DAMPING CAPACITY OF Zn-Al ALLOY CASTINGS

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DAMPING CAPACITY OF Zn-Al ALLOY CASTINGS

T. Otani, T. Sakai, K. Hoshino, T. Kurosawa

To cite this version:

T. Otani, T. Sakai, K. Hoshino, T. Kurosawa. DAMPING CAPACITY OF Zn-Al AL- LOY CASTINGS. Journal de Physique Colloques, 1985, 46 (C10), pp.C10-417-C10-420.

�10.1051/jphyscol:19851094�. �jpa-00225479�

JOURNAL DE PHYSIQUE

Colloque C10, supplkment au n012, Tome 46, dkcembre 1985 page C10-417

DAMPING CAPACITY OF Zn-A1 ALLOY CASTINGS

T. OTANI, T. SAKAI, K. HOSHINO and T. KUROSAWA

College of Industrial Technology, Nihon University, Chiba 275, Japan

A b s t r a c t

-

T h i s paper d e s c r i b e s t h e damping c a p a c i t y o f Zn-15

-

27%A1 and Zn-15

-

'27%A1-0.02%Mg a l l o y s c a s t i n g . Such a l l o y s a r e d e s i r a b l e t o p r o v i d e h i g h damping of v i b r a t i o n . C o o l i n g r a t e s o f s o l i d i f i c a t i o n and quenching f o r t h e i n t e r i o r o f c a s t i n g s a r e lower t h a n t h a t o f t h e edge o f c a s t i n g s . The damping c a p a c i t y o f b o t h t h e edge and t h e i n t e r i o r o f t h e c a s t i n g was i n v e s t i g a t e d and parameter c o n t r o l l i n g t h e damping e f f e c t of t h e a l l o y a r e discussed.

I

-

INTRODUCTION

Zn-A1 a l l o y s show h i g h .damping when quenched from above e u t e c t o i d temperature /1,2/.

Most s t u d i e s o f t h i s phenomenon have been c a r r i e d o u t f o r r o l l e d o r drawn

specimens. Generally, small amount o f magnesium a r e added t o t h e s e Zn-A1 a l l o y s t o improve r e s i s t a n c e t o i n t e r g r a n u l a r c o r r o s i o n . The a u t h o r s have proposed t h a t t h e amount o f magnesium added t o t h e s e a l l o y s should be l e s s t h a n 0.02% / 3 / .

The phase diagram o f Al-Zn has two i m p o r t a n t f e a t u r e s . F i r s t , a e u t e c t i c i s formed f o r a composition o f about 5 wt%Al, t h e e u t e c t i c temperature i s 655K. A e u t e c t o i d decomposition p o i n t i s found f o r 22 wt% a t a temperature o f 548K. Thus c o n s i d e r a b l e l a t i t u d e e x i s t s i n t h e m e t a l l u r g i c a l v a r i a b l e s f o r t h e s e a l l o y s . High A1 a l l o y s a r e advantageous f o r h i g h e r s t r e n g t h and l o w ~ r d e n s i t y t h a n t h o s e of t h e e u t e c t i c composition. However i n c r e a s i n g aluminum c o n t e n t g i v e s a wide temperature range f o r s o l i d i f i c a t i o n . Thus, c a s t i n g a1 l o y s o f d i f f e r e n t aluminum composition can produce q u i t e d i f f e r e n t phases and m e t a l l u r g i c a l s t r u c t u r e s . I n t h i s study we i n v e s t i g a t e d t h e i n t e r n a l f r i c t i o n as a f u n c t i o n o f processing v a r i a b l e s f o r b i n a r y a l l o y s i n t h e composition range 15 t o 27%A1 and t e r n a r y a l l o y s i n t h e same aluminum range w i t h 17.02 w t % ~ g .

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19851094

JOURNAL

DE

_PHYSIQUE

I 1

-

EXPERIMENTAL PROCEDURE

The experiments were c a r r i e d o u t f o r a l l o y s o f c o m p o s i t i o n Zn-15

-

27%A1 and Zn- 15

-

27%A1-0.02%Mg w h i c h had been c a s t i n t o molds o f s i z e 1 1 0 x 1 1 0 ~ 2 8 0 rnm. The c a s t i n g t e m p e r a t u r e was a t t h e m e l t i n g p o i n t o f each a l l o y c o m p o s i t i o n +50K and t h e t e m p e r a t u r e of t h e mold was 290K. Then specimens of s i z e 2 x 1 0 ~ 1 5 0 mm were c u t f r o m t h e edge and t h e i n t e r i o r o f t h e c a s t i n g s f o r damping c a p a c i t y measurements. These measurements were made f o r t h e f r e e decay of v i b r a t i o n i n bending o s c i l l a t i o n as i l l u s t r a t e d i n F i g . 1. The specimen was s u p p o r t e d v e r t i c a l l y w i t h i t s b o t t o m edge h e l d f i x e d . The t o p end was f r e e t o v i b r a t e . The s p e c i f i c damping c a p a c i t y

( h e r e i n a f t e r termed S.0.C) /4/ was d e t e r m i n e d o v e r t h e frequency range 20 t o 100 Hz.

r -

1

Armature

&Polarizing magnet

, ^I$=+=,

1 11 el

Spec.

Steel pedestal

a, ^{1 1-}

F i g . 1 Schematic o f t h e a p p a r a t u s .

A f t e r measurement of t h e i n i t i a l damping c a p a c i t y , t h e specimens were h e a t t r e a t e d a t 573K f o r two h o u r s f o l l o w e d by a w a t e r quench. The damping c a p a c i t y o f t h e h e a t t r e a t e d specimens was t h e n measured. Specimens were made from t h e edge and t h e

i n t e r i o r o f t h e c a s t i n g s f o r c o m p a r a t i v e measurement. Specimens were a l s o examined a f t e r t h e e n t i r e i n g o t was heated t o 573K and quenched. I n a d d i t i o n t h e damping c a p a c i t y o f specimens r o l l e d t o 90% r e d u c t i o n and h e a t t r e a t e d as d e s c r i b e d was a l s o i n v e s t i g a t e d .

I 1 1

-

RESULTS AND DISCUSSION

The damping c a p a c i t y o f as-cast and h e a t t r e a t e d a l l o y s i s shown i n Figs. 2 and 3 f o r b i n a r y zinc-aluminum a l l o y s o f 15, 20 and 27%A1. The measurements a r e shown f o r t h r e e f r e q u e n c i e s f r o m 20 t o 100Hz. The c a s t i n g s and specimens were t h e n h e a t e d a t 573K f o r t w o hours and w a t e r quenched. The i n t e r n a l f r i c t i o n was h i g h e r under a l l c o n d i t i o n s as t h e f i l l e d p o i n t s i n Figs. 2 and 3 show. F o r t h e a l l o y s w i t h 27XA1 t h e damping c a p a c i t y f r o m t h e i n t e r i o r o f t h e c a s t i n g i s h i g h e r t h a n t h a t f r o m t h e edge.

The measurements show t h a t t h e damping c a p a c i t y of t h e s e c a s t b i n a r y a l l o y s depends s t r o n g l y on t h e c o o l i n g r a t e f r o m above t h e e u t e c t o i d t e m p e r a t u r e . The r e s u l t s may a l s o b e r e l a t e d t o m i c r o s h r i n k a g e caused by t h e w i d e range o f s o l i d i f i c a t i o n t e m p e r a t u r e o f t h e s e a l l o y s . The e x c i t a t i o n f r e q u e n c y has v e r y l i t t l e i n f l u e n c e on t h e damping c a p a c i t y of e i t h e r t h e a s - c a s t o r h e a t t r e a t e d a l l o y s .

S i m i l a r d a t a f o r t h e damping c a p a c i t y of a s - c a s t and h e a t t r e a t e d t e r n a r y a l l o y s c o n t a i n i n g 0.02XMg a r e shown i n F i g s . 4 and 5. Small amount o f magnesium reduced t h e damping c a p a c i t y f o r t h e a l l o y s of 15 and 20XAl b u t had l i t t l e e f f e c t f o r t h e 27% a l l o y s . F o r a l l specimens t h e h e a t t r e a t m e n t i n c r e a s 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 .

0

l

^{I 1 1 1 1 1}

10 50 100

E x c i t e d f r e q u e n c y I Hz Fig.

4

Influence of excitation frequency

on the ternary alloy castings.

I . m i '

A A 27%AI

A A

2 a

-

⁰ _{0 0}

1 1 1 1 1 1

20%AI

-

^A

A

A A

-

m ^fo ₀

1 1 1 1 1 ,

-

15%A1

2 U Y

-

is 60

- 6

1 1 1 1 1 1

10 50 100

x10-2

as-cast 573K x 2h. W.Q.

edge 0

interior A A

E x c i t e d f r e q u e n c y I Hz E x c i t e d f r e q u e n c y I Hz

Fig. 2 Influence of excitation frequency Fig, 3 Influence of excitation frequency on the binary alloy castings. on damping capacity of binary

as-cast 573K x 2h. W . Q . alloy castings and cut specimens.

edge 0

cut and

interior A A as-cast 5733 x 2h. W . Q .

edge 0

a

interior A A

x10-2 15 1 0 -

5 0 .

e l 5 - 2

^{1 0 -}

5 0 15 10 5 0

lS%AI-0.02%Mg

50 100

E x c l t e d f r e q u e n c y 1 H z

Fig. 5 Influence of excitation frequency on the ternary alloy castings and cut specimens.

I I I 1 1 1 1 1 1

27%AI

-

^{A A} _A A

A A

-

⁰ _{0 0}

I I I I L I I I I

20%AI

A* 4 A

- *

^'a A

0

I 1 I 1 , 1 1 1 1

15%AI

-

-

^A

t 2

- * ^{i a}

^m

L 1 1 1 1

10 5 0 100

cut and as-cast 573K x 2h. W . Q .

edge

o

interior A A

1 5 - 1 0 - 5 0 20

e

^{1 5 -}

2

^{1 0 -}

5 0 1 5 - 10

5 0

C10-420 JOURNAL DE PHYSIQUE

The e f f e c t of p r i o r c o l d r o l l i n g and heat t r e a t m e n t on b o t h t h e b i n a r y and t e r n a r y a l l o y s i s shown i n Fig. 6. For t h e a l l o y s o f l o w e r c o m p o s i t i o n t h e damping c a p a c i t y was reduced by magnesium a d d i t i o n s .

F i g . 6

I n f l u e n c e o f e x c i t a t i o n frequency on damping c a p a c i t y o f r o l l e d a l l o y s a f t e r quenching.

5

10 5 0 100

E x c i t e d frequency /

Hz

CONCLUSIONS 1"

-

^--

These r e s u l t s show t h a t t h e damping c a p a c i t y o f t h e s e b i n a r y and t e r n a r y a l l o y s i n t h e l o w audio frequency range depends markedly on t h e c o o l i n g r a t e from above t h e e u t e c t o i d temperature. Small amounts o f magnesium which a r e added f o r improved c o r r o s i o n r e s i s t a n c e do n o t a f f e c t t h e S.0.C o f t h e a l l o y s f o r t h e a l l o y s a t 27%A1, b u t t h e y do reduce t h e damping c a p a c i t y f o r t h e lower aluminum compositions. Cold r o l l i n g t h e s e a l l o y s changes t h e damping c a p a c i t y o n l y s l i g h t l y . For a l l

compositions and f o r b o t h o f t h e h e a t t r e a t m e n t s used, t h e damping c a p a c i t y i s q u i t e h i g h , t h e v i b r a t i o n s damp o u t near room temperature i n o n l y a few c y c l e s .

E s p e c i a l l y a t t h e aluminum concent r a t i o n o f 27%, h i g h damping c a p a c i t y m i g h t be expected f o r heavy castings. At t h i s time, we do n o t have a d e t a i l e d atomic model f o r t h e mechanism of t h e energy l o s s .

REFERENCES

/I/ K. N u t t a l : J. I n s t . Met.,

2

(1971) 766.

/2/ A. S. Nowick: J. Appl. Phys.,

22

(1951) 975.

/3/ T. Otani, K. Hoshino and T. Kurosawa: J. Phys. c o l . N5 (1981) C5-935.

/ 4 / A. S. Nowick and B. S. B e r r y : " A n e l a s t i c R e l a x a t i o n i n C r y s t a l l i n e S o l i d s "

(1972)

2,

New York.