Deformation resistance and structure-forming processes of iron aluminides in hot rolling
We have developed simple mathematical models of mean equivalent stress dependence on temperature and strain for selected iron aluminides. Four similar melts with 16.5-19.2 wt.% of Al, 4 wt.% of Cr and with various contents of Ti and B were studied and compared. Flat specimens graded by thickness wer...
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Інститут проблем міцності ім. Г.С. Писаренко НАН України
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| Zitieren: | Deformation resistance and structure-forming processes of iron aluminides in hot rolling / P. Suchanek, I. Schindler, P. Kratochvil, P. Hanus // Проблемы прочности. — 2008. — № 1. — С. 44-47. — Бібліогр.: 4 назв. — англ. |
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irk-123456789-484632013-08-19T23:08:22Z Deformation resistance and structure-forming processes of iron aluminides in hot rolling Suchanek, P. Schindler, I. Kratochvil, P. Hanus, P. Научно-технический раздел We have developed simple mathematical models of mean equivalent stress dependence on temperature and strain for selected iron aluminides. Four similar melts with 16.5-19.2 wt.% of Al, 4 wt.% of Cr and with various contents of Ti and B were studied and compared. Flat specimens graded by thickness were hot rolled. Deformation resistance was calculated from the roll force values obtained using a laboratory mill Tandem. Postdynamic structure-forming processes of the tested aluminides, as well as their cracking susceptibility, were investigated by metallography. The differences in the deformation behavior and formability of the tested aluminides were described. Разработаны простые математические модели зависимости среднего эквивалентного напряжения от температуры и деформации для выбранных алюминидов железа. Были изучены и сравнены четыре одинаковые плавки, содержащие 16,5...19,2 вес.% Al, и 4 вес.% Сг и различное количество титана и бора. Плоские образцы, рассортированные по толщине, подвергались горячей прокатке. Сопротивление деформированию рассчитывали по величине усилия на валки, определенной с использованием лабораторного прокатного стана Тандем. Процессы структурообразования испытанных алюминидов после динамического воздействия и их склонность к трещинообразованию исследовали с использованием металлографии. Описаны наблюдавшиеся различия в поведении испытанных алюминидов при деформировании и в способности к формоизменению. 2008 Article Deformation resistance and structure-forming processes of iron aluminides in hot rolling / P. Suchanek, I. Schindler, P. Kratochvil, P. Hanus // Проблемы прочности. — 2008. — № 1. — С. 44-47. — Бібліогр.: 4 назв. — англ. 0556-171X http://dspace.nbuv.gov.ua/handle/123456789/48463 539. 4 en Проблемы прочности Інститут проблем міцності ім. Г.С. Писаренко НАН України |
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Научно-технический раздел Научно-технический раздел Suchanek, P. Schindler, I. Kratochvil, P. Hanus, P. Deformation resistance and structure-forming processes of iron aluminides in hot rolling Проблемы прочности |
| description |
We have developed simple mathematical models of mean equivalent stress dependence on temperature and strain for selected iron aluminides. Four similar melts with 16.5-19.2 wt.% of Al, 4 wt.% of Cr and with various contents of Ti and B were studied and compared. Flat specimens graded by thickness were hot rolled. Deformation resistance was calculated from the roll force values obtained using a laboratory mill Tandem. Postdynamic structure-forming processes of the tested aluminides, as well as their cracking susceptibility, were investigated by metallography. The differences in the deformation behavior and formability of the tested aluminides were described. |
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Article |
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Suchanek, P. Schindler, I. Kratochvil, P. Hanus, P. |
| author_facet |
Suchanek, P. Schindler, I. Kratochvil, P. Hanus, P. |
| author_sort |
Suchanek, P. |
| title |
Deformation resistance and structure-forming processes of iron aluminides in hot rolling |
| title_short |
Deformation resistance and structure-forming processes of iron aluminides in hot rolling |
| title_full |
Deformation resistance and structure-forming processes of iron aluminides in hot rolling |
| title_fullStr |
Deformation resistance and structure-forming processes of iron aluminides in hot rolling |
| title_full_unstemmed |
Deformation resistance and structure-forming processes of iron aluminides in hot rolling |
| title_sort |
deformation resistance and structure-forming processes of iron aluminides in hot rolling |
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Інститут проблем міцності ім. Г.С. Писаренко НАН України |
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2008 |
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Научно-технический раздел |
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http://dspace.nbuv.gov.ua/handle/123456789/48463 |
| citation_txt |
Deformation resistance and structure-forming processes of iron aluminides in hot rolling / P. Suchanek, I. Schindler, P. Kratochvil, P. Hanus // Проблемы прочности. — 2008. — № 1. — С. 44-47. — Бібліогр.: 4 назв. — англ. |
| series |
Проблемы прочности |
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| first_indexed |
2025-07-04T08:58:53Z |
| last_indexed |
2025-07-04T08:58:53Z |
| _version_ |
1836706204948103168 |
| fulltext |
UDC 539. 4
D e fo r m a t io n R e s is ta n c e a n d S tr u c tu r e -F o r m in g P r o c e s s e s o f I r o n A liim in id e s
in H o t R o llin g
P. S u ch an ek ,1a I. S ch in d ler , 1 P . K ra toch v il,2 and P . H an u s2,b
1 Institute o f Modeling and Control o f Forming Processes, VSB - Technical University o f Ostrava,
Ostrava-Poruba, Czech Republic
2 Department o f Material Science, Technical University o f Liberec, Liberec, Czech Republic
a pavel.suchanek@vsb.cz, b pavel.hanus@tul.cz
We have developed simple mathematical models o f mean equivalent stress dependence on
temperature and strain fo r selected iron aluminides. Four similar melts with 16.5-19.2 wt.% o f Al,
4 wt.% o f Cr and with various contents o f Ti and B were studied and compared. Flat specimens
graded by thickness were hot rolled. Deformation resistance was calculated from the roll force
values obtained using a laboratory mill Tandem. Postdynamic structure-forming processes o f the
tested aluminides, as well as their cracking susceptibility, were investigated by metallography. The
differences in the deformation behavior and formability o f the tested aluminides were described.
K eyw o rd s : iron aluminides, hot rolling, deformation resistance, microstructure, formability.
In troduction . Fe3A l-based iron alum inides have been an object o f investigation for
m any years. These alloys feature lo w material costs and a low er specific weight.
Compared w ith expensive corrosion-resistant types o f steel, they guarantee savings in
elem ents, such as Cr, N i, and som e others. Their tensile strength is comparable w ith that
o f m any other steels. T hey have a h igh resistance in sulphidic and oxid ic atmospheres,
especially at h igh temperatures, and therefore, are prom ising materials for manufacturing,
e.g., structural parts for aviation, heating elem ents, heat exchangers, equipm ent for
chem ical production, etc. [ 1].
A problem w ith Fe3A l-based materials consists in their preparation and subsequent
processing. T hey feature brittleness at the ambient temperature and a drop o f strength
above 600oC, w hich w as the reason for not using them as structural materials. Attention
has recently been focussed m ainly on utilization o f corrosion-resistant properties o f iron
alum inides at h igh temperatures. A n essential step forward in their application is an
increase in their creep resistance at temperatures above 600oC. This is achieved by the
additives that form stable phases thus increasing the strength o f the material at the
temperatures o f their operation. H ow ever, this strengthening m ay adversely affect the
production o f com ponents, as the case m ay be, e.g., during hot forming. It is the
introductory experim ents involving determination o f the deform ation resistance o f iron
alum inides hardened for a later application as the materials exhibiting creep resistance at
high temperatures that are the subject o f this work.
E xp erim en ta l. Four m elts o f iron alum inides w ith similar chem ical com positions
and various contents o f Cr, Ti, and B (Table 1) w ere studied and compared. The chromium
content in the range from 2 to 5 at.% has no effect on the basic m echanical properties o f
the alum inide, and its function is on ly to im prove the form ability at low er temperatures
[1]. The experim ent w as divided in tw o parts. First, the m ean equivalent stress (M ES) was
determ ined using a laboratory rolling m ill Tandem, and then postdynam ic structure-
form ing processes in the investigated alum inides rolled in a laboratory rolling m ill K350
were studied [2 ].
M ean E q u iva len t Stress. Flat specim ens graded by thickness, w hich have been
prepared by water cutting and grinding, were hot rolled. Each specim en w as carefully
measured and afterwards directly heated in an electric resistance furnace to the rolling
© P. SUCHA NEK, I. SCHINDLER, P. KRATOCHVIL, P. HANUS, 2008
44 ISSN 0556-171X. Проблемы прочности, 2008, N 1
mailto:pavel.suchanek@vsb.cz
mailto:pavel.hanus@tul.cz
Deformation Resistance and Structure-Forming Processes
temperature (9 0 0 -1 2 0 0 oC). The heated specim en w as im m ediately rolled dow n in the m ill
A o f the laboratory m ill Tandem [2] (roll diameter approx. 159 m m ). The roll forces and
actual revolutions o f the rolls w ere recorded using a computer. A fter cooling dow n o f the
rolled stock, the w idth and thickness o f individual specim ens w ere also measured. A ll the
recorded variables m entioned above were presented in the table and recalculated to obtain
the values o f the equivalent (logarithm ic) height reduction eh , strain rate e (in s 1) and
M ES a m (in M Pa) [3].
T a b l e 1
Chemical Composition of the Investigated Iron Aluminides in wt.%/at.%
Alloy Al Cr Ti B C
M1 16.5/28.9 4.0/3.6 TiB2 = 0.33/0.76 — 0.01/0.04
M2 19.2/32.8 4.9/4.3 0.68/0.65 - 0.04/0.12
M3 16.8/29.3 4.0/3.6 - 0.06/0.27 0.02/0.08
M4 18.4/31.7 4.9/4.4 0.61/0.59 0.07/0.30 0.02/0.08
The resulting equation for the description o f the M ES should m ake possib le a quick
prediction o f the force parameters during adaptive control o f the rolling m ill. B ased on
previous experience, a sim ple m odel for the description o f the M ES o f the investigated
material in relation to strain (strengthening and dynam ic softening are taken into account),
temperature and strain rate, w hich is dependent on the deform ation, w as chosen [4]:
2 v
S I,d
e h , ( 1)
w here v r (in m m /s) is the actual peripheral speed o f the rolls w ith radius R (in m m ), and
ld (in m m ) represents the roll bite length. For calculation o f the M ES, the fo llow ing
relationship w as chosen:
°m c = AeB exp ( - C e h )eD exp ( - G T X (2 )
w here a mc (in M Pa) is the m ean equivalent stress (c m eans “as calculated”). During
calculation o f the material constants A , . . . , G (by m eans o f the statistical software
U N IST A T 5.5) appearing in the equation o f type (2), an observation w as made for all the
materials studied (M 1, M 2, M 3, and M 4) that enabled us, w ithout any registered loss o f
accuracy, to sim plify this relation by exclusion o f the strain member. The fo llow ing
m odels were the result o f this mathem atical processing:
о mc = 2 0 1 7 e0 032 exp(—0.00225Г ) for M 1, (3)
о mc = 6763e0159 exp(—0.00395Г) for M 2, (4)
о mc = 4 9 5 4 e 0 040 exp(—0.00311Г) for M 3, (5)
о mc = 8832e0083 exp(—0.00389Г ) for M 4. (6 )
The sim plified m odels o f the M ES according to Eqs. (3 )-(6 ) do not include the
strain parameter eh , w hich is sufficiently represented in the parameter o f the strain rate e
[see Eq. (1)], as it has already been found and verified by previous experim ents [3].
ISSN 0556-171X. Проблемы прочности, 2008, N2 1 45
P. Suchdnek, I. Schindler, P. Kratochvil, and P. Hanus
The accuracy o f the obtained m odels can be evaluated by a sim ply defined relative
error (in %) according to the relation: (o m — o mc) / o m ■ 100, w here o m and o mc are the
observed and calculated values o f the m ean equivalent stress, respectively. R elative errors
did not exceed approx. ± 10% for alloys M l and M3 or ± 7% for alloys M 2 and M4,
w hich is quite sufficient for the g iven purposes.
The mathem atical m odel o f the M ES calculated on the basis o f the m ethodology
m entioned above is capable to compare different deform ation behaviour o f the materials
M 1-M 4. For this purpose, graphs in Fig. 1 were plotted. It fo llow s from Fig. 1 that alloys
M 2 and M 4, on the one hand, exhibit a sharper rise in the o m value w ith increasing strain
as against alloys M1 and M 3, and on the other hand, their deform ation resistance is
approx. 20 to 30 M Pa lower. M oreover, for alloys M 2 and M 4, a decrease in the MES
w ith increased form ing temperature is more pronounced.
Fig. 1. Comparison of behavior o f M1-M4 alloys in dependence on (a) height strain eh [see Eq. (1)
for dependence e = f (eh)] and (b) temperature T .
E valuation o f M icrostructure. The forming temperatures used for all four aluminides
w ere 900, 1100, and 1300°C, and for alloy M3 a temperature o f 1200°C w as used
additionally. Specim ens w ere rolled w ith one draught (height reduction) in the rolling m ill
K 350, the rotation speed o f the rolls w as 80 rpm. The relative height reduction
corresponded to a value o f 33%.
Im m ediately after rolling, three m odes o f cooling were applied: quenching o f the
specim en in o il directly or after a dw ell at the form ing temperature during 1 m inute or 5
m inutes. The resulting microstructure w as analyzed by m eans o f optical metallography
(Figs. 2 and 3).
S u m m ary o f R esu lts. Figure 2 show s an exam ple o f the structure evolution
depending on the m ode o f coolin g for the chosen iron alum inide M 3. This exam ple proves
the observation com m on for all four investigated materials that recrystallization proceeded
only in during the temperature dw ell. H ence, softening o f the investigated alloys by static
recrystallization has becom e apparent.
R olling at a temperature o f 1100°C fo llow ed by a 1 or 5 m in dw ell at the same
temperature (Fig. 2b, c and Fig. 3c) seem ed to be the best w ay o f form ing from the
view point o f the deform ed structure. A more pronounced refining o f the structure due to
recrystallization occurred in the areas o f more intensively form ed edges o f specim ens.
R olling at a temperature o f 900°C led to on ly average-level recrystallization processes,
w hich can be seen from the photo in Fig. 3b). R olling at a temperature o f 1300°C did not
result in grain refinem ent because, during subsequent temperature dw ell, a com plete
recrystallization and subsequent grain coarsening occurred virtually to the original size
corresponding to the initial state (com pare the photos in Fig. 3a and 3d).
B ased on laboratory rolling o f flat specim ens graded b y thickness, the values o f o m
were obtained for iron alum inides M 1, M 2, M 3, and M 4 - after recalculation from roll
forces - nam ely in the range o f logarithmic height strain eh from 0.20 to 0.76 and strain
rate e from 20 to 96 s —1. The rolling temperature T w as in range from 960 to 1200°C.
46 ISSN 0556-171X. npo6n.eubi npounocmu, 2008, № 1
Deformation Resistance and Structure-Forming Processes
c
Fig. 2. Comparison o f structure evolution in case o f selected M3 samples depending on schedule of
cooling from deformation temperature 1100°C: (a) 1100°C/oil quenching; (b) 1100°C/1 min, oil
quenching; (c) 1100°C/5 min, oil quenching.
c d
Fig. 3. Structure o f selected samples o f M2 alloy: (a) initial state; (b) 900°C/5 min, oil quenching;
(c) 1100°C/5 min, oil quenching; (d) 1300°C/5 min, oil quenching.
A s far as the accuracy o f the derived m odels o f the M ES is concerned, for M l alloy
the root-mean-square error w as 17.3 and the value o f R = 0.91; for M 2 alloy the
respective m agnitudes w ere 6.1 and 0.97; for M3 alloy 9.9 and 0.95; and for M 4 alloy
10.1 and 0.95. It m ay be concluded that the scatter o f deviations betw een the values o f
o m obtained from the experim ents and recalculated using Eqs. (3 )-(6 ) is uniform in the
w hole range (and, moreover, these relative deviations do not exceed ± 10% for M1 and M3
and ± 7% for M 2 and M 4 alloys).
The M ES m odels o f iron alum inides - alloys M 2 and M 4 - exhibited a higher
sensitivity to the changes in the form ing conditions (deform ation scale and forming
temperature) compared to alloys M1 and M3 as demonstrated in Fig. 1. The cause for
different deform ation behavior can be found in the origin o f various phases after the
thermal history o f each o f the materials, i.e ., in the presence and m orphology o f phases,
w hose formation is connected w ith the presence o f the additives used. Those phases
(w hich function as som e obstacles) influence both recrystallization (by b locking the
m ovem ent o f the grain boundaries) and proper deform ation during rolling. In case o f M3
alloy, stresses along the grain boundaries, densely occupied by heterogeneous phases,
initiate intercrystalline fracture.
Acknowledgment. The investigation was made in the framework of research plans MSM
6198910015 and MSM 4674788501 (Ministry of Education o f the Czech Republic).
1. C. G. Mc Kamey, J. H. Devan, P. F. Tortoreili, and V. K. Sikka, “A review o f recent
developments in Fe3Al-based alloys,” J. Mater. Res., 6, No. 8, 1779-1804 (1991).
2 . www.fmmi.vsb.cz/model
3. P. Kratochvil and I. Schindler, “Conditions for hot rolling o f iron aluminide,” Adv. Eng.
M ater, 6, No. 5, 307-310 (2004).
4. N. N. Krejndlin, Reduction Calculation fo r Hot Rolling [in Russian], Metallurgizdat, Moscow
(1963).
Received 28. 06. 2007
ISSN 0556-171X. npo6neMU npouHocmu, 2008, № 1 47
http://www.fmmi.vsb.cz/model
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