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Relation entre la ségrégation des impuretés et l'autodiffusion inter granulaire dans le fer
LETTERS
TO
THP:
EDITOR
compression
69 I
was noticed.
A slight ditference between
the initial curves in compression proved
and in tension was
to be due to buckling:
specimens
were particularly
to which
t’he nickel
susceptible.
Acknowledgments The author Rathenau
is much indebted
for his stimulating
to Professor
interest.
tion of the material was determined and his staff of this laboratory. Mr. J. Raadsen,
by Mr. J. Kroonen
The able assistance of
Mr. J. N. Helle and Mr. D. de Graag
during the experiments
was much appreciated. A. TV.
lionilbkltjke
Fig. 2. Xcrocraok formed at O’C 400 x magnifirittion. rwgativr 3 x enlarged.
Becker(G)).
Although
a detailed
t’hat the micro-cracks
tensile plastic
deformation
this movement, induction. formed
in
thus causing a falling-off
If in addition
we assume
tension
be
may
The difference mechanical ductile-brittle
transition
that
without
with this concept.
plastic
it shon-s
the
in tension
well with the known
temperatures
below
temperature
temperature
preceding
compression
at
iron
in
breaks
deformation. usual
in
increases
with
of a Griffith
stable
Grifith
increasing
stress
crack
crack requires
ideas
mentioned
opened
only with up.
A
more stress if it is to
that creation
of vacancies
to check
It was initially might
the
surmised
play the principal
r81e in explaining the phenomena. Keeping plastically deformed specimens for 2 months at 120°C did not, however,
introduce
induction. Jt was realized
any
change
8.
Relation entre la sCgrCgation des impure& et l’autodiffusion intergranulaire dans le fer* Differentes
etudes,
in
the
magnetic
was thus far made of the occurrence
no mention
of microcracks
determiner
laire des impuretes. Bmis
l’hypothese
ou exp&rimentales,
perturbee
des joints de
la segregation
intergranu-
Ainsi ,llcLean et Northcott’r) de
segr6gations
ont
intergranulaires
d’atomes de solute, meme aux temperatures sup6rieures B la temperature
limite de solubilite.
On sait d’autrc
part que la structure des joints depend non seulement de I’orientation aussi
t,hat in the literature
theoriques
ont sugger6 que la structure grains pouvait
were performed
above.
5. 6. 5.
in
be opened up further (Cottrell(*)). A fen- experiments
3. 4.
phenomena
is consistent
being
,“.
tension
(Lo&i’). The finding that the decrease of permeability t,he idea
the
tension.
whereas
yield
References 1.
during
enumerated
behaviour
correlates
behaviour
a crack
closed
points
in magnetic
and in compression
to
of magnetic that
partly
it
during
may act as obstacles
compression, the subsequent above are seen to be compatible
Below
created
SLEIWVYK
Shell-Laboratori/l’n/
Amsterda,m
model is lacking,
is conceivable
G. iV_.
The composi-
de
relative
I’orientation
des cristaux du
reseaux des grains adjacents.
,joint
par
contigus,
mais
rapport
aux
En consequence,
plus
la st,ructure des joints cst pert,urbce (joints s6parant
at temperatures higher than about -90°C. Fig. 2 is a microphotograph of a crack on the surface of an Armco ingot iron specimen that had been successively
des cristaux de forte d&orientation). et plus la tendance a la segregation dcs impure& doit 6tre prononc6e.
electropolished,
nous avons compare
annealed
at’ 960°C and strained
to
4O/‘0 in tension at 0°C. A small number of nickel specimens was tested in the same manner as t’he iron: no restorative effect of
Pour obtenir une preuve directe de cette hypothesc, les phbnomitncs
d’autodiffusion
intergranulairc. a ceux de pr6cipitation d’un solute dissous k unc teneur nettement infirieure & la limite Les techniques autoradiographiqucs dc solubilitc.
692
ACTA
METALLURGICA,
171~. 1. Diffusion pr&fkentiolle de fer radiomctif dans un kchantillon de fer recuit 8. 700°C. Autoradiographio G = 50 obtenue :tp&s abrasion de 10~. G = 50 E’x. 2. M&me plage sprks abrasion de 30,u. YIP. 3. Autoradiogrnphie montrant la diffusion p&f&entie110 de ferradioactif danslessous-jointsdepolygollisation G = 50 d’un for pur (recuit de 66 h B iOOT).
VOL.
7,
1959
FIG. 4. Nicrogritphic d’una plage dr fixrcontenant 0,005%, (: ~: 40 de souf’re radioactif. FIG. 5. Wgl$gRt,ion du souf’re radiowtif’ dans 1~s joints dr la m&me plage observbe JSI~ :Lu~orw,cliographie. G ~ 40 prkfPrant,ielle drr for rudioacM FIG. 6. dutodiffusion dans les joints do la mBme pla,ge (rrcwit do 66 h it 700°C). c: = 10
LETTERS
permettent
seules
par
1’Btude de phkomknes
leur
THE
693
EDITOR
d’aborder
qui intkressent une Bpaisseur
de metal nettement infkieure des autres techniques
sensibilitk
TO
au pouvoir de rksolution
expkimentales.
Les autoradiographies (Figs. 1 et 2) montrent en effet l’autodiffusion pr6firentielle du fer radioactif (mklange de Fe55 + Fe5g) dans les joints de grains d’un Bchantillon de fer inerte apr&s un recuit de diffusion de 74 h ?I 700°C. fer
radioactif,
Aprbs dissolution des
du dBp6t initial
autoradiographies
de
effect&es
B
diffkrents niveaux paralkles & l’interface montrent une diffirenco
de p&&ration
fois dc l’orientation
tion propre du joint.‘“) de macle coherent joints
intergranulaire
fonction
Elle est t&s faible dans un joint
et tr&s j’aihle
aussi
dam
les sous-
comme le montre la Fig. 3.c3)
de polygonisation
Dans unc autre s&ie d’exphriences,
on ajoute & un
fer pur unc teneur totale en soufre radioactif nettement
k la
des rkseaux contigus et de l’orienta-
(0,005“/‘)
infkrieure B la limite de solubilitk actuelle-
ment admise (0,02:{,
k 900°C).
PIG. S. Mkna plage, attaquke avrc une solution d‘aride m~t;lnitrobenz8ne_sulfonique dam l’bthanol. ks trace rroircs correspondent BUX nnriens joints. c: : 7.i
prononckc,
Apr&s recuit de 16 h
c’est & dire les joints de grains de plus forte
R 75O”C, puis de 32 h h 870°C et refroidissement
lent
d&orientation. Nous avons enfin Btendu ces observations
jusqu’k
uni-
joints y du fer.
WC,
formbment
graphie
primitivement
rkparti
dans la structure brute de coulke du m&al
se rassemble structure
le soufre
dans les joints.
micrographique
La comparaison
de la
(Fig. 4) et de l’autoradio-
de la m&me plage
(Fig.
5) montre
soufrc rw s‘est pas prGcipit@ uniform&lent
que le
les ,joints de grains. Lorsquc indkelable. d+o&
awns
du soufre
est devenue
sur ce m&me Bchantillon
graphie
(66 h k 700°C)
comparable
celui ayant donnb les autoradiographies
montre
la
aux traces
B
joints
qui sont frkquents
joints
oil l’autodiffusion
int,ergranulaire
est la
plus
dans l’alcool
l’image
dir&c
de
l’orientation joints
puretb
a k% prBfbren-
Ies contours
dans l’austbnite
de rnacles
n’appara,isscnt ni
sur
ni
l’irnage
ces experiences apportent unc preuvc des
des joints
et des cristaus
de
d&orientation correspondent
sensible
mbtsnitro-
Bthylique) rdvkle quc
l’influence
l’autodiffuaion les
d’acidc
autoradiographique.
micrographique. En ronclusion,
fer
est surt,out localis@ dans les
8). Par contre,
sur
du
La m&me plage
de grains y oh l’autodiffusion
tiellet5) (Fig.
skgr@gation cn soufre correspondent
les
prkf&entiellc
(solution
pm
l’autoradio-
avec un r&a&if chimiyue
d’impuret&
2. La Fig. A montre aussit6t qu’aux joints j, plus forte pr6ci&ment
diffusion
Aprks
du fer
de fer ra,dioactif,
la rkseau des impuretbs
des Figs. 1 et
intergranulaire.(*)
radioact,if dans les joints y (Fig. 7).
benzene sulfonique
dufw radioactif et effect& unrecuit de diffusion
B basse ternphrature
d’un dBp6t
au cas des du domaine
de 100 h B 1000°C effectuG sur
repolie et attaquee
la radioactivitk now
y, il y a aussi autodiffusion recuit
recouvert
dans tous
Dans la partie infirieurc
paramBtres
et la &gr@gation grains.
Aux
d6finissant contigus
des impuretPs joints
de
plus
sur dans forte
en phase a. comme en phase y lcs plus fortes concentrations d’im-
s@gr6$6es.
Bibliographie
Frc:. 7. Autodiffusion prtYbrent~irlle dam fer rccuit 100 h B 1000°C.
les joints
y d’un G = 75
1. D. RloLmx ct L. NORTHCOTT, J. Imt. Metds 72, 5X3 (1946). 2. et P. LACOMBE. Rev. Nt+. 54. 653 (1957). _. C. _. T>P.Y\~~NIE __~_.~ 3. P. COULOMB, C. LEYXONIE et P. L,WOiMsE,i'. R:Aml: sci., Pwis 246, 1209 (1958).
ACTA
(i!H
METALLURGIC
A . VOL.
7.
1959
4. S. %. BOGSTEIN, S. T. KISECHINet L. N. MOROZ. (“orlf&vw I~afwwarrtio~mlrBUT Ien Rnrlioisotopes U.K.E.S.C.0. Paris (19.57) ;?Emoire RIG/193. .‘,. 1’. (:OCLOXB et P. LACOMBE. Rev.Xc%. 55,918 (l%%).
'I' lbrrnived
Cracks
hley 5, 1959.
due to the piling-up
two intersecting
of dislocations
slip planes in MgO
on
crystals*
In MgO crystals, two types of crack have been reported.(ls2) One was associated with the Stroh mechanism,(l)
and
mechanism.(2)
The purpose of this communication
the
other
to report the observation
with
the
Cottrell is
of a new type of crack in
MgO and LiF crystals and to propose a mechanism for the initiation
of such a crack.
In 19.58 Cottrrll(3) suggested nucleation
a mechanism
of cleavage cracks on
(100) planes in b.c.c.
structures due to the coalescence of dislocations intersecting observed tests.
slip
planes.
This
type
in MgO by Washburn The
dislocation
of
reaction
on two
crack
et CA.(~)
was
in tension
involved
in
this
process in a structure like MgO is shown schematically in Fig.
1 and can be represented
YIG. 2. Crack formation
for the
by the following
vector equation: + $a.[OiT] = a[OTO]
(1)
cryst,als.
In Fig. 2, two slip planes (011) and (101) intersect along the (1x1) axis and make each other. slip vector
angle of 120” with
an
If we consider a dislocation
loop with a
$a[Oil J)on the (011) plane and another loop with vector v(v = &[lOi])on the (101) U(U =
plane, then the sections O,P, and O,P, parallel to the line of intersection dislocation
@[Oil]
OII C110)plane in XgO
combine
together and form a new
OP with a Burger’s
This dislocation
vector
reaction can be written
P = &u[liO]. as
u
+
v
=
r,
01'
However.
in contrast
struct,ure considered
with the case of the b.c.c.
by Cottrell, there is no change of
elastic energy in the above reaction. Nevertheless,
it’ can be shown that in crystals like
11g0, a different type of dislocation
reaction is more
favorable
$a.[oii] + ',a[1011 = +a[lio] It’ is to be noticed Therefore, reaction
this (1).
t’han reaction (1) above. If this reaction operates, it will lead to a crack on the slip plane (110) understood components instead of the usual cleavage plane. It is to be noticed
that this type of crack is different Stokes et rrl.“) observed piling
up
of
that
in so combining
the
elastic
reaction
is
This reaction by
more
is
the
the two released.
favorable
can probably
considering
of the individual
energy
edge
than
be better and
screw
dislocations :
from that which
in compression
dislocations
half
dislocations.
(4)
against
tests, where a
a kink
band
is
involved.
The first term in each reaction is the edge component, and the second term the screw component.
As shown
in Fig. 3> the two screw components and the edge components
cancel each other combine together. This may
be represent’ed bp the following
Flc,. 1. (‘rack
formation on (010) 11go crystals.
cleavage
plane
in
two
equations:
Therefore the elastic energy due to the coalescence
of
TO
THP:
EDITOR
compression
69 I
was noticed.
A slight ditference between
the initial curves in compression proved
and in tension was
to be due to buckling:
specimens
were particularly
to which
t’he nickel
susceptible.
Acknowledgments The author Rathenau
is much indebted
for his stimulating
to Professor
interest.
tion of the material was determined and his staff of this laboratory. Mr. J. Raadsen,
by Mr. J. Kroonen
The able assistance of
Mr. J. N. Helle and Mr. D. de Graag
during the experiments
was much appreciated. A. TV.
lionilbkltjke
Fig. 2. Xcrocraok formed at O’C 400 x magnifirittion. rwgativr 3 x enlarged.
Becker(G)).
Although
a detailed
t’hat the micro-cracks
tensile plastic
deformation
this movement, induction. formed
in
thus causing a falling-off
If in addition
we assume
tension
be
may
The difference mechanical ductile-brittle
transition
that
without
with this concept.
plastic
it shon-s
the
in tension
well with the known
temperatures
below
temperature
temperature
preceding
compression
at
iron
in
breaks
deformation. usual
in
increases
with
of a Griffith
stable
Grifith
increasing
stress
crack
crack requires
ideas
mentioned
opened
only with up.
A
more stress if it is to
that creation
of vacancies
to check
It was initially might
the
surmised
play the principal
r81e in explaining the phenomena. Keeping plastically deformed specimens for 2 months at 120°C did not, however,
introduce
induction. Jt was realized
any
change
8.
Relation entre la sCgrCgation des impure& et l’autodiffusion intergranulaire dans le fer* Differentes
etudes,
in
the
magnetic
was thus far made of the occurrence
no mention
of microcracks
determiner
laire des impuretes. Bmis
l’hypothese
ou exp&rimentales,
perturbee
des joints de
la segregation
intergranu-
Ainsi ,llcLean et Northcott’r) de
segr6gations
ont
intergranulaires
d’atomes de solute, meme aux temperatures sup6rieures B la temperature
limite de solubilite.
On sait d’autrc
part que la structure des joints depend non seulement de I’orientation aussi
t,hat in the literature
theoriques
ont sugger6 que la structure grains pouvait
were performed
above.
5. 6. 5.
in
be opened up further (Cottrell(*)). A fen- experiments
3. 4.
phenomena
is consistent
being
,“.
tension
(Lo&i’). The finding that the decrease of permeability t,he idea
the
tension.
whereas
yield
References 1.
during
enumerated
behaviour
correlates
behaviour
a crack
closed
points
in magnetic
and in compression
to
of magnetic that
partly
it
during
may act as obstacles
compression, the subsequent above are seen to be compatible
Below
created
SLEIWVYK
Shell-Laboratori/l’n/
Amsterda,m
model is lacking,
is conceivable
G. iV_.
The composi-
de
relative
I’orientation
des cristaux du
reseaux des grains adjacents.
,joint
par
contigus,
mais
rapport
aux
En consequence,
plus
la st,ructure des joints cst pert,urbce (joints s6parant
at temperatures higher than about -90°C. Fig. 2 is a microphotograph of a crack on the surface of an Armco ingot iron specimen that had been successively
des cristaux de forte d&orientation). et plus la tendance a la segregation dcs impure& doit 6tre prononc6e.
electropolished,
nous avons compare
annealed
at’ 960°C and strained
to
4O/‘0 in tension at 0°C. A small number of nickel specimens was tested in the same manner as t’he iron: no restorative effect of
Pour obtenir une preuve directe de cette hypothesc, les phbnomitncs
d’autodiffusion
intergranulairc. a ceux de pr6cipitation d’un solute dissous k unc teneur nettement infirieure & la limite Les techniques autoradiographiqucs dc solubilitc.
692
ACTA
METALLURGICA,
171~. 1. Diffusion pr&fkentiolle de fer radiomctif dans un kchantillon de fer recuit 8. 700°C. Autoradiographio G = 50 obtenue :tp&s abrasion de 10~. G = 50 E’x. 2. M&me plage sprks abrasion de 30,u. YIP. 3. Autoradiogrnphie montrant la diffusion p&f&entie110 de ferradioactif danslessous-jointsdepolygollisation G = 50 d’un for pur (recuit de 66 h B iOOT).
VOL.
7,
1959
FIG. 4. Nicrogritphic d’una plage dr fixrcontenant 0,005%, (: ~: 40 de souf’re radioactif. FIG. 5. Wgl$gRt,ion du souf’re radiowtif’ dans 1~s joints dr la m&me plage observbe JSI~ :Lu~orw,cliographie. G ~ 40 prkfPrant,ielle drr for rudioacM FIG. 6. dutodiffusion dans les joints do la mBme pla,ge (rrcwit do 66 h it 700°C). c: = 10
LETTERS
permettent
seules
par
1’Btude de phkomknes
leur
THE
693
EDITOR
d’aborder
qui intkressent une Bpaisseur
de metal nettement infkieure des autres techniques
sensibilitk
TO
au pouvoir de rksolution
expkimentales.
Les autoradiographies (Figs. 1 et 2) montrent en effet l’autodiffusion pr6firentielle du fer radioactif (mklange de Fe55 + Fe5g) dans les joints de grains d’un Bchantillon de fer inerte apr&s un recuit de diffusion de 74 h ?I 700°C. fer
radioactif,
Aprbs dissolution des
du dBp6t initial
autoradiographies
de
effect&es
B
diffkrents niveaux paralkles & l’interface montrent une diffirenco
de p&&ration
fois dc l’orientation
tion propre du joint.‘“) de macle coherent joints
intergranulaire
fonction
Elle est t&s faible dans un joint
et tr&s j’aihle
aussi
dam
les sous-
comme le montre la Fig. 3.c3)
de polygonisation
Dans unc autre s&ie d’exphriences,
on ajoute & un
fer pur unc teneur totale en soufre radioactif nettement
k la
des rkseaux contigus et de l’orienta-
(0,005“/‘)
infkrieure B la limite de solubilitk actuelle-
ment admise (0,02:{,
k 900°C).
PIG. S. Mkna plage, attaquke avrc une solution d‘aride m~t;lnitrobenz8ne_sulfonique dam l’bthanol. ks trace rroircs correspondent BUX nnriens joints. c: : 7.i
prononckc,
Apr&s recuit de 16 h
c’est & dire les joints de grains de plus forte
R 75O”C, puis de 32 h h 870°C et refroidissement
lent
d&orientation. Nous avons enfin Btendu ces observations
jusqu’k
uni-
joints y du fer.
WC,
formbment
graphie
primitivement
rkparti
dans la structure brute de coulke du m&al
se rassemble structure
le soufre
dans les joints.
micrographique
La comparaison
de la
(Fig. 4) et de l’autoradio-
de la m&me plage
(Fig.
5) montre
soufrc rw s‘est pas prGcipit@ uniform&lent
que le
les ,joints de grains. Lorsquc indkelable. d+o&
awns
du soufre
est devenue
sur ce m&me Bchantillon
graphie
(66 h k 700°C)
comparable
celui ayant donnb les autoradiographies
montre
la
aux traces
B
joints
qui sont frkquents
joints
oil l’autodiffusion
int,ergranulaire
est la
plus
dans l’alcool
l’image
dir&c
de
l’orientation joints
puretb
a k% prBfbren-
Ies contours
dans l’austbnite
de rnacles
n’appara,isscnt ni
sur
ni
l’irnage
ces experiences apportent unc preuvc des
des joints
et des cristaus
de
d&orientation correspondent
sensible
mbtsnitro-
Bthylique) rdvkle quc
l’influence
l’autodiffuaion les
d’acidc
autoradiographique.
micrographique. En ronclusion,
fer
est surt,out localis@ dans les
8). Par contre,
sur
du
La m&me plage
de grains y oh l’autodiffusion
tiellet5) (Fig.
skgr@gation cn soufre correspondent
les
prkf&entiellc
(solution
pm
l’autoradio-
avec un r&a&if chimiyue
d’impuret&
2. La Fig. A montre aussit6t qu’aux joints j, plus forte pr6ci&ment
diffusion
Aprks
du fer
de fer ra,dioactif,
la rkseau des impuretbs
des Figs. 1 et
intergranulaire.(*)
radioact,if dans les joints y (Fig. 7).
benzene sulfonique
dufw radioactif et effect& unrecuit de diffusion
B basse ternphrature
d’un dBp6t
au cas des du domaine
de 100 h B 1000°C effectuG sur
repolie et attaquee
la radioactivitk now
y, il y a aussi autodiffusion recuit
recouvert
dans tous
Dans la partie infirieurc
paramBtres
et la &gr@gation grains.
Aux
d6finissant contigus
des impuretPs joints
de
plus
sur dans forte
en phase a. comme en phase y lcs plus fortes concentrations d’im-
s@gr6$6es.
Bibliographie
Frc:. 7. Autodiffusion prtYbrent~irlle dam fer rccuit 100 h B 1000°C.
les joints
y d’un G = 75
1. D. RloLmx ct L. NORTHCOTT, J. Imt. Metds 72, 5X3 (1946). 2. et P. LACOMBE. Rev. Nt+. 54. 653 (1957). _. C. _. T>P.Y\~~NIE __~_.~ 3. P. COULOMB, C. LEYXONIE et P. L,WOiMsE,i'. R:Aml: sci., Pwis 246, 1209 (1958).
ACTA
(i!H
METALLURGIC
A . VOL.
7.
1959
4. S. %. BOGSTEIN, S. T. KISECHINet L. N. MOROZ. (“orlf&vw I~afwwarrtio~mlrBUT Ien Rnrlioisotopes U.K.E.S.C.0. Paris (19.57) ;?Emoire RIG/193. .‘,. 1’. (:OCLOXB et P. LACOMBE. Rev.Xc%. 55,918 (l%%).
'I' lbrrnived
Cracks
hley 5, 1959.
due to the piling-up
two intersecting
of dislocations
slip planes in MgO
on
crystals*
In MgO crystals, two types of crack have been reported.(ls2) One was associated with the Stroh mechanism,(l)
and
mechanism.(2)
The purpose of this communication
the
other
to report the observation
with
the
Cottrell is
of a new type of crack in
MgO and LiF crystals and to propose a mechanism for the initiation
of such a crack.
In 19.58 Cottrrll(3) suggested nucleation
a mechanism
of cleavage cracks on
(100) planes in b.c.c.
structures due to the coalescence of dislocations intersecting observed tests.
slip
planes.
This
type
in MgO by Washburn The
dislocation
of
reaction
on two
crack
et CA.(~)
was
in tension
involved
in
this
process in a structure like MgO is shown schematically in Fig.
1 and can be represented
YIG. 2. Crack formation
for the
by the following
vector equation: + $a.[OiT] = a[OTO]
(1)
cryst,als.
In Fig. 2, two slip planes (011) and (101) intersect along the (1x1) axis and make each other. slip vector
angle of 120” with
an
If we consider a dislocation
loop with a
$a[Oil J)on the (011) plane and another loop with vector v(v = &[lOi])on the (101) U(U =
plane, then the sections O,P, and O,P, parallel to the line of intersection dislocation
@[Oil]
OII C110)plane in XgO
combine
together and form a new
OP with a Burger’s
This dislocation
vector
reaction can be written
P = &u[liO]. as
u
+
v
=
r,
01'
However.
in contrast
struct,ure considered
with the case of the b.c.c.
by Cottrell, there is no change of
elastic energy in the above reaction. Nevertheless,
it’ can be shown that in crystals like
11g0, a different type of dislocation
reaction is more
favorable
$a.[oii] + ',a[1011 = +a[lio] It’ is to be noticed Therefore, reaction
this (1).
t’han reaction (1) above. If this reaction operates, it will lead to a crack on the slip plane (110) understood components instead of the usual cleavage plane. It is to be noticed
that this type of crack is different Stokes et rrl.“) observed piling
up
of
that
in so combining
the
elastic
reaction
is
This reaction by
more
is
the
the two released.
favorable
can probably
considering
of the individual
energy
edge
than
be better and
screw
dislocations :
from that which
in compression
dislocations
half
dislocations.
(4)
against
tests, where a
a kink
band
is
involved.
The first term in each reaction is the edge component, and the second term the screw component.
As shown
in Fig. 3> the two screw components and the edge components
cancel each other combine together. This may
be represent’ed bp the following
Flc,. 1. (‘rack
formation on (010) 11go crystals.
cleavage
plane
in
two
equations:
Therefore the elastic energy due to the coalescence
of