MECHANICAL DAMPING AT HIGH TEMPERATURES IN ALUMINIDES

HAL Id: jpa-00225473

https://hal.archives-ouvertes.fr/jpa-00225473

Submitted on 1 Jan 1985

HAL is a multi-disciplinary open access archive for the deposit and dissemination of sci- entific research documents, whether they are pub- lished or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.

L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

MECHANICAL DAMPING AT HIGH TEMPERATURES IN ALUMINIDES

A. Wolfenden, M. Harmouche, J. Hartman, Jr.

To cite this version:

A. Wolfenden, M. Harmouche, J. Hartman, Jr.. MECHANICAL DAMPING AT HIGH TEMPER- ATURES IN ALUMINIDES. Journal de Physique Colloques, 1985, 46 (C10), pp.C10-391-C10-394.

�10.1051/jphyscol:19851088�. �jpa-00225473�

MECHANICAL DAMPING AT HIGH TEMPERATURES IN ALUMINXDES

A. WOLFENDEN, M.R. HARMOUCHE and J.T. HARTMAN, Jr.

Mechanical Engineering Department, Texas A&M University, College Station, Texas 77843, U.S.A.

A b s t r a c t

-

a r e !-eported. The technique used i s t h e PUCOT, where E and f o r t h e ordered 52 FeAl were measured as a f u n c t i o n o f tempera- t u r e T and s t r a i n amplitude ^{E ,} r e s p e c t i v e l y . I t i s shown t h a t t h e Granato-Luecke theory p r e d i c t s low mobile d i s l o c a t i o n d e n s i t i e s . E decreases 1 in e a r l y w i t h T such t h a t 0.080 ,<dE/dT< 0.095 GPa/K i n t h e temperature range 300-998 K.

I

-

Superalloys, w h i l e o f f e r i n g remarkable mechanical p r o p e r t i e s , have become vulnerable f o r two c h i e f reasons : 1) superalloys c o n t a i n l a r g e q u a n t i t i e s o f s t r a t e g i c metals t h e supply o f which i s u n c e r t a i n , and 2 ) on a long term b a s i s , these expensive metals need t o be con- served. Today, t h e e f f o r t t o i d e n t i f y a1 t e r n a t i v e m a t e r i a l s f o r h i g h temperature o p e r a t i o n i s more e s s e n t i a l than ever. I n t e r m e t a l l i c compounds such as t h e ordered 92 FeAl o f f e r such an a l t e r n a t i v e , since t h e contents o f these a l l o y s a r e r e a d i l y a v a i l a b l e and a l u m i n i - des o f f e r e l a s t i c p r o p e r t i e s c o m p e t i t i v e w i t h those o f t h e super- a l l o y s . Thus, t h e i r p o t e n t i a l t o ease t h e burden on t h e use o f s t a t e g i c m a t e r i a l s need n o t be f o r g o t t e n . Experimental r e s u l t s 0 f . Q -

i!

versus ^E are analyzed I n terms o f t h e Granato-Luecke (G-L) theory o f d i s l o c a t i o n damping /1/ t o y i e l d estimated values f o r minor and ,major p i n n i n g lengths o f d i s l o c a t i o n s , and t h e d e n s i t y o f mobile

d i s l o c a t i o n s . A d d i t i o n a l l y , Young's moduli a r e given as a f u n c t i o n of temperature.

I 1

-

The p i e z o e l e c t r i c u l t r a s o n i c composite o s c i l l a t o r technique (PUCOT) f o r measuring E , E and Q-1 i s described elsewhere /2-4/. The compositions o f t h e m a t e r i a l t e s t e d appear i n Table 1.

I 1 1

-

The r e s u l t s obtained f o r t h e moduli appear i n Table 2. For a1 1

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19851088

C10-392 JOURNAL DE PHYSIQUE

p r a c t i c a l purposes E versus T f o l l o w s t h e form E=E ( 0 )

-

I n t e r n a l F r i c t i o n .

The s t r a i n amplitude E dependence o f i n t e r n a l f r i c t i o n ~ - 1 i n two FeAl a l l o y s a t t h r e e temperatures i s shown i n F i g u r e 1. The curves have a v a r i e t y o f shapes, i n c l u d i n g s t r a i g h t l i n e s . Most o f t h e curves a r e o f t h e form Q-1 = Q T ~ + Q,j1 where Q j1 i s t h e amplitude independent p a r t o f Q - l ( h o r i z o n t a 7 p a r t ) and Q-1 i s t h e amplitude dependent p o r t i o n . These curves are now analyged i n terms o f t h e 1981 v e r s i o n o f the G-L t h e o r y o f amplitude dependent damping due t o d i s l o c a t i o n l i n e s and t h e i r break away from p i n n i n g p o i n t s a t h i g h s t r a i n amplitude. Thermal depinning i s taken i n t o account. G-L p l o t s

/E versus 1/ were made t o o b t a i n estimates o f t h e minor p i n n i n g o f d i s l o c a t i o n 1 in e s LC and the m o b i l e d i s l o c a t i o n d e n s i t y A.

Such p l o t s are shown i n F i g u r e 2. E s s e n t i a l l y , a l l data p o i n t s f a l l on s t r a i g h t l i n e s as p r e d i c t e d by t h e theory. The c a l c u l a t e d values f o r LC and A a r e given i n Table 1. Values o f LC andA are found t o be i n t h e range 20 t o 600 nm and 10 1 t o 10 3 cm -2, r e s p e c t i v e l y . Such values a r e reasonable f o r t h i s i n t e r m e t a l l i c m a t e r i a l i n view o f t h e expected low d i s l o c a t i o n d e n s i t i e s . The reasonableness o f t h e e s t i m a t e d values o f LC i s judged as f o l l o w s . These m a t e r i a l s c o n t a i n i m p u r i t i e s such as C, H, N and 0 t o a t o t a l o f 0.23 atomic %. Such i m p u r i t i e s a r e l i k e l y t o be s i t u a t e d on d i s l o c a t i o n l i n e s and c o u l d a c t as minor p i n n i n g points. For a g i v e n value o f L , say 5 nm, t h e number o f p i n n i n g p o i n t s expressed as atomic f r a c t i o f i would be near 0.3 atomic %. T h i s number i s c o n s i s t e n t w i t h the i n t e r p r e t a t i o n o f t h e i m p u r i t i e s i n FeAl a c t i n g as p i n n i n g p o i n t s f o r d i s l o c a t i o n l i n e s . F u r t h e r a n a l y s i s o f t h i s k i n d w i l l be undertaken f o r s i m i l a r a l l o y s a t h i g h e r temperatures, and t h e e f f e c t o f thermal depinning w i l l be exami ned

.

XV - CONCLUSIONS

1. Young's modulus decreases from about 260 GPa a t 300 K t o about 200 GPa o u t 988 K w i t h dE/dT near 0.085 GPa/K.

2. The G-L theory p r e d i c t s v a l u s f o r LC and A i n t h e ranges o f 20-600 rim and

lo1

REFERENCES

/1/ Granato, A. V. and Luecke, K., J. o f A p p l i e d Phys.

52

7136. .

/2/ Marx, J., Rev. Sci. I n s t r . 22 (1951) 503.

/3/ Robinson, W. H. and Edgar, AT; IEEE Trans. on Sonics and U l t r a s o n i c s SU-21 (1974) 98.

/4/ Wolfenden, A.anZIRobinson, W. H., Acta Met. 25 (1977) 823.

/5/ Moutural, P. e t al., J. Nucl. Mat.

21

Composition of Specimens and R e s u l t s of t h e Granato-Luecke Analysis

Composition Temperature Binding Major M i nor Pinning D i s l o c a t i o n (K) Energy Pinning Pinning P o i n t s Density

(eV) Length Length p e r Major (cm-2)

(pm) (nm) Pin

55.27 at.% 783 0.2 0.1 21.3 4.68 849

FeAl 1.0 21.3 46.8 8.49

1 .O 0.1 106 .935 379

55.27 at.% 473 0.2 0.1 615 .16 5.45

FeAl 1.0 0.1 3070 ,032 2.4

2.0 0.1 6150 .016 1.7

51.74 at.% 683 0.2 0.1 18.2 5.48 20.5

FeAl 1 .O 0.1 91.2 1.09 9.1

2.0 0.1 182 .548 6.5

51.74 at.% 473 0.2 0.1 29.4 3.4 8.06

FeAl 1.0 0.1 147 .679 3.6

2.0 0.1 294 .339 2.5

TABLE 2. Temperature Dependence of Young's Modulus f o r FeAl A1 loy s Young's Modul us/GPa

I.D. A t % Fe 298 K 473 K 638 K 783 K 983 K

IMI I-ZB 51.74 262 241 231 221 205

IMII-3B 52.30 263 240 234 215 206

IMI 1-48 53.03 264 244 232 217 201

IMI I-5B 54.14 266 249 238 224 210

IMI I-6B 55.27 268 244 234 219 205

IMI 1-76 56.60 270 235

IMI I-8B 58.15 260 244 229 217 194

Research sponsored by NASA-Lewis Research Center, Program Manager Dr.

J. D. Whittenberger.

C10-394 JOURNAL DE PHYSIQUE

12 I I I 1 2

1 55.27 at. % Fe-AI

10 - 0 58.15 _-, 10

- T/K=473 - ₈

Fig. 1 - S t r a i n amplitude dependence of internal f r i c t i o n in two FeAl alloys a t t h r e e temperatures.

0 - 3 ~ - 1

Fig. 2

-