Fracture toughness and tensile properties of two titanium alloys befor and after proton and neutron irradiations at 150°C
Two titanium alloys, the α+β Ti6Al4V and the α phase Ti5Al2.5Sn alloy, have been irradiated at 150°C with neutrons, in the reactor of the Atomic Energy Research Institute, in Budapest and with 590 MeV protons in the PIREX facility of the Paul Scherrer Institute, in Switzerland, to doses of the order...
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irk-123456789-804002015-04-18T03:01:23Z Fracture toughness and tensile properties of two titanium alloys befor and after proton and neutron irradiations at 150°C Marmy, P. Физика радиационных повреждений и явлений в твердых телах Two titanium alloys, the α+β Ti6Al4V and the α phase Ti5Al2.5Sn alloy, have been irradiated at 150°C with neutrons, in the reactor of the Atomic Energy Research Institute, in Budapest and with 590 MeV protons in the PIREX facility of the Paul Scherrer Institute, in Switzerland, to doses of the order of 0.15 dpa. The proton irradiation induced hydrogen as a product from spallation reactions. Some of the neutron irradiated specimens were previously loaded with 150 wppm hydrogen. The tensile and fracture toughness properties have been analyzed as a function of the measured hydrogen content. At low levels, hydrogen is not influencing significantly the tensile properties. The effect of irradiation on ductility and strength is more pronounced in the α+β Ti6Al4V, due to radiation induced phase instabilities. At a test temperature of 150°C, hydrogen levels up to 150 wppm have moderate effect on fracture toughness, in the unirradiated condition. For the irradiated specimens in both alloys, increasing the hydrogen content decreases the fracture toughness.The fracture toughness after irradiation is strongly reduced at room temperature, in both alloys. Два титанові сплави α+β Ті6A14V та α-фаза Ti5A12.5Sn були опромінені при 150ºС нейтронами в реакторі дослідницького Інституту ядерної енергії в Будапешті та 590 МеВ протонами на установці ПІРЕКС в Швейцарії до доз порядку 0.15 зна. Опромінення протонами зумовлює утворення водню як продукта розщеплення. Декілька опромінених нейтронами зразків були попередньо навантажені 150 wppm водню. Міцність на розтяг та в`язкість руйнування були проаналізовані як функція вмісту водню. При низьких рівнях водень не має суттєвого впливу на міцність на розтяг. Вплив опромінення на пластичність та на міцність більш виразний у сплаві α+β Ті6A14V внаслідок радіаційно-обумовленої фазової нестабільності. При температурі випробування в 150ºС водень у кількості 150wppm має помірний вплив на в`язкість руйнування в неопроміненному стані. Для опроміненних зразків в двох сталях зростання вмісту водню знижує в`язкість руйнування. В`язкість руйнування сильно зменьшується при кімнатній температурі в обох сплавах. Два титановых сплава α+β Ті6A14V и α-фаза Ti5A12.5Sn были облучены при 150ºС нейтронами в реакторе исследовательского Института ядерной энергии в Будапеште и 590 МэВ протонами на установке ПИРЕКС в Институте Поль- Шеррер, в Швейцарии до доз порядка 0.15 сна. Облучение протонами обусловливает образование водорода как продукта реакций расщепления. Несколько облученных нейтронами образцов были предварительно нагружены 150 wppm водорода. Прочность на растяжение и вязкость разрушения были проанализированы как функция содержания водорода. При низких уровнях водород не оказывает существенного влияния на прочность на растяжение. Влияние облучения на пластичность и прочность более выражено в α+β Ті6A14V вследствие радиационно-обусловленной фазовой нестабиль¬ ности. При температуре испытания в 150ºС водород в количестве 150 wppm оказывает умеренное влияние на вязкость разрушения в необлученном состоянии. Для облученных образцов в двух сталях увеличение содержания водорода понижает вязкость разрушения. Вязкость разрушения после облучения сильно уменьшается при комнатной температуре в обоих сплавах. 2005 Article Fracture toughness and tensile properties of two titanium alloys befor and after proton and neutron irradiations at 150°c / P. Marmy // Вопросы атомной науки и техники. — 2005. — № 3. — С. 18-23. — Бібліогр.: 12 назв. — англ. 1562-6016 http://dspace.nbuv.gov.ua/handle/123456789/80400 621.039 en Вопросы атомной науки и техники Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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Физика радиационных повреждений и явлений в твердых телах Физика радиационных повреждений и явлений в твердых телах |
| spellingShingle |
Физика радиационных повреждений и явлений в твердых телах Физика радиационных повреждений и явлений в твердых телах Marmy, P. Fracture toughness and tensile properties of two titanium alloys befor and after proton and neutron irradiations at 150°C Вопросы атомной науки и техники |
| description |
Two titanium alloys, the α+β Ti6Al4V and the α phase Ti5Al2.5Sn alloy, have been irradiated at 150°C with neutrons, in the reactor of the Atomic Energy Research Institute, in Budapest and with 590 MeV protons in the PIREX facility of the Paul Scherrer Institute, in Switzerland, to doses of the order of 0.15 dpa. The proton irradiation induced hydrogen as a product from spallation reactions. Some of the neutron irradiated specimens were previously loaded with 150 wppm hydrogen. The tensile and fracture toughness properties have been analyzed as a function of the measured hydrogen content. At low levels, hydrogen is not influencing significantly the tensile properties. The effect of irradiation on ductility and strength is more pronounced in the α+β Ti6Al4V, due to radiation induced phase instabilities. At a test temperature of 150°C, hydrogen levels up to 150 wppm have moderate effect on fracture toughness, in the unirradiated condition. For the irradiated specimens in both alloys, increasing the hydrogen content decreases the fracture toughness.The fracture toughness after irradiation is strongly reduced at room temperature, in both alloys. |
| format |
Article |
| author |
Marmy, P. |
| author_facet |
Marmy, P. |
| author_sort |
Marmy, P. |
| title |
Fracture toughness and tensile properties of two titanium alloys befor and after proton and neutron irradiations at 150°C |
| title_short |
Fracture toughness and tensile properties of two titanium alloys befor and after proton and neutron irradiations at 150°C |
| title_full |
Fracture toughness and tensile properties of two titanium alloys befor and after proton and neutron irradiations at 150°C |
| title_fullStr |
Fracture toughness and tensile properties of two titanium alloys befor and after proton and neutron irradiations at 150°C |
| title_full_unstemmed |
Fracture toughness and tensile properties of two titanium alloys befor and after proton and neutron irradiations at 150°C |
| title_sort |
fracture toughness and tensile properties of two titanium alloys befor and after proton and neutron irradiations at 150°c |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| publishDate |
2005 |
| topic_facet |
Физика радиационных повреждений и явлений в твердых телах |
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http://dspace.nbuv.gov.ua/handle/123456789/80400 |
| citation_txt |
Fracture toughness and tensile properties of two titanium alloys befor and after proton and neutron irradiations at 150°c / P. Marmy // Вопросы атомной науки и техники. — 2005. — № 3. — С. 18-23. — Бібліогр.: 12 назв. — англ. |
| series |
Вопросы атомной науки и техники |
| work_keys_str_mv |
AT marmyp fracturetoughnessandtensilepropertiesoftwotitaniumalloysbeforandafterprotonandneutronirradiationsat150c |
| first_indexed |
2025-07-06T04:21:26Z |
| last_indexed |
2025-07-06T04:21:26Z |
| _version_ |
1836869943162830848 |
| fulltext |
УДК 621.039
FRACTURE TOUGHNESS AND TENSILE PROPERTIES
OF TWO TITANIUM ALLOYS BEFORE AND AFTER PROTON
AND NEUTRON IRRADIATIONS AT 150°C
P. Marmy
Centre de Recherche en Physique des Plasmas
Technologie de la Fusion
Association Euratom - Confédération Suisse, CH-5232 VILLIGEN-PSI
Two titanium alloys, the α+β Ti6Al4V and the α phase Ti5Al2.5Sn alloy, have been irradiated at 150°C with
neutrons, in the reactor of the Atomic Energy Research Institute, in Budapest and with 590 MeV protons in the
PIREX facility of the Paul Scherrer Institute, in Switzerland, to doses of the order of 0.15 dpa. The proton irradia
tion induced hydrogen as a product from spallation reactions. Some of the neutron irradiated specimens were previ
ously loaded with 150 wppm hydrogen. The tensile and fracture toughness properties have been analyzed as a func
tion of the measured hydrogen content. At low levels, hydrogen is not influencing significantly the tensile proper
ties. The effect of irradiation on ductility and strength is more pronounced in the α+β Ti6Al4V, due to radiation in
duced phase instabilities. At a test temperature of 150°C, hydrogen levels up to 150 wppm have moderate effect on
fracture toughness, in the unirradiated condition. For the irradiated specimens in both alloys, increasing the hydro
gen content decreases the fracture toughness.The fracture toughness after irradiation is strongly reduced at room
temperature, in both alloys.
1. INTRODUCTION
The ITER first wall modules are attached to the vac
uum vessel by a set of four radial flexible cartridges.
Due to their excellent elasticity and strength properties,
titanium alloys have been proposed as materials for fab
ricating the supports. Among a set of internationally
proposed alloys, two alloys widely used in the industry,
the α+β Ti6Al4V and the α-phase Ti5Al2.5Sn have
been chosen as main candidates for the ITER applica
tion. In previous works, the tensile, fatigue and fracture
toughness properties have been studied before and after
irradiation (see references [1-3]). The influence of hy
drogen loading up to 400 wppm on the fracture tough
ness properties has also been reported. The uptake of
hydrogen in large quantities induces structural changes
in the alloys but does not degrade much the resistance to
fracture at high temperature. At room temperature a
clear degradation of the unirradiated frac ture resistance
takes place. The fracture toughness properties are
strongly affected in both alloys, after an irradiation with
neutrons at 60 and 350°C, specially when testing at
room temperature [2-3]. Since the mean operating tem
perature of the cartridges is around 150°C, a new set of
experiments was necessary to check the effective degra
dation during ITER operation.
It was been decided to use two types of irradiating
particles, protons and neutrons, and to center the atten
tion onto the effects of hydrogen, since the previous
work had shown that the embrittlement is mainly con
trolled by the hydrogen content. The irradiation with
high energy protons is generating hydrogen through
spallation reactions, with possible detrimental effects on
the properties. Because the neutrons do not generate any
hydrogen, some specimens have been previously loaded
with 150 wppm hydrogen. The hydrogen content has
been accurately measured. The effects of proton and
neutron irradiation on the tensile and fracture toughness
properties are described and discussed taking particular
attention to the role of hydrogen.
2. EXPERIMENTAL DETAILS
Materials and as received microstructure: After hot
forming to a diameter of 31.75 mm, the Ti5Al2.4Sn al
loy has been annealed 1hr at 815°C and then air cooled.
The structure consists of equiaxed grains of 20 µm.
Some larger grains of about 40 µm or more also exist.
Usually the larger grains contain smaller ones. A precip
itation of an iron riched phased has been detected in the
grains, both by optical and transmission microscopy.
The TiFe precipitates have a size around 100 nm and are
located at the grain boundaries and inside the grains.
They are generated by the high iron concentration (0.36
wt%) in the alloy.
After hot forming to a stock diameter of 150mm in
the α+β field, the Ti6Al4V alloy has been annealed for
1.5 hr at 730 °C and then air cooled. The structure con
sists of equiaxed α grains of about 20 µm, containing
secondary α zones surrounded by β intergranular phase.
The fraction volume of the β phase is around 13 %. Due
to its different composition, the β phase is quite visible
at the boundaries and appears as intergranular bands of
0.05 to 1 µm width. Some small quantities of residual
martensite can be observed in the larger β grains
No hydrides are present in the as received mi
crostructure of both alloys [3-5].The chemical specifica
tion is given in table 1.
______________________________________________________________________________
ВОПРОСЫ АТОМНОЙ НАУКИ И ТЕХНИКИ. 2005. № 3.
Серия: Физика радиационных повреждений и радиационное материаловедение (86), с.18-23.
Specimens: The fracture toughness specimen is a
mini-charpy DIN 50115 KLST with a size of 3x4x27
mm. It is labeled **C**, for easy differentiation. The
pre/crack of 1mm length has been grown at the notch
before the irradiation (total crack depth 2 mm), at high
frequency, in a fatigue pre-test. The specimens for the
neutron irradiation have been cracked after the irradia
tion, before the test, at low frequency. The tensile speci
men for the proton irradiation is a PIREX flat specimen
with a gauge size of 4x0.34x5.5 mm [5]. It is labeled
**T**. The tensile specimen for the neutron irradiation
is a DIN 50125 cylindrical specimen with a geometrical
gauge length of 18 mm and 3 mm diameter. It is labeled
**D**.
Table 1
Chemical compositions: [wt %]
Al C Fe Sn
Ti5Al2.5Sn 5.0 0.17 0.36 2.4
Ti6Al4V 6.08 0.0056 0.1399 -
H2 N2 O2 V Others
0.0036 0.010 0.179 -
<0.0060 0.0065 0.176 3.95 <0.4
Proton Irradiation : The tensile and charpy speci
mens have been irradiated in the PIREX facility [6]
where the heat deposited by the proton beam is removed
by pressurized helium. The tensile flat specimens have
been irradiated with a beam of 3 mm width and 4 mm
height. The wobbler amplitude was ±2.5 mm, in order to
distribute the protons evenly. The mini Charpy speci
men was equipped with a central thermocouple placed
into an hole that ended very close, at 1.5 mm from the
pre/crack. A beam with a width of 6mm and a height of
3mm has been centered onto the specimen. It was not
wobbled because only the center of the specimen had to
be irradiated. In the cooling flow of pressurized helium,
at 115 Nm3/hr ,30 bars and 40°C, a proton beam intensi
ty of 7μa has been adjusted in order to get a specimen
irradiation temperature of 150°C. A dosimetry evalua
tion based on Sc46, which production cross section
σ(Ti(p,x)) is estimated to 27.2 mbarn [7], has given the
results listed in table 2. The specimens irradiated with
the high energy protons are all in the as received condi
tion. The materials already contain some level of hydro
gen, as indicated in table 1.
Table 2
Fluence and displacements per atom
after the irradiations in PIREX
SPECIMEN Fluence p/cm2 Dose dpa
I25T12 5.09E+19 0.1342
I25T14 1.63E+19 0.0428
I25C55 6.18E+19 0.1628
I25C54 6.16E+19 0.1623
I14T27 2.32E+19 0.0611
I14T28 6.4E+19 0.1685
I14C53 4.96E+19 0.1308
I14C54 4.99E+19 0.1315
The high energy proton irradiation increases the hy
drogen content by spallation reactions [8].Therefore the
hydrogen concentration has been determined carefully
using a method based on gas mass spectrometry [9]. The
results from five specimens are indicated in table 3.
Table 3
Measured hydrogen in proton irradiated samples
Net 1H
Sample wppm
Unirradiated:
N14C62 47.9
N25C77 20.4
Irradiated:
I14C53 63.6
I14C54 60.7
I25C54 62.4
I25C55 53.4
I25T12 47.2
It is also interesting to note that the predicted hydro
gen production in titanium is around 650 appm/dpa [8],
which corresponds to about 14 wppm H/dpa. The irradi
ated values of table 3 are for about 0.2 dpa. Therefore
the observed rates of hydrogen deposition in alloy 14
and 25 were around 70 wppm/dpa and 150 wppm/dpa.-
much higher than the prediction. The reason for this sig
nificantly higher deposition is currently not known.
Neutron Irradiation: The neutron irradiation has
been performed at the Atomic Energy Research Institute
in Budapest, in a VVRSZM research reactor of 10MW
power. The mean flux at nominal power is 3.5x1013
n/cm2 s (E>1MeV). The neutron spectrum of the reactor
is closed to a fission spectrum. The specimens have
been irradiated using the rig BAGIRA, in which a flow
of He/N2 gas mixture is used for temperature control.
The temperature has been monitored with five thermo
couples and was kept between 140 and 150 °C during
all the experiment. A dosimetry analysis based on the
radioisotope Sc46, indicates that the mean neutron flu
ence is 1.08x1020 n/cm2. Assuming a dpa cross section
in the AEKI reactor of 1420 barn ( n E>1MeV), the
dose is estimated to 0.154 dpa.
The specimens I14C46 and 69, I25C46 and 49,
I14D40 and I25D45 are all in the as received condition.
Two specimens loaded with 150 wppm hydrogen have
also been irradiated (I14C38 and I25C39), together with
two annealed specimens (I14C6 and I25C30). The an
nealed specimens have an hydrogen level close to zero.
3. RESULTS AND DISCUSSION
3.1. TENSILE TESTS
All tests have been conducted at the same strain rate,
2.5x10-4 s-1. To take into account the effect of specimen
size, unirradiated tests have been performed with both
specimen geometries. The total and uniform elongation
values are similar in both geometries, whereas the re
duction of area is clearly higher in the DIN cylindrical
specimens. The yield stress and the ultimate stress are
slightly higher in the DIN specimens. The Streckgrenze
effect (sharp yield point) was visible in both geometries
______________________________________________________________________________
ВОПРОСЫ АТОМНОЙ НАУКИ И ТЕХНИКИ. 2005. № 3.
Серия: Физика радиационных повреждений и радиационное материаловедение (86), с. 18-23.
19
and slightly sharper in the cylindrical geometry.
Figure 1 shows the effect of the proton irradiation.
The α alloy is less affected by the irradiation as com
pared to the α+β alloy. The hardening Δσ irr at 150°C
and 0.06 dpa is only 14 MPa for the α alloy as compared
to 150 MPa for the α+β alloy.
0 5 10 15 20
0
100
200
300
400
500
600
700
800
900
1000 Ti5Al2.5Sn
T
test
=150°C
T
test
= 21 °C
N14T30
I14T28
N14T32
I14T27
S
tre
ss
[M
P
a]
Strain [%]
0 5 10 15 20 25
0
100
200
300
400
500
600
700
800
900
1000
1100
T
test
=150°C
T
test
=21°C Ti6Al4V
S
tr
es
s
[M
P
a]
Strain [%]
N25T21
I25T14
N25T16
I25T12
Fig. 1. Tensile curves of Ti6Al4V and Ti5Al2.5Sn before and after irradiation with protons at 150°C. I25T12, has
a dose of 0.13 dpa, I25T14 has a dose of 0.04 dpa, I14T28 has a dose of 0.17 dpa and I14T27 has a dose
of 0.06 dpa
The hardening Δσ irr at Ttest=21°C and 0.13 dpa is
clearly larger for the α+β alloy. Furthermore the
Ti6Al4V tensile curves have an unstable shape with a
low uniform elongation after irradiation. Although less
strong in amplitude as compared to what was measured
after an irradiation with neutrons at 350°C, the response
observed is similar. It is probable that some phase insta
bilities already occur after the irradiation at 150°C, after
a dose of only 0.04 dpa.
Figure 2 presents the effects after the irradiation
with neutrons at the same temperature of 150°C. It is in
teresting to note that for the alpha alloy, the sharp yield
point in the unirradiated case is reinforced after the irra
diation. Nevertheless the material is still able to deform
homogenously and reaches a uniform elongation of
7.5%. In the Ti6Al4V, the situation is worst as indicated
by the unstable deformation curve of I25D45. The uni
form elongation is very low after irradiation, consider
ing that most of the deformation is elastic at the stability
limit.
0 5 10 15 20
0
200
400
600
800
1000
T
test
=150°C
N25D56
I25D45
I14D40
N14D52
S
tre
ss
[M
P
a]
Strain [%]
Fig. 2. Tensile curves of Ti6Al4V (N25D56, I25D45)
and Ti5Al2.5Sn (N14D52,I14D40), irradiated with neu
trons at 150°C to 0.154 dpa (Ttest =150°C)
The irradiation dose of the proton irradiated speci
mens is significantly less than the dose reached in the
neutron irradiated specimens. Comparing figures 1 and
2, the relative hardening after irradiation appears clearly
stronger in the case of the Ti6Al4V alloy, after both the
proton and the neutron irradiation. Compared on a dpa
base, the neutrons seem more damage effective than the
protons, in terms of ductility loss. The stronger irradia
______________________________________________________________________________
ВОПРОСЫ АТОМНОЙ НАУКИ И ТЕХНИКИ. 2005. № 3.
Серия: Физика радиационных повреждений и радиационное материаловедение (86), с. 18-23.
20
tion hardening in the α+β alloy is probably due to the
formation of irradiation induced vanadium precipitates,
as shown in previous works in the same materials irradi
ated at 350°C [1, 2].The radiation induced precipitation
is temperature assisted as it does not occur after a neu
tron irradiation at 50°C [2].
The hydrogen intake after proton irradiation is of the
order of 20 to 40 wppm, as shown in table 3. Apparently
this increase in the hydrogen level does not modify the
tensile properties.
Dynamic strain ageing has not been observed during
the experiments except in the case of N14D50 and
N25D56, where it was qualified as very weak. Sharp
yield points have been observed at 150°C only, in both
alloys before irradiation and only in the α alloy after ir
radiation. Nevertheless it is possible that the flow insta
bility appearing in the Ti6Al4V is hiding the sharp yield
point.
3.2. FRACTURE TOUGHNESS TESTS
The fracture tests have been accomplished according
to the ASTM norm E813, in a three point bend fixture.
All specimens have been loaded with a deformation rate
of 8.33x 10-3 mm/s. The measurement of crack exten
sion was done using the compliance method which
measures the apparent elasticity of the specimen. The
effective crack length is then calculated using the com
pliance transfer relation of Jablonski [10].
For the unirradiated material, the values of JQ are
very similar in both alloys. The value at RT is around 60
kJ/m2. This is in accordance with previous measure
ments [11]. The fracture toughness increases at 150°C ,
to reach a value around 100 kJ/m2. The irradiated
Ti5Al2.5Sn material is only slightly affected by the irra
diation when tested at 150°C, whereas the Ti6Al4V al
loy shows a clear reduction in the JQ value. When tested
at RT both irradiated alloys show a large reduction of JQ.
The data are easy to understand, if presented as a func
tion of their hydrogen content, as shown in figures 3 and
4. As explained previously, hydrogen is already present
in the material in the as received condition. It has also
been loaded in a vacuum furnace or removed after an
nealing in vacuum. The proton irradiation introduces
some hydrogen (see table 2) and the neutron irradiation
is not changing the initial content.
0 20 40 60 80 100 120 140 160 180
0
50
100
150
200
250
Ti6Al4V
J Q
[k
J/
m
2 ]
Hydrogen content [wppm]
neutrons, 150°C
protons, RT
protons, 150°C
Unirradiated, 150°C
Unirradiated, RT
Fig. 3. Fracture toughness of Ti6Al4V alloy, unirradiat
ed, irradiated at 150°C, with protons to 0.163 dpa and
neutrons to 0.154 dpa. The data are plotted as a func
tion of their hydrogen level
0 20 40 60 80 100 120 140 160 180
0
20
40
60
80
100
120
140
160
180
Ti5Al2.5SnJ Q
[k
J/
m
2 ]
Hydrogen content [wppm]
neutrons, 150°C
protons, RT
protons, 150°C
unirradiated, 150°C
unirradiated, RT
Fig. 4. Fracture toughness of Ti5Al2.5Sn alloy, unirra
diated, irradiated at 150°C, with protons to 0.131 dpa
and neutrons to 0.154 dpa. The data are plotted as a
function of their hydrogen level
For the case of the α+β alloy shown in figure 3, we
see that the fracture toughness of the unirradiated mate
rial is improved, when increasing the temperature from
RT to 150°C. It is also improved if the hydrogen content
is decreased. Nevertheless the dependence on hydrogen
content at 150°C is not strong and for the highest level
of the diagram (170 wppm H), JQ remain of the order of
100 kJ/m2. This is more than the value of the as re
ceived material at room temperature. At RT., the irradi
ated data show more dispersion than the unirradiated
data, an indication for radiation embrittlement. The pro
ton irradiated data fit quite well the trend of the neutron
irradiated data. Since the fracture toughness of the 150
wppm H loaded material is clearly lower after than be
fore irradiation, we can argue that the damage from the
irradiation and from the hydrogen are additive.
The data for the alpha alloy are presented in figure 4.
They show a similar behavior. At 150°C, as the hydro
gen content increases, the fracture toughness decreases,
whereas in the unirradiated material a reverse response
is observed. This behavior is in fact not a consequence
of the hydrogen impurity atoms but rather a conse
quence of the microstructural changes introduced by the
hydrogen charging (see report [11]). Despite the tough
ness improvement observed at 150°C and 150 wppm H,
after neutron irradiation a drastic decrease of toughness
is observed. Nevertheless the value is approximately
four times higher, as compared with the Ti6Al4V case.
The proton irradiated data are slightly lower than the
neutron irradiated data, when plotted against their hy
drogen content (see figure 4).
The lowest fracture toughness value is measured at
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RT, after proton irradiation.
Comparing Fig.3 and 4, it seems that the Ti6Al4V
data show more dependence on hydrogen level, as com
pared to the Ti5Al2.5Sn data. It is possible that more
hydrides are present in the α+β alloy. At higher temper
atures, the hydrides are expected to be dissolved [12].
In a previous work [3], the same alloys had been ir
radiated near room temperature and at 350°C. Using
these data, figure 5 shows the behavior of JQ as a func
tion of the irradiation temperature, for a constant level
of hydrogen. Figure 5,a shows the dependence when the
alloys are hydrogen free, after a vacuum annealing of 5
hours at 750°C. Figure 5,b shows the behavior of the al
loys when they are loaded with 150 wppm hydrogen. In
the case of the hydrogen free alloys, increasing the irra
diation temperature induces embrittlement, whereas for
the hydrogen loaded alloys, increasing the irradiation
temperature improves the fracture toughness. This may
be the result of a structural stabilizing effect of hydro
gen. This unexpected but positive effect of hydrogen is
shown here in both alloys, for relatively low doses. It is
unclear whether the effect will subsist at higher doses.
Figure 5,a shows the dependence when the alloys are
hydrogen free, after a vacuum annealing of 5 hours at
750°C. Figure 5,b shows the behavior of the alloys
when they are loaded with 150 wppm hydrogen. In the
case of the hydrogen free alloys, increasing the irradia
tion temperature induces embrittlement, whereas for the
hydrogen loaded alloys, increasing the irradiation tem
perature improves the fracture toughness. This may be
the result of a structural stabilizing effect of hydrogen.
This unexpected but positive effect of hydrogen is
shown here in both alloys, for relatively low doses. It is
unclear whether the effect will subsist at higher doses.
The fractographs of the unirradiated and irradiated spec
imens have been analyzed under the scanning electron
microscope. The general aspect of all fractographs is
ductile. Relatively large effects are measured in the me
chanical test but the difference does not show up in the
appearance of the fractographs. This is shown in figure
6 which compares two extreme cases, I25C54 irradiated
at 150°C and showing a low JQ value and N25C95b,
unirradiated and having a relatively high JQ value.
0 50 100 150 200 250 300 350 400
0
20
40
60
80
100
120
140
160
180
200
220
Hydrogen free
(a)
J Q
[
kJ
/m
2 ]
T
irr
=T
test
Ti5Al2.5Sn, unirradiated
Ti5Al2.5Sn, irradiated
Ti6Al4V, unirradiated
Ti6Al4V, irradiated
0 50 100 150 200 250 300 350 400
0
20
40
60
80
100
120
140
160
180
150 wppm H
(b)
J Q
[
kJ
/m
2 ]
Tirr=Ttest
Ti5Al2.5Sn, unirradiated
Ti5Al2.5Sn, irradiated
Ti6Al4V, unirradiated
Ti6Al4V, irradiated
Fig. 5. Fracture toughness of Ti5Al2.5Sn and Ti6Al4V alloys as a function of the irradiation temperature. The crack
initiation fracture toughness values are shown in (a) for the hydrogen free condition and in (b) for an hydrogen lev
el of 150 wppm. Note the reduced fracture toughness values after irradiation at elevated temperatures, for the hy
drogen free condition
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22
Fig. 6. Fractographs of the irradiated specimen I25C54 (a) with a JQ value of 16 kJ/m2 and of the unirradiated spec
imen N25C95b (b) with a JQ value of 64 kJ/m2, both tested at RT and showing a ductile appearance
Both fractographs show a fracture surface with dim
ples, indicating large local deformations. Careful obser
vation, nevertheless, reveals a higher density of micro-
cracks in the irradiated material. This difference is more
apparent in the irradiated material tested at room tem
perature but also applies to the unirradiated material
when comparing material tested at low and high temper
ature.
4. CONCLUSIONS
Tensile and fracture toughness specimens of
Ti6Al4V and Ti5Al2.5Sn have been irradiated with high
energy protons to a dose between 0.04 and 0.17 dpa, at
150°C. Tensile and fracture toughness specimens of
Ti6Al4V and Ti5Al2.5Sn, some of them loaded with
hydrogen, have been irradiated with neutrons at 150°C,
to 0.15dpa.
The tensile tests seem to indicate that the Ti6Al4V is
more affected by the 150°C irradiation in terms of
hardening and reduction of ductility, as compared with
the Ti5Al2.5Sn alloy. The irradiation at 150°C seems to
induce vanadium rich precipitates in the α+β alloy, as it
was shown earlier after an irradiation at 350°C.
The crack initiation fracture toughness values are
strongly reduced after irradiation, especially when
tested at room temperature. At 150°C, the reduction in
toughness is more pronounced in the Ti6Al4V alloy.
Nevertheless the fractographs indicate a ductile fracture
for all conditions in both materials.
The fracture toughness data can be well understood,
if represented as a function of their hydrogen content.
Hydrogen levels up to 150 wppm have moderate effect
on toughness, at a test temperature of 150°C. For the ir
radiated specimens in both alloys, increasing the hydro
gen content decreases the fracture toughness.
The neutron and proton fracture toughness data
show a consistent behaviour, when compared in relation
to their associated hydrogen content.
Acknowledgements:
The Paul Scherrer Institute at Villigen, PSI, is sin
cerely thanked for its logistical and technical support
throughout this project. The contributions of R. Brьtsch
for the SEM microscopy, F. Hegedues for the dosimetry
and B.Oliver for the gas spectrometry are greatly appre
ciated.
REFERENCES
1.P. Marmy and T. Leguey. Impact of irradiation on the
tensile and fatigue properties of two titanium alloys
//Journal of Nuclear Materials. 2001, v. 296, p. 155–164.
2.S. Tдhtinen et al. Tensile and fracture toughness prop
erties of unirradiated and neutron irardiated titanium al
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3.P. Marmy and M. Luppo. Effect of hydrogen on the
fracture toughness of the titanium alloys Ti6Al4V and
Ti5Al2.5Sn before and after neutron irradiation //Plas
ma Devices and Operations. 2003, v. 11(2), p. 71–79.
4.T. Leguey et al. Microstructure of Ti5Al2.5Sn and
Ti6Al4V deformed in tensile and fatigue tests //Journal
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6.P. Marmy et al. PIREX II- A new irradiation facility
for testing fusion first wall materials //Nuclear Instru
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7.F. Hegedues et al. Fracture toughness and tensile
properties of the titanium alloys Ti6Al4V and
Ti5Al2.5Sn before and after proton and neutron irradi
ations at 150°C. 2004, CRPP-EPFL: Lausanne, p. 1–28.
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System for the Determination of Low Levels of Hydro
gen in Irradiated Materials //Journal of Nuclear Mate
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10.D.A. Jablonski et al. Compliance Functions for Vari
ous Fracture Mechanics Specimens //Engineering Frac
ture Mechanics. 1985, v. 22, N 5, p. 819–827.
11.P. Marmy et al. The effect of hydrogen on the frac
ture toughness of the titanium alloys Ti6Al4V and
Ti5Al2.5Sn before and after neutron irradiation. 2003,
CRPP, Centre de Recherches en Physique des Plasmas,
EPFL Lausanne, p. 1–27.
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ВЯЗКОСТЬ РАЗРУШЕНИЯ И ПРОЧНОСТЬ НА РАСТЯЖЕНИЕ ДВУХ ТИТАНОВЫХ СПЛАВОВ
ДО И ПОСЛЕ ОБЛУЧЕНИЯ ПРОТОНАМИ И НЕЙТРОНАМИ ПРИ 1500 С
П. Марми
Два титановых сплава α+β Ті6A14V и α-фаза Ti5A12.5Sn были облучены при 150ºС нейтронами в реакторе исследо
вательского Института ядерной энергии в Будапеште и 590 МэВ протонами на установке ПИРЕКС в Институте Поль-
Шеррер, в Швейцарии до доз порядка 0.15 сна. Облучение протонами обусловливает образование водорода как продук
та реакций расщепления. Несколько облученных нейтронами образцов были предварительно нагружены 150 wppm во
дорода. Прочность на растяжение и вязкость разрушения были проанализированы как функция содержания водорода.
При низких уровнях водород не оказывает существенного влияния на прочность на растяжение. Влияние облучения на
пластичность и прочность более выражено в α+β Ті6A14V вследствие радиационно-обусловленной фазовой нестабиль
ности. При температуре испытания в 150ºС водород в количестве 150 wppm оказывает умеренное влияние на вязкость
разрушения в необлученном состоянии. Для облученных образцов в двух сталях увеличение содержания водорода пони
жает вязкость разрушения. Вязкость разрушения после облучения сильно уменьшается при комнатной температуре в
обоих сплавах.
В`ЯЗКІСТЬ РУЙНУВАННЯ ТА МІЦНІСТЬ НА РОЗТЯГ ДВОХ ТИТАНОВИХ СПЛАВІВ ДО ТА ПІ
СЛЯ ОПРОМІНЕННЯ ПРОТОНАМИ
ТА НЕЙТРОНАМИ ПРИ 150оС
П. Мармі
Два титанові сплави α+β Ті6A14V та α-фаза Ti5A12.5Sn були опромінені при 150ºС нейтронами в реакторі дослідни
цького Інституту ядерної енергії в Будапешті та 590 МеВ протонами на установці ПІРЕКС в Швейцарії до доз порядку
0.15 зна. Опромінення протонами зумовлює утворення водню як продукта розщеплення. Декілька опромінених
нейтронами зразків були попередньо навантажені 150 wppm водню. Міцність на розтяг та в`язкість руйнування були
проаналізовані як функція вмісту водню. При низьких рівнях водень не має суттєвого впливу на міцність на розтяг.
Вплив опромінення на пластичність та на міцність більш виразний у сплаві α+β Ті6A14V внаслідок радіаційно-об
умовленої фазової нестабільності. При температурі випробування в 150ºС водень у кількості 150wppm має помірний
вплив на в`язкість руйнування в неопроміненному стані. Для опроміненних зразків в двох сталях зростання вмісту
водню знижує в`язкість руйнування. В`язкість руйнування сильно зменьшується при кімнатній температурі в обох
сплавах.
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