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INTERNAL- FRICTION STUDY ON THE STRUCTURE CHANGE OF COLD-WORKED
METALS ANNEALED AT VARIOUS TEMPERATURES
T. Kê
To cite this version:
T. Kê. INTERNAL- FRICTION STUDY ON THE STRUCTURE CHANGE OF COLD-WORKED
METALS ANNEALED AT VARIOUS TEMPERATURES. Journal de Physique Colloques, 1985, 46
(C10), pp.C10-351-C10-354. �10.1051/jphyscol:19851078�. �jpa-00225463�
INTERNAL- FRICTION STUDY ON T H E STRUCTURE CHANGE OF COLD-WORKED METALS ANNEALED A T VARIOUS TEMPERATURES
T.S. K;
Institute of Solid State Physics, Academia Sinica, Hefei, China
Abstract
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The structure changes and the movement of the defects (mainly dislocations) in cold-worked and annealed aluminium were studied by internal-friction measurements with a torsion pendu- lum. Plentiful new results obtained signify that this type of approach initiated early in 1950 /I/ is worthwhile for further exploration. The correlation of electron microscopic observa- tions with internal-friction measurements renders a successful interpretation of the micro-processes found in various anneal- ing stages.I. Introduction
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In the process of the annealing of cold-worked me- tals, recovery, polygonization, recrystallization and grain growth oc- cur successively as the annealing temperature is raised. Each anneal- ing stage corresponds to a different configuration and distribution of the internal structure defects. Measurements on the internal-friction changes and the factors (as previous cold-working and impurities) af- fecting these changes can furnish information concerning the peculari- ties and configurations of the structure defects in each annealing stage.In Fig. 1 are shown the low-frequency internal friction changes in 99.991 wt % aluminium (cold-worked by195 $ RA) annealed at various
temperatures for 1 h. It is seen that the Q of cold-worked specimen increases with the temperature of measurement, but is lowered by annealing at successive higher temperatures. This is considered to be associated with the recovery process in the specimen. The dislocation density decreases with annealing and its mobility increa- ses with the temperature of measurement.
It is to be noticed that the internal friction at 250sC after an annealing at 2509C reaches a very high value of 0.18. This corresponds to the stage of recovery and polygonization. The internal friction curve begins to bow down after an anneal at 290aC, indicating the on- set of recrystallization. An internal friction peak appeared around 290°C (f=f HZ)' aiftsrsnanneal at 350eC. This peak has been attributed to the viscous slip along the grain boundaries in metals. /2/ The cold-worked specimen has now been completely recrystallized after this anneal, with the emergence of regular and uniformly distributed grains.
When the annealing temperature is further raised (higher than 450°
C), the internal friction peak displaces toward a high temperature.
This reflects the process of grain growth. And, as the grains exceed the diameter of the wire specimen with the appearance of bamboo boun- daries, the height of the internal friction peak is lowered and the
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19851078
C10-352 JOURNAL DE PHYSIQUE
peak tends to shift toward a lower temperature.
Fig. 1
.
Effect of annealing tempe- rature on the internal-friction curve (versus temperature) of cold- worked (95 % R A ) 99.991 % aluminium.The temperature marked on each cur- ve is the annealing temperature
(1 h). Frequency of vibration = 1 Hz.
The maximum strain amplitude on the surface. of the specimen = 1 o - ~ .
TemvrrQlur. 0 , Heoru.rm.nl K,
It is seen that the internal friction background beyond the grain- boundary peak increases with temperature. This background is very sen- sitive to the previous deformation before annealing and the deforma- tion after annealing. It also increases with the impurity content in the specimen. However, the micro-mechanism of the high-temperature internal friction background in terms of structure defects is very poorly explored.
11. Origin of the grain boundary internal-friction peak (K$ peak) In 1976, the question was rai-
sed that the grain boundary peak
-
TIKIobserved by K'$ in 1947 is not originated from grain boundary process but is, on the contrary, connected with the dislocations inside the grains./?/ Recently, it is shown definitely that the grain boundary peak did not ap- pear in aluminium single crys- tals prepared by three different methods./4/ Fig. 2. gives the internal friction curve of po- lycrystalline 99.999 % A1 and of single-crystal 99.999 % A1 prepared by method of growth by zone-melting. So the grain boun-
dary peak is, to be &re, asso- Fig. 2. Internal friction curves ciated with the grain boundary of polycrystalline 99.999 % A1 and process in fine-grain single-crystal 99.999 % A1 without
any bamboo boundaries. Vibration frequency = 1.7 Hz. Curve 1: poly- crystal. Curve 2: single crystal prepared by method of growth by zone melting.
111. Origin of the internal friction peak appeared nearby but lower than the temperature of the grain boundary peak (macro-crystal- line peak)
When a completely recrystallized specimen was annealed at an eleva- ted temperature so that the grain size exceeded the diameter of a wire specimen (or the thickness of a sheet specimen), another internal friction peak appeared at a temperature which is about 20°C lower (f = T Hzlthan that of the grain boundary peak.
mm is shown by curve 1 in Pig. 5./5/
For a specimen with grain size of 9 1,) mm which exceeded the diameter 8
of the specimen, the height of the
peak was slightly lowered, and the 7 position of the peak was shifted to
a lower temperature (curve 2). The re l6 5
specimen was further annealed to get O
bamboo-like grains having an average
-
Llength of 1.8 mm. Curve 3 shows 3
.that the peak shifts considerably to
a lower temperature in comparison 2 with curve 1. The height of the peak 1 is 0.096 which is even higher than
that shown in curve 1 (0.08, the grain boundary peak). This shows that when the length of the bamboo-
like grains is much larger than the Fig. 3. Internal friction specimen diameter in which case the curves of 99.999 % A1 with conventional peak (K$ peak) should various grain sizes: 0.5, not appear, an internal friction 1.1, 1.8, 5 mm, single peak higher than K$ peak appeared crystal for curves I to V.
instead. So we can conclude with Specimen diameter = 1 mm.
confidence that this high internal friction peak is not the K& peak,
it is a new peak of a different type. Experiments with 99.9999 A1 showed a much larger separation between the K$ peak and this new peak.
/ 6
/
Results of TEM observations showed that pofygonization boundaries existed abundantly in the specimen in which 10
the grain size exceeded the specimen diameter./5/ So we consider that the new internal friction peak is related to the polygonization boundaries.
As is shown by curve 5 of Fig. 3 , this new peak did not appear in A1 '0 6 single crystals which did not contain 'b
any bamboo boundaries. Latest experi- 4
ments carried out by B. S. Zhang in our laboratory confirmed definitely
that the presence of some bamboo boun-
*
daries in the specimen is another ne- cessary condition for the appearance
-
-
-
-
-
#'
Y
F J4
o ~ ' " c ' s ' L 7 ' 4
of this new peak. Fig 4 shows the o 1 0 20 30 4 0 50 linear relationship between the
height of this macro-crystalline Fig. 4. The relationship internal friction peak and the num- between the height of the ber of bamboo boundaries contained macro-crystalline internal in the specimen. friction peak Q-Aax (with
It turns out thus that the exis- background subtracted) and tence of both polygonization boun- the number of bamboo boun- daries and bamboo boundaries is ne- daries N. f = 1 Hz, A = cessary for the appearance of this 5 x
to-=.
new peak. One possible answer to this question is that polygoniza- tion boundaries do not appear in a
single crystal specimen without containing any bamboo boundaries. TEM observations showed that polygonization boundaries appear abundantly only nearby the grain boundaries and the border of macro-crystalline specimens of 99.999 % Al. As such, it seems that the new internal
C10-354 JOURNAL DE PHYSIQUE
friction peak may be attributed to the combined effect of the bamboo and polygonization boundaries.
- -
References:
/ I T. S. Ke, Trans. AIME 188 575, 581 (1950).
/2f T. S.
KO,
Phys. Rev. ~ ~ $ (1947). 3 3/3/ E. Bonetti, E . Evangelista, E. Gondi and R. Tagnato, Nuovo Cimento
m,
408 (1976); J. Woirgard, ibid, 424./4/ T. S. K$, P. Cui, and C. M. Su, phys. stat. sol. (a)
84,
157 (1984)./5/ T. S. K$, L. D. Zhang, P. Cui, Huang, and B. S. Zhang, phys. stat.
sol. (a)
84,
465 (1984)./6/ T. S. Kk, P. Cui, S. C. Yan, and Q. Huang, phys. stat. sol. (a) 86, 964 (1984).
/7/
C.
M. Su and T. S. K g , this Conference./8/ J. Shi, L. D. Zhang and T. S. ~'8, this Conference.
IT. Origin of the internal friction peak found at a temersrz
higher than that of the grain boundary peak (single crystal peak
or 365OC peak) T
An internal-friction peak si- 400 350 300 '230 Zoo
tuated at 365'C (f = 1 Hz) was ob- served in 99.991 and 99.999 % alu- minium single crystal prepared by the static and dynamic-annealing method
/4/
and the latest results will be reported by Su and Ke in a separate paper during this con- ference./7/ Fig. 5 shows the inter-:
nal friction curves of 99.999 76 A1 o
single crystal grown by low tem- 2 perature dynamic annealing (at 450'
C) and then annealed at 600eC for 2 h. Measurements were taken in descending-temperature with two frequencies 0.477 and 1.26 Hz for
curves 1 and 2. The activation 3
m !L= ~fl, \ \
P \
\ \
-
I-\
\=\
\\L.
, , , , , , , ,
1 4 1 6 I 8 2 0 2 2
energy determined is (1.84 $ 0.1) 100olT ( < I,
eV with 9.=, 1.4 x $0'4 Hz. In Fig. 5. Internal friction peaks correlation with results of TEM of 99.999 A1 single crystal observations, this peak is con- grown by low-temperature dynamic sidered as originating from the annealing (at 4606C) and then formation and the movement (climb- annealed at 600°C for 2' h. Fre- ing) of the jogs on the disloca- quency of vibration: curve 1
,
tions constituting the spatial 0.477 Hz; curve 2, 1.26 Hz.
network. The anomalously ampli- tude-de endent effect exhibited by
P
the 365 C peak is explained as due to the piling up of the jogs and the subsequent release because of the shift or the breaking down of the nodes of the dislocation network.
V. On the high-temperature internal-friction background
The high-temperature background beyond the 365wC peak was found to increase markedly by deforming a macro-crystalline or single-crystal specimen slightly at room temperature or under creep conditions./7,8/
TEM observations on these specimens showed that cell structures are formed and cannot be destroyed simply by an annealing at an elevated temperature. This indicates that the high-temperature background is connected with the existence of cell structures.
BI. The analysis and interpretation concerning the conditions for the appearance and disappearance of the various types of internal friction in high-purity A1 can be generalized to other pure metals as well as to metals containing impurities.
