Effect of Forging on Cyclic Hardening Behavior of CW 614 Brass Alloy
Проведено исследование циклического упрочнения латуни CW 614 на образцах, изготовленных по двум технологиям: промышленная и путем ковки. Для каждого типа образца установлены особенности циклического упрочнения и циклической петли гистерезиса. Представлены результаты анализа процесса разрушения на...
Saved in:
| Date: | 2011 |
|---|---|
| Main Authors: | , , , , |
| Format: | Article |
| Language: | English |
| Published: |
Інститут проблем міцності ім. Г.С. Писаренко НАН України
2011
|
| Series: | Проблемы прочности |
| Subjects: | |
| Online Access: | http://dspace.nbuv.gov.ua/handle/123456789/112749 |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| Journal Title: | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| Cite this: | Effect of Forging on Cyclic Hardening Behavior of CW 614 Brass Alloy / R. Mnif, R. Elleuch, K. Elleuch, N. Haddar, F. Halouani // Проблемы прочности. — 2011. — № 2. — С. 145-152. — Бібліогр.: 17 назв. — англ. |
Institution
Digital Library of Periodicals of National Academy of Sciences of Ukraine| id |
irk-123456789-112749 |
|---|---|
| record_format |
dspace |
| spelling |
irk-123456789-1127492017-01-28T03:02:06Z Effect of Forging on Cyclic Hardening Behavior of CW 614 Brass Alloy Mnif, R. Elleuch, R. Elleuch, K. Haddar, N. Halouani, F. Научно-технический раздел Проведено исследование циклического упрочнения латуни CW 614 на образцах, изготовленных по двум технологиям: промышленная и путем ковки. Для каждого типа образца установлены особенности циклического упрочнения и циклической петли гистерезиса. Представлены результаты анализа процесса разрушения на основе фрактографических исследований. Проведено дослідження циклічного зміцнення латуні CW 614 на зразках, що виготовлені за двома технологіями: промислова і шляхом кування. Для кожного типу зразка встановлено особливості циклічного зміцнення і циклічної петлі гістерезиса. Представлено результати аналіза процесу руйнування на основі фрактографічних досліджень. 2011 Article Effect of Forging on Cyclic Hardening Behavior of CW 614 Brass Alloy / R. Mnif, R. Elleuch, K. Elleuch, N. Haddar, F. Halouani // Проблемы прочности. — 2011. — № 2. — С. 145-152. — Бібліогр.: 17 назв. — англ. 0556-171X http://dspace.nbuv.gov.ua/handle/123456789/112749 539.4 en Проблемы прочности Інститут проблем міцності ім. Г.С. Писаренко НАН України |
| institution |
Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| collection |
DSpace DC |
| language |
English |
| topic |
Научно-технический раздел Научно-технический раздел |
| spellingShingle |
Научно-технический раздел Научно-технический раздел Mnif, R. Elleuch, R. Elleuch, K. Haddar, N. Halouani, F. Effect of Forging on Cyclic Hardening Behavior of CW 614 Brass Alloy Проблемы прочности |
| description |
Проведено исследование циклического упрочнения латуни CW 614 на образцах, изготовленных
по двум технологиям: промышленная и путем ковки. Для каждого типа образца установлены
особенности циклического упрочнения и циклической петли гистерезиса. Представлены результаты анализа процесса разрушения на основе фрактографических исследований. |
| format |
Article |
| author |
Mnif, R. Elleuch, R. Elleuch, K. Haddar, N. Halouani, F. |
| author_facet |
Mnif, R. Elleuch, R. Elleuch, K. Haddar, N. Halouani, F. |
| author_sort |
Mnif, R. |
| title |
Effect of Forging on Cyclic Hardening Behavior of CW 614 Brass Alloy |
| title_short |
Effect of Forging on Cyclic Hardening Behavior of CW 614 Brass Alloy |
| title_full |
Effect of Forging on Cyclic Hardening Behavior of CW 614 Brass Alloy |
| title_fullStr |
Effect of Forging on Cyclic Hardening Behavior of CW 614 Brass Alloy |
| title_full_unstemmed |
Effect of Forging on Cyclic Hardening Behavior of CW 614 Brass Alloy |
| title_sort |
effect of forging on cyclic hardening behavior of cw 614 brass alloy |
| publisher |
Інститут проблем міцності ім. Г.С. Писаренко НАН України |
| publishDate |
2011 |
| topic_facet |
Научно-технический раздел |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/112749 |
| citation_txt |
Effect of Forging on Cyclic Hardening Behavior of CW 614 Brass Alloy / R. Mnif, R. Elleuch, K. Elleuch, N. Haddar, F. Halouani // Проблемы прочности. — 2011. — № 2. — С. 145-152. — Бібліогр.: 17 назв. — англ. |
| series |
Проблемы прочности |
| work_keys_str_mv |
AT mnifr effectofforgingoncyclichardeningbehaviorofcw614brassalloy AT elleuchr effectofforgingoncyclichardeningbehaviorofcw614brassalloy AT elleuchk effectofforgingoncyclichardeningbehaviorofcw614brassalloy AT haddarn effectofforgingoncyclichardeningbehaviorofcw614brassalloy AT halouanif effectofforgingoncyclichardeningbehaviorofcw614brassalloy |
| first_indexed |
2025-07-08T04:34:45Z |
| last_indexed |
2025-07-08T04:34:45Z |
| _version_ |
1837051977254567936 |
| fulltext |
UDC 539.4
Effect of Forging on Cyclic Hardening Behavior of CW 614 Brass Alloy
R. Mnif,
a
R. Elleuch,
a
K. Elleuch,
a
N. Haddar,
b
and F. Halouani
a
a Laboratoire des Systèmes Electro-Mécanique (LASEM), Ecole Nationale d’Ingénieurs de
Sfax, Tunisie
b Centre des Matériaux (UMR CNRS 7633), Ecole Nationale Supérieure des Mines de
Paris, France
ÓÄÊ 539.4
Âëèÿíèå êîâêè íà öèêëè÷åñêîå óïðî÷íåíèå ëàòóíè CW 614
Ð. Ìíèô
à
, Ð. Ýëëþø
à
, Ê. Ýëëþø
à
, Í. Õàääàð
á
, Ô. Õàëóàíè
à
à Ëàáîðàòîðèÿ ýëåêòðîìåõàíè÷åñêèõ ñèñòåì, Íàöèîíàëüíûé èíæåíåðíûé èíñòèòóò,
Ñôàêñ, Òóíèñ
á Öåíòð ìàòåðèàëîâåäåíèÿ, Íàöèîíàëüíûé ãîðíûé èíñòèòóò, Ïàðèæ, Ôðàíöèÿ
Ïðîâåäåíî èññëåäîâàíèå öèêëè÷åñêîãî óïðî÷íåíèÿ ëàòóíè CW 614 íà îáðàçöàõ, èçãîòîâëåííûõ
ïî äâóì òåõíîëîãèÿì: ïðîìûøëåííàÿ è ïóòåì êîâêè. Äëÿ êàæäîãî òèïà îáðàçöà óñòàíîâëåíû
îñîáåííîñòè öèêëè÷åñêîãî óïðî÷íåíèÿ è öèêëè÷åñêîé ïåòëè ãèñòåðåçèñà. Ïðåäñòàâëåíû ðå-
çóëüòàòû àíàëèçà ïðîöåññà ðàçðóøåíèÿ íà îñíîâå ôðàêòîãðàôè÷åñêèõ èññëåäîâàíèé.
Êëþ÷åâûå ñëîâà: ëàòóíü, óñòàëîñòü, êîâêà, óïðî÷íåíèå, ïîâðåæäåíèå.
Introduction. Copper and its alloys submitted to forming processes such as
forging and rolling are widely used in various components of sanitary installations
(valves, pipe couplings, etc.). The components are often subjected to cyclic loading
due to internal pressure variation and impact reaction caused by fluid shock and
temperature fluctuation. Therefore, fatigue characteristics are critical for the safe
life design of components. The stress-strain behavior of a material after forming
process should account for temperature, strain amplitude and hardening–softening
rate. Work-hardening behavior also occurs in deformation of metals with different
structures [1, 2]. In monotonic deformation, a considerable insight into the effect of
microstructure and operating conditions on thermomechanical properties was
provided in studies [3–8]. The mechanical behavior and microstructural changes
under cyclic deformation were also studied in recent works [9, 10].
El Madhoun et al. [11] have explored the relationship of cyclic deformation
behavior with microstructure of materials by means of investigation of stress–strain
response and dislocation evolution during low-cycle fatigue. The main effect of
grain size was attributed to the cyclic strain hardening. Jia et al. [12] claim that the
microscopic substructure developed during cyclic loading is affected by the grain
size. In a large grain, strain accommodation occurs in the vicinity of grain
boundary. In a smaller grain (20 �m), the dislocation structure evolves in a more
© R. MNIF, R. ELLEUCH, K. ELLEUCH, N. HADDAR, F. HALOUANI, 2011
ISSN 0556-171X. Ïðîáëåìû ïðî÷íîñòè, 2011, ¹ 2 145
continuous manner by a partial dissolution of the prestrained substructure.
Systematic investigation of cyclic deformation behavior of Cu–30 wt.% Zn alloy
conducted by Gong et al. [13, 14] has shown that the cyclic deformation behavior
is usually dependent on the dislocation structure, its evolution in materials and the
strain amplitude applied. The objective of the present study is to evaluate the effect
of forging on cyclic stress–strain response and hardening–softening behavior of
CW 614 brass alloy. In addition, surface damage was characterized using SEM
observation.
1. Experimental Procedure. The material under study is a CW 614 brass alloy
with the following chemical composition in weight percent: 58.5% Cu, 2.8% Pb,
0.21% Fe, 0.25% Sn, 0.11% Ni, 0.01% Al and the balance Zn. Specimens are
obtained from an extruded bar (3000 18�� mm). Tests are carried out on cylindrical
specimens with 6 mm diameter and 12 mm gauge length. After machining, the
working surface area of the specimen is polished mechanically until a granulometry
of 3 �m is reached.
The present work investigated two types of fatigue specimen: (i) specimens
manufactured from extruded bar, namely CW 614 and (ii) specimens obtained by
severe plastic deformation using forging process, namely CW 614SP. In this process,
each specimen is preheated to a temperature within the range of 400–450�C and
pressed through a die. In this study, the low-cycle fatigue tests were performed.
Microstructure was examined via optical microscope after etching (using
Keller reagent). For CW 614 structure, microscope examination revealed that
lightly colored � phase precipitated in the darkly colored � phase matrix (Fig. 1).
Figure 2 shows that the optical microstructure of brass after forging process is
characterized by lamellar and ultrafine structure.
In order to understand the forging process effect on mechanical properties,
monotonic tensile tests for these two structures of CW 614 alloy were conducted.
R. Mnif, R. Elleuch, K. Elleuch, et al.
146 ISSN 0556-171X. Ïðîáëåìû ïðî÷íîñòè, 2011, ¹ 2
Fig. 1. Initial microstructure of CW 614 brass alloy (�/� structure).
Fig. 2. Microstructure of CW 614SP brass alloy after forging process.
The representative stress–strain curves before and after forging process are shown
in Fig. 3. As compared to the initial CW 614 structure, the forging process induces
a pronounced decrease of both yield stress and flow stress that may be attributed to
the consequent substantial grain refinement introduced through forging process
leading to modification of the dislocation structure and it evolution in the material.
Fatigue tests were performed using a servo-hydraulic test machine (Fig. 4) with
a symmetrical tensile-compressive loading scheme (R � 1) within the temperature
range 25 to 200�C and a frequency of 0.1 Hz. A triangular wave signal was used
for the total control strain. Strain was measured using a longitudinal extensometer
of 10 mm gauge length. During test, the stress values were continually recorded.
The stress–strain hysteresis loops were registered by X–Y chart recorder.
2. Experimental Results and Discussion.
2.1. Cyclic Stress–Strain Response. Figure 5 shows the typical stress–strain
loops recorded at the tenth cycle under two mechanical strains (
0 3. and
0 9. %)
for CW 614 and CW 614SP. The main differences between these two structures are
the following ones: (i) at the same mechanical strain, the stress level recorded for
Effect of Forging on Cyclic Hardening Behavior ...
ISSN 0556-171X. Ïðîáëåìû ïðî÷íîñòè, 2011, ¹ 2 147
Fig. 3. Monotonic stress–strain curves tested at 25�C [(1) CW 614; (2) CW 614SP].
Fig. 4. Thermal mechanical fatigue test [15].
the CW 614 structure is lower than that of CW 614SP, while the loop shape
changes towards a more opened shape for forged structure; (ii) for high mechanical
strain such as ��
0 9. %, we note that the material exhibits a pronounced visco-
plastic character accompanied with small increase in the stress level.
Results are summarized in the form of a cyclic hardening curve as shown in
Fig. 6. It was observed that the hardening character is distinguishable in CW
614SP. However, for CW 614 stress saturation was observed (Fig 6a). This
mechanical behavior can be attributed to the dislocation arrangement and strain
localization in shear bands [16]. In addition, FP specimen exhibits 10% higher
saturated flow stress than the initial structure at the same plastic strain amplitude.
In contrast to the monotonic test, the yield stress of specimens obtained by forging
process was less affected by the cyclic loading (Fig 6b).
Furthermore, a particular attention was given to characterize the temperature
effect in the hardening behavior of CW 614 structure. The effect of temperature on
the elastic modulus is shown in Fig. 7 for the CW 614 brass alloy tested at room
temperature between 25 and 200�C. For the 25–150�C range, the elastic modulus
148 ISSN 0556-171X. Ïðîáëåìû ïðî÷íîñòè, 2011, ¹ 2
R. Mnif, R. Elleuch, K. Elleuch, et al.
a b
Fig. 5. Mechanical stress–strain loops at tenth cycle in fatigue test (T � �25 C, f � 0 1. Hz): (a) � �
�
0 3. %; (b) � �
0 9. %; (1) CW 614; (2) CW 614SP.
a b
Fig. 6. Cyclic curves of work-hardening: (a) according to the mechanical strain; (b) according to the
plastic strain (T � �25 C, f � 01. Hz); (�) CW 614; (�) CW 614SP.
decreased gradually as a function of temperature. However, a significant decrease
of the elastic modulus is observed when the temperature increases from 150 to
200�C. Therefore, it should be expedient to study the mechanical behavior in the
range of transition temperature.
Figure 8 compares the stress–strain loops recorded at the tenth cycle under two
mechanical strains and temperatures (25 and 200�C) for CW 614 structure. We note
that the material has an important viscoplastic behavior with wider loops at 200�C.
Results are summarized in the form of a cyclic hardening curve shown in
Fig. 9. In addition to the decrease of the elastic modulus, we observe the decrease
of the elastic limit. Nevertheless, the material preserves an important power of
hardening at 200�C.
2.2. Hardening–Softening Behavior. Figure 10a illustrates the cycling
hardening–softening curves for an isothermal test at 200�C. The cyclic response for
CW 614SP shows a pronounced cyclic hardening behavior with a hardening rate
about 42%. However, for CW 614 structure the cyclic behavior is characterized by
an initial strain-hardening after 10 cycles followed by a continuous cyclic softening.
The rapid decrease in stress for both structures is attributed to the formation of
macroscopic cracks. At the same strain level, we observe that the failure of CW
614 SP specimen occurs after 10,300 cycles, while that of manufactured specimen
CW 614 – after 6960 cycles. The cyclic hardening behavior results for CW 614SP
ISSN 0556-171X. Ïðîáëåìû ïðî÷íîñòè, 2011, ¹ 2 149
Effect of Forging on Cyclic Hardening Behavior ...
Fig. 7. Elastic modulus evolution as a function of temperature for CW 614.
a b
Fig. 8. Mechanical stress–strain loops at tenth cycle in isothermal fatigue test for CW 614 ( f �� 01.
Hz): (a) � �
0 3. %; (b) � � 0 9. %; (1) T � �25 C; (2) T � �200 C.
can be attributed to the generation of dislocations and their interaction leading to a
continuous decrease in plastic strain as shown in Fig. 10. The difference in fatigue
life values therefore has to reflect the effect of forging process on grain boundary
which modifies the structure and the evolution of dislocations [17].
2.3. Damage Analysis. Surface fracture analysis of specimens cycled at strain
amplitude ��
0 4. % is shown in Fig. 11. Fracture mechanism for both specimens
is due to coalescence of pores observed in the specimen center region and close to
150 ISSN 0556-171X. Ïðîáëåìû ïðî÷íîñòè, 2011, ¹ 2
R. Mnif, R. Elleuch, K. Elleuch, et al.
a b
Fig. 9. Cyclic curves of work-hardening: (a) mechanical strain; (b) plastic strain [(�) T � �25 C;
(�) T � �200 C; f � 01. Hz].
a b
Fig. 10. Hardening–softening curves of isothermal fatigue tests (a) and stress–strain loops of the first
cycle and half life value (b) for CW 614SP ( f � 01. Hz, � �
0 4. %, T � �200 C).
a b
Fig. 11. SEM image of fracture surface: (a) CW 614 structure and (b) CW 614SP structure
( ,T � �200 C f � 01. Hz, � �
0 4. %).
the external surface. In fact, the process of fatigue damage begins by formation of
pores or voids and continues by the linking of these pores into embryo cracks
which grow inward and slowly propagate leading to fatigue failure. Isolated
pockets of shallow dimples are indicative of the ductile nature of failure of the
microstructure.
Conclusions. We present results of experimental tests on the cyclic stress–strain
response and hardening–softening behavior of CW 614 and CW 614SP alloys.
A difference in stress response to cyclic loading was identified between the
original (CW 614) and forged (CW 614SP) structures. Moreover, the hardening
pattern is more pronounced in the CW 614SP alloy. A significant decrease of the
elastic modulus was observed at 150�C.
In terms of fatigue life, the cyclic behavior is characterized by cyclic
hardening for CW 614SP structure. However, a stress stabilization was observed
for CW 614. The fatigue life values of CW 614SP structure in isothermal fatigue
tests are more higher than those of CW 614.
Ð å ç þ ì å
Ïðîâåäåíî äîñë³äæåííÿ öèêë³÷íîãî çì³öíåííÿ ëàòóí³ CW 614 íà çðàçêàõ, ùî
âèãîòîâëåí³ çà äâîìà òåõíîëîã³ÿìè: ïðîìèñëîâà ³ øëÿõîì êóâàííÿ. Äëÿ
êîæíîãî òèïó çðàçêà âñòàíîâëåíî îñîáëèâîñò³ öèêë³÷íîãî çì³öíåííÿ ³ öèêë³÷-
íî¿ ïåòë³ ã³ñòåðåçèñà. Ïðåäñòàâëåíî ðåçóëüòàòè àíàë³çà ïðîöåñó ðóéíóâàííÿ
íà îñíîâ³ ôðàêòîãðàô³÷íèõ äîñë³äæåíü.
1. C. Mapelli and R. Venturi, “Dependence of the mechanical properties of �/�
brass on the microstructural features induced by hot extrusion,” Scripta
Mater., 54, 1169–1173 (2006).
2. E. C. S. Correa, M. T. P. Aguilar, and P. R. Cetlin, “The effect of tension/
torsion strain path changes on the work hardening of Cu–Zn brass,” J. Mater.
Proc. Technol., 124, 384–388 (2002).
3. K. Neishi, T. Uchida, A. Yamauchi, et al., “Low temperature superplasticity in
a Cu–Zn–Sn alloy processed by severe plastic deformation,” Mater. Sci. Eng.,
A307, 23–28 (2001).
4. D. Y. Li, L. Wang, and W. Li, “Effects of grain size from micro scale to
nanoscales on the yields strain of brass under compressive and tensile stresses
using a Kelvin probing technique,” Mater. Sci. Eng., A384, 355–360 (2004).
5. R. Nowosielki, “Ductility minimum temperature in selected mono-phase,
binary brasses,” J. Mater. Proc. Technol., 109, 142–153 (2001).
6. K. Neishi, Z. Horita, and T. G. Langdon, “Achieving superplasticity in a
Cu–40%Zn alloy trough severe plastic deformation,” Scripta Mater., 45, 965–
970 (2001).
7. N. Mostafa, E. Gomaa, and M. Mohsen, “Correlation of thermo-mechanical
properties with microstructure in commercial pure Cu an Cu–Zn alloys
studied by positron annihilation,” Mater. Sci. Eng., A373, 250–254 (2004).
ISSN 0556-171X. Ïðîáëåìû ïðî÷íîñòè, 2011, ¹ 2 151
Effect of Forging on Cyclic Hardening Behavior ...
8. V. Bursikova, J. Bursik, V. Navratil, and K. Milicka, “Creep behavior of lead
brass,” Mater. Sci. Eng., A324, 235–238 (2002).
9. D. Peter, M. Ahmad, and G. B. Ian, “Cyclic response of plate steels under
large inelastic strain,” J. Constr. Steel Res., 63, 156–164 (2007).
10. Z. Jixi and J. Yanayo, “Fatigue of polycrystalline copper with different grain
sizes and texture,” Int. J. Plasticity, (2005) (in press).
11. Y. El Madhoun, A. Moamed, M. N. Bassim, “Cyclic stress-strain behavior of
polycristalline nickel,” Mater. Sci. Eng., A385, 140–147 (2004).
12. W. P. Jia and J. V. Fernandes, “Mechanical behaviour and the evolution of the
dislocation structure of copper polycrystal deformed under fatigue/tension and
tension/fatigue sequential strain path,” Mater. Sci. Eng., A348, 133–144
(2003).
13. Z. Wang, B. Gong, and Z. G. Wang, “Cyclic deformation behavior of
Cu–30wt.% Zn single crystals oriented for single slip. ². Cyclic deformation
response and slip band behavior,” Acta Metall., 47, 307–315 (1999).
14. B. Gong, Z. Wang, B. Gong, and Z. G. Wang, “Cyclic deformation behavior
of Cu–30wt.% Zn single crystals oriented for single slip. ²². Dislocations
structures,” Acta Metall., 47, 317–324 (1999).
15. A. Koster, E. Fleury, E. Vasseur, and L. Remy, “Thermal mechanical fatigue
test,” in: ASTM STP 1231 (1994), pp. 559–576.
16. H. L. Huang, “A study of dislocation evolution in polycrystalline copper
during low cycle fatigue at low strain amplitudes,” Mater. Sci. Eng., A342,
38–43 (2003).
17. J. V. Carstensen, PhD Thesis, Technical University of Denmark (1998).
Received 03. 07. 2009
152 ISSN 0556-171X. Ïðîáëåìû ïðî÷íîñòè, 2011, ¹ 2
R. Mnif, R. Elleuch, K. Elleuch, et al.
|