DAMPING CAPACITY OF Fe-Cr AND Fe-Cr BASED HIGH DAMPING ALLOYS

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DAMPING CAPACITY OF Fe-Cr AND Fe-Cr BASED

HIGH DAMPING ALLOYS

W. Schneider, P. Schrey, G. Hausch, E. Török

To cite this version:

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DAMPING CAPACITY OF F e - C r AND F e - C r BASED HIGH DAMPlNG ALLOYS

W. Schneider, P . Schrey, G. Hausch and E . ~ ~ r g k *

VacuwnschmeZze GIMBH, 0-6450 Hanau, F. i?. G.

"~nstitut

Dr. R.

Straumunn AG, CH-4437 WaZdenburg, SwitzerZand

A b s t r a c t . - The damping p r o p e r t i e s of Fe-Cr and Fe-Cr b a s e d a l l o y s have been i n v e s t i g a t e d by t h e c a n t i l e v e r method and t h e r e s o n a n t b a r method. The change i n damping c a p a c i t y i s s t u d i e d a s a f u n c t i o n of s e v e r a l p a r a m e t e r s i n c l u d i n g t e m p e r a t u r e , magnetic f i e l d , c o l d work and h e a t t r e a t m e n t . The r e s u l t s a r e c o r r e l a t e d w i t h measurements of t h e c o e r c i v e f o r c e . Binary Fe-Cr a l l o y s w i t h 12-14 % C r e x h i b i t e d damping c a p a c i t i e s a s h i g h a s 80 % when h e a t t r e a t e d a t 1200°C w h i l e t h e a l l o y Fe-12Cr-3A1 a l r e a d y e x h i b i t e d damping c a p a c i t i e s of t h e o r d e r of 40-60 % when h e a t t r e a t e d a t t e m p e r a t u r e s above 750°C. 1 . I n t r o d u c t i o n . - I n f e r r o u s a l l o y s a h i g h damping c a p a c i t y i s found f o r v a r i o u s f e r r i t i c s t e e l s such a s Fe-Cr (12-16 w t . % C r ) [ I ] Fe-Mo (2-5 w t . % Mo) [ 2 ] and Fe-Co (10-50 w t . % C O ) 131.

The h i g h damping c a p a c i t y , P , of t h e s e a l l o y s ( t y p i c a l l y P

>

30 i s c a u s e d by a l a r g e magneto-mechanical h y s t e r e s i s l o s s . A s s u c h , t h e damping c a p a c i t y d o e s n o t depend on t h e f r e q u e n c y of t h e v i b r a t i o n b u t , on t h e o t h e r hand, s t r o n g l y depends on t h e s t r a i n a m p l i t u d e and on t h e domain w a l l m o b i l i t y . For t h i s mechanism t h e damping c a p a c i t y e x h i b i t s a c h a r a c t e r i s t i c peak when p l o t t e d a s a f u n c t i o n of t h e v i b r a t i o n a m p l i t u d e .

For Fe-Cr based a l l o y s we have s y s t e m a t i c a l l y i n v e s t i g a t e d t h e damping c a p a c i t y a s a f u n c t i o n of C r c o n t e n t and o f t e r n a r y a d d i t i o n s such a s Mo, T i and Cu a s w e l l a s t h e i n f l u e n c e of t h e a n n e a l i n g t r e a t m e n t .

A part from the damping c a p a c i t y we measured t h e c o e r c i v e f o r c e and t h e mechanical p r o p e r t i e s . For t h e commercial a l l o y VACROSIL 010 which c o n t a i n s 1 2 % C r , 3 % Al, b a l . Fe, w e have a l s o measured Young's

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modulus, E , and t h e i n t e r n a l f r i c t i o n , Q

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a s a f u n c t i o n of tempera- t u r e and of an e x t e r n a l l y a p p l i e d magnetic f i e l d .

2 . Experimental.- The chemical composition of t h e a l l o y s s t u d i e d a r e l i s t e d i n Table 1 t o g e t h e r w i t h t h e mechanical p r o p e r t i e s a s measured i n t h e a n n e a l e d c o n d i t i o n . Samples w i t h dimensions of

200 x 10 x 1 mm3 were p r e p a r e d from h o t r o l l e d m a t e r i a l and a n n e a l e d

i n a

hydrogen atmosphere a t t e m p e r a t u r e s r a n g i n g from 650-1200°C

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C5-636 JOURNAL DE PHYSIQUE

Table 1: Physical properties of FeCr based a l l o y s a f t e r annealing a t llOO°C/l h. HV5

qn

R p0.2 %50 Hc pS N/rn2 N/mn2 % k N / m 2

Man

% F e l OCr 114

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206 1.2 13 Fe-1 Zr 123 268 157 26 177 0.28 39 Fe- 1 4Cr 132 287 149 20 1 76 0.33 35 Fe-1 6Cr 137 310 144 24 173 0.33 35

@ = registered trade mark

f o l l o w e d by s l o w c o o l i n g down t o room t e m p e r a t u r e .

The damping c a p a c i t y , P I was measured a t v a r i o u s s t r e s s l e v e l s u s i n g t h e c a n t i l e v e r beam method ( f -20 H z ) . I n t h i s method P i s o b t a i n e d from t h e d e c a y of f r e e o s c i l l a t i o n s by

where A w i s t h e e n e r g y d i s s i p a t e d i n o n e c y c l e and An a n d A n + l a r e s u c c e s s i v e a m p l i t u d e s of t h e o s c i l l a t i o n s . S t r e s s l e v e l s up t o 150

N/mm2 c o u l d b e s t u d i e d .

The t e m p e r a t u r e and m a g n e t i c f i e l d d e p e n d e n c e of Y o u n g ' s modulus, E , and o f i n t e r n a l f r i c t i o n , Q - l , were s t u d i e d on s p e c i m e n s 5 0 x 5 ~ 1

mm3

u s i n g t h e r e s o n a n t b a r method ( f

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2 kHz).

3. R e s u l t s and D i s c u s s i o n . - The r e s u l t s o f o u r c a n t i l e v e r beam m e a s - u r e m e n t s a r e shown i n F i g s . 1 and 2. F i g . 1 shows t h e damping c a p a c i t y a s a f u n c t i o n o f s t r e s s , a, f o r some t y p i c a l Fe-Cr b a s e d a l l o y s h e a t t r e a t e d a t 1000 and 1100 OC. The o b t a i n e d P (a) c u r v e s e x h i b i t a maximum a t s t r e s s l e v e l s o f a b o u t 10-20 N/mm2 which i s t y p i c a l f o r

the m a g n e t o - m e c h a n i c a l damping p r o c e s s .

F o r Fe-Cr a l l o y s w i t h 12-14 % C r , h e a t t r e a t e d a t 1200 O C , w e ob-

t a i n e d damping c a p a c i t i e s a s h i g h a s 80 % a s shown i n F i g . 2. To o u r knowledge s u c h h i g h v a l u e s h a v e n o t b e e n r e p o r t e d s o f a r .

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F i g . 1 : Damping c a p a c i t y o f v a r i o u s Fe-Cr a l l o y s h e a t t r e a t e d a t 1000°C and llOO°C. t r a n s f o r m a t i o n i n t r o d u c e s i n t e r n a l s t r e s s e s r e d u c i n g t h e domain w a l l m o b i l i t y which l e a d s t o a c o r r e s p o n d i n g l y h i g h c o e r c i v e f o r c e a n d low damping c a p a c i t y

.

For Fe-Cr b a s e d a l l o y s t h e i n f l u e n c e of s m a l l a d d i t i o n s o f Mo, T i , A 1 and Cu was s t u d i e d . T a b l e 1 shows t h a t Mo, Cu, A 1

and e s p e c i a l l y Mo + Cu a r e b e n e f i c i a l i n t h a t t h e y improve t h e m e c h a n i c a l p r o p e r t i e s w i t h o u t r e d u c i n g t h e damping b e h a v i o u r . T i , on t h e o t h e r hand, was d e l e t e r i o u s ; i t r e d u c e d t h e damping c a p a c i t y c o n s i d e r a b l y

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i n c o n t r a s t t o t h e f i n d i n g s o f F i g . 2 : Maximum damping c a p a c i t y Masumoto e t a l . [ 5 ]

.

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C5-638 JOURNAL DE PHYSIQUE F i g . 4 : E f f e c t of c o l d work on t h e damping c a p a c i t y F i g . 3 : Maximum damping c a p a c i t y ( P ) and t h e c o r r e s - ponding s t r e s s a m p l i t u d e ( o )

,

t e n s i l e s t r e n g t h ( R ) and h a r d n e s s ( H V ) a s a F u n c t i o n of a n n e a l i n g t e m p e r a t u r e ( a n n e a l i n g t i m e 1 h )

F i g . 3 shows t h e maximum damping c a p a c i t y P , t h e s t r e s s a m p l i t u d e

o a t Pmax, t h e t e n s i l e s t r e n g t h and h a r d n e s s a s a f u n c t i o n o f t h e a n n e a l i n g t e m p e r a t u r e f o r t h e a l l o y VACROSIL 010. T h i s a l l o y i s o u t - s t a n d i n g i n t h a t i t a l r e a d y e x h i b i t s a h i g h damping c a p a c i t y when a n n e a l e d a t r e l a t i v e l y low t e m p e r a t u r e s .

The damping c a p a c i t y i s s t r o n g l y d e t e r i o r a t e d by c o l d work, F i g . 4 . A r e d u c t i o n of

2

5 % c o m p l e t e l y d e s t r o y s t h e damping e f f e c t ; however, it can be f u l l y r e s t o r e d by a s u c c e e d i n g h e a t t r e a t m e n t .

F i g . 5 shows t h e t e m p e r a t u r e dependence o f Young's modulus, E ,

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and o f i n t e r n a l f r i c t i o n , Q

,

f o r t h e a l l o y VACROSIL 010. Q-' i s r e l a t e d t o t h e damping c a p a c i t y by P a, 600

-

Q-I

[ % I .

A t room t e m p e r a t u r e P i s 3 , 6 8. T h i s lower v a l u e o f P i s due t o t h e much lower v i b r a t i o n a m p l i t u d e used i n t h e r e s o n a n t b a r method which was a b o u t 0 , 2 N/mm2. The h i g h damping o f t h i s a l l o y i s e f f e c t i v e up t o 400°C.

The i n f l u e n c e o f a magnetic f i e l d H i s shown i n F i g . 6.

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a t a b o u t 1 0 0 A / c m . Acknowledgements. The a u t h o r s a r e much i n d e b t e d t o M r s . G . S t e u e r n a g e l a n d t o M r . K . R e h b e i n f o r a s s i s t a n c e i n t h e c a n t i l e v e r beam m e a s u r e - m e n t s . F i n a n c i a l h e l p f r o m t h e B u n d e s m i n i s t e r i u m f i i r F o r s c h u n g

I

.

,

.

und Technologic i s g r a t e f u l l y -200

o

200 LOO 600 a c k n o w l e d g e d . Temperature ( O C ) R e f e r e n c e s : F i g . 5: T e m p e r a t u r e d e p e n d e n c e

o f Y o u n g ' s m o d u l u s , E , and i n t e r n a l [ I

1

H. Masumoto, S. Sawaya &

f r i c t i o n , Q - I . _{M . H i n a i , T r a n s . J I M}

₂₀

H( A l c m 1

[ 2 1 H . Masumoto, S. Sawaya &

M. H i n a i , T r a n s . JIM

18

( 1 9 7 7 ) 281