The influence of preparational parameters on stage II recovery of deformed gold

Mat. Res. Bull. Vol. 3, pp. 79-82, 1968.

P e r g a m o n Press, Inc. Printed in

the United States.

• rm L THE I ~ U E N C ~ OF PREPARATIONAL PARA~.~I~S ON STAGE II RECOW:TRY OF DEFOE~'~D GOLD*

H. I. Dawson Universit~r of Washington Division of Metallurzy Seattle, ~ s h i n ~ t o n

(Received

December

18,

1967;

Communicated

b y R. A.

Huggins)

ABSTRACT The depend~nce of the fine structure of stace II recovery in ~zol@ on the pre-deformation annealing treatment is discussed.

Introduction Point defect properties in gold have frequently been studied without much precaution t.~ken to prevent contamination of the specimens by caseous impurities dur~n~ h:~jh temperature annealin?;.

In quenchin~ stud:ies, it

has been realized recentl~f that the pre-quench annealing atmosphere c~n have a siTnifics_nt -~nfluence on the recovery of quenched in defects (1-3). Possib].e effects of annea!inc t ~ e

and ~nnealinc temperature durin!~ specimen

preparation have not been considered systematic~.li"j.

The oresent paper will

show t_hat for the study of the recove~r after plastic deformation, the anne~inL: etmosphere as we]]. as annea).inc time and temperature~ are import~tnt pzrameters which will have to be taken into account ~n fut~,re ~.,~orkon the recovery of deformed metals.

The ~nfluence of the ~,egree of defomuation

on Sta
*Uork supported in part b~I the National Science Foundation.

79

80

T

RECOVERY

OF DEFORMED

Vol. 3, No. Z

Experimental Results and Discussion

Au (99999%)

&/'X : 319 x I0-10~cm

GOLD

! HOUR AT 4 5 0 ° C IN AIR

FiLulre 1 shows recove~r curves of the electric~l resistivity of o9,,.o99 ¢ pure_ go].~ wires, ~.nnealed for 1 hour %t 450°C in air and then deformed to various de,zrees in tension. The deformation,

c

, is indicated for

each run at the end of the curve.

The

point on the vertical axis where A p equals zero is not the same for each 10.6%

6.7%

curve since the curves have been

5.8%

-2OO

-150

-I00

-50

TEMPERATURE (%)

shifted in the vertical direction for simplicity of presentation.

FIG. 1 Recovery curves of the electrical resistivity in Stage II of gold. Pre-deformation annealing treatment: 1 hr. at 450°C in air. recovery is s h ~ m Apx

were

taken at

77°K after

The data

annealing

the specimens for five minutes at each of the temperat,~res specified.

up to -60°C, being the end of Stage II.

The

The value of

, indicated at the beginning of each c~n~ve, gives the resistivity

difference between the beginning and the end point of each curve: i.e., the net effect of Stage Iio

The curves exhibit four prono~mced substages.

Between the first two substages there is~ provided the deformation is sufficiently s~all, an increase of resistivity which is larger than the exper ~mental error. In figure 2. recover[ c1~rves are plo'oted for specimens which were pre-defonmat~on annealed for two hours at lO00°C in vacuo or in air. both cases the shapes of the curves are quite different from those of figure i, and similar to those observed in s_~iver and copper (4).

The

three local maxima are more pronotmced after annealing in vacuo than

In

Vol. 3, Noo

Z

RECOVERY

OF

DEFORMED

GOLD

81

Au (99.999%) Au (99999%)

Ap~= 6 , 3 x IO'lO,O, c m

30 -

t

/,

• I hr, 450 °C, air A 2 hrs, 1000°C, air

/ /

Ap 2c

\ 7 `° IO

•

"~Z2%

• -200

- 150

%7.3% - IO0

TEMPERATURE

(°C)

- 50

=

FIG. 2 Recovery curves of the electrical resistivity in Stage II of gold. Pre-defonnation annealing treatment: 2 hrs. at 1000°C in vacuo or in air.

o

I 5

IO

~,%

FIG. 3 Net resistivity change in Stage II as a f~mction of the degree of defon~ation for different pre-deformation annealing treatments.

after annealing in ai r , indicating that the effect could be related to the influence of impurities on the recovery mechanisms; according to Ytterhus, Siegel and ~ l l u f f i

(3), the bulk purity of cold increases by annealinc~ it

in air. In figure 3

the net resistivity effect of Stage II, A # ~ ,

plotted as a fln~ct~on of deforTnation.

is

For a given defo_nnation~ A p ~ is

lar~Te:~ in specimens which ~ere pre-deformation annealed for one hour at 450°C, than in the s~ecS]nens annealed for tvo hours at lO00°C. After anneal'n~ at 450°C, the dislocation density is larger~ and consequently, a larger point defect concentration is produced by the same elongation (5).

Since all the A p x points taken from figure 2 fall on the

/

8Z

RECOVERY

OF DEFOR/~ED

GOLD

Vol. 3, No. Z

same line as shown in figure 3, the difference in the recovery curves for specimens annealed for two hours in vacuo or in air is probably due to a difference in the details of the recovery mechanisms rather than in the production of the defects.

The observed increase in resistivity during

annealing could be due to the breaking up of small interstitial clusters (14,6). The free interstitials can disappear at sinks or become trapped at impurities.

The relative importance of the latter

possibility is larger for smaller deformations ~nd for more impure specimens.

Consistent with this suggestion is the observation that the

resistivity maxima of figure 2 are larger for the specimens annealed in air, which should purify the gold (3).

References 1.

D. Jeannotte and E. S. Machlln, Phil. Mag., 8, 1835 (1963).

2.

R. L. Segall and L. M. Clarebrough, Phil. Mag., ~

3-

J. A. Ytterhus, R. W. Siegel, and R. W. Baluffl in Lattice Defects in

865 (1964).

Quenched Metals, p. 679, Academic Press, New York (1965). ~.

H. I. Dawson, Physlca, 3]-, 1046 (1965).

5.

H. I. Dawson, Physlca, 3]., 342 (1965).

6.

D. Schumacher and A. Seeger, Phys. Lett.,_~

184 (1963).