INTERNAL FRICTION IN TITANIUM AND ITS HYDRIDES

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INTERNAL FRICTION IN TITANIUM AND ITS

HYDRIDES

K. Tanaka

To cite this version:

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INTERNAL FRICTION I N TITANIUM AND ITS HYDRIDES

K. TANAKA

Department o f Metallurgical Engineering, Nagoya I n s t i t u t e o f Technology. Showa, Nagoya 4 6 6 , Japan

Abstract

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Internal friction in TiHx with 0 2 x 5 1.5 is measured

at frequencies near 1Hz and IkHz. Four relaxation peaks are

generally observed, two of which are attributable to dislocation

motion in hcp a phase while the others to hydrogen redistribution

in fcc or fct hydrides. I

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INTRODUCTION

Titanium absorbs a large quantity of hydrogen precipitating fcc y

hydrides. The equilibrium phase diagram and the crystal structures of

TiH are now well established /1,2/. The hydrogen solubility in a Ti is

low& than x=0.001 at room temperature. Above this concentration a mix- ed region of (a+y) phase extends up to $1.5; the y monophase region exists between $1.5 and 2.0. In spite of the accumulation of sufficient crystallographic data for this system, study on the internal friction has been rather limited. Koster, Bangert and Evers / 3 / observed a damping peak above 400K which is associated with hydride precipitation in the a phase. Ritchie and Sprungmann / 4 / showed that the precipitation

causes an instability of the amplitude dependence of damping. Someno

and Saito /5/ found two relaxation peaks (200k and 254K for 1Hz) which increase with increasing hydrogen concentration in samples with x < 0.4. They interpreted both peaks in terms of stress-induced ordering of hy-

drogen atoms within the y hydrides. Similar peaks were observed by

Tinivella and Povolo / 6 / , who ascribed a lower-temperature peak to the

interaction between hydrogen atoms and dislocations in the ct phase

while the other peak to the redistribution of hydrogen in the hydrides. In the present study, we measure the internal friction of TiH over wider hydrogen concentration and wider frequency range than e5er repor- ted, and discuss the origins of the above relaxation peaks.

I1

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EXPERIMENTAL

Titanium wires or plates of 9 9 . : % purity were charged with hydrogen

from x = 0 to 1.5 using a Sieverts type apparatus described elsewhere

/ 7 / . Formation of hydrides in the samples was checked by X-ray diffrac-

tion analysis. These samples, very brittle particularly for x 2 1.0,

were carefully mounted on a tortion pendulum or a vibrating-reed apparatus for the internal friction measurements. The measurements were carried out using computer-controlled systems.

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JOURNAL DE PHYSIQUE

I11

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RESULTS

Figure 1 shows internal friction spectra of as annealed and 3 % 10%

deformed samples measured at 1.7Hz. A broad maximum, which may be de-

composed into peaks A and B, is seen to grow with deformation at low

temperature. In TiHx two other prominent peaks C and D develop at higher temperatures, as shown in Fig.2. The heights of these peaks corrected for the background damping increase almost linearly with hy-

drogen concentration from x = 0 to 1.0. Note that peaks A and B are

present as a small bump superimposed on the tail of peak C,

"

pure Ti

l 6 _{f - 1 . 7 H z}

12 .. B

Fig. 1. Internal friction spectra of uncharged titanium measured in torsional. vibration at f$1.7Hz after deformation by 0, 3, 5 and 10% by tension.

1

0 100 200 300 400 TEMPERATURE l K 1 100 200 300 400 TEMPERATURE 1 K ) ea 60 48 20 .. 0 i

Figure 3 shows the result for TiHOv5 measured at 1.3kHz, where one

can see all the peaks A, B, C and D, the temperatures of which,

however, being shifted upward. The results for TiHx with x = 0 to 1.0

are shown together in Fig.4, where only peak C is found to increase

linearly with x; note that peak D shrinks markedly in comparison with

the one observed at lower frequencies (Fig.2), and that peaks A and B

are first enhanced and then depressed with increasing x. Figure 5 shows

a result for TiHIe5 (Y monophase) compared with those of lower x. One

finds peak C is still more enhanced and narrowed in TiH1+5 accompa-

TiHx .. f -1.7Hz

C

,fi: : .f-, .: . . . , .. : _

.

..:/

:

D :: . . . . .. .---..../

Fig. 2. Internal friction spectra of TiHx measured in torsional vibration at f%l. 7Hz. The -hydrogen concentration H/Ti is indi- cated for each spectrum.

,,

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been successful owing to the brittleness of the samples.

Fig. 3. Internal friction spectrum of TiHo.5 measured in flexure vibration at fcl.3kHz. . . f

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1.6 kHz

_.'.

&x)) _.. O !0.8:;, i

..

100 206 3BB 481 TEMPERATURE ( K l

Fig. 4. Internal friction

spectra of TFH, measured in flexure vibration at fQl.6kHz. The hydrogen concentration H/Ti is in- dicated for each spectrum.

286..

Fig. 5. Internal friction

spectrum of TiH mea-

sured in flexurk' 5vibra- tion compared with those

TiHx

f

-

1.6 kHz

C

. .

.. '

D of TiH and TiHleO. ~ Q J

1 . 6 k ~ z ? ' ~

0 166 208 300

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JOURNAL DE PHYSIQUE

IV

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DISCUSSION

The peak temperatures Tp of the A, B, C and D peaks are listed in

Table 1 together with their frequency factors f and activation enthal- pies H derived from the shift of T with measur!?ng frequency f. Peaks

A and B are caused by deformation 'in pure samples or by hydrogenation

in the two-phase region. They are interpreted to be due to motion of

dislocations in the hcp a phase. Now, peak C increases with increasing

Table 1. List of the peak temperatures and activation parameters for the internal friction peaks observed.

Peak Tp (K) fo (sec-l) H (eV)

1. /Hz 1.6kH.z .,

.

A 125 175 1 x 1 0 ~ ~ 0.26 B 175 215 4x10'~ 0.50 C 210 270 lXlol4 0.58 D 257 325 2xl~14 0.72

amount of y hydrides reaching the maximum strength in the y monophase region. The activation parameters, fo andly, of-fhis peak are very

close to an attempt frequency of 1.5 x 10 sec and activation ener-

gy of 0.54eV, respectively, for the hydrogen diffusion in the y hyd-

rides obtained by an NMR study 181. It seems, therefore, reasonable to

relate this peak with stress-induced ordering of hydrogen atoms in the

fcc y phase (Zener-type relaxation). On the other hand, it is shown

that peak D increases with hydrogen concentration when it appears at s260K (1.7Hz), but it is much depressed at s325K (1.6kHz). This beha- vior cannot simply be explained by the rearrangement of hydrogen atoms

in the y phase as proposed by Someno and Saito 151. It is well known

that the y hydride undergoes fcc + fct phase transition below about

320K for x

z

1.8 121. Though it is not clear whether this kind of st-

ructural transition (stable or metastable) also takes place in the

hydrides with x 5 1.5, the present data may be accounted for by assu-

ming that tetragonal hydrides are formed coexisting with cubic y hyd-

rides. Namely, we propose that peak D arises.from hydrogen rearrange-

ment in the tetragonal hydrides formed below %320K, which transform to the cubic hydrides above this temperature making peak D quite insig- nificant. In this respect, it is interesting to note that metastable tetragonal hydrides are really observed in titanium of low hydrogen

concentration (x Q, 0.03) 191. Further structural study of titanium hyd-

rides is necessary to substantiate the above interpretation. REFERENCES

/I/ A.D.McQuillan, Proc. Roy. Soc. London A204 (1950) 309.

/2/ C.Korn and D.Zamir, J. Phys. Chem. Solids31 (1970) 489.

/3/ W.Klister, L.Bangert and M.Evers, Z. Metallme 47 (1956) 564.

/4/ 1.G.Ritchie and K.W.Sprungmann, Scripta Metallrl6 (1982) 1423.

/5/ Somen0 and Sait0, The S c i e n c e , T e c h n o l o g y a n d ~ p z i c a t i o n o f T i t a n i urn (Pergamon Press, Oxford, 1970) , p. 393.

/6/ R.J.Tinivella and F.Povolo, Mater. Sci. Eng. 20 (1975) 29.

/7/ K.Tanaka, T.Inukai, K-Uchida and M.Yamada, J.xppl. Phys.

2

(1983)

6890.

/8/ L.D.Bustard, R.M.Cotts and E.F.W.Seymour, Phys. Rev. B z (1980) 12.