Short range order in aluminium bronze

ACTA

170

Short

range

Several

order

in aluminium

investigators

measurements

METALLURGICA,

have

bronze*

recently

by u

from which short range

order

used filings

containing

and Averbach

14.5 at. y0 Al, Kagan et aZ.@) used filings or

solid alloy (unspecified)

containing

18.6 at. o/o Al, and

Boriec3) examined a single crystal with about 15 at. y0 Al.

After anneal at 700°C Kagan et a,l., claimed an cur

SRO parameter admission

as high as (-) 0.43 (though

that

Houska

and

this

might

Averbach

Kagan et al. attempted the

heat-treatment,

of the electrical resistivity at various temperatures

found

that

However,

temperature,

and

heating

z a b

measurements

to the

suggestion

has

recently been reinforced by resistivity measurements due to Kiister and Rave’s). Again, the phenomenon of anneal hardening of some copper-base

from

OYenched

fra

35O’C

quenched

from

25OT

quenched

from

200°C

quenched

from

15OT

i .E

0.5

-

E 2

28. FIG.

solid solutions,

degrees

1. Corrected diffuse scattering various heat treatments.

250, 200 and equilibrium

150°C

order.

respectively,

profiles

so as to achieve

All profiles show clearly the presence of a SRO peak near 20 = 28-30’;

this angle is close to that found

by the other investigators (allowing for the different The height of the peak, and wavelength used). consequently

the

degree

of

SRO,

increases

annealing temperature from below 400°C. but reproducible, feature is the anomalous,

This was also found by Houska and Averbach

In the light of these considerations,

2 years ago by the authors. Fine-grained 15 at. y0 Al,

sheet ground

of

a Cu-Al

flat

examined in an evacuated

and

Co KK X-rays

crystal were used,

containing was

diffuse scattering apparatus

provided with a proportional analysis.

alloy

electropolished,

counter with pulse height

monochromated

by a bent

Rough correction for Compton and

thermal scattering was achieved by measuring the scattering profiles from pure copper and aluminium and weighing

these appropriately.

atomic scattering

The variation

factor and polarization

convergence

of the profiles

may be due to simultaneous

it is of interest to present briefly some results obtained

proportionality

intensity

in electron

constant

was not

correct for long term fluctuations profiles

were normalized

at small Bragg and compensating

angles. and changes

in SRO and the size effect factor due to the displaceIn Fig. 2, ment of atoms from lattice points. uncorrected

scattering

profiles

are reproduced

for a

sample which was partly disordered, first by quenching and later by cold rolling.

After

each disordering,

(The low-angle

tail of the profile of the rolled sample

was lower than for the sample disordered by quenching, or for the ordered sample;

this again is anomalous.)

of

factor with

units, though

the

determined.

(To

A

quenched

from

6OO’C

B C

quenched quenched.

from then

600°C+165h rolled 46%

01 15Z°C

in incident intensity,

at 20 = 40”, since it was

observed that at this angle scattered intensity almost independent of previous heat treatment.)

a

prolonged heat treatment at 150°C re-established very substantial order which was the same in both cases.

Bragg angle f3 was also allowed for; the corrected scattering profile was then at all angles proportional to the scattered

with

decreasing

attributed

the deformation.

diffuse

scattering profiles obtained after these heat treatments.

An

of SRO destroyed by

after

Fig. 1 shows the corrected

including Cu-Al, (hardening due to a low temperature anneal following heavy deformation) has by some been to there-establishment

400-700

1.0 -

at

and Kernohant4))

this

qusnched

B

z

Only

of Cu-AI alloys heat treated (Wechsler

n C

1.5-

overestimate).

tcl = -0.14.

that SRO might be quite sensitive

annealing

o : 3

at.% AL

with an

the anneal at 7OO”C, made very

little difference to the SRO.

suggested

an

h-15

to relate the degree of SRO to and

300~5OO”C, following

be

found

1962

-_

solid solutions of aluminium in copper, they inferred the presence of substantial Houska

10,

published

of the diffuse scattering of X-rays

(SRO).

VOL.

was

A sample was heat-t,reated at 350,250,20Oand 150°C in each case following a brine quench from 550°C; further heat treatments were given at 600°C and 700°C (followed by the brine quenches). Annealing times of 3 hr, 1 week, 1 month and 2 months were used at 350,

I

30 28,

I

I

40

50

degrees

FIG. 2. Uncorrected scattering profiles, showing effects of quenching, rolling and annealing.

1

LETTERS

The

Russian

considerable

workers(2)

were also able

TO TKE

to produce

The increase of order as the annealing temperature

with the resistivity

still higher quenching begins to increase, measurements; vacancies

measurements.(5)

this was attributedt4)

which accelerate

diffusion

to quenched-in during the later

did not go high enough to test this; interesting

For

temperatures the order again according to the resistivity

stages of the quench. Our heat-treatment

The

Further

SRO by annealing at 260°C after rolling.

is lowered below 35O”C, and its insensitivity to annealing temperature in the range 400-7OO”C, is consistent

EDITOR

temperatures

it would

171

evidence for the atomic size effect in dilute binary liquid metal solutions*

A knowledge

of the parameters

the factors which control corrosion and mass transfer in nuclear power plants employing

of any

pronounced

as working

fluids.

between alloys annealed at 700,500 Russian workers@) is consistent

to fit experimental

solubility

in

expression

metals

employed

A T

B,

+

(1)

SRO

with the observations quoted

metals as

data is:

be an

and 300°C by the

of our Fig. 1, and with the conclusion

A common

log,,, N =

difference

liquid

heat transfer media and boiling and condensing

theme for future examination.

lack

which determine

the absolute solubility and its temperature coefficient is an important prerequisite to an understanding of

in the

where N is the atomic fraction of solute in the saturated solution

T”K, and A and B are

at the temperature

assumed

to be constants.

In a previous

a

order one

was presented

must either anneal below 250°C or quench from above

coefficients

of solubility-2.303

800°C.

gas constant-in

The creation of substantial short range order at low temperatures is consistent with a dilatometric anomaly below 265°C discovered by Chevenard(6), and also with

the ratio of the atomic radius of the solvent atom divided by the atomic radius of the solute atom. A

a calorimetric

further

preceding

paragraph.

To get substantial

anomaly

found by ~asumoto

in the range 17&33O”C

et o1.‘7) and confirmed

and Zenkova(8);

this calorimetric

t,o that recently

explored

anomaly

by Clarebrough

first

described

RA

where R is the

dilute binary liquid metal solutions

and the atomic

size factor,

analysis

is’, which was defined as

of the solubility

data,“)

including

by Panin is similar

between B in equation (I) and S, and the results are given in the present communication.

et CL(~) in

The present investigation

desirable that future measurements

the temperature

more recently reported data:t2-@ yielded a correlation

their study of a brass. In view of the observations

between

paper(l)

correlation

above,

it is

of SRO in alloys

was restricted

mainly

to

dilute binary metallic systems in which the phase in equilibrium with the saturated solution is essentially

should be made on samples which have been subjected

pure solute in the concentration

to well defined heat treatments.

a few systems

One of us (R. G. D.) is indebted to Her Majesty’s Department of Scientific and Industrial Research for

also considered.u)

a maintenance

the solutes in the systems designated by squares are for 6-fold co-ordination and all other atomic radii are

grant.

R. G. DAVIES

Department of Physical Metallurgy

R. W. Carry

University of Birmingham Birmingham

15, U.K.

containing

region considered;u’

carbon

Figure 1 is a plot of B vs. 8.

for

12-fold

previously,(i)

co-ordination.(l)

as the solute were The atomic radii for

For

reasons

discussed

certain systems are represented in Fig. 1

by both circles and squares. References

1. C. R. HOUSKA and B. L. AVERBACH,J. Appl. Phys. 30,

1525 (1959). 2. A. S. KAG~N, V. A. SOMENGOVand Y-4. S. UMANSKII, ~~~~~~~g~~~yu 5, 540 (1960); (English version) i%vi& Phys. Cry&. 5, 519 (1961). 3. B. S. BORIE, private communication. 4. M. S. WECNSLERand R. H. KERNOHAN,Aeta Met. 7, 599 (1959). 5. W. KBSTBX and II. P. RAVE, 2. Metallic. 52, 158 (1961). 6. P. CHEVENARD,J. Inst. Met. 38, 39 (1926). 7. H. MASU~~OTO,H. SAITO and M. TAKARASHI, Sci. Rept. Res. In&s. To?wku Univ. A7, 465 (1955). 8. V. E. PANIN and E. K. ZENKOVA, DoleI. Akad. Nauk SSSR 129, 1024 (1959); (English version) Soviet Phys. Dokl. 4, 1368 (1960). 9. L. M. GLARESROUGH, M. E. HARGREAVES and M. A. LORETTO, Proe. Roy. 2%. (London), A257, 326, 338, 363 (1960). * Received August 21, 1961.

Although

the total

number

of plotted

points

in

Fig. 1 is not very large, especially in the region of atomic size factor less than unity, and there is some scatter in the data,t

a general trend is still indicated.

The data suggest two concave-upward

curves which

are quite similar to those shown in Fig. 1 of Ref. 1. Thus,

for the systems

studied,

the disparity

in the

atomic radii of solvent and solute atoms appears to be an important factor which determines the value of each of the two unknown parameters, A and B, in t The scatter in Fig. 1 may be attributed in part to the fact that atomic radii we not constantc) and that liquid metal solubil~ty data available in the literature frequently lack the precision and reliability typical of data for systems involving less serious experimental difficulties.