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7272019 Mechanical Properties of Directly Air Cooled Copper Added Microalloyed Steels (Dual Phase)
httpslidepdfcomreaderfullmechanical-properties-of-directly-air-cooled-copper-added-microalloyed-steels 16
P u b l i s h e d b y M a n e y P u b l i s h i n g ( c ) I O M C
o m m u n i c a t i o n s L t d
Mechanical properties of directly air cooledcopper added microalloyed steels
S K Ghosh1 A Haldar 2 and P P Chattopadhyay1
An attempt has been made to develop dual phase like microstructures in directly air cooled
15 wt-Cu added TindashB microalloyed steels The chosen compositions have allowed to avoid
pearlite formation during air cooling and yielded continuous work hardening behaviour with
attractive combination of strength and ductility Aging treatment has effectively improved the
ductility without deterioration of strength Differential JaoultndashCrussard analysis of the tensile
results has explained contributions of the constituent phases in work hardening behaviour of the
investigated steels
Keywords Dual phase Directly air cooled Work hardening JaoultndashCrussard analysis
Introduction
Formable structural steels warrant continuous yielding
behaviour and hence the absence of pearlite in the
microstructure1 Strengthndashductility combination in the
formable structural steels such as dual phase (DP)
steels is achieved through continuous work hardening
of the microstructures contributed by sequential plastic
deformation of the soft ferrite and hard martensite2 The
presence of martensite at the ferrite grain boundary aswell as strain induced transformation of austenite to
martensite significantly influences the work hardening of
ferrite3 Earlier it has been demonstrated that work
hardening behaviour of DP steels is essentially non-
linear and cannot be described completely by Hollomon
equation4 Different stages of work hardening in DP
steels have been successfully described by carrying out
differential and modified Jaoult5 ndashCrussard6 analyses In
a recent work the ranges of strain for three stages of
deformation are identified on the basis of Jaoultndash
Crussard analysis and the work hardening exponent
values at the third stage are determined to compare the
roles of martensite at different strain rates in the chosen
steels7 In DP and transformation induced plasticity
(TRIP) aided steels alloy partitioning during intercritical
annealing improves the hardenability of austenite and
suppresses the pearlite formation89 Suitable microal-
loying addition such as Ti B etc improves the
hardenability to the extent that bainite may form in
low carbon steels even under air cooling condition10
The addition of Cu in high strength low alloy (HSLA)
steels is also known to retard austenite (c)Rferrite (a)
transformation11 In Cu bearing steels Ni is generally
added for minimising hot shortness which additionally
improves the hardenability of austenite12
Ni also
retards Cu precipitation during air cooling of the hotrolled steels particularly at higher temperature dueto segregation at the precipitatematrix interfaces13
Therefore finer precipitates form heterogeneouslyat lower temperature and effectively contribute tostrengthening14
The present study aims to utilise the benefits of Cu
addition and microalloy with Ti and B in low carbonsteel to form the microstructures containing soft ferrite
hard bainite andor martensite along with fine Cuprecipitates by direct air cooling (DAC) of hot rolledsteels To understand the genesis of the strengthndash ductility combination and contributions of the micro-
structural constituents therein the work hardeningbehaviour of the steels has been examined by carryingout differential JaoultndashCrussard analysis vis a vis theHollomon plot
Experimental
In the present study the alloys are prepared by judiciousaddition of Ti B Cu and Ni in low carbon grade steelscraps Melts were prepared in a laboratory scale
induction melting furnace (5 kg crucible capacity)Table 1 presents the compositions of the steels obtainedafter spectroscopic analysis using an optical emissionspectrometer (SPECTROLABndashM8)
The cast ingots after homogenisation at 1200uC for
120 min were forged into bars of 1256125 mmsection The forged bars were soaked at 1200uC andhot rolled with finish rolling temperatures (FRT) of 750uC down to a thickness of 6 mm in three passesAfter completion of rolling samples were cooled in air
To study the microstructures the samples were etched
with Vilellarsquos reagent (composition 1 g picric acid 5 mLhydrochloric acid and 95 mL ethyl alcohol)15
Microstructures of the etched samples were examinedusing a SEM (Model JEOL JSM-5510) operated at
20 kV Transmission electron microscopy of selectedsamples was carried out using a transmission electronmicroscope (PHILIPS CMndash200 with EDAX) at an
1Department of Metallurgy and Materials Engineering Bengal Engineeringand Science University Shibpur Howrah 711 103 India2RampD Division Tata Steel Limited Jamshedpur 831 001 India
Corresponding author email skghoshmetalbecsacin
szlig 2007 Institute of Materials Minerals and Mining Published by Maney on behalf of the InstituteReceived 8 June 2007 accepted 19 July 2007DOI 101179174328407X239046 Materials Science and Technology 2007 VOL 23 NO 11 1375
7272019 Mechanical Properties of Directly Air Cooled Copper Added Microalloyed Steels (Dual Phase)
httpslidepdfcomreaderfullmechanical-properties-of-directly-air-cooled-copper-added-microalloyed-steels 26
P u b l i s h e d b y M a n e y P u b l i s h i n g ( c ) I O M C
o m m u n i c a t i o n s L t d
operating voltage of 200 kV Energy dispersive Xndashray
spectroscopic analysis (EDS) was conducted to deter-
mine the composition of the precipitates
Room temperature tensile testing was conducted
using the Instronndash4204 testing machine with a crosshead
velocity of 05 mm min21 The test specimen was
prepared as per the ASTM Standard (ASTM
Vol 0301 E8Mndash96) The error in yield strength (YS)and ultimate tensile strength (UTS) measurement was
recorded asiexcl3 and the same for per cent elongation
was iexcl5
Results
Tensile propertiesFigures 1ndash4 present the results obtained from the tensile
testing of the experimental steels Figure 1 shows that
the addition of Ni in 15CundashTindashB steel has improved the
YS values for both the DAC and aged samples For all
the samples a significant improvement of YS values has
been achieved after aging Figure 2 reveals that both
microalloying and aging have generally contributed to
the improvement of the UTS values Figures 3 and 4
show that in DAC samples microalloying of 15Cu steel
has lowered the elongations and the addition of Ni
in 15CundashTindashB steel has simultaneously improved
However for all the three aged steels the elongation
values are comparable It is important to note that
among the three compositions 15CundashNindashTindashB steel has
yielded the best combination of strength and ductility
for both the DAC and aged samples
Work hardening behaviour of directly air cooledsteelsWork hardening behaviour is generally expressed by
Hollomon equation416 that describes the true stress
1 Yield strength values for various investigated steels 2 Ultimate tensile strength values for various investi-
gated steels
3 Ultimate elongation UEL () values for various inves-
tigated steels
Table 1 Chemical composition of investigated steels wt-
Steel identification C Mn Si S P Ti B Cu Ni N
15Cu 004 160 048 0022 0014 ndash ndash 151 ndash 0005115CundashTindashB 004 169 057 0021 0013 0032 00013 154 ndash 0008015CundashNindashTindashB 003 168 053 0020 0013 0032 00012 155 079 00058
Ghosh et al Mechanical properties of directly air cooled copper added microalloyed steels
1376 Materials Science and Technology 2007 VOL 23 NO 11
7272019 Mechanical Properties of Directly Air Cooled Copper Added Microalloyed Steels (Dual Phase)
httpslidepdfcomreaderfullmechanical-properties-of-directly-air-cooled-copper-added-microalloyed-steels 36
7272019 Mechanical Properties of Directly Air Cooled Copper Added Microalloyed Steels (Dual Phase)
httpslidepdfcomreaderfullmechanical-properties-of-directly-air-cooled-copper-added-microalloyed-steels 46
P u b l i s h e d b y M a n e y P u b l i s h i n g ( c ) I O M C
o m m u n i c a t i o n s L t d
dislocation and tempering of martensite hardening is
contributed by precipitation of Cu
Generally the JaoultndashCrussard plots of the aged steels
exhibit a faster decrease in the work hardening rate than
the DAC steel at the first stage (stage 1) due to the fact
that the dislocations in ferrite of the air cooled steel are
effectively recovered during aging In contrast with the
Hollomon plots the JaoultndashCrussard plots of the agedsamples have revealed a distinct second stage (stage 2)
hardening (Fig 5a vis a vis Fig 5b2d ) Earlier con-
strained deformation of ferrite was held responsible for
the appearance of a second stage with higher work
hardening in the JaoultndashCrussard plots23 In the present
study prominent appearance of the second stage of work
hardening particularly for the aged steels may reason-
ably be attributed to the finer Cu precipitates which
constrain the deformation of ferrite by pinning down the
dislocations The third stage of work hardening is due to
concomitant plastic deformation of martensite and
dynamic recovery of ferrite under isostrain condition
It may be noted that the influence of aging is not
prominent at the third stage and the DAC and agedsamples exhibit approximately comparable deformation
behaviour
Thus it is apparent that precipitation of Cu by virtue
of hardening of ferrite results in sequential work
hardening characteristic which enhances the strengthndash
ductility combination in multiphase microstructures
5 a Hollomon analysis of ln s (s is in MPa) versus ln e for DAC and aged steels differential JaoultndashCrussard analysis
of ln(ds de) versus ln e for DAC and aged b 15Cu c 15CundashTindashB and d 15CundashTimdashBndashNi steel arrow indicated changes
in slope and numerals represent (n rsquo21) values
Ghosh et al Mechanical properties of directly air cooled copper added microalloyed steels
1378 Materials Science and Technology 2007 VOL 23 NO 11
7272019 Mechanical Properties of Directly Air Cooled Copper Added Microalloyed Steels (Dual Phase)
httpslidepdfcomreaderfullmechanical-properties-of-directly-air-cooled-copper-added-microalloyed-steels 56
P u b l i s h e d b y M a n e y P u b l i s h i n g ( c ) I O M C
o m m u n i c a t i o n s L t d
6 Image (SEM) of 15Cu alloy in a DAC condition with smooth appearance of islands and b peak aged condition
(500uC 60 min) showing etching effected islands at ferrite boundaries
7 a image (TEM) of 15Cu2Ti2B sample showing ferrite grains with formation of precipitate at dislocation structures
and b EDS plot and chemical composition (inset) from arrowed region in Fig 7a confirms presence of e- Cu
precipitate
8 a image (TEM) of 15CundashTindashB peak aged (500oC 15 min) sample showing fine precipitates (10ndash40 nm) and b EDS plot
along with chemical composition (inset) from region arrowed in Fig 8a
Ghosh et al Mechanical properties of directly air cooled copper added microalloyed steels
Materials Science and Technology 2007 VOL 23 NO 11 1379
7272019 Mechanical Properties of Directly Air Cooled Copper Added Microalloyed Steels (Dual Phase)
httpslidepdfcomreaderfullmechanical-properties-of-directly-air-cooled-copper-added-microalloyed-steels 66
P u b l i s h e d b y M a n e y P u b l i s h i n g ( c ) I O M C
o m m u n i c a t i o n s L t d
Conclusions
1 Addition of 15 wt-Cu in the Ti2B microalloyedsteel has adequately enhanced the hardenability result-ing in the DP microstructures in directly air cooledcondition
2 Differential JaoultndashCrussard analysis of the tensile
results has demonstrated that Cu precipitation in ferrite
during aging treatment improves the work hardeningbehaviour at the intermediate stage of straining andresulted into attractive strengthndashductility combination
3 The 15Cu2NindashTindashB steel has yielded most attrac-tive strengthndashductility combination in the directly aircooled steels with and without aging
References1 W S Owen Met Technol 1980 7 1ndash13
2 R K Piplani and V Raghavan Steel India 1981 4 (1) 1ndash22
3 P J Jacques J Ladriere and F Delannay Metall Mater Trans
A 2001 32A 275922768
4 J H Hollomon Trans AIME 1945 162 2682290
5 B Jaoult J Mech Phys Solids 1957 5 95ndash114
6 C Crussard Rev Metall (Paris) 1953 10 697ndash710
7 N D Beynon S Oliver T B Jones and G Fourlaris Mater Sci
Technol 2005 21 771ndash778
8 E Navara Proc Int Conf on lsquoHigh strength low alloy steelsrsquo (ed
D P Dunne and T Chandra) 302ndash307 1984 Wollongong
University of Wollongong
9 N R Bandyopadhyay and S Datta ISIJ Int 2004 44 927ndash934
10 X M Wang and X L He ISIJ Int Suppl 2002 42 S38ndashS46
11 A L De Sy Trans Iron Steel Inst Jpn 1974 14 139ndash154
12 G F Vander Voort in lsquoASM Metals hand bookrsquo 10th edn Vol 1
lsquoProperties and selection iron steels and high performance alloysrsquo
389ndash423 1995 Materials Park OH ASM International
13 M E Fine and D Isheim Scr Mater 2005 53 115ndash118
14 M K Banerjee D Ghosh and S Datta ISIJ Int 2001 41 (3)
257ndash261
15 G F Vander Voort lsquoMetallography ndash principles and practicersquo 632
1984 New York McGrawndashHill
16 L F Ramos D K Matlock and G Krauss Metall Trans A
1979 10A 259ndash261
17 T S Byun and I S Kim J Mater Sci 1993 28 2923ndash2932
18 Z Jiang Z Guan and J Lian Mater Sci Eng A 1991 A147 55ndash
65
19 S N Monteiro and R E Reed-Hill Met Trans 1971 2 2947ndash
2949
20 P Ludwik lsquoElement der technolnischen mechanickrsquo 32 1909
Berlin Julius Springer
21 E Girault P Jacques P Harlet K Mols J Van Humbeeck
E Aernoudt and F Delannay Mater Charact 1998 40 111ndash118
22 S Kim and S Lee Metall Mater Trans A 2000 31A 1753ndash1760
23 S Sankaran S Sangal and K A Padmanabhan Mater Sci
Technol 2005 21 1152ndash1160
Ghosh et al Mechanical properties of directly air cooled copper added microalloyed steels
1380 Materials Science and Technology 2007 VOL 23 NO 11
7272019 Mechanical Properties of Directly Air Cooled Copper Added Microalloyed Steels (Dual Phase)
httpslidepdfcomreaderfullmechanical-properties-of-directly-air-cooled-copper-added-microalloyed-steels 26
P u b l i s h e d b y M a n e y P u b l i s h i n g ( c ) I O M C
o m m u n i c a t i o n s L t d
operating voltage of 200 kV Energy dispersive Xndashray
spectroscopic analysis (EDS) was conducted to deter-
mine the composition of the precipitates
Room temperature tensile testing was conducted
using the Instronndash4204 testing machine with a crosshead
velocity of 05 mm min21 The test specimen was
prepared as per the ASTM Standard (ASTM
Vol 0301 E8Mndash96) The error in yield strength (YS)and ultimate tensile strength (UTS) measurement was
recorded asiexcl3 and the same for per cent elongation
was iexcl5
Results
Tensile propertiesFigures 1ndash4 present the results obtained from the tensile
testing of the experimental steels Figure 1 shows that
the addition of Ni in 15CundashTindashB steel has improved the
YS values for both the DAC and aged samples For all
the samples a significant improvement of YS values has
been achieved after aging Figure 2 reveals that both
microalloying and aging have generally contributed to
the improvement of the UTS values Figures 3 and 4
show that in DAC samples microalloying of 15Cu steel
has lowered the elongations and the addition of Ni
in 15CundashTindashB steel has simultaneously improved
However for all the three aged steels the elongation
values are comparable It is important to note that
among the three compositions 15CundashNindashTindashB steel has
yielded the best combination of strength and ductility
for both the DAC and aged samples
Work hardening behaviour of directly air cooledsteelsWork hardening behaviour is generally expressed by
Hollomon equation416 that describes the true stress
1 Yield strength values for various investigated steels 2 Ultimate tensile strength values for various investi-
gated steels
3 Ultimate elongation UEL () values for various inves-
tigated steels
Table 1 Chemical composition of investigated steels wt-
Steel identification C Mn Si S P Ti B Cu Ni N
15Cu 004 160 048 0022 0014 ndash ndash 151 ndash 0005115CundashTindashB 004 169 057 0021 0013 0032 00013 154 ndash 0008015CundashNindashTindashB 003 168 053 0020 0013 0032 00012 155 079 00058
Ghosh et al Mechanical properties of directly air cooled copper added microalloyed steels
1376 Materials Science and Technology 2007 VOL 23 NO 11
7272019 Mechanical Properties of Directly Air Cooled Copper Added Microalloyed Steels (Dual Phase)
httpslidepdfcomreaderfullmechanical-properties-of-directly-air-cooled-copper-added-microalloyed-steels 36
7272019 Mechanical Properties of Directly Air Cooled Copper Added Microalloyed Steels (Dual Phase)
httpslidepdfcomreaderfullmechanical-properties-of-directly-air-cooled-copper-added-microalloyed-steels 46
P u b l i s h e d b y M a n e y P u b l i s h i n g ( c ) I O M C
o m m u n i c a t i o n s L t d
dislocation and tempering of martensite hardening is
contributed by precipitation of Cu
Generally the JaoultndashCrussard plots of the aged steels
exhibit a faster decrease in the work hardening rate than
the DAC steel at the first stage (stage 1) due to the fact
that the dislocations in ferrite of the air cooled steel are
effectively recovered during aging In contrast with the
Hollomon plots the JaoultndashCrussard plots of the agedsamples have revealed a distinct second stage (stage 2)
hardening (Fig 5a vis a vis Fig 5b2d ) Earlier con-
strained deformation of ferrite was held responsible for
the appearance of a second stage with higher work
hardening in the JaoultndashCrussard plots23 In the present
study prominent appearance of the second stage of work
hardening particularly for the aged steels may reason-
ably be attributed to the finer Cu precipitates which
constrain the deformation of ferrite by pinning down the
dislocations The third stage of work hardening is due to
concomitant plastic deformation of martensite and
dynamic recovery of ferrite under isostrain condition
It may be noted that the influence of aging is not
prominent at the third stage and the DAC and agedsamples exhibit approximately comparable deformation
behaviour
Thus it is apparent that precipitation of Cu by virtue
of hardening of ferrite results in sequential work
hardening characteristic which enhances the strengthndash
ductility combination in multiphase microstructures
5 a Hollomon analysis of ln s (s is in MPa) versus ln e for DAC and aged steels differential JaoultndashCrussard analysis
of ln(ds de) versus ln e for DAC and aged b 15Cu c 15CundashTindashB and d 15CundashTimdashBndashNi steel arrow indicated changes
in slope and numerals represent (n rsquo21) values
Ghosh et al Mechanical properties of directly air cooled copper added microalloyed steels
1378 Materials Science and Technology 2007 VOL 23 NO 11
7272019 Mechanical Properties of Directly Air Cooled Copper Added Microalloyed Steels (Dual Phase)
httpslidepdfcomreaderfullmechanical-properties-of-directly-air-cooled-copper-added-microalloyed-steels 56
P u b l i s h e d b y M a n e y P u b l i s h i n g ( c ) I O M C
o m m u n i c a t i o n s L t d
6 Image (SEM) of 15Cu alloy in a DAC condition with smooth appearance of islands and b peak aged condition
(500uC 60 min) showing etching effected islands at ferrite boundaries
7 a image (TEM) of 15Cu2Ti2B sample showing ferrite grains with formation of precipitate at dislocation structures
and b EDS plot and chemical composition (inset) from arrowed region in Fig 7a confirms presence of e- Cu
precipitate
8 a image (TEM) of 15CundashTindashB peak aged (500oC 15 min) sample showing fine precipitates (10ndash40 nm) and b EDS plot
along with chemical composition (inset) from region arrowed in Fig 8a
Ghosh et al Mechanical properties of directly air cooled copper added microalloyed steels
Materials Science and Technology 2007 VOL 23 NO 11 1379
7272019 Mechanical Properties of Directly Air Cooled Copper Added Microalloyed Steels (Dual Phase)
httpslidepdfcomreaderfullmechanical-properties-of-directly-air-cooled-copper-added-microalloyed-steels 66
P u b l i s h e d b y M a n e y P u b l i s h i n g ( c ) I O M C
o m m u n i c a t i o n s L t d
Conclusions
1 Addition of 15 wt-Cu in the Ti2B microalloyedsteel has adequately enhanced the hardenability result-ing in the DP microstructures in directly air cooledcondition
2 Differential JaoultndashCrussard analysis of the tensile
results has demonstrated that Cu precipitation in ferrite
during aging treatment improves the work hardeningbehaviour at the intermediate stage of straining andresulted into attractive strengthndashductility combination
3 The 15Cu2NindashTindashB steel has yielded most attrac-tive strengthndashductility combination in the directly aircooled steels with and without aging
References1 W S Owen Met Technol 1980 7 1ndash13
2 R K Piplani and V Raghavan Steel India 1981 4 (1) 1ndash22
3 P J Jacques J Ladriere and F Delannay Metall Mater Trans
A 2001 32A 275922768
4 J H Hollomon Trans AIME 1945 162 2682290
5 B Jaoult J Mech Phys Solids 1957 5 95ndash114
6 C Crussard Rev Metall (Paris) 1953 10 697ndash710
7 N D Beynon S Oliver T B Jones and G Fourlaris Mater Sci
Technol 2005 21 771ndash778
8 E Navara Proc Int Conf on lsquoHigh strength low alloy steelsrsquo (ed
D P Dunne and T Chandra) 302ndash307 1984 Wollongong
University of Wollongong
9 N R Bandyopadhyay and S Datta ISIJ Int 2004 44 927ndash934
10 X M Wang and X L He ISIJ Int Suppl 2002 42 S38ndashS46
11 A L De Sy Trans Iron Steel Inst Jpn 1974 14 139ndash154
12 G F Vander Voort in lsquoASM Metals hand bookrsquo 10th edn Vol 1
lsquoProperties and selection iron steels and high performance alloysrsquo
389ndash423 1995 Materials Park OH ASM International
13 M E Fine and D Isheim Scr Mater 2005 53 115ndash118
14 M K Banerjee D Ghosh and S Datta ISIJ Int 2001 41 (3)
257ndash261
15 G F Vander Voort lsquoMetallography ndash principles and practicersquo 632
1984 New York McGrawndashHill
16 L F Ramos D K Matlock and G Krauss Metall Trans A
1979 10A 259ndash261
17 T S Byun and I S Kim J Mater Sci 1993 28 2923ndash2932
18 Z Jiang Z Guan and J Lian Mater Sci Eng A 1991 A147 55ndash
65
19 S N Monteiro and R E Reed-Hill Met Trans 1971 2 2947ndash
2949
20 P Ludwik lsquoElement der technolnischen mechanickrsquo 32 1909
Berlin Julius Springer
21 E Girault P Jacques P Harlet K Mols J Van Humbeeck
E Aernoudt and F Delannay Mater Charact 1998 40 111ndash118
22 S Kim and S Lee Metall Mater Trans A 2000 31A 1753ndash1760
23 S Sankaran S Sangal and K A Padmanabhan Mater Sci
Technol 2005 21 1152ndash1160
Ghosh et al Mechanical properties of directly air cooled copper added microalloyed steels
1380 Materials Science and Technology 2007 VOL 23 NO 11
7272019 Mechanical Properties of Directly Air Cooled Copper Added Microalloyed Steels (Dual Phase)
httpslidepdfcomreaderfullmechanical-properties-of-directly-air-cooled-copper-added-microalloyed-steels 36
7272019 Mechanical Properties of Directly Air Cooled Copper Added Microalloyed Steels (Dual Phase)
httpslidepdfcomreaderfullmechanical-properties-of-directly-air-cooled-copper-added-microalloyed-steels 46
P u b l i s h e d b y M a n e y P u b l i s h i n g ( c ) I O M C
o m m u n i c a t i o n s L t d
dislocation and tempering of martensite hardening is
contributed by precipitation of Cu
Generally the JaoultndashCrussard plots of the aged steels
exhibit a faster decrease in the work hardening rate than
the DAC steel at the first stage (stage 1) due to the fact
that the dislocations in ferrite of the air cooled steel are
effectively recovered during aging In contrast with the
Hollomon plots the JaoultndashCrussard plots of the agedsamples have revealed a distinct second stage (stage 2)
hardening (Fig 5a vis a vis Fig 5b2d ) Earlier con-
strained deformation of ferrite was held responsible for
the appearance of a second stage with higher work
hardening in the JaoultndashCrussard plots23 In the present
study prominent appearance of the second stage of work
hardening particularly for the aged steels may reason-
ably be attributed to the finer Cu precipitates which
constrain the deformation of ferrite by pinning down the
dislocations The third stage of work hardening is due to
concomitant plastic deformation of martensite and
dynamic recovery of ferrite under isostrain condition
It may be noted that the influence of aging is not
prominent at the third stage and the DAC and agedsamples exhibit approximately comparable deformation
behaviour
Thus it is apparent that precipitation of Cu by virtue
of hardening of ferrite results in sequential work
hardening characteristic which enhances the strengthndash
ductility combination in multiphase microstructures
5 a Hollomon analysis of ln s (s is in MPa) versus ln e for DAC and aged steels differential JaoultndashCrussard analysis
of ln(ds de) versus ln e for DAC and aged b 15Cu c 15CundashTindashB and d 15CundashTimdashBndashNi steel arrow indicated changes
in slope and numerals represent (n rsquo21) values
Ghosh et al Mechanical properties of directly air cooled copper added microalloyed steels
1378 Materials Science and Technology 2007 VOL 23 NO 11
7272019 Mechanical Properties of Directly Air Cooled Copper Added Microalloyed Steels (Dual Phase)
httpslidepdfcomreaderfullmechanical-properties-of-directly-air-cooled-copper-added-microalloyed-steels 56
P u b l i s h e d b y M a n e y P u b l i s h i n g ( c ) I O M C
o m m u n i c a t i o n s L t d
6 Image (SEM) of 15Cu alloy in a DAC condition with smooth appearance of islands and b peak aged condition
(500uC 60 min) showing etching effected islands at ferrite boundaries
7 a image (TEM) of 15Cu2Ti2B sample showing ferrite grains with formation of precipitate at dislocation structures
and b EDS plot and chemical composition (inset) from arrowed region in Fig 7a confirms presence of e- Cu
precipitate
8 a image (TEM) of 15CundashTindashB peak aged (500oC 15 min) sample showing fine precipitates (10ndash40 nm) and b EDS plot
along with chemical composition (inset) from region arrowed in Fig 8a
Ghosh et al Mechanical properties of directly air cooled copper added microalloyed steels
Materials Science and Technology 2007 VOL 23 NO 11 1379
7272019 Mechanical Properties of Directly Air Cooled Copper Added Microalloyed Steels (Dual Phase)
httpslidepdfcomreaderfullmechanical-properties-of-directly-air-cooled-copper-added-microalloyed-steels 66
P u b l i s h e d b y M a n e y P u b l i s h i n g ( c ) I O M C
o m m u n i c a t i o n s L t d
Conclusions
1 Addition of 15 wt-Cu in the Ti2B microalloyedsteel has adequately enhanced the hardenability result-ing in the DP microstructures in directly air cooledcondition
2 Differential JaoultndashCrussard analysis of the tensile
results has demonstrated that Cu precipitation in ferrite
during aging treatment improves the work hardeningbehaviour at the intermediate stage of straining andresulted into attractive strengthndashductility combination
3 The 15Cu2NindashTindashB steel has yielded most attrac-tive strengthndashductility combination in the directly aircooled steels with and without aging
References1 W S Owen Met Technol 1980 7 1ndash13
2 R K Piplani and V Raghavan Steel India 1981 4 (1) 1ndash22
3 P J Jacques J Ladriere and F Delannay Metall Mater Trans
A 2001 32A 275922768
4 J H Hollomon Trans AIME 1945 162 2682290
5 B Jaoult J Mech Phys Solids 1957 5 95ndash114
6 C Crussard Rev Metall (Paris) 1953 10 697ndash710
7 N D Beynon S Oliver T B Jones and G Fourlaris Mater Sci
Technol 2005 21 771ndash778
8 E Navara Proc Int Conf on lsquoHigh strength low alloy steelsrsquo (ed
D P Dunne and T Chandra) 302ndash307 1984 Wollongong
University of Wollongong
9 N R Bandyopadhyay and S Datta ISIJ Int 2004 44 927ndash934
10 X M Wang and X L He ISIJ Int Suppl 2002 42 S38ndashS46
11 A L De Sy Trans Iron Steel Inst Jpn 1974 14 139ndash154
12 G F Vander Voort in lsquoASM Metals hand bookrsquo 10th edn Vol 1
lsquoProperties and selection iron steels and high performance alloysrsquo
389ndash423 1995 Materials Park OH ASM International
13 M E Fine and D Isheim Scr Mater 2005 53 115ndash118
14 M K Banerjee D Ghosh and S Datta ISIJ Int 2001 41 (3)
257ndash261
15 G F Vander Voort lsquoMetallography ndash principles and practicersquo 632
1984 New York McGrawndashHill
16 L F Ramos D K Matlock and G Krauss Metall Trans A
1979 10A 259ndash261
17 T S Byun and I S Kim J Mater Sci 1993 28 2923ndash2932
18 Z Jiang Z Guan and J Lian Mater Sci Eng A 1991 A147 55ndash
65
19 S N Monteiro and R E Reed-Hill Met Trans 1971 2 2947ndash
2949
20 P Ludwik lsquoElement der technolnischen mechanickrsquo 32 1909
Berlin Julius Springer
21 E Girault P Jacques P Harlet K Mols J Van Humbeeck
E Aernoudt and F Delannay Mater Charact 1998 40 111ndash118
22 S Kim and S Lee Metall Mater Trans A 2000 31A 1753ndash1760
23 S Sankaran S Sangal and K A Padmanabhan Mater Sci
Technol 2005 21 1152ndash1160
Ghosh et al Mechanical properties of directly air cooled copper added microalloyed steels
1380 Materials Science and Technology 2007 VOL 23 NO 11
7272019 Mechanical Properties of Directly Air Cooled Copper Added Microalloyed Steels (Dual Phase)
httpslidepdfcomreaderfullmechanical-properties-of-directly-air-cooled-copper-added-microalloyed-steels 46
P u b l i s h e d b y M a n e y P u b l i s h i n g ( c ) I O M C
o m m u n i c a t i o n s L t d
dislocation and tempering of martensite hardening is
contributed by precipitation of Cu
Generally the JaoultndashCrussard plots of the aged steels
exhibit a faster decrease in the work hardening rate than
the DAC steel at the first stage (stage 1) due to the fact
that the dislocations in ferrite of the air cooled steel are
effectively recovered during aging In contrast with the
Hollomon plots the JaoultndashCrussard plots of the agedsamples have revealed a distinct second stage (stage 2)
hardening (Fig 5a vis a vis Fig 5b2d ) Earlier con-
strained deformation of ferrite was held responsible for
the appearance of a second stage with higher work
hardening in the JaoultndashCrussard plots23 In the present
study prominent appearance of the second stage of work
hardening particularly for the aged steels may reason-
ably be attributed to the finer Cu precipitates which
constrain the deformation of ferrite by pinning down the
dislocations The third stage of work hardening is due to
concomitant plastic deformation of martensite and
dynamic recovery of ferrite under isostrain condition
It may be noted that the influence of aging is not
prominent at the third stage and the DAC and agedsamples exhibit approximately comparable deformation
behaviour
Thus it is apparent that precipitation of Cu by virtue
of hardening of ferrite results in sequential work
hardening characteristic which enhances the strengthndash
ductility combination in multiphase microstructures
5 a Hollomon analysis of ln s (s is in MPa) versus ln e for DAC and aged steels differential JaoultndashCrussard analysis
of ln(ds de) versus ln e for DAC and aged b 15Cu c 15CundashTindashB and d 15CundashTimdashBndashNi steel arrow indicated changes
in slope and numerals represent (n rsquo21) values
Ghosh et al Mechanical properties of directly air cooled copper added microalloyed steels
1378 Materials Science and Technology 2007 VOL 23 NO 11
7272019 Mechanical Properties of Directly Air Cooled Copper Added Microalloyed Steels (Dual Phase)
httpslidepdfcomreaderfullmechanical-properties-of-directly-air-cooled-copper-added-microalloyed-steels 56
P u b l i s h e d b y M a n e y P u b l i s h i n g ( c ) I O M C
o m m u n i c a t i o n s L t d
6 Image (SEM) of 15Cu alloy in a DAC condition with smooth appearance of islands and b peak aged condition
(500uC 60 min) showing etching effected islands at ferrite boundaries
7 a image (TEM) of 15Cu2Ti2B sample showing ferrite grains with formation of precipitate at dislocation structures
and b EDS plot and chemical composition (inset) from arrowed region in Fig 7a confirms presence of e- Cu
precipitate
8 a image (TEM) of 15CundashTindashB peak aged (500oC 15 min) sample showing fine precipitates (10ndash40 nm) and b EDS plot
along with chemical composition (inset) from region arrowed in Fig 8a
Ghosh et al Mechanical properties of directly air cooled copper added microalloyed steels
Materials Science and Technology 2007 VOL 23 NO 11 1379
7272019 Mechanical Properties of Directly Air Cooled Copper Added Microalloyed Steels (Dual Phase)
httpslidepdfcomreaderfullmechanical-properties-of-directly-air-cooled-copper-added-microalloyed-steels 66
P u b l i s h e d b y M a n e y P u b l i s h i n g ( c ) I O M C
o m m u n i c a t i o n s L t d
Conclusions
1 Addition of 15 wt-Cu in the Ti2B microalloyedsteel has adequately enhanced the hardenability result-ing in the DP microstructures in directly air cooledcondition
2 Differential JaoultndashCrussard analysis of the tensile
results has demonstrated that Cu precipitation in ferrite
during aging treatment improves the work hardeningbehaviour at the intermediate stage of straining andresulted into attractive strengthndashductility combination
3 The 15Cu2NindashTindashB steel has yielded most attrac-tive strengthndashductility combination in the directly aircooled steels with and without aging
References1 W S Owen Met Technol 1980 7 1ndash13
2 R K Piplani and V Raghavan Steel India 1981 4 (1) 1ndash22
3 P J Jacques J Ladriere and F Delannay Metall Mater Trans
A 2001 32A 275922768
4 J H Hollomon Trans AIME 1945 162 2682290
5 B Jaoult J Mech Phys Solids 1957 5 95ndash114
6 C Crussard Rev Metall (Paris) 1953 10 697ndash710
7 N D Beynon S Oliver T B Jones and G Fourlaris Mater Sci
Technol 2005 21 771ndash778
8 E Navara Proc Int Conf on lsquoHigh strength low alloy steelsrsquo (ed
D P Dunne and T Chandra) 302ndash307 1984 Wollongong
University of Wollongong
9 N R Bandyopadhyay and S Datta ISIJ Int 2004 44 927ndash934
10 X M Wang and X L He ISIJ Int Suppl 2002 42 S38ndashS46
11 A L De Sy Trans Iron Steel Inst Jpn 1974 14 139ndash154
12 G F Vander Voort in lsquoASM Metals hand bookrsquo 10th edn Vol 1
lsquoProperties and selection iron steels and high performance alloysrsquo
389ndash423 1995 Materials Park OH ASM International
13 M E Fine and D Isheim Scr Mater 2005 53 115ndash118
14 M K Banerjee D Ghosh and S Datta ISIJ Int 2001 41 (3)
257ndash261
15 G F Vander Voort lsquoMetallography ndash principles and practicersquo 632
1984 New York McGrawndashHill
16 L F Ramos D K Matlock and G Krauss Metall Trans A
1979 10A 259ndash261
17 T S Byun and I S Kim J Mater Sci 1993 28 2923ndash2932
18 Z Jiang Z Guan and J Lian Mater Sci Eng A 1991 A147 55ndash
65
19 S N Monteiro and R E Reed-Hill Met Trans 1971 2 2947ndash
2949
20 P Ludwik lsquoElement der technolnischen mechanickrsquo 32 1909
Berlin Julius Springer
21 E Girault P Jacques P Harlet K Mols J Van Humbeeck
E Aernoudt and F Delannay Mater Charact 1998 40 111ndash118
22 S Kim and S Lee Metall Mater Trans A 2000 31A 1753ndash1760
23 S Sankaran S Sangal and K A Padmanabhan Mater Sci
Technol 2005 21 1152ndash1160
Ghosh et al Mechanical properties of directly air cooled copper added microalloyed steels
1380 Materials Science and Technology 2007 VOL 23 NO 11
7272019 Mechanical Properties of Directly Air Cooled Copper Added Microalloyed Steels (Dual Phase)
httpslidepdfcomreaderfullmechanical-properties-of-directly-air-cooled-copper-added-microalloyed-steels 56
P u b l i s h e d b y M a n e y P u b l i s h i n g ( c ) I O M C
o m m u n i c a t i o n s L t d
6 Image (SEM) of 15Cu alloy in a DAC condition with smooth appearance of islands and b peak aged condition
(500uC 60 min) showing etching effected islands at ferrite boundaries
7 a image (TEM) of 15Cu2Ti2B sample showing ferrite grains with formation of precipitate at dislocation structures
and b EDS plot and chemical composition (inset) from arrowed region in Fig 7a confirms presence of e- Cu
precipitate
8 a image (TEM) of 15CundashTindashB peak aged (500oC 15 min) sample showing fine precipitates (10ndash40 nm) and b EDS plot
along with chemical composition (inset) from region arrowed in Fig 8a
Ghosh et al Mechanical properties of directly air cooled copper added microalloyed steels
Materials Science and Technology 2007 VOL 23 NO 11 1379
7272019 Mechanical Properties of Directly Air Cooled Copper Added Microalloyed Steels (Dual Phase)
httpslidepdfcomreaderfullmechanical-properties-of-directly-air-cooled-copper-added-microalloyed-steels 66
P u b l i s h e d b y M a n e y P u b l i s h i n g ( c ) I O M C
o m m u n i c a t i o n s L t d
Conclusions
1 Addition of 15 wt-Cu in the Ti2B microalloyedsteel has adequately enhanced the hardenability result-ing in the DP microstructures in directly air cooledcondition
2 Differential JaoultndashCrussard analysis of the tensile
results has demonstrated that Cu precipitation in ferrite
during aging treatment improves the work hardeningbehaviour at the intermediate stage of straining andresulted into attractive strengthndashductility combination
3 The 15Cu2NindashTindashB steel has yielded most attrac-tive strengthndashductility combination in the directly aircooled steels with and without aging
References1 W S Owen Met Technol 1980 7 1ndash13
2 R K Piplani and V Raghavan Steel India 1981 4 (1) 1ndash22
3 P J Jacques J Ladriere and F Delannay Metall Mater Trans
A 2001 32A 275922768
4 J H Hollomon Trans AIME 1945 162 2682290
5 B Jaoult J Mech Phys Solids 1957 5 95ndash114
6 C Crussard Rev Metall (Paris) 1953 10 697ndash710
7 N D Beynon S Oliver T B Jones and G Fourlaris Mater Sci
Technol 2005 21 771ndash778
8 E Navara Proc Int Conf on lsquoHigh strength low alloy steelsrsquo (ed
D P Dunne and T Chandra) 302ndash307 1984 Wollongong
University of Wollongong
9 N R Bandyopadhyay and S Datta ISIJ Int 2004 44 927ndash934
10 X M Wang and X L He ISIJ Int Suppl 2002 42 S38ndashS46
11 A L De Sy Trans Iron Steel Inst Jpn 1974 14 139ndash154
12 G F Vander Voort in lsquoASM Metals hand bookrsquo 10th edn Vol 1
lsquoProperties and selection iron steels and high performance alloysrsquo
389ndash423 1995 Materials Park OH ASM International
13 M E Fine and D Isheim Scr Mater 2005 53 115ndash118
14 M K Banerjee D Ghosh and S Datta ISIJ Int 2001 41 (3)
257ndash261
15 G F Vander Voort lsquoMetallography ndash principles and practicersquo 632
1984 New York McGrawndashHill
16 L F Ramos D K Matlock and G Krauss Metall Trans A
1979 10A 259ndash261
17 T S Byun and I S Kim J Mater Sci 1993 28 2923ndash2932
18 Z Jiang Z Guan and J Lian Mater Sci Eng A 1991 A147 55ndash
65
19 S N Monteiro and R E Reed-Hill Met Trans 1971 2 2947ndash
2949
20 P Ludwik lsquoElement der technolnischen mechanickrsquo 32 1909
Berlin Julius Springer
21 E Girault P Jacques P Harlet K Mols J Van Humbeeck
E Aernoudt and F Delannay Mater Charact 1998 40 111ndash118
22 S Kim and S Lee Metall Mater Trans A 2000 31A 1753ndash1760
23 S Sankaran S Sangal and K A Padmanabhan Mater Sci
Technol 2005 21 1152ndash1160
Ghosh et al Mechanical properties of directly air cooled copper added microalloyed steels
1380 Materials Science and Technology 2007 VOL 23 NO 11
7272019 Mechanical Properties of Directly Air Cooled Copper Added Microalloyed Steels (Dual Phase)
httpslidepdfcomreaderfullmechanical-properties-of-directly-air-cooled-copper-added-microalloyed-steels 66
P u b l i s h e d b y M a n e y P u b l i s h i n g ( c ) I O M C
o m m u n i c a t i o n s L t d
Conclusions
1 Addition of 15 wt-Cu in the Ti2B microalloyedsteel has adequately enhanced the hardenability result-ing in the DP microstructures in directly air cooledcondition
2 Differential JaoultndashCrussard analysis of the tensile
results has demonstrated that Cu precipitation in ferrite
during aging treatment improves the work hardeningbehaviour at the intermediate stage of straining andresulted into attractive strengthndashductility combination
3 The 15Cu2NindashTindashB steel has yielded most attrac-tive strengthndashductility combination in the directly aircooled steels with and without aging
References1 W S Owen Met Technol 1980 7 1ndash13
2 R K Piplani and V Raghavan Steel India 1981 4 (1) 1ndash22
3 P J Jacques J Ladriere and F Delannay Metall Mater Trans
A 2001 32A 275922768
4 J H Hollomon Trans AIME 1945 162 2682290
5 B Jaoult J Mech Phys Solids 1957 5 95ndash114
6 C Crussard Rev Metall (Paris) 1953 10 697ndash710
7 N D Beynon S Oliver T B Jones and G Fourlaris Mater Sci
Technol 2005 21 771ndash778
8 E Navara Proc Int Conf on lsquoHigh strength low alloy steelsrsquo (ed
D P Dunne and T Chandra) 302ndash307 1984 Wollongong
University of Wollongong
9 N R Bandyopadhyay and S Datta ISIJ Int 2004 44 927ndash934
10 X M Wang and X L He ISIJ Int Suppl 2002 42 S38ndashS46
11 A L De Sy Trans Iron Steel Inst Jpn 1974 14 139ndash154
12 G F Vander Voort in lsquoASM Metals hand bookrsquo 10th edn Vol 1
lsquoProperties and selection iron steels and high performance alloysrsquo
389ndash423 1995 Materials Park OH ASM International
13 M E Fine and D Isheim Scr Mater 2005 53 115ndash118
14 M K Banerjee D Ghosh and S Datta ISIJ Int 2001 41 (3)
257ndash261
15 G F Vander Voort lsquoMetallography ndash principles and practicersquo 632
1984 New York McGrawndashHill
16 L F Ramos D K Matlock and G Krauss Metall Trans A
1979 10A 259ndash261
17 T S Byun and I S Kim J Mater Sci 1993 28 2923ndash2932
18 Z Jiang Z Guan and J Lian Mater Sci Eng A 1991 A147 55ndash
65
19 S N Monteiro and R E Reed-Hill Met Trans 1971 2 2947ndash
2949
20 P Ludwik lsquoElement der technolnischen mechanickrsquo 32 1909
Berlin Julius Springer
21 E Girault P Jacques P Harlet K Mols J Van Humbeeck
E Aernoudt and F Delannay Mater Charact 1998 40 111ndash118
22 S Kim and S Lee Metall Mater Trans A 2000 31A 1753ndash1760
23 S Sankaran S Sangal and K A Padmanabhan Mater Sci
Technol 2005 21 1152ndash1160
Ghosh et al Mechanical properties of directly air cooled copper added microalloyed steels
1380 Materials Science and Technology 2007 VOL 23 NO 11