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NUCLEATION OF RECRYSTALLIZED GRAINS NEAR BOUNDARY IN COPPER BICRYSTALS
F. Inoko, T. Hama, M. Tagami, T. Yoshikawa
To cite this version:
F. Inoko, T. Hama, M. Tagami, T. Yoshikawa. NUCLEATION OF RECRYSTALLIZED GRAINS
NEAR BOUNDARY IN COPPER BICRYSTALS. Journal de Physique Colloques, 1990, 51 (C1),
pp.C1-525-C1-529. �10.1051/jphyscol:1990182�. �jpa-00230350�
COLLOQUE DE PHYSIQUE
Colloque Cl, supplBment au nol, Tome 5 1 , j a n v i e r 1990
NUCLEATION OF RECRYSTALLIZED GRAINS NEAR BOUNDARY IN COPPER BICRYSTALS
F. INOKO, T. HAMA, M. TAGAMI and T. YOSHIKAWA
Department o f Mechanical E n g i n e e r i n g , F a c u l t y of E n g i n e e r i n g , The U n i v e r s i t y o f Tokushima, Minamijosanjima, Tokushima 7 7 0 , Japan
Abstract - The recrystallization at a common r / 9 rad near <110> tilt grain boundary in copper bicrystals was studied. The bicrystals had such orientation that screw dislocations of each primary slip system in both component crystals mainly piled-up to the boundary while edge dislocations of each corresponding coplanar slip system did. The recrystallized grains at each boundary were progressed by the three mechanisms of the <Ill> rotation, the strain induced boundary migration and the formation of twins. The twins were frequently formed before the accomplishment of polygonizat ion.
I - INTRODUCTION
It has been reported that in deformed copper bicrystals recrystallized grains were remarkably formed at grain boundaries by the <211> slip nucleation mechanisn/l/, and by the three mechanisms of the
<Ill> rotation, the strain induced boundary migration (SIBM), and the twin-formation/Z/. In our previous works on the recrystallization of alminum bicrystald3-7/ recrystallized grains were formed by the <Ill> rotation or(and) the SIBM mechanism(s) as shown in Fig. l. In order to further clarify the mechanisms of the recrystallization at grain boundaries in copper, deformed bicrystal specimens were observed in situ by TEM with a heating apparatus.
Z - EXPERlMENTAL PROCEDURE
99.99 mass% copper bicrystals with a common r r / 9 rad near <11D> t i l t grain boundary were prepared by using a *soft-mold" Bridgman technique /8.9/
.
The relationship between component crystals A and B in each bicrystal was given in Fig.2. The mark PlDlA presents the slip system with the slip plane P1 and the slip direction D1 in crystal A. PlDlA and PlDlB corresponded to the primary slip systems in crystals A and B, respectively. Screw dislocations of the primary slip systems PlDlA and PlDlB mainly piled-up to the boundary while edge dislocations of the corresponding coplanar slip systems P132A and PlD2B also did. In Fig. 2 and 3 the two faces of the bicrystal normal to the X-axis and the X-one were called "front face" and "back face". respectively. The tensile direction was parallel to the Z-axis.Bicrystal specimens were electropolished and deformed in tension to the strain of 0.3 at room temperature. Then, the behavior of slip bands and deformation bands was examined under an optical microscope, SEM and ECP. Then. the bulk specimens were annealcd at 6333 for 765sec. and then at 663K for 300sec. They were examined by using SEM and ECP. From the deformed bicrystals TEM specimens including each boundary were prepared. Recovery and recrystallization near the boundary were observed in situ by TEM with the heating apparatus at various temperatures from room temperature to 623K.
3
-
RESULTS and DISCUSSIONOptical micrographs of slip bands and deformation bands on crystals A and B. and near the grain boundary on the front and back faces in deformed bicrystal were shown in Pig.4. Double slip bands were observed in the regions far from and ne& the boundary. Near the boundary additional slip bands were also formed. The deformation bands far from and near the boundary on the front face of bicrystal
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1990182
Cl-526 COLLOQUE DE PHYSIQUE
corresponded to those of the secondary slip bands. In bulk specimen annealed at 633K for 165sec and then at 663K for 300sec. recrystallized grains were formed mainly by the SIBM of crystals A and B.
especially by that of crystal A into crystal B as shown in Fig.S(a). Twin-relationships between recrystallized grains and deformed crystal A were frequently detected by ECP. An example was shown between recrystallized grain D and deformed crystal A in Fig. 5(b). Just near the original boundary in the recrystallized grains formed by the SIBM of crystal A into crystal B many small subgrains were observed and their sizes grew with the progress of the boundary migration. It was recognized that recrystallized grains were surrounded by near (111) planes in the side of the recrystallized grain.
Photographs of ECP in Fig. 5(a) and (b) for as-annealed crystals A and B
.
respectively. indicated that even after annealing residual strain fairly existed. On the other hand, those in Fig.S(c). and (d) for both recrystallized grains presented that i t little existed. In other areas recrystallized grains obtained by the <Ill> rotation of deformed matrix were often observed. Ilowever, the frequency of their formation were less than that of the previous work /2/ .As-deformed. recovery and recrystallized phenomena of bicrystal specimens including each boundary were observed in situ by TEM at various temperatures. Fig. 6(a) showed a micrograph of deformation structure near an original boundary with the length of approximately 300 p m in the as-deformed bicrystal. Cell structures with the cell sizes of 0. 5 - 3 p m appeared. Fig. 6(b) showed a micro- graph of annealing structures at the same regions. Polygonized structures and recrystallized grains could be observed. Fig. 6 (c) and (d) indicated the enlarged photographs of the grains E and F in Fig. 6
(d). The crystal orientations of the recrystallized grains E' and F' were obtained by analyzing the slip traces. The visible length of the annealed boundary was fairly longer than that of the as- deformed original boundary because after annealing the dislocation density decreased. Main crystal orientations of as-deformed crystals A and B, and crystal orientations of recrystallized grains E'and F' were shown in Fig. 'l. Particular crystal orientations. maybe for deformation bands, distributed in the area of n/10 rad around each main orientation. Unfortunately, the precise relationships between original deformed orientations and annealed ones of the recrystallized grains E' and F'.
respectively, were not obtained, for the pseferred orientations of the deformed matrix were obtained as shown in Fig. I. but the orientations of the deformed matrix just for the regions of the recrystallized grains E' and F' were not measured. The grain size of the recrystallized grain E' was approximately 30 lr m.
The formation of twins during annealing at 623K was shown in Fig.8(a) and (b). The progress of the recrystallization by the formation of twin was observed in situ by TEM. Dislocations forming cell walls decreased with increasing the combination of them with twinning dislocations. As the result of i t , the recrystallizing of the area gradually progressed from the upper to the bottom micrograph as shown in Fig. 8(c).
In aluminum bicrystals there were two recrystallization mechanisms of the <Ill> rotation and the SlBM
3 7 . In our previous/Z/ and present results near certain grain boundaries in copper bicrystals
there were three recrystallizat ion mechanisms of the twin-formation ( <211> slip nucleation ), the
<Ill> rotation and the SIBM.
4 - CONCLUSIONS
The recrystallization near a common 7r/9 rad near <110> tilt grain boundary in copper bicrystals occurred by the three mechanisms of the <Ill> rotation. the SlBM and the twin-formation. Dislocations forming cell walls were gradually due to the combination of then with twinning dislocations.
REFERENCES
/l/ Ileller. f1.W.. Verbraak. C.A. and Kolster. B. H.. Acta Mctall. 32(1984) 1395.
/2/ Inoko. F., Kobayashi. M.. Sejima, A., Tatsumi, K. and Mcshii, M.M.. J. Japan Inst. Metals, 52(1988) 1169.
/3/ Inoko, F. and Fujita, T.. Proc. 4th Inter. Symp. on Grain Boundary Structure and Related Phenomena. Supplement to Trans. J lhl. 21 (1986) 435.
/4/ Inoko. F. and Mima. G.. Scripta Met., 21(1981) 1039.
/5/ Inoko, F. and Fujita. T. and Akizono. K.. Scripta Met.. 21(1981) 1399.
/6/ Inoko, F.. Kobayashi. M. and Kawaguchi. S.. Scripta Met.. 21(1981)1405.
/l/ Inoko. F. and Kobayashi. M.. Journal de Physique. C5(1988) 605.
/8/ Inoko, F. Akizono, K.,Yamaji. II. and Mima. G.. Proc. ICM-2, Boston, p. 13 (1916).
/9/ Mima. C.. Inoko. F. and Atagi. K.. Trans. JIM. 21(1980) 89.
Component Pole
-
Primary slipCrystal (1 10)<l 1 1) trace
A 0
a
--- Secondary sliptrace
B m
A
Fig.1 - Shematic diagrams of the formation of re- Pig.2 - Orientation relationship between crystallized grains at general grain boundaries : component crystals A and U in a bicrystal (a) Four kinds of recrystallized grains. C. D, E The plane of projectior~ was near <110>.
and F have four different < I l l > rotations, respec- tively. and (b) Two kinds of recrystallized grains.
A ' and B' formed by the SIBM of crystals A and B.
respectively. In general subboundaries were left on the original boundary as shown with dotted lines.
Crystal A G.B. Crystal B
Front
Crystal B G.B. Crystal A
Fig.3 - Schematic diagram on the slip Fig.4 - Optical micrographs of slip bands and systems of the bicrystal. deformation bands on the front and back faces
on crystals A and B, and near the boundary.
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