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The heating method used in the ultra-high vacuum (UHV) system was similar to that employed by Yen et a l 4. The specimen holder is shown in Fig. 3; the specimen was heated by conduction from the resistively heated tungsten ribbons to which it was spot-welded. This configuration gives a reduced electric field in the central portion of the specimen, and it permits Auger analysis at elevated temperatures (with the heating current on). The maximum current used was 20A. A thermocouple spot-welded to the back of the specimen was used to control the temperature, which Was held constant within 5 ~ up to 700 ~ The temperature variation over the 10 x 5 mm 2 area of the sample was estimated to be less than 10 ~ The segregation behavior of 9 grains was studied at 50 ~ intervals over the temperature range 25 to 700 ~ The sample surface was initially sputtered clean with Ar § at 25 ~ the temperature was then raised to 50 ~ and the Auger peak heights were obtained for individual elements using a multi-channel analyser as a function of time until a steady state was reached. Then the temperature was increased by 50 ~ and the process was repeated up to 700 ~ thereupon the process was reversed until the sample returned to 25 ~ The Auger measurements were made with a Physical Electronics scanning Auger microprobe (SAM) using a primary beam size of 150 btm at 3 k eV and 50/ta beam current. The modulation volatage was 6 V. The Auger peaks used for analysis were (in eV): Fe 703, Sn 430, C 270, Si 92, and O 503. It should be noted that the 92 eV Si peak contains a contribution of uncertain magnitude from the 86 eV peak of Fe and that the latter decreases rapidly as the Fe is covered by segregating elements. RESULTS Initial Cleaning

YONG-XIN ZHOU is Graduate Research Fellow, SHIN-CHENG FU is Research Specialist, and CHARLES J. MCMAHON, JR. is Professor, University of Pennsylvania, Department of Materials Science and Engineering, Philadelphia, PA 19104. Manuscript submitted August 8, 1980. METALLURGICAL TRANSACTIONS A

The surface composition of grain no. 15 as a function of sputtering time is shown in Fig. 4. This shows that the surface was initally contaminated with C and O, due to contact with the air and cleaning in alcohol. It also

ISSN 0360-2133 / 81 / 0611-0959500.75 / 0 9 1981 AMERICAN SOCIETY FOR METALS AND THE METALLURGICAL SOCIETY OF AIME

VOLUME 12A, JUNE 1981--959

fCERAMIC

T a b l e I. C o m p o s i t i o n

Elements Wt Pct

Si 3.1

C 0.004

of the S a m p l e

S 0.004

Sn 0.06

Fe Balance

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.......

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UcRoN E I

I OOC

W n-

nw 0_

TO DC POWER SUPPLY

Cr - At ~

I

.

STAINLESS STEEL

//,7/1"

Fig. 3--Details of specimen holder

50C

COOL R

W

I O0

I00 5

0

I0

15

20

25

90

.50

X

/

T I M E , HRS

x - Fe

Fig. 1--Annealing schedule for producingcoarse-grained specimens.

"

o-C

80

t3

/

t~(lll)

"~

A - Si a - Sn O-N -~-0

70

O

F-"I-

60

W -r Y < W

'2 \ / /,200 o| 1001)

X

/x_x.x.X,,'x- x ,X X

50

/

40

(011)

Fig. 2--Orientations of surface normals of the grains studied.

showed a sma