e zones a t t h e g r a i n boundary and heterogeneous s l i p producing g r a i n boundary stress c o n c e n t r a t i o n s a t t h e e n d s o f s l i p bands a r e b e l i e v e d t o p l a y o n l y s u p p o r t i n g r o l e s . The l a c k o f d u c t i l i t y shown i n t h e EB welds ( F i g 4 b ) , i n s p i t e o f t h e much f i n e r g r a i n s i z e , i n d i c a t e s t h a t t h e i n t e r g r a n u l a r f r a c t u r e is a s s o c i a t e d w i t h t h e g r a i n boundary s t r u c t u r e , r a t h e r t h a n t h e l e n g t h o f s l i p bands w i t h i n t h e g r a i n . I t is a l s o i n t e r e s t i n g t h a t t h e r e f i n e m e n t o f g r a i n s i z e produced by adding zirconium t o a n A1-5Mg f i l l e r ( T a b l e 3) d o e s n o t s i g n i f i c a n t l y i n c r e a s e t e n s i l e s t r e n g t h o r d u c t i l i t y .
Conclusions
( a ) S p e c i f i c t e n s i l e s t r e n g t h s s i m i l a r t o t h e s t r o n g e s t commercially a v a i l a b l e weldable A1-Zn-Mg a l l o y s , and h i g h e r s p e c i f i c proof s t r e n g t h s , a r e a t t a i n a b l e with TIG weldments o f 8090 a l l o y , u s i n g a n 8090 f i l l e r . T e n s i l e d u c t i l i t y i s low w i t h an i n t e r g r a n u l a r f r a c t u r e .
( b ) Welds made with an A1-5Mg f i l l e r e x h i b i t t r a n s g r a n u l a r d u c t i l e f r a c t u r e , b u t t h e s p e c i f i c t e n s i l e s t r e n g t h is o n l y 75% o f t h a t o f t h e s t r o n g e s t c u r r e n t a l l o y s , w i t h t h e c o r r e s p o n d i n g s p e c i f i c p r o o f s t r e n g t h 90% o f c u r r e n t a l l o y s . ( c ) Post-weld h e a t t r e a t m e n t i n c r e a s e s t h e s t r e n g t h o f 8090 weldments.
( d ) Weld zone p o r o s i t y is a s s o c i a t e d with a d s o r p t i o n o f water vapour by t h e l i t h i u m - c o n t a i n i n g o x i d e , formed d u r i n g h o t r o l l i n g o r s o l u t i o n t r e a t m e n t . I t can be minimised by machining o f f t h e s u r f a c e l a y e r s p r i o r t o welding.
( e ) The tendency t o h o t c r a c k i n g , a s measured i n tests w i t h o u t t h e u s e o f f i l l e r r o d s , is comparable t o t h a t o f 2014-T6. T h i s i n d i c a t e s t h a t t h e a l l o y is c a p a b l e o f b e i n g welded w i t h o u t c r a c k i n g p r o v i d e d t h a t t h e r m a l g r a d i e n t s a r e n o t t o o s e v e r e and t h a t t h e r e is n o t e x c e s s i v e r e s t r a i n t p r e s e n t .
Acknowledgements
F i n a n c i a l s u p p o r t f o r t h i s work was q i v e n by t h e M i n i s t r y o f Defence (Procurement E x e c u t i v e ) . D i s c u s s i o n s w i t h Mr B Evans and Dr C J P e e l (RAE Farnborough) have been v e r y h e l p f u l . We wish t o thank A W L Edwards and S Moynihan f o r t e c h n i c a l a s s i s t a n c e , and P r o f e s s o r R L Apps ( C r a n f i e l d I n s t i t u t e o f Technology) f o r t h e p r o v i s i o n o f a d d i t i o n a l l a b o r a t o r y f a c i l i t i e s .
C3-298 JOURNAL DE PHYSIQUE
References
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TABLE 1 - EFFECT OF SCRFAE PREPARATION ON WELD METAL POROSITY
-
TABLE 2 - EFFECT OF HEAT TREATMENT ON WELD METAL POROSITY Preparation
Unmachined
Machined > 96h before welding Machined < 48h before As 5,6 but chemically pickled
Heat Treatment porosity(% weld metal area)
Machine, solution t r e a t , weld 20h a f t e r solution treatment
AS I , but weld immediately a f t e r 0.5
solution treatment
porosity(% weld metal area)
11.0 1.8 0.8 1.3
TABLE 3 - TENSILE BEHAVIOLR OF AS-WELDED SPECIMENS
TABLE 4 - EFFECT OF POST-WELD HEAT TREATMENT ON TENSILE EHAVIOUR OF 8090-T6
F i l l e r
A1 Al-5Si A1-5Mg A1-5Mg (+Zr) 8090
8090-T6 unwelded
TASLE 5 - SPECIFIC STRENGTH - COMPARISON WITH OTHER WELDABLE A L l M I N I l M ALLOYS T e n s i l e S t r e n g t h
(MPa)
165 205 228 235 31 J
5W
1
( a ) a f t e r 30 days n a t u r a l ageing 0.2% Proof Strength (MPa)
137 165 176 183 285
429
I I
E l o n g a t i o n (%I
5 3 4 4 2
6
F i l l e r
A1-5Mg
A l l o y
7017-T6 (Al-5Mg f i l l e r ) ( a )
2219-T851 (2319 f i l l e r )
8090-T6 ( A l - 5 ~ g f i l l e r )
8090-T6 (8090 f i l l e r I
T e n s i l e S t r e n g t h (MPa)
235 302
311 367 Heat Treatment
As-welded AS-welded + -T6
T e n s i l e Strength
( M P ~ )
360
300
235
311 8090 As-welded
I
As-welded + -T60.2% Proof Strength
(MPa)
220
185
183
285
0.2% Proof Strength (MPa)
183 245
285 315
Density (Mg m-l)
2.78
2.87
2.53
2.53
T e n s i l e Density
122
Elongation (%)
4 4
2 4
Proof Density
79
Elongation ( % )
8
5
4
2
I
lo5 j 65
I
93 72
i
123 113
