Comments on stacking fault energy of thorium

Comments on stacking fault energy of thorium

LETTERS TO ;i. J. B. COHEN and C. N. J. WAGNER, J. Metals (Abstt.) 14, 82 (19.57). 6. C. N. J. WAGNER, Acta Met. 5, 427 (1957). 7. G. B. GREENOUQH, ...

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LETTERS

TO

;i. J. B. COHEN and C. N. J. WAGNER, J. Metals (Abstt.) 14, 82 (19.57). 6. C. N. J. WAGNER, Acta Met. 5, 427 (1957). 7. G. B. GREENOUQH, Progr. hlet. Phys. 3, 176 (1952). 8. D. MICHELL and A. P. SMITH, Phil. Ma,g. 7, 737 (1962). 9. NORMAN BROWN, Trans. Amer. Inst. Min. (Metall.) Engrs. 221. 236 119611. 10. G. SCHOE& and A. SEEGER, Repts. Cor4f. Defects Solids p. 340. Phys. Sot. London (1955). 11. L. K. JETTER and C. J. MCHARGUE, The Metal Thorium. Amer. Sot. Metals, Cleveland (1958). * Received

August

24, 1962.

THE

EDITOR

cross-slip with

225

occurs.

These

the earlier work

a stacking

fault

results

are in agreement

of McHargue(‘)

probability

for

which

thorium

gave

approxi-

mately equal to that of silver, a metal of intermediate stacking fault energy (y _N 25-60 erg cm-z).(g) It is not clear from this type of study of interpretation

what sort

should be given to the term “stacking

fault probability”

as deduced from X-ray

line shifts.

There does indeed appear to be a relationship the

stacking

fault

probability

and

between

stacking

fault

energy.

Comments

on stacking

fault energy of thorium*

In recent years enough evidence lated that the stacking be

roughly

deformed

by

studies.(l-5)

consideration

t,ransmission

These

of dislocation

studies

beam.

stacking

energies

fault (y -

such as many

are visible

These dislocations

the

in lightly

motion

induced

In materials having very low

2-5 erg cm-2),

dislocations

electron

involve

distributions

material and of dislocation

by the electron alloys

are faulted does not seem to be borne out by electron

has been accumu-

fault energy of a metal may

estimated

microscope

However, the interpretation of the stacking fault probability as the fraction of { 11 l} planes which

copper-aluminum widely extended

after slight deformation.(lt2)

can be induced

to move

only in

straight

lines upon examination at high beam inIn materials no cross-slip is evident. tensities; having high stacking fault energies (for example, aluminum produced

with y N 238 erg cm-2)(5) the dislocations by deformation

three-dimensional

free of dislocations.(4) detected,

No

and profuse

together

and form

cells relatively

stacking

faults

can be

cross-slip occurs under intense

electron illumination.(5) is

tangle

walls surrounding

In general the cell structure

more clearly defined the higher the stacking

energy.(l) With the

background

made to resolve X-ray

studies

in mind

an attempt

the discrepancies

of stacking

faults

between

fault was

the two

in thorium(‘p*)

by

observing lightly deformed thorium foils with transmission electron microscopy. The foils were prepared by

electropolishing

0.010 in.

thick

iodide

thorium

sheet which has been deformed approximately per cent by cold rolling after recrystallization. Tangled dislocations were

observed

in

fringes

characteristic

During

examination

forming

the

high

material.

faults were visible. beam

intensity

the

stacking fault energy, greater than stainless steel in which no cells are formed by light deformation but less than

probability after

observations.

deformed

severe

Studies

of 0.017

Bailey(lO)

(i.e. 1 plane in ~60

deformation),

of stacking faults.

by

silver, which has a stacking have

shown

Some annealing

is faulted no

was not done at low temperature.

studies of other f.c.c. fault probabilities

appar-

However,

metals having similar stacking

have shown

even after low-temperature

no images

of faults

deformation.t3)

Metals and Ceramics Division Oak

images

out of faults may

have occurred in this case as the deformation ently

of

fault

Ridge National Laboratory-f

J. 0. C. J.

STIEGLER MCHARGUE

References 1. A. HOWIE, Direct Observation of Imperfections in Crystals edited bv J. B. NEWIRK and J. H. WERNICK, (1962). 2. P. R. &ANN and J. NUTTING, J. Inst. Met. 9d, ‘133 (i961). 3. D. H. WARRINGTON, Proceedings of European Regional Conference on Electron Microscopy Vol I, p. 354, Delft De Netherlandse Vereniging DOOP Electronen(1960); microscope Delft (1961). in Solids. 4. JACK WASHBURN, Strengthening Mechanisms Amer. Sot. Metals. (1962). 5. P. B. HIRSCH, R. W. HORNE and M. J. WHEL_4N, Phil. Mag. 1, 677 (1956). in Crystal? p. 165. 6. H. G. VAN BUEREN, Imperfections North-Holland Publishing Company (1960). 7. C. J. MCHARGUE, Acta Met. 9, 851 (1961). 8. V. S. ARUNACHALAM and K. TANGRI, Actn Met., this issue p. 223. 9. P. R. THORNTON and P. B. HIRSCH, Phil. Mao. 3. 738 (1958). 10. J. E. BAILEY, Phil. Mug. 5, 833 (1960). * Received

October

22, 1962.

t Operated for U.S. Atomic Carbide Corporation.

Energy

Commission

by Union

No

dislocations moved readily but only in straight lines. No example of cross-slip was observed. These observations suggest that thorium has an intermediate

considerably

heavily

a crude cell structure

as-deformed

of stacking at

10

microscope

aluminum

where

abundant

Sur la cinetique d’oxydation dans temperatures elevees de deux alliages a faibles teneurs d’addition* L’Btude de l’influence

des additions

l’air aux de cuivre

de silicium ou

d’aluminium au cuivre, sur la cinbtique de l’oxydation de ce metal dans I’air ou I’oxyg8ne aux temperatures BlevBes, a d&j& fait l’objet de plusieurs travaux parmi lesquels il faudrait titer tout particuli&rement ceux de