CONNECTION BETWEEN THE MICRO-STRUCTURE AND THE INTERNAL FRICTION OF COLD ROLLED IRON

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CONNECTION BETWEEN THE

MICRO-STRUCTURE AND THE INTERNAL FRICTION OF COLD ROLLED IRON

I. Harangozó, P. Arató, F. Kedves, L. Gergely, S. Kiss

To cite this version:

I. Harangozó, P. Arató, F. Kedves, L. Gergely, S. Kiss. CONNECTION BETWEEN THE MICRO- STRUCTURE AND THE INTERNAL FRICTION OF COLD ROLLED IRON. Journal de Physique Colloques, 1983, 44 (C9), pp.C9-735-C9-739. �10.1051/jphyscol:19839111�. �jpa-00223346�

CONNECTION BETWEEN THE MICRO-STRUCTURE AND THE INTERNAL FRICTION OF COLD ROLLED IRON

I.Z. Harangoz6, P. ~ r a t 6 * , F.J. Kedves, L. Gergely and S. Kiss

I n s t i t u t e f o r A p p Z i e d p h y s i c s , K o s s u t h L . U n i v e r s i t y , Debrecen, P.O. Boc , H- 4 0 10, Hungary

* c s e p e Z M e t a l W o r k s , CsepeZ I , P.O. Box 4 9 , H-1751, Hungary

RQsumd

-

On a observQ du fer de 99.9% produit de technologic habituelle de lamination. On a aper@u des ph6nimdnes anomaux

dans le matiere qui contient 0.022 p% droxigdn3 en dtat de dd- formation de 35% et dgalement en dtat de traitement thermique et en Btat de deformation tandfs que dans le matidre qui contient 0.009 p% d~oxigdne lvanomalie ne ~a zidn-tre pas.

Abstract

-

We observed an 99.9% purity iron, produced by common rolling industrial technology. An anomslic behaviour was ob- served both in deformed and annealed state after 35% rolling reduction in a material containing 0.22 wt% oxygen, but it have not occured in alloy with 0.009 wt% oxygen.

Experimental and theoretical studies of high temperature internal friction suggest (1, 23 tkat a definite connection exists between damping a.nd dislocation density, The energy losses of deformed metals decrease with annealing as dislocations are annealed-out 13). !Phis makes it possible that the recrystallization of heavily deformed metals can be studied by high temperature internal friction measure- ments. The ain of the preeent ivork was to investigate the micro-

structure af mild steel plates with a thickness less than 1 mm, ha- produced by common industrial technology using cold rolling up to about 63% and appropriate heat treatments.

Experimental procedure

Two batches of high purity iron were prepared with different inter- stitial contents. Tbe chemical composition of the two series of s- ples /called 4 and 5/ is given in wt%:

The ingots were melted in vacuo an& remelted in an electron-bean fur- nace. They were forged and hot rolled to 2.2

-

^{2,5 rmn} thickness. The

slabs were cold rolled to about 1.0 mm, annealed for 1 h at 700°C in vacuo and cold rolled to the final thickness applying small steps, Samples were prepared after each step. The effect of cold work /CW/

was studied after the following amounts of deformation /thickness reduction %/.

t

Material 4 5

Si A 1 G S P _{N2 02}

cO.1 0,03 0.01 0.002 0,004 0.007 0.004 0.022 CO.1 0,03 0,Ol 0.003 0,005 0.008 0,003 0,009

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19839111

C9-736 JOURNAL DE PHYSIQUE

A number of specimens of each sample of every state were heat treated at 7 0 0 ~ ~ for 1 h /called HT1/, Several samples received different heat treatments /235OC

-

HT2, 3150C

-

HT3, 4 0 0 ~ ~

-

HT4, 550°C

-

^HT5/

for 1 h either after cold work or after HT1.

' Naterial 4 5

The internal friction measurements of the specimens were carried out in an inverted torsion pendulum working between 240 K and 980 K twing a heating rate of 60 K/h. The electrical resistance was measured by the conventional four probes method on 50 mm long and 5 mm wide strips at 78 K and 273 K, The Tickers hardness was determined on po- lished surfaces at 10 N load. Tensile tests were carried out using an Instron machine. The grain structure was studied with an optical mi- croscope. X-ray texture studies were carried out on thinned specimens,

amount of cold work /%/

0 5 19 29 35 38 45 47 54 61 63

-

^{12 19 26 32.5} 37 43 48 53.5 56 63

Nost measurements were carried out on the series of material 4 con- taining more oxygen, only some checking tests were made on specimens of material 5,

Results

The IF spectra of specimens in CW condition and after HTl were deter- mLned up to 700°C, Since in the present work only the high temperatu- re groperties were relevant for us we investigated the range above 250 C in more details,

4

0 7 yo

'OoO'

800.

600

400

200.

t

4 HT1

Several spectra of heat treated

specimens are shown in Fig. I, It can at once be seen from the

o 0 *lo positions of the curves that

o 29'1. the effect of the previous

cold work did not disappear

35'10

.

^47% completely during the heat

treatment. Two main characte- ristic features can be observed:

/a/ the curves shift to lower temperatures with increasing previous deformation,

/b/ the curve belonging to 35%

deformation differs completely from the others. It starts at an even higher temperature than that of the undeformed sample, Furthermore, the curve runs flat after the small peak, The curves of the cold worked samples have similar features but they start at lower tempe- ratures and their slopes are also lower,

The separation of the high tem- perature background and the Fig. 1 grain boundary peak is diffi-

cult because the latter over-

&

^{, : :} laps a wide temperature range

400 500 600 TPC) 700 and the shape of the background

curve seems to have change4toa

The exponential background can be described in general by an equation

= A exp (-B/kBl), [3

-

⁶¹

^,

where A and B cannot be deetned in a simple form. We suppose that A = K

9

D / ~ m n , where K is approxima- tely constant depending on the geometry of defects,

PD

is the dislo- cation density and 3=w/2!!C is the frequency of the measurement, The

"activation energy" of the process can be expressed by, B = n Uo, where Uo equals the self diffusion activation energy [a, which refers to the fact that the exponential portion of the IF is caused by viscous climb of dislocations.

Accepting the above supposition we detfrmine the values of the 9100 temperature belonging to 'Q = 10 [2].

-9

It can clearly B and 5HTI be seen in Fig. 2 that the T10

4 H T l belonging to deformation 35% an8

38% do not fit in the curve deter-

4 C w mined by the other points. The T ~ O O

values of the other series of

--*/ samples 5 give a curve without any

'*---*-

peaks.

'*- -*--*.*-

The electrical resistivity and the mechanical parameters

/HV -

^Vicbrs

hardness, E

-

Young modulus, R,

-

flow stress, k

-

contraction/ show also anomaly in the neighbourhood of deformation 35% /see Fig.4 and5L The electrical resistivity measured at 78 K increases with about 75%

at 35% deformation and it returns to the original run only at about 47% deformation, We dons t consider the

4HTI 0 2 9 %

difference between the measured values

on samples in GW and HT1 condition sig- ^{0 35%}

nificant, although the difference be-

-

^{+ 4 7 %}

tween the curves increase a little bit

'

with increasing deformation. The mecha- nical parameters were measured only on CV condition when a very high value in the Young-modulus and a low value of contraction was found,

650.

600

550

Fig. 3

Im

200 3 M 4 M 5@,(cqm

The grain structure was studied on HT1 samples in the section perpen*

dicular to the transverse direction. A duplex grain structure was ob- served after the deformation of 35% in addition to the equaxial p i n s elongated grains occured. According to microhardness measurements the hardness of equaxial grains was the same as after 29% but the elon- gated grains was harder by 30%.

I A \ Further heat treatments /HT2

-

^HT5/

I \ were performed on three variously I \ deformed /29%, 35%, 47%/ samples

t--c--/ \ in order to clear how stable is the state of 35% deformation, The 1100

'--*-*

values depending on the tempera-

ture of heat treatments can be seen

f

^{in Fig, 3.} The curves are similar

to each other and the anomalously

2 0 40 60 Oef(*l.) high TlO0 values remain on the

whole range.

Fig, 2

C9-738 JOURNAL DE PHYSIQUE

Discussion

4

4 5

The investigations of the texture

2.00..

100,

temperature region of ^A

-

the IF of the samples ^{0 20 40 60 Def ('10)}

deformed for 35% starts Fig. 5

at higher temperature than

that of those which had no deformation, It is more likely that a fun- damental redistribution of the dislocation structure takes place.

This would mean that K also must have been changed and n would be sensitive for the structure even if accepting the relation B = n Uo.

3

^em, have shown that the rolling texture m HT1 of the metals and alloy of bcc struc-

o C W ,, cw ture has been formed already for 15%

reduction, and for higher reduction the scatter~ng is increased and the ratio of the components has changed a little. The recrystallieation tex- ture contains the common components.

7e did not observe any sudden changes in the texture at deformations where several other parameters have shown jumps.

Fig. 4

!!?he shape of the curves ^A of the deformation de- f

pendence of all meas- ured parameters fits t-2P' gether for the low and

-

high deformation range

2

except an anomalous por-

-,

tion, In this deforma-

-

tion range, having a centnun between 35% and 38%, either a maximum or a minimum appears. There is not reason to suppose that any of the rolling steps performed after lo..

each other could cause a decrease of the disloca-, tion density. As this would be suggested by the fact that the high

The changes of the mechanical parameters in the critical region and the shift of the IF curve refer to a structure in which the motion of dislocations is strongly'hindered, high internal stresses cumulate and a great number of new scattering centers for the electrons app-, The cell structure of dislocation formed already by several percent deformation at room temperature

171.

We suppose that this cell struc- ture gets rearranged and a more homogeneous dislocation distribution takes place.

-

Thus, our investimtions have shown t M t the oxygen could play a fun- damental role in the rearrangement of the cell structure and in deve- lopment a more homogeneous dislocation distribution but we do not

more information on the above problem.

!Phis research work was sponsored by Csepel EBetal Works, References

[a

SCHOECK G,

,

BISCOGNI E. and SHYNE J., Acta Met.

12

/1964/ 1466, [2] LUCCI A,, ANTONZONE C., Met,Sci,J.

3

/1977/ 100,

31 NIBLETT DOH,, WILKS J,

,

Advances on Physics

2

/1960/ 1.

4 3

SZEMES G,

,

Thesis, Budapest, 1973.

[5] NOWICK A, S,

,

^{BERRY B, S,}

,

Anelastic Relax. in Cryst, Sol,, Acad,Pr, 1972, (61 LFBEDEV R.S,, POS!rNIKOV V.S,, Relaxation Phenomena in Uetals and

Alloys, New York, 1963.

[7] COTTERILL P,, MOULD P,R,, Recrystallization and Grain Growth in Metals, Surrey Univ. Press, London,1976.