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HAL Id: jpa-00223375

https://hal.archives-ouvertes.fr/jpa-00223375

Submitted on 1 Jan 1983

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THE INTERNAL FRICTION BEHAVIOUR OF MARTENSITIC Cu-Zn-Al ALLOYS

J. van Humbeeck, L. Delaey

To cite this version:

J. van Humbeeck, L. Delaey. THE INTERNAL FRICTION BEHAVIOUR OF MARTEN- SITIC Cu-Zn-Al ALLOYS. Journal de Physique Colloques, 1983, 44 (C9), pp.C9-217-C9-221.

�10.1051/jphyscol:1983928�. �jpa-00223375�

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THE INTERNAL FRICTION BEHAVIOUR O F MARTENSITIC Cu-Zn-A1 ALLOYS

J. Van Humbeeck and L. Delaey

Departernent MetaaZkunde, KathoZieke U n i v e r s i t e i t Leuven, HeuerLee-Leuven, Belgium

Rgsumb : Dans cet article, nous prgsentons une description des deux pics de frottement intbrieur observgs dans la phase martensitique des alliages de Cu-Zn-Al.

Le pic h basse tempkrature (215 K) a BtB reconnu comme "pic de relaxationff tandis que celui observb 2 315 K serait dG h l'entrainement des dgfauts par les dislocations.

Abstract : In this paper, internal friction peaks, occurring in martensitic Cu-Zn-A1 alloys are described. The peak at 215 K is explained as a relaxa- tion peak while the peak at 315 K is explained as due to the dragging of point defects by dislocations.

INTRODUCTION

Due to the technological interest in the high damping capacity of martensitic Cu- Zn-A1 alloys (1, 2) a detailed study of the damping in these alloys was performed as a function of temperature, amplitude and heat-treatment.

Since the necessity of stable damping characteristics up to at least 323 K , alloys with martensite-to-beta-transformation-temperatures well above this temperature were investigated. The internal friction measured below the transformation tempe- ratures is usually much higher than in the beta-phase and is strongly amplitude- dependent (3). This high internal friction in the martensite is attributed to the stress-induced movement of the interfaces which exist between the martensite plates (reorientation) (3, 4, 5 , 6) and to the dislocations which are present in the mar- tensite plates or plate-boundaries (3, 7). When the internal friction is measured as a function of temperature with a constant temperature rate, three peaks are ob- served (fig. I ) . During heating, starting from 173 K, a first peak appears around 215 K, a second around 315 K and a third one at the transformation temperature.

The positions of the first two peaks were found to be independent of composition.

The resonance frequency as a function of temperature exhibits also a typical be- haviour. A drop in frequency over the first peak indicates a modulus defect. A small minimum is found about halfway the low temperature side of the second peak, while a strong minimum occurs at the same temperature in the transformation zone where the internal friction is maximum. The first peak is explained as a relaxa- tion peak, the second as an "integrated peaking effect" (8) while the third one is called the transformation peak and is due to the movement of the interphase be- tween parent and martensite phase (9, 10).

In the present paper the parameters influencing the characteristics of the first two peaks will be discussed.

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1983928

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EXPERIMENTAL PROCEDURE

The composition and the corresponding transformation temperatures of the alloys analysed in the present paper are given in table 1.

TABLE 1

No Weight % C u Zii A1 Ms (K)

The procedure of sample preparation and damping experiments are already described elsewhere (9).

RESULTS AND DISCUSSION

1. The relaxation peak at 215 K.

This peak shows the properties of a relaxation peak. The peak is present after the sample was quenched from the high temperature beta-phase immediately to room temperature as well when quenched to a temperature above the Ms-temperatures and holding there for about 15 minutes prior to further cooling.

Only the back-ground damping, i.e. the martensitic damping-level was influenced by the heat-treatment (8). The intensity of the peak when measured shortly af- ter the heat-treatment showed a rather large scatter but was at about 0.01 on the average. However its height slightly increased up to 0.02 after the sample was aged at about 323 K for one month.

The peak shows a hysteresis in peak position when cycled over the temperature range of its existence (fig. 2), the intensity of the peak being lower during heating if compared with the intensity of the peak measured during cooling.

Many times a double peak was registered with increasing temperature, but never upon cooling the sample (fig. 3).

It should be remarked that, as shown in both figures 2 and 3 , the tempera- ture hysteresis of the respnance frequency is smaller than that of the relaxation peak. The activation energy of this peak was obtained from the half-peak value method as well as from the slope of the peak since it was not possible for tech- nical reasons to use the peak-shift method. From both methods we found that the activation energy was 0.38 5 0.05 eV. This rather large scatter as well as the appearance of a double peak on heating indicates that we are not dealing with a single relaxation phenomenon.

At last, the relaxation times T~ of this peak were found to be between 1.10 -12 and 3.10-12.

These results indicate that the peak at 215 K finds most probably its origin in point-defect-dislocation interactions.

2. The "integrated peaking effect" peak at 315 K.

The characteristics of this peak are quite different from those of the relaxation peak. First of all, temperature cycling over the peak makes the peak to disappear (fig. 4) providing the temperature do not exceeds the As-tempera- ture, otherwise the peak is restored completely. If temperature cycling is carried out until a hysteresis in peak position is found, the intensity of the peak measured on cooling is smaller than on heating, in contrast to the beha- viour of the relaxation peak. The peak at 315 K was strongly amplitude depen-

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On heating a small minimum is found at the low-temperature side of the peak, this minimum is also more intensive with higher amplitudes. The origin of this peak is thought to be due to the dragging of point defects with dislocations.

As a result, a peaking effect occurs in the internal friction behaviour at con- stant temperature as observed in other alloy systems (11, 12) (fig. 6). When the internal friction is measured at constant temperature rate, an integra- tion of this peaking effect over the influencing temperature range results in the peak observed at 315 K, called therefore "integrated peaking effect" (8).

CONCLUSION

It can be concluded that point defects play an important role in the internal fric- tion characteristics of martensitic Cu-based alloys. The concentration and mobili- ty of these defects greatly influence the internal friction as well as the stabi- lisation of the martensite (13). The concentration is thereby strongly dependent on the heat-treatment and the alloy type while the mobility is temperature depen- dent. Since this last factor is inherent to the material, most attention should be paid to the thermo-mechanical treatments of these alloys.

REFERENCES

1. VAN HUMBEECK J., DELAEY L., VANDEURZEN U., RAATS J., Paper NO N in "Modal Ana- lysis", 24-26 sept. 1980, Dept. Werktuigkunde, K.U.Leuven.

2. VANDEURZEN U., VERELST H., SNOEYS R., DELAEY L., J. Physique

42

(1981) C5-1169.

3. DEJONGHE W., DELAEY L., DE BATIST R., VAN HUMBEECK J., Metal Science J.

11

(1977) 523.

4. DEJONGHE W., DE BATIST R., DELAEY L., Scripta Met.

10

(1976) 1125.

5. MORIN M., GUENIN G., GOBIN P.F., J. Physique

42

(1981) C5-1013.

6. MORIN M., GUENIN G., P.F. GOBIN, J. Physique

2

(1982) C4-685.

7. GOTTHARDT R., MERCLER O., J. Physique

2

(1981) C5-995.

8. VAN HUMBEECK J . , DELAEY L., J. Physique

43

(1982) C4-691.

9. DEJONGHE W., Ph. Thesis, Leuven 1976.

10. KOSHIMIZU K . , Ph. Thesis, Lausanne 1981.

11. SIMPSON H.M., SOSIN A., EDWARDS Q.R., SEIFERT S.L., Phys. Rev. Letters

6

(1971) 897.

12. CAR0 J.A., MONDINO M., J. Appl. Physics

11

(1981) 7147.

13. JANSSEN J., VAN HUMBEECK J., CHANDRASEKARAN M., MWAMBA N., DELAEY L . , J - Phy- sique

43

(1982) C4-715.

ACKNOWLEDGEMENT

This work was carried out with the financial support of the "Dienst voor Weten- schapsbeleid" of the Belgian Government. The authors would like to thank R. De Batist for valuable discussions.

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Figure 1 : Schema,tic representation of the internal friction (full line) and Youngs modulus (dashed line) for Cu-Zn-A1 alloys as a function of temperature.

The peak at

-

200 K is a relaxation peak, while the peak at

-

300 K

is due to dragging and/or pinning of point defects (vacancies) by inter- face dislocations. Both peaks are composition independent. The peak at 400 K occurs between M and it

( f

< 0) or between A and Af ('? > 0).

~ t s position is compositioz depen$ent.

Fig. 2 The relaxation peak (full line) Fig. 3 The relaxation peaks measured and the frequency (dashed line), during heating and cooling measured during heating and and superimposed on the back- cooling. (The back-ground dam- ground damping. The dashed ping is substracted:) line shows the frequency be-

haviour

.

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third

'ig. 4 The effect of thermal cycling on the "integrated peaking effect"

$hen the maximum temperature is below A

.

( - : first heating run,

-.'I

second heating run,

-..

third heating run).

---0, --, o-_.-?-'o

----_

-A---A--?--.*

0 2 I 4 6 I lo4 e

Fig. 5 The amplitude dependence of the height of the integrated peaking effect, the transformation peak (full curves) and the minimum of the respective frequencies at the maximum of the peaks (das- hed curves).

Fig. 6 Schematic curve of the peaking effect measured at constant temperature with indication of the influencing parameters.

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