Wrought Aluminum-Nickel Alloys for High Strength-High Conductivity Applications P. K. ROHATGI AND K. V. PRABHAKAR A l u m i n u m - N i c k e l a l l o y s r a n g i n g f r o m 0.06 p c t to 6.1 p c t (by wt) Ni h a v e b e e n d e v e l o p e d for high s t r e n g t h - h i g h c o n d u c t i v i t y a p p l i c a t i o n s . T h e s e a l l o y s w e r e p r o d u c e d by s o l i d i f i c a t i o n in a p e r m a n e n t m o l d followed by h o m o g e n i z a t i o n , hot e x t r u s i o n o r hot r o l l i n g and c o l d d r a w ing to w i r e f o r m . This s e q u e n c e of f a b r i c a t i o n a) l e d tn the p r n d u c t i o n of fine f i b r o u s d i s p e r s o i d s of NiA1 s a s p a r t of the A1-NiAl 3 e u t e c t i c d u r i n g the i n i t i a l c a s t i n g o p e r a t i o n , b) p e r m i t t e d the r e t e n t i o n of fine f i b r o u s d i s p e r s i o d s of NiAl 3 p r o d u c e d d u r i n g c a s t i n g without a n y s i g n i f i c a n t c o a r s e n i n g d u r i n g p r o c e s s i n g and c) l e d to u n i f o r m d i s p e r s i o n and g e n e r a l a l i g n m e n t of t h e s e f i b r o u s d i s p e r s o i d s a l o n g a given d i r e c t i o n in the p r o d u c t without any m e a s u r a b l e f i b e r - m a t r i x s e p a r a t i o n , e x t e n s i v e f i b e r - f r a g m e n t a t i o n o r c r a c k p r o d u c t i o n in the m a t r i x . T h e s e a l l o y s can be p r o c e s s e d to w i r e f o r m a s e a s i l y a s a l u m i n u m and when p r o c e s s e d by the above s e q u e n c e , p o s s e s s v e r y a t t r a c t i v e c o m b i n a t i o n of high s t r e n g t h high e l e c t r i c a l c o n d u c t i v i t y . T e n s i l e s t r e n g t h s r a n g e f r o m 173 N / m m 2 (at 0.6 p c t Ni) to 241 N / m m 2 (at 6.1 p c t Ni) in c o m b i n a t i o n with c o r r e s p o n d i n g c o n d u c t i v i t y v a l u e s b e t w e e n 62 p c t IACS and 55.5 p c t IACS. The w i r e s a l s o p o s s e s s a t t r a c t i v e y i e l d s t r e n g t h ; f o r i n s t a n c e , the 0.2 p c t o f f - s e t s t r e n g t h of A l - 6 . 1 p c t Ni w i r e is 213 N / r a m 2. U s i n g s i m p l e c o m p o s i t e r u l e s , the e s t i m a t e d s t r e n g t h and the c o n d u c t i v i t y of NiA13 f i b e r s w e r e found to be 1380 N / m m 2 and 18 p c t IACS r e s p e c t i v e l y , in t h e s e w i r e s .

IN

r e c e n t y e a r s t h e r e h a s b e e n a r a p i d i n c r e a s e in the use of a l u m i n u m a l l o y s a s s t r a n d e d c o n d u c t o r s f o r t r a n s m i s s i o n and d i s t r i b u t i o n of e l e c t r i c a l e n e r g y , p a r t l y b e c a u s e of the i n c r e a s i n g s h o r t a g e of c o p p e r and p a r t l y b e c a u s e of the r a p i d l y e x p a n d i n g e n e r g y m a r k e t . A l u m i n u m of c o n t r o l l e d p u r i t y (EC G r a d e ) h a s a m i n i m u m c o n d u c t i v i t y of about 61.0 p c t IACS and is n e x t only to s i l v e r (108 pct) and c o p p e r (100 pct). EC g r a d e a l u m i n u m h a s only m o d e r a t e m e c h a n i c a l s t r e n g t h even in h a r d d r a w n condition, n e c e s s i t a t i n g a c l o s e s p a c i n g of p o l e s and p y l o n s to l i m i t the c a t e n a r y s e l f s u p p o r t . EC g r a d e a l u m i n u m h a s a m i n i m u m of 99.45 p c t a l u m i n u m with c o n t r o l l e d i m p u r i t i e s (Table II). To i m p a r t m e c h a n i c a l s t r e n g t h to a l u m i n u m c o n d u c t o r s , w i r e s can be s t r a n d e d on a s t e e l c o r e w i r e (ACSR) o r a l l o y i n g can be r e s o r t e d to. While the f o r m e r r e d u c e s the c o n d u c t i v i t y f o r the t o t a l v o l u m e , the l a t t e r r e d u c e s c o n d u c t i v i t y b e c a u s e of a l l o y i n g . L e n y r e and Roche 1 have d e v e l o p e d an a l u m i n u m m a g n e s i u m - s i l i c o n a l l o y for c o n d u c t o r a p p l i c a t i o n , 6201-T81, to r e p l a c e ACSR f o r high v o l t a g e t r a n s m i s sion. This h a s b e t t e r t e n s i l e s t r e n g t h at 1 p e t e l o n g a tion than ACSR and the e l e c t r i c a l c o n d u c t i v i t y is e q u i v a l e n t to o r b e t t e r than that of ACSR. Dean 2 h a s r e p o r t e d an i n c r e a s e in the s t r e n g t h of a l u m i n u m b y a d d i t i o n of up to 2 p c t Ni. K u m a r 3 h a s p r o p o s e d a new p o w e r t r a n s mission conductor alloy, PM-2, developed by making a b i n a r y s o l u t e a d d i t i o n of a n u m b e r of e l e m e n t s to a l u m i n u m . This a l l o y is r e p o r t e d to p o s s e s s i m p r o v e d e l e c t r i c a l c o n d u c t i v i t y (61.5 p c t IACS) and h i g h e r s t r e n g t h (184 N / m m 2) a s c o m p a r e d to c o n v e n t i o n a l a l u m i n u m c o n d u c t o r s . N i c k e l is r e p o r t e d 3 to be i n n o c P. K. ROHATGI and K. V. PRABHAKAR are with Department of Mechanical Engineering, Indian Institute of Science, Bangalore 560012, India. Manuscript submitted May 24, 1974. METALLURGICAL TRANSACTIONS A

uous on the e l e c t r i c a l c o n d u c t i v i t y of a l u m i n u m and h e n c e an a t t e m p t w a s m a d e in t h i s i n v e s t i g a t i o n to s t u d y the p o s s i b i l i t y of d e v e l o p i n g high s t r e n g t h A l - N i a l l o y s f o r p o s s i b l e c o n d u c t o r a p p l i c a t i o n s . The o b j e c t was to s t u d y the s t r e n g t h - c o n d u c t i v i t y c o m b i n a t i o n s of A1-0 to 6.1 p c t Ni a l l o y s , c a s t in p e r m a n e n t m o l d s and d r a w n to w i r e f o r m . A l u m i n u m - N i c k e l s y s t e m e x h i b i t s an e u t e c t i c r e a c t i o n at 5.7 p c t (Fig. 1) and the s o l u b i l i t y

~ L I Q U I D + Ni2 At3

900

LIQUID

~

,

~

e0Q ~.O.'~y

700

LIQUID+ NiAI.3

6~o'c ( 5.7 % )

-~600 LU g n. 500

z

~" 40~ O( ALUMINIUM + NiAI.3

+

300 z

700 100

0

0

10

•

20 30 /d? NICKEL WEIGHT PERCENT Fig. 1 - - A I - N i E q u i l i b r i u m diagram. 4 VOLUME 6A, MAY 1975

50

1003

of Nickel in a l u m i n u m is l i m i t e d to 0.05 pct. 4 The v e r y l i m i t e d s o l u b i l i t y does not c o n t r i b u t e s i g n i f i c a n t l y to m a t r i x s t r e n g t h e n i n g . With a d d i t i o n s , beyond the s o l u b i l i t y l i m i t , n i c k e l a p p e a r s as i n t e r d e n d r i t i c a A1-NiAls e u t e c t i c (Fig. 2). M i c r o s c o p i c e x a m i n a t i o n at h i g h e r m a g n i f i c a t i o n s shows the f i b r o u s d i s p e r s o i d s of NiAI 3 in the i n t e r d e n d r i t i c e u t e c t i c . The v o l u m e p e r c e n t of NiA13 p r e s e n t in the s t r u c t u r e i n c r e a s e s with n i c k e l c o n t e n t up to the e u t e c t i c l i m i t . In the h y p e r e u t e c t i c alloys n i c k e l a p p e a r s as l a r g e p r i m a r y NiA13 p a r t i cles which a r e d e t r i m e n t a l to the d u c t i l i t y of t h e s e a l l o y s . Also, additions of n i c k e l up to 1.5 pct a r e r e p o r t e d s to i n c r e a s e the s t r e n g t h of pure a l u m i n u m with s l i g h t d e c r e a s e in conductivity. A1-6.1 pct Ni a l l o y c a s t in p e r m a n e n t mold shows f i b r o u s d i s p e r s o i d s of AlsNi a r r a n g e d in c o l o n i e s with o - a l u m i n u m m a t r i x (Fig. 3). Under the r a p i d f r e e z i n g conditions in the p e r m a n e n t mold, Al-6.1 pct Ni alloy s o l i d i f i e s with an all e u t e c t i c s t r u c t u r e . M i c r o s c o p i c e x a m i n a t i o n at higher m a g n i f i c a t i o n s shows the f i b r o u s d i s p e r s o i d s d i v e r g i n g t o w a r d s colony b o u n d a r i e s . It was c o n c e i v e d that if these f i b r o u s d i s p e r s o i d s of NiA13 could be a l i g n e d in the m a t r i x of worked a l u m i n u m , they could s i g n i f i c a n t l y s t r e n g t h e n the a l u m i n u m m a t r i x without c o n s i d e r a b l y d e c r e a s i n g the e l e c t r i c a l conductivity, l e a d i n g to the d e v e l o p m e n t of high s t r e n g t h - h i g h e l e c t r i c a l c o n d u c t i v i t y a l l o y s . H e r t z b e r g 6 has r e p o r t e d that the t e n s i l e s t r e n g t h of such an a s - c a s t A1-Ni e u t e c t i c (A1-5.7 pct Ni) c o n t a i n i n g about 10 vol pct of r a n d o m l y o r i e n t e d NiAl~ f i b e r s is about 93.8 N / m m 2 and the t e n s i l e e l o n g a t i o n 15 to 20 pct. However, by u n i d i r e c t i o n a l l y s o l i d i f y i n g AI-A13Ni eutectic, a m i c r o s t r u c t u r e c o n t a i n i n g aligned r o d s of NiA13 d i s p e r s e d in the m a t r i x of a - a l u m i n u m can be obtained. U n i d i r e c t i o n a l s o l i d i f i c a t i o n l e a d s to a m a r k e d i m p r o v e m e n t in t e n s i l e s t r e n g t h to as high v a l u e s as 300 N / m m z and a total e l o n g a t i o n of about 2 pct. The s t r e n g t h e n i n g effect is a t t r i b u t e d to p e r f e c t l y aligned, long f i b e r s of NiAl 3 d i s p e r s e d in the s i n g l e c r y s t a l m a t r i x of a - a l u m i n u m . However, u n i d i r e c t i o n a l s o l i d i f i cation is a v e r y e x p e n s i v e t e c h n i q u e for p r o d u c i n g s m a l l a m o u n t s of m a t e r i a l e s p e c i a l l y in w i r e f o r m s for conductor a p p l i c a t i o n s . Hence in this i n v e s t i g a t i o n we a t t e m p t e d to p r o d u c e u n i f o r m d i s p e r s i o n and a l i g n m e n t of s h o r t NiA13 f i b e r s p r o d u c e d by c o n v e n t i o n a l c a s t i n g t e c h n i q u e s followed by m e c h a n i c a l p r o c e s s i n g . By this m e a n s our a i m was to develop wrought a l u m i n u m - n i c k e l a l l o y s e s p e c i a l l y in w i r e f o r m for high strength-high electrical conductivity applications.

cold work in the f i n i s h e d w i r e s (designed as H-19) was 95.6 pct. L i m i t e d e x p e r i m e n t s were also done where the 37 m m d i a m r o d s w e r e hot r o l l e d to 12.7 m m

(a)

E X P E R I M E N T A L PROCEDURE P u r e a l u m i n u m (99.9 pct) and A1-20 pct Ni m a s t e r alloy w e r e used to p r e p a r e the following a l l o y s : Al0.6 pct Ni, A I - I . 1 pct Ni, Al-3.2 pct Ni, A1-5.0 pct Ni, Al-6.1 pct Ni. The d e t a i l e d c h e m i c a l c o m p o s i t i o n of the a l l o y s p r e p a r e d is l i s t e d in Table I. 5 Kg h e a t s of the alloys w e r e b r o u g h t to a t e m p e r a t u r e of 730~ d e g a s s e d with an 80 pct N i t r o g e n - 2 0 pct c h l o r i n e m i x t u r e for 15 m i n and c a s t into 200 m m long and 41 m m d i a m r o d s in g r a p h i t e m o l d s . The r o d s w e r e m a c h i n e d to 37 m m d i a m and 152.5 m m long e x t r u s i o n b i l l e t s . The b i l l e t s w e r e soaked for one h at 430~ and e x t r u d e d to 8.5 m m d i a m r o d s . The e x t r u d e d r o d s w e r e then d r a w n to 1.78 m m d i a m w i r e s u s i n g c a r b o - a l l o y and d i a m o n d dies without a n y i n t e r m e d i a t e a n n e a l s . The a m o u n t of 1004-VOLUME 6A, MAY 1975

(b) Fig. 2 - A s - c a s t s t r u e t u r e of 3.8 pet Ni alloys showing ran domly oriented fibrous dispersoids of NiAI3 within the interdendritic network of a aluminum-NiA13 eutectic near the wall of permanent mold, (a) Magnification 97 times, (b) Magnification 1940 times.

METALLURGICALTRANSACTIONS A

square after 2 h at 430~ cold rolled to 6.85 mm square section, further cold rolled to 3.425 mm in 8 passes, swaged and wire drawn to 0.43 mm diam wire form. However, all the property data reported in this

Table I. Chemical Composition of Aluminum-Nickel* Conductor Wires

Actual Composition, Wt Pct

Nominal Composition

Ni

Fe

Si

Ti

Cr

Zr

AI Al-0.6 Ni Al-l.1 Ni A1-3.2 Ni A1-5.0 Ni Al-6.1 Ni

0.0 0.6 1.12 3.20 4.98 6.1

0.01 0.02 0.05 0.01 0.03 0.01

0.01 0.03 0.03 0.03 0.03 0.01

0.01 0.01 0.01 0.01 0.01 0.01

0.01 0.01 0.03 0.01 0.01 0.01

0.01 0.01 0.01 0.01 0.01 0.01

0.01 0.01 0.01 0.01 0.01 0.01

Note: Cu, Mg, Mn and B in all alloys were individually <0.005 pct. Ti, Cr, V in all alloys were individually <0.01 pct. *The alloys were made from commercially pure aluminum and AI-20 pct Ni master alloy of following compositions: Pure aluminum (99.9 pct): 0.004Cu- 0.002Fe- 0.01 Si- 0.004Mg- 0.00Ti0.002Mn- 0.01 Cr- 0.04Zn- 0.002Ga A1-20 Ni Alloy: 18.9NP 0.015Cu- 0.13Fe- 0.21Si- <0.01 Mg- 0.02Mn0.035Cr- 0.01Zn

paper is on wires where the cast rods were extruded. Measurements of conductivity were made on 254 mm long wires using a standard wheatstone bridge technique in accordance with ASTM standards. Measurements of tensile properties were made on 458.0 mm long wire in 254.0 mm gage length in accordance with ASTM standards. Longitudinal and transverse microstructural observations were made of the wire after the usual method of metallographic polishing and etching with 0.5 pct HF.

RESULTS A N D DISCUSSION (a)

(b) Fig. 3 - A s - c a s t s t r u c t u r e of A1-6.1 p c t Ni a l l o y n e a r t h e w a l l of p e r m a n e n t m o l d , (a) M a g n i f i c a t i o n 97 t i m e s , (b) M a g n i f i c a t i o n 1940 t i m e s . METALLURGICAL TRANSACTIONS A

In Figs. 2 and 3 the micro-structures of as cast A13.8 pct Ni and Al-6.1 pct Ni alloys are shown where fine and randomly oriented NiAls fibers either as interdendritic network or dispersed in the colonies are present. Figs. 4 and 5 show the transverse and longitudinal sections of AI-3.2 pct Ni and A1-6.1 pct Ni alloy after processing to wire form by the extrusion sequence described in the previous section. The longitudinal sections show short fibrous dispersoids of NiAls uniformly dispersed, and generally aligned parallel to the length of the wire; the transverse sections show a uniform distribution of the cross sections through the fibers. The uniform distribution and general alignment of the fibrous dispersoids of NiA13took place without any significant fiber-matrix separation, fiber coarsening, and fiber fragmentation or cracking. The microstructure shows an increase in the volume percent of NiAI3 phase dispersed in the matrix with an increase in the nickel content, as expected. As determined by the photographs, the smaller dimension of the fibrous dispersoids of NiA1s in the wires is of the order of 0.25 vm and their longer dimension is of the order of 2 to 3 vm. As a comparison the diam of NiAIa fibers in unidirectionally solidified eutectic (growth rate 8.6 cm per h) are of the order of 0.5gm; of course the length of the NiAIs fibers in unidirectionally solidified eutectic is of the order of 5000~m. In addition, the distribution and alignment of fibrous dispersoids of NiAls in processed wires (of the A1-Ni eutectic of the present study) is considerably more nonuniform and imperfect compared to the unidirectionally solidified ones. Fig. 6 shows the strength-conductivity combinations in the wires of various alloys investigated during this VOLUME 6A, MAY 1 9 7 5 - 1 0 0 5

(a)

(a)

(b) F i g . 4 - - ( a ) L o n g i t u d i n a l a n d (b) T r a n s v e r s e p e t N i w i r e , M a g n i f i c a t i o n 810 t i m e s .

(h) s e c t i o n of A 1 - 3 . 2

F i g . 5 - - ( a ) L o n g i t u d i n a l a n d (b) T r a n s v e r s e pct Ni wire, Magnification 840 times.

s e c t i o n of A I - 6 . 1

Table II. Tensile Properties and Conductivity Values

Nominal Composition/Designation AI AI-0.6 Ni AI-I.1 Ni A1-3.2 Ni AI-5.0 Ni A1-6.! Ni EC* 5005t 6201 ~ AI-AI3Ni Eutectic 6 A1-AI3Ni Eutectic 6

Condition H- 19 H- 19 H-19 H- 19 H-19 H-19 H-19 H-19 H- 19 Conventionally cast Unidirectionally solidified

0.2 Pct Offset Strength (N/mm 2) 142.9 154.5 171.5 191.5 213.5 110.0 248.0 -

Tensile Strength (N/mm 2) 146.5 173.0 186.5 218.0 246.0 193.0 268.5 365.0 93.6 300.0

Elongation, Pct 0.8 0.7 0.6 0.5 1.4 1.5 3.0 15.20 2.0

Conductivity, Pct IACS 60.30 62.01 61.50 59.20 56.60 55.50 61.00 53.50 52.50 -

99.45 pct A1 with controlled impurities. *EC: t 5005:AI-0.8 pct Mg with controlled impurities. 26201:A1-0.7 pct Mg-0.7 pct Si with controlled impurities. (Taken from Aluminum, Vol. II, American Society for Metals, Ohio, 1967).

1006

V O L U M E 6A, MAY 1975

METALLURGICAL TRANSACTIONSA

Table III. Fracture Strength of NiAI3 as Determined in the Present Investigation

62

(Assuming role of mixture is applicable, calculation of fracture strength of NiAI3 fibers) 61

Ocomp = Ofiber l'rf+ Omatrix Vm

Ni, Pet

or, N/mm 2

0.6 1.1 3.2 6.1

1331 1696 1293 1062

6O

s9 )-.

600 9 9

ALLOYS DEVELOPED COMMERCJAL ALLOYS

zO58 8

50(

57

| ; 400

56

9 6201 ( T-811

z~

~, "4 300

soos

9

'55

(H-lg)

9 A t - 6.1Ni (H-19)

i

9 A!.-3.2 Ni { H-191

IO0 50

I 52

I 5&

I I I 56 58 60 CONDUCTIVITY (% IACS)

I 62

6s

Fig. 6--Strength-conductivity combinations of alloys developed in the present investigation and commercial conductor wire alloys. study, and t h o s e of c o m m e r c i a l c o n d u c t o r w i r e a l l o y s . It c l e a r l y d e m o n s t r a t e s the a t t r a c t i v e c o m b i n a t i o n s in the a l l o y s of p r e s e n t s t u d y . A1-0.6 p c t and A I - I . 1 p c t Ni a l l o y s of the p r e s e n t s t u d y have h i g h e r s t r e n g t h s a s w e l l a s h i g h e r c o n d u c t i v i t i e s c o m p a r e d to EC g r a d e (H-16) a l u m i n u m . A1-3.2 p c t Ni and A1-6.1 p c t Ni a l l o y s have c o n s i d e r a b l y h i g h e r c o n d u c t i v i t i e s at about the s a m e s t r e n g t h l e v e l c o m p a r e d to c o m m e r c i a l a l l o y 5005 (H-19). C o m m e r c i a l a l l o y 6201 h a s h i g h e r s t r e n g t h c o m p a r e d to the a l l o y s of t h i s i n v e s t i g a t i o n but i t s c o n d u c t i v i t y i s v e r y much l o w e r . T a b l e 1I g i v e s the t e n s i l e p r o p e r t i e s and c o n d u c t i v i t y v a l u e s of A1-Ni c o n d u c t o r w i r e s u s e d in t h i s i n v e s t i g a t i o n , c o m m e r c i a l a l u m i n u m c o n d u c t o r w i r e s and the c o n v e n t i o n a l l y and u n i d i r e c t i o n a l l y s o l i d i f i e d A1-Ni e u t e c t i c a l l o y s . Table II and Fig. 7 show t h a t a d d i t i o n of 0.6 p c t n i c k e l i n c r e a s e s the c o n d u c t i v i t y of p u r e a l u m i n u m , p r e s u m a b l y b y s c a v e n g i n g the i m p u r i t i e s f r o m the m a t r i x . Any d e c r e a s e in the c o n d u c t i v i t y due to f o r m a t i o n of c o m pounds with s c a v e n g e d i m p u r i t i e s is r e l a t i v e l y low. A d d i t i o n s of n i c k e l b e t w e e n 0.6 and 6.1 p c t c a u s e a l i n e a r d e c r e a s e in c o n d u c t i v i t y . This d e c r e a s e is a p p a r e n t l y due to the i n c r e a s e in the v o l u m e of NiA13 p h a s e which h a s a l o w e r c o n d u c t i v i t y . P u r e a l u m i n u m h a s an a s c a s t s t r e n g t h of 69 N / m m 2 which can be i n c r e a s e d to 146.5 N / m m 2 b y w o r k i n g , r e f l e c t i n g an i n c r e a s e of n e a r l y 110 pct, w h e r e a s the s t r e n g t h of a s c a s t A1-Ni e u t e c t i c (94 N / m m 2) can be METALLURGICAL TRANSACTIONSA

I

1

I

I

I

2 3 & WEIGHT PERCENT NICKEL

F i g . 7 - - V a r i a t i o n of c o n d u c t i v i t y of a l u m i n u m nickel content in H-19 condition,

9 AL-I.1 Ni 9 AL-0.6 Ni 9 (H-19) At (H-19) 9 EC (H-16)

"~00

I

I

5;

wires

with

i n c r e a s e d b y m o r e than 160 p c t b y m e c h a n i c a l p r o c e s s ing (246.5 N / m m 2) u s e d in t h i s s t u d y . T a b l e II a l s o shows t h a t the s a m e v o l u m e p e r c e n t a g e of NiA13 ( a p p r o x . 10 p c t at e u t e c t i c c o m p o s i t i o n ) l e a d s to a much g r e a t e r i n c r e a s e in s t r e n g t h in the w r o u g h t a l l o y s c o m p a r e d to t h a t o b s e r v e d in a s c a s t a l l o y s . In the a s c a s t a l l o y s the s t r e n g t h is r a i s e d f r o m 69 N / m m 2 to 94 N / m m 2 w h e r e a s in the p r o c e s s e d a l l o y the s t r e n g t h is r a i s e d f r o m 146.5 N / m m e to 246.5 N / m m 2. A p p l i c a t i o n of a s i m p l e r u l e of m i x t u r e s to the s t r e n g t h p r o p e r t i e s e x h i b i t e d b y the v a r i o u s p r o c e s s e d A1-Ni a l l o y s show t h a t d i s c o n t i n u o u s NiA13 f i b e r s c o n t r i b u t e d s t r e n g t h s e q u i v a l e n t to 1062 N / m m z to 1696 N / m m 2 (Table III). As e x p e c t e d t h e s e s t r e n g t h s a r e l o w e r than the s t r e n g t h s c o n t r i b u t i o n s of c o n t i n u o u s f i b e r s p r o d u c e d b y u n i d i r e c t i o n a l s o l i d i f i c a t i o n which is of the o r d e r of 2070 N / m m 2 . 7 H o w e v e r , the m o s t r e m a r k a b l e i m p r o v e m e n t is o b s e r v e d in the y i e l d s t r e s s of the m e c h a n i c a l l y p r o c e s s e d c o n d u c t o r w i r e s of the p r e s e n t s t u d y . F i g . 8 shows the t e n s i l e d e f o r m a t i o n b e h a v i o r of p r o c e s s e d w i r e s , u n i d i r e c t i o n a l l y s o l i d i f i e d 6 and a s - c a s t 6 A1-A13Ni e u t e c t i c a l l o y s . It m a y be s e e n t h a t while u n i d i r e c t i o n a l s o l i d i f i c a t i o n b r i n g s about a c o n s i d e r a b l e i m p r o v e m e n t in t e n s i l e s t r e n g t h (300 N / m m 2) o v e r that of a s c a s t A1-A13Ni e u t e c t i c (93.6 N / m m 2 ) , the y i e l d s t r e n g t h c o n t i n u e s to be low at 35 N / m m 2. Howe v e r , in the p r o c e s s e d f o r m , y i e l d s t r e n g t h i s of the o r d e r of 213 N / m m 2 (Table H), even though the t e n s i l e s t r e n g t h is s l i g h t l y l e s s c o m p a r e d to the u n i d i r e c t i o n a l l y s o l i d i f i e d e u t e c t i c a l l o y . This i m p r o v e d y i e l d s t r e n g t h could l e a d to c o n s i d e r a b l e m a t e r i a l s a v i n g s in o v e r h e a d c o n d u c t o r d e s i g n . H o w e v e r , the p e r c e n t a g e e l o n g a t i o n s e x h i b i t e d b y the w i r e s a m p l e s of the a l l o y s of p r e s e n t s t u d y a r e l o w e r than the o t h e r c o m m e r c i a l alloys. The c o n d u c t i v i t y of c o m p o s i t e s w h e r e one p h a s e is V O L U M E 6A, MAY 1 9 7 5 - 1 0 0 7

Applying the above e q u a t i o n to the c o n d u c t i v i t y v a l u e e x h i b i t e d by A1-0.6 p ct Ni alloy, i n d i c a t e s that the c o n d u c t i v i t y of NiAl 3 f i b e r is a p p r o x i m a t e l y 18 pct IACS.

350

30(3

C ONC LUS IONS

~E 200 I= z w

AS 10C

01 r 0

I 1

I 2

l 3

I I 4 5 STRAIN PERCENT

I 6

I 7

Fig. 8--Tensile deformation behavior of eutectic A1 Ni~tl loys--proeessed, unklirectionally solidifiedfi and as castfi d i s p e r s e d in the continuous m a t r i x of the o t h e r is g i v e n by:

1) A l u m i n u m - N i c k e l a l l o y s r a n g i n g f r o m 0 to 6.1 pct Ni (by weight), s o l i d i f i e d in 41 m m d i a m p e r m a n e n t m o l d s , can be p r o c e s s e d to 1.78 m m d i a m w i r e us i ng e i t h e r hot e x t r u s i o n , o r hot r o l l i n g , f o l l o w e d by cold drawing. 2) The p r o c e s s i n g s e q u e n c e , d e v e l o p e d in this i n v e s t i g at i o n , to r e d u c e A1-Ni a l l o y s f r o m c a s t f o r m to w i r e f o r m l ed to g e n e r a l a l i g n m e n t of f i b r o u s d i s p e r s o i d s of NiAl 3 without f i b e r - f r a g m e n t a t i o n o r c o a r s e n i n g or fiber-matrix separation. 3) T h e s e a l l o y s in w i r e f o r m p o s s e s s e x c e l l e n t c o m bination of high s t r e n g t h and high e l e c t r i c a l c o n d u c t i v ity. T e n s i l e s t r e n g t h r a n g e f r o m 173 N / r a m z (at 0.6 pct Ni) to 246 N / m m z (at 6.1 pct Ni) in c o m b i n a t i o n with c o r r e s p o n d i n g c o n d u c t i v i t y v a l u e s b e t w e e n 62 pct IACS and 55.5 pct IACS. 4) The p r o c e s s e d a l l o y s a l s o p o s s e s s e x c e l l e n t yi e l d s t r e n g t h ; f o r i n s t a n c e - - A l - 6 . 1 pct Ni a l l o y w i r e has a 0.2 pct o f f s e t s t r e n g t h of 213.5 N / m m z. 5) S t r e n g t h and c o n d u c t i v i t y of the fine f i b r o u s d i s p e r s o i d s of NiAl 3 in t h e s e w i r e s , e s t i m a t e d using s i m ple c o m p o s i t e r u l e s , a r e e q u i v a l e n t to 1380 N / m m 2 and 18 pct IACS r e s p e c t i v e l y . RE F E R E N C E S

km

= lec

1 -- f d ( _ 1 = kc/kd_ "~ \2kc/kd

[11

+ 1]

where krn = A v e r a g e c o n d u c t i v i t y of the c o m p o s i t e m a t e r i a l k c = C o n d u c t i v i t y of the m a t r i x (continuous phase) k d = C o n d u c t i v i t y of the d i s p e r s e d p h a s e

and f d = V o l u m e f r a c t i o n of the d i s p e r s e d phase.

1008 VOLUME6A, MAY 1975

I. J. R. Lenyre and J. B. Roche: Wire & WireProd., 19t~6, vol. 41, p. 904.

2. W. A. Dean: Aluminum, vol. I, p. 207, AmericanSociety for Metals,Ohio, 1967. 3. R. Kumar: Indian East. Eng., 1969, w)l. 3, p. 459. 4. M. |tansen: Gmstitution of Bina~. Alloys, pp. 118-21, McGraw-HillBookCo., New York, 1958. 5. Y. M. Kruptokm and M. B. (;okshtein: lzv. Vyssh. Ucheb. Zaved., Energ, 1965, wfl. 10, pp. 112-16. 6. R. W. Hertzberg:Fiber Composite Materials, p. 77, AmericanSocietyfor Metals,Ohio, 1965. 7. R. W. ttertzberg, F. D. Lcmkey,and J. A. Ford: Trans. TMS-AIME, 1965, vol. 233, p. 342.

METALLURGICAL TRANSACTIONS A