CA 03185880 2022-12-02
DESCRIPTION
Title of Invention: ALUMINUM ALLOY MATERIAL AND HYDROGEN
EMBRITTLEMENT INHIBITOR FOR ALUMINUM ALLOY MATERIALS
Technical Field
[0001] The present invention relates to an aluminum alloy material and to a
hydrogen
embrittlement inhibitor for aluminum alloy materials.
Background Art
[0002] Aluminum alloy materials, which have a wide range of applications,
suffer from
the problem of hydrogen embrittlement cracks, and proposals have been made to
solve this problem (see PTL 1 to 4).
[0003] PTL 1 discloses an aluminum alloy material for a high pressure gas
vessel,
which has an aluminum alloy composition that contains, in terms of mass%, 4.0
to
6.7% of Zn, 0.75 to 2.9% of Mg, 0.001 to 2.6% of Cu, 0.05 to 0.40% of Si,
0.005 to
0.20% of Ti and 0.01 to 0.5% of Fe, and contains one or two or more of 0.01 to
0.7% of
Mn, 0.02 to 0.3% of Cr, 0.01 to 0.25% of Zr and 0.01 to 0.10% of V so as to
satisfy the
relationship 1.0% Fe+Mn+Cr+Zr+V 0.1%, with the remainder comprising Al and
unavoidable impurities, and in which the relationship between electrical
conductivity
(%IACS) and the total content of Fe, Mn, Cr, Zr and V satisfies the following
relationship: electrical conductivity (%) -4.9x(Fe+Mn+Cr+Zr+V)+40.0, and which
has
a 0.2% proof stress of 275 MPa or more and exhibits excellent hydrogen
embrittlement
resistance.
[0004] PTL 2 discloses a method for producing a thick aluminum alloy thick
plate
having excellent strength and ductility, in which a thick plate in which the
total area
ratio of intermetallic compounds having an equivalent circle diameter of more
than 5
pm is controlled to 2% or less is obtained by using an Al-Zn-Mg-Cu-based
aluminum
alloy, which contains 5.0 to 7.0% of Zn, 1.0 to 3.0% of Mg and 1.0 to 3.0% of
Cu, also
contains a total of 0.05 to 0.5% of one or two or more of 0.05 to 0.3% of Cr,
0.05 to
0.25% of Zr, 0.05 to 0.40% of Mn and 0.05 to 0.35% of Sc, and further contains
0.25%
or less of Si and 0.25% or less of Fe as impurities, with the remainder
comprising Al
and unavoidable impurities, subjecting an ingot of this alloy to a
homogenizing
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treatment by holding the ingot at a temperature of 450 to 520 C for 1 hour or
longer,
then regulating the average cooling rate at least to 400 C to 100 C/hr or more
in a step
for cooling the ingot, then carrying out hot rolling to a plate thickness of
50 mm or more
at a temperature within the range 300 to 440 C, and then carrying out a
solution
treatment, quenching and an artificial aging treatment.
[0005] PTL 3 discloses a method for producing a high strength Al-Zn-Mg-based
aluminum alloy forging material having excellent resistance to stress
corrosion
cracking by regulating the Fe content in the alloy to 0.15 wt% or less when an
aluminum alloy, which contains 4.5 to 8.5 wt% of Zn, 1.5 to 3.5 wt% of Mg and
0.8 to
2.6 wt% of Cu and further contains at least one of Mn, Cr, Zr, V and Ti, with
the
remainder comprising Al and impurities, is molded into a forging material
having an H-
section by forging.
[0006] PTL 4 discloses a high strength aluminum alloy for welded structures,
which
exhibits excellent stress corrosion cracking resistance and which contains 5
to 8 wt%
of Zn, 1.2 to 4.0 wt% of Mg, more than 1.5 wt% and not more than 4.0 wt% of
Cu, 0.03
to 1.0 wt% of Ag, 0.01 to 1.0 wt% of Fe, 0.005 to 0.2 wt% of Ti and 0.01 to
0.2 wt% of
V, and further contains one or two or more of 0.01 to 1.5 wt% of Mn, 0.01 to
0.6 wt% of
Cr, 0.01 to 0.25 wt% of Zr, 0.0001 to 0.08 wt% of B and 0.03 to 0.5 wt% of Mo,
with the
remainder comprising aluminum and unavoidable impurities.
Citation List
Patent Literature
[0007]
PTL 1: Japanese Patent Application Publication No. 2009-221566
PTL 2: Japanese Patent Application Publication No. 2011-058047
PTL 3: Japanese Examined Patent Publication No. H01-025386
PTL 4: Japanese Patent No. 2915487
Summary of Invention
Technical Problem
[0008] However, no aluminum alloy materials are known that can effectively
prevent or
inhibit hydrogen embrittlement to the extent required in the aerospace
industry.
The problem to be solved by the present invention is to provide: an aluminum
alloy material that can effectively prevent or inhibit hydrogen embrittlement;
and a
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hydrogen embrittlement inhibitor for aluminum alloy materials.
Solution to Problem
[0009] According to the present invention, it was found that hydrogen
embrittlement
could be prevented or inhibited by an aluminum alloy material having a
specific alloy
composition and by a hydrogen embrittlement inhibitor for aluminum alloy
materials
which comprises specific second phase particles, and the problem mentioned
above
was thereby solved.
This type of alloy is novel. In PTL 1 to 4, the amount of Fe is higher than
that
specified in Alloy No. 7050 in JIS H 4100: 2014 "Aluminum and Aluminum Alloy
Plates
and Strips", but all of these fall outside the range of the aluminum alloy
material of the
present invention.
For example, the composition of invention example 6 in table 1 in PTL 1
contains 0.21
mass% of Si, 0.28 mass% of Fe, and the like, the composition of alloy A in
table 1 on
page 11 of PTL 2 contains 0.21 mass% of Si, 0.28 mass% of Fe, and the like,
the
composition of sample 4 in table 1 on page 4 of PTL 3 contains 0.10 mass% of
Si, 0.19
mass% of Fe, and the like, and the composition of comparative alloy 10 in
table 1 on
page 4 of PTL 4 contains 0.10 mass% of Si, 0.20 mass% of Fe, and the like, but
these
compositions all fall outside the scope of the aluminum alloy material of the
present
invention.
The constitution of the present invention, which is a specific means for
solving
the problem mentioned above, and a preferred constitution of the present
invention will
now be described.
[0010] [1] An aluminum alloy material which has an aluminum alloy composition
of any
one of aluminum alloy compositions (1) to (7) below.
Aluminum alloy composition (1)
0.30 mass% or less of Si, more than 0.35 mass% of Fe, 0.20 mass% or less of
Cu, 0.20 to 0.70 mass% of Mn, 1.0 to 2.0 mass% of Mg, 0.30 mass% or less of
Cr, 4.0
to 5.0 mass% of Zn, 0.10 mass% or less of V, 0.25 mass% or less of Zr, and
0.20
mass% or less of Ti, while additionally containing Al.
Aluminum alloy composition (2)
0.12 mass% or less of Si, more than 0.15 mass% of Fe, 1.5 to 2.0 mass% of
Cu, 0.10 mass% or less of Mn, 2.1 to 2.6 mass% of Mg, 0.05 mass% or less of
Cr, 5.7
to 6.7 mass% of Zn, 0.05 mass% or less of Ni, 0.10 to 0.16 mass% of Zr, and
0.06
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mass% or less of Ti, while additionally containing Al.
Aluminum alloy composition (3)
0.12 mass% or less of Si, more than 0.25 mass% of Fe, 2.0 to 2.6 mass% of
Cu, 0.10 mass% or less of Mn, 1.9 to 2.6 mass% of Mg, 0.04 mass% or less of
Cr, 5.7
to 6.7 mass% of Zn, 0.08 to 0.15 mass% of Zr, and 0.06 mass% or less of Ti,
while
additionally containing Al.
Aluminum alloy composition (4)
0.40 mass% or less of Si, more than 0.50 mass% of Fe, 1.2 to 2.0 mass% of
Cu, 0.30 mass% or less of Mn, 2.1 to 2.9 mass% of Mg, 0.18 to 0.26 mass% of
Cr, 5.1
to 6.1 mass% of Zn, and 0.20 mass% or less of Ti, while additionally
containing Al.
Aluminum alloy composition (5)
More than 0.7 mass% of Si+Fe, 0.10 mass% or less of Cu, 0.10 mass% or less
of Mn, 0.10 mass% or less of Mg, and 0.8 to 1.3 mass% of Zn, while
additionally
containing Al.
Aluminum alloy composition (6)
0.12 mass% or less of Si, more than 0.12 mass% of Fe, 2.0 to 2.6 mass% of
Cu, 0.06 mass% or less of Mn, 1.9 to 2.6 mass% of Mg, 0.04 mass% or less of
Cr, 5.7
to 6.7 mass% of Zn, 0.08 to 0.15 mass% of Zr, and 0.05 mass% or less of Ti,
while
additionally containing Al.
Aluminum alloy composition (7)
0.40 mass% or less of Si, more than 0.50 mass% of Fe, 1.6 to 2.4 mass% of
Cu, 0.30 mass% or less of Mn, 2.4 to 3.1 mass% of Mg, 0.18 to 0.28 mass% of
Cr, 6.3
to 7.3 mass% of Zn, and 0.20 mass% or less of Ti, while additionally
containing Al.
[2] The aluminum alloy material set forth in [1] in which the aluminum alloy
composition
is aluminum alloy composition (3).
[3] The aluminum alloy material set forth in [1] or [2], which includes second
phase
particles having a higher hydrogen trapping energy than that of a semi-
coherent
precipitate interface.
[4] The aluminum alloy material set forth in [3], wherein the second phase
particles are
Al7Cu2Fe particles.
[5] A hydrogen embrittlement inhibitor for aluminum alloy materials, which
comprises
Al7Cu2Fe particles and can prevent hydrogen embrittlement of aluminum alloy
materials.
[6] The hydrogen embrittlement inhibitor set forth in [5], which can prevent
hydrogen
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embrittlement of an aluminum alloy material having aluminum alloy composition
(A)
below.
Aluminum alloy composition (A)
0.40 mass% or less of Si, 2.6 mass% or less of Cu, 0.70 mass% or less of Mn,
3.1 mass% or less of Mg, 0.30 mass% or less of Cr, 7.3 mass% or less of Zn,
and 0.20
mass% or less of Ti, while additionally containing Fe and Al.
[7] The hydrogen embrittlement inhibitor set forth in [5] or [6], which can
prevent
hydrogen embrittlement of an aluminum alloy material having any one of
aluminum
alloy compositions (1) to (7) below.
Aluminum alloy composition (1)
0.30 mass% or less of Si, more than 0.35 mass% of Fe, 0.20 mass% or less of
Cu, 0.20 to 0.70 mass% of Mn, 1.0 to 2.0 mass% of Mg, 0.30 mass% or less of
Cr, 4.0
to 5.0 mass% of Zn, 0.10 mass% or less of V, 0.25 mass% or less of Zr, and
0.20
mass% or less of Ti, while additionally containing Al.
Aluminum alloy composition (2)
0.12 mass% or less of Si, more than 0.15 mass% of Fe, 1.5 to 2.0 mass% of
Cu, 0.10 mass% or less of Mn, 2.1 to 2.6 mass% of Mg, 0.05 mass% or less of
Cr, 5.7
to 6.7 mass% of Zn, 0.05 mass% or less of Ni, 0.10 to 0.16 mass% of Zr, and
0.06
mass% or less of Ti, while additionally containing Al.
Aluminum alloy composition (3)
0.12 mass% or less of Si, more than 0.25 mass% of Fe, 2.0 to 2.6 mass% of
Cu, 0.10 mass% or less of Mn, 1.9 to 2.6 mass% of Mg, 0.04 mass% or less of
Cr, 5.7
to 6.7 mass% of Zn, 0.08 to 0.15 mass% of Zr, and 0.06 mass% or less of Ti,
while
additionally containing Al.
Aluminum alloy composition (4)
0.40 mass% or less of Si, more than 0.50 mass% of Fe, 1.2 to 2.0 mass% of
Cu, 0.30 mass% or less of Mn, 2.1 to 2.9 mass% of Mg, 0.18 to 0.26 mass% of
Cr, 5.1
to 6.1 mass% of Zn, and 0.20 mass% or less of Ti, while additionally
containing Al.
Aluminum alloy composition (5)
More than 0.7 mass% of Si+Fe, 0.10 mass% or less of Cu, 0.10 mass% or less
of Mn, 0.10 mass% or less of Mg, and 0.8 to 1.3 mass% of Zn, while
additionally
containing Al.
Aluminum alloy composition (6)
0.12 mass% or less of Si, more than 0.12 mass% of Fe, 2.0 to 2.6 mass% of
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Cu, 0.06 mass% or less of Mn, 1.9 to 2.6 mass% of Mg, 0.04 mass% or less of
Cr, 5.7
to 6.7 mass% of Zn, 0.08 to 0.15 mass% of Zr, and 0.05 mass% or less of Ti,
while
additionally containing Al.
Aluminum alloy composition (7)
0.40 mass% or less of Si, more than 0.50 mass% of Fe, 1.6 to 2.4 mass% of
Cu, 0.30 mass% or less of Mn, 2.4 to 3.1 mass% of Mg, 0.18 to 0.28 mass% of
Cr, 6.3
to 7.3 mass% of Zn, and 0.20 mass% or less of Ti, while additionally
containing Al.
[8] The hydrogen embrittlement inhibitor set forth in [5] or [6], which can
prevent
hydrogen embrittlement of an aluminum alloy material having any one of
aluminum
alloy compositions (A1) to (A7) below.
Aluminum alloy composition (Al)
0.30 mass% or less of Si, 0.35 mass% or less of Fe, 0.20 mass% or less of Cu,
0.20 to 0.70 mass% of Mn, 1.0 to 2.0 mass% of Mg, 0.30 mass% or less of Cr,
4.0 to
5.0 mass% of Zn, 0.10 mass% or less of V, 0.25 mass% or less of Zr, and 0.20
mass%
or less of Ti, while additionally containing Al.
Aluminum alloy composition (A2)
0.12 mass% or less of Si, 0.15 mass% or less of Fe, 1.5 to 2.0 mass% of Cu,
0.10 mass% or less of Mn, 2.1 to 2.6 mass% of Mg, 0.05 mass% or less of Cr,
5.7 to
6.7 mass% of Zn, 0.05 mass% or less of Ni, 0.10 to 0.16 mass% of Zr, and 0.06
mass% or less of Ti, while additionally containing Al.
Aluminum alloy composition (A3)
0.12 mass% or less of Si, 0.15 mass% or less of Fe, 2.0 to 2.6 mass% of Cu,
0.10 mass% or less of Mn, 1.9 to 2.6 mass% of Mg, 0.04 mass% or less of Cr,
5.7 to
6.7 mass% of Zn, 0.08 to 0.15 mass% of Zr, and 0.06 mass% or less of Ti, while
additionally containing Al.
Aluminum alloy composition (A4)
0.40 mass% or less of Si, 0.50 mass% or less of Fe, 1.2 to 2.0 mass% of Cu,
0.30 mass% or less of Mn, 2.1 to 2.9 mass% of Mg, 0.18 to 0.26 mass% of Cr,
5.1 to
6.1 mass% of Zn, and 0.20 mass% or less of Ti, while additionally containing
Al.
Aluminum alloy composition (A5)
0.7 mass% or less of Si+Fe, 0.10 mass% or less of Cu, 0.10 mass% or less of
Mn, 0.10 mass% or less of Mg, and 0.8 to 1.3 mass% of Zn, while additionally
containing Al.
Aluminum alloy composition (A6)
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0.12 mass% or less of Si, 0.12 mass% or less of Fe, 2.0 to 2.6 mass% of Cu,
0.06 mass% or less of Mn, 1.9 to 2.6 mass% of Mg, 0.04 mass% or less of Cr,
5.7 to
6.7 mass% of Zn, 0.08 to 0.15 mass% of Zr, and 0.05 mass% or less of Ti, while
additionally containing Al.
Aluminum alloy composition (A7)
0.40 mass% or less of Si, 0.50 mass% or less of Fe, 1.6 to 2.4 mass% of Cu,
0.30 mass% or less of Mn, 2.4 to 3.1 mass% of Mg, 0.18 to 0.28 mass% of Cr,
6.3 to
7.3 mass% of Zn, and 0.20 mass% or less of Ti, while additionally containing
Al.
Advantageous Effects of Invention
[0011] The present invention is capable of providing: an aluminum alloy
material that
can effectively prevent or inhibit hydrogen embrittlement; and a hydrogen
embrittlement inhibitor for aluminum alloy materials.
Brief Description of Drawings
[0012]
[Fig. 1]
Fig. 1 is a virtual cross section of a tomographic image of a microstructure
of a (High
Fe) aluminum alloy material of Working Example 1.
[Fig. 2]
Fig. 2 is a virtual cross section of a tomographic image of a fracture surface
of the
(High Fe) aluminum alloy material of Working Example 1.
[Fig. 3]
Fig. 3 is a virtual cross section of a tomographic image of a (Low Fe)
aluminum alloy
material of Reference Example 2.
[Fig. 4]
Fig. 4 is a virtual cross section of a tomographic image of a fracture surface
of the
(Low Fe) aluminum alloy material of Reference Example 2.
[Fig. 5]
Fig. 5 is a schematic diagram of separation at n/AI interfaces as a result of
hydrogen
trapping.
[Fig. 6]
Fig. 6 is a number line diagram of hydrogen trapping energies of
microstructures in an
aluminum alloy material.
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[Fig. 7]
Fig. 7 is a schematic diagram of the crystal structure (space group P4/mnc) of
Al7Cu2Fe particles.
[Fig. 8]
Fig. 8 is a bar chart showing trapped hydrogen amounts at sites in the
aluminum alloy
materials of Working Example 1 (High Fe) and Reference Example 2 (Low Fe).
[Fig. 9]
Fig. 9 is a graph that shows the relationship between hydrogen distribution to
IMC
(A17Cu2Fe) particles (H at IMC), hydrogen distribution to a semi-coherent
precipitate
interface (H at q2), and hydrogen embrittlement (quasi-cleavage creak) area
fraction
QCF.
Description of Embodiments
[0013] The present invention will now be explained in detail. Explanations of
the
constituent features described below are based on representative embodiments
and
specific examples, but it should be understood that the present invention is
not limited
to such embodiments. Moreover, numerical ranges expressed using the symbol "2
mean ranges that include the numerical values before and after the "2 as lower
and
upper limits of the range.
[0014] [Aluminum alloy material]
In the aluminum alloy material of the present invention, the aluminum alloy
composition is any one of aluminum alloy compositions (1) to (7) below.
Aluminum alloy composition (1)
0.30 mass% or less of Si, more than 0.35 mass% of Fe, 0.20 mass% or less of
Cu, 0.20 to 0.70 mass% of Mn, 1.0 to 2.0 mass% of Mg, 0.30 mass% or less of
Cr, 4.0
to 5.0 mass% of Zn, 0.10 mass% or less of V, 0.25 mass% or less of Zr, and
0.20
mass% or less of Ti, while additionally containing Al.
Aluminum alloy composition (2)
0.12 mass% or less of Si, more than 0.15 mass% of Fe, 1.5 to 2.0 mass% of
Cu, 0.10 mass% or less of Mn, 2.1 to 2.6 mass% of Mg, 0.05 mass% or less of
Cr, 5.7
to 6.7 mass% of Zn, 0.05 mass% or less of Ni, 0.10 to 0.16 mass% of Zr, and
0.06
mass% or less of Ti, while additionally containing Al.
Aluminum alloy composition (3)
0.12 mass% or less of Si, more than 0.25 mass% of Fe, 2.0 to 2.6 mass% of
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Cu, 0.10 mass% or less of Mn, 1.9 to 2.6 mass% of Mg, 0.04 mass% or less of
Cr, 5.7
to 6.7 mass% of Zn, 0.08 to 0.15 mass% of Zr, and 0.06 mass% or less of Ti,
while
additionally containing Al.
Aluminum alloy composition (4)
0.40 mass% or less of Si, more than 0.50 mass% of Fe, 1.2 to 2.0 mass% of
Cu, 0.30 mass% or less of Mn, 2.1 to 2.9 mass% of Mg, 0.18 to 0.26 mass% of
Cr, 5.1
to 6.1 mass% of Zn, and 0.20 mass% or less of Ti, while additionally
containing Al.
Aluminum alloy composition (5)
More than 0.7 mass% of Si+Fe, 0.10 mass% or less of Cu, 0.10 mass% or less
of Mn, 0.10 mass% or less of Mg, and 0.8 to 1.3 mass% of Zn, while
additionally
containing Al.
Aluminum alloy composition (6)
0.12 mass% or less of Si, more than 0.12 mass% of Fe, 2.0 to 2.6 mass% of
Cu, 0.06 mass% or less of Mn, 1.9 to 2.6 mass% of Mg, 0.04 mass% or less of
Cr, 5.7
to 6.7 mass% of Zn, 0.08 to 0.15 mass% of Zr, and 0.05 mass% or less of Ti,
while
additionally containing Al.
Aluminum alloy composition (7)
0.40 mass% or less of Si, more than 0.50 mass% of Fe, 1.6 to 2.4 mass% of
Cu, 0.30 mass% or less of Mn, 2.4 to 3.1 mass% of Mg, 0.18 to 0.28 mass% of
Cr, 6.3
to 7.3 mass% of Zn, and 0.20 mass% or less of Ti, while additionally
containing Al.
By having such features, the aluminum alloy material of the present invention
can effectively prevent or inhibit hydrogen embrittlement. In particular, it
is possible to
effectively prevent or inhibit hydrogen embrittlement to the extent required
in the
aerospace industry.
[0015] In the past, there have been a variety of discussions regarding the
relationship
between metal structures and hydrogen embrittlement. As means for preventing
hydrogen embrittlement, three types of microstructure control methods have
been
proposed, namely (i) making the distribution of precipitates at grain
boundaries low
density and coarse, (ii) making the grain boundary tilt angle (twist angle)
small (a
structure is not recrystallized), and (iii) refining crystal grains (for
example, see Goro
ITOH, Takehiko ETOH, Yoshimitsu MIYAGI, Mikihiro KANNO, "Al-Zn-Mg-based
alloy",
Light Metals, 38 (1988), pages 818 to 839. Moreover, in the table on page 822,
a
tetragonal Al7Cu2Fe crystal is described as a stable phase). However, the
effectiveness of these means is unclear, and specific mechanisms are also
unclear.
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Although the effectiveness thereof is insufficient, addition of alloying
elements such as
zirconium and chromium, which is actually carried out as a method for
preventing
hydrogen embrittlement, was based on method (ii) or (iii) above.
[0016] In the present invention, however, attention was paid to the fact that
local
distribution behavior and accumulation behavior of hydrogen in the aluminum
alloy
material govern hydrogen embrittlement cracks. Particular attention was paid
to the
fact that a controlling factor responsible for hydrogen embrittlement was
hydrogen
trapped in precipitates (see Engineering Fracture Mechanics 216 (2019)
106503). In
addition, the amount of hydrogen at hydrogen trapping sites that causes
hydrogen
embrittlement was grasped by determining the binding energy between aluminum
microstructures and hydrogen and calculating the hydrogen distribution in the
aluminum alloy material. An aluminum alloy material having a specific alloy
composition was found that can effectively prevent or inhibit hydrogen
embrittlement in
an aluminum alloy by concentrating hydrogen at sites that can strongly trap
hydrogen.
In addition, it was found that second phase particles having a higher hydrogen
trapping
energy than that of a semi-coherent precipitate interface are used as the
hydrogen
trapping site.
In addition, the hydrogen embrittlement inhibitor for aluminum alloy materials
of
the present invention, which is described later, comprises Al7Cu2Fe particles
having
the hydrogen trapping sites mentioned above.
Moreover, hydrogen embrittlement cracks include grain boundary cracks and
quasi-cleavage cracks, and quasi-cleavage cracks in particular can be
effectively
prevented or inhibited in the present invention.
Preferred aspects of the present invention will now be explained.
[0017] <Aluminum alloy composition>
In the aluminum alloy material of the present invention, the aluminum alloy
composition is any one of aluminum alloy compositions (1) to (7) above.
Among these aluminum alloy compositions, the aluminum alloy composition is
preferably aluminum alloy composition (3) above in the present invention.
The aluminum alloy material of the present invention preferably has an Fe
content of more than 0.12 mass%, more preferably more than 0.15 mass%,
particularly
preferably more than 0.25 mass%, and yet more preferably 0.30 mass% or more,
relative to the entire aluminum alloy material. As the amount of Fe increases,
the
volume ratio of the second phase particles (preferably Al7Cu2Fe particles),
the number
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density of the second phase particles, and the particle diameter of the second
phase
particles can also be increased.
However, the upper limit of the amount of Fe is not particularly limited. For
example, the amount of Fe relative to the entire aluminum alloy material can
be, for
example, 1.0 mass% or less, 0.8 mass% or less, or 0.6 mass% or less. If the
amount
of Fe is less than these upper limits, the volume ratio, number density and
particle size
of the second phase particles are reduced to a certain extent, meaning that it
is easier
to inhibit deterioration of material properties caused by aggregation and
localization of
second phase particles.
The aluminum alloy material of the present invention contains aluminum as a
primary component, and preferably contains 0.50 mass% or more of aluminum.
More preferred ranges for the aluminum alloy composition will be described in
order.
[0018] Aluminum alloy composition (1) is as shown below.
0.30 mass% or less of Si, more than 0.35 mass% of Fe, 0.20 mass% or less of
Cu, 0.20 to 0.70 mass% of Mn, 1.0 to 2.0 mass% of Mg, 0.30 mass% or less of
Cr, 4.0
to 5.0 mass% of Zn, 0.10 mass% or less of V, 0.25 mass% or less of Zr, and
0.20
mass% or less of Ti, while additionally containing Al.
In aluminum alloy composition (1), the content of Fe is preferably more than
0.35 mass% and not more than 1.0 mass%, and more preferably more than 0.35
mass% and not more than 0.6 mass%.
[0019] Aluminum alloy composition (2) is as shown below.
0.12 mass% or less of Si, more than 0.15 mass% of Fe, 1.5 to 2.0 mass% of
Cu, 0.10 mass% or less of Mn, 2.1 to 2.6 mass% of Mg, 0.05 mass% or less of
Cr, 5.7
to 6.7 mass% of Zn, 0.05 mass% or less of Ni, 0.10 to 0.16 mass% of Zr, and
0.06
mass% or less of Ti, while additionally containing Al.
In aluminum alloy composition (2), the content of Fe is preferably more than
0.15 mass% and not more than 1.0 mass%, and more preferably more than 0.15
mass% and not more than 0.6 mass%.
[0020] Aluminum alloy composition (3) is as shown below.
0.12 mass% or less of Si, more than 0.25 mass% of Fe, 2.0 to 2.6 mass% of
Cu, 0.10 mass% or less of Mn, 1.9 to 2.6 mass% of Mg, 0.04 mass% or less of
Cr, 5.7
to 6.7 mass% of Zn, 0.08 to 0.15 mass% of Zr, and 0.06 mass% or less of Ti,
while
additionally containing Al.
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In aluminum alloy composition (3), the content of Fe is preferably more than
0.25 mass% and not more than 1.0 mass%, and more preferably more than 0.25
mass% and not more than 0.6 mass%.
[0021] Aluminum alloy composition (4) is as shown below.
0.40 mass% or less of Si, more than 0.50 mass% of Fe, 1.2 to 2.0 mass% of
Cu, 0.30 mass% or less of Mn, 2.1 to 2.9 mass% of Mg, 0.18 to 0.26 mass% of
Cr, 5.1
to 6.1 mass% of Zn, and 0.20 mass% or less of Ti, while additionally
containing Al.
In aluminum alloy composition (4), the content of Fe is preferably more than
0.55 mass% and not more than 1.0 mass%, and more preferably more than 0.55
mass% and not more than 0.6 mass%.
[0022] Aluminum alloy composition (5) is as shown below.
More than 0.7 mass% of Si+Fe, 0.10 mass% or less of Cu, 0.10 mass% or less
of Mn, 0.10 mass% or less of Mg, and 0.8 to 1.3 mass% of Zn, while
additionally
containing Al.
In aluminum alloy composition (5), it is preferable for 0.7 mass%<Si+Fe 1.0
mass%. In addition, the content of Fe is preferably more than 0.35 mass% and
not
more than 1.0 mass%, and more preferably more than 0.35 mass% and not more
than
0.6 mass%.
[0023] Aluminum alloy composition (6) is as shown below.
0.12 mass% or less of Si, more than 0.12 mass% of Fe, 2.0 to 2.6 mass% of
Cu, 0.06 mass% or less of Mn, 1.9 to 2.6 mass% of Mg, 0.04 mass% or less of
Cr, 5.7
to 6.7 mass% of Zn, 0.08 to 0.15 mass% of Zr, and 0.05 mass% or less of Ti,
while
additionally containing Al.
In aluminum alloy composition (6), the content of Fe is preferably more than
0.12 mass% and not more than 1.0 mass%, and more preferably more than 0.12
mass% and not more than 0.6 mass%.
[0024] Aluminum alloy composition (7) is as shown below.
0.40 mass% or less of Si, more than 0.50 mass% of Fe, 1.6 to 2.4 mass% of
Cu, 0.30 mass% or less of Mn, 2.4 to 3.1 mass% of Mg, 0.18 to 0.28 mass% of
Cr, 6.3
to 7.3 mass% of Zn, and 0.20 mass% or less of Ti, while additionally
containing Al.
In aluminum alloy composition (7), the content of Fe is preferably more than
0.50 mass% and not more than 1.0 mass%, and more preferably more than 0.50
mass% and not more than 0.6 mass%.
[0025] <Shape of alloy material>
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The shape of the aluminum alloy material of the present invention is not
particularly limited. The aluminum alloy material may be bulky or particulate,
but is
preferably bulky.
[0026] <Second phase particles>
The aluminum alloy material of the present invention preferably contains
second phase particles having a higher hydrogen trapping energy than that of a
semi-
coherent precipitate interface.
The term second phase particles means particles having a composition that is
different from the constituent composition of a parent phase. The second phase
particles in the aluminum alloy material are particles having a composition
that is
different from that of Al or the aluminum alloy material.
Second phase particles having a higher hydrogen trapping energy than that of
a semi-coherent precipitate interface are not particularly limited. Second
phase
particles having a higher hydrogen trapping energy than that of a semi-
coherent
precipitate interface can be determined using first principle calculations.
The term "first
principle calculations" means theoretically representing an electronic state
by
mathematically solving the Schrodinger equation (without using experimental
data or
empirical parameters). The distribution of hydrogen at each trapping site can
be
calculated from the density of other hydrogen trapping sites, such as grain
boundaries,
precipitates and lattices, and the binding energy with hydrogen. Moreover, by
observing the deformation process of the aluminum alloy material by radiation
tomography and carrying out 3D or 4D image processing, a large number of
second
phase particles dispersed in the aluminum alloy material can be traced, and
the
internal plastic strain distribution can be determined by means of 3D mapping.
From
the 3D strain distribution, geometrically required dislocations, statistically
required
dislocations, and concentration distributions of atomic vacancies can be
calculated.
In the present invention, second phase particles having a hydrogen trapping
energy higher than that of a semi-coherent precipitate interface are
preferably
Al7Cu2Fe particles. Moreover, similar effects can be expected from particles
having an
Al:Cu:Fe atomic ratio that deviates from the stoichiometric composition of
7:2:1 by
approximately 30% (for example, Al7Cu2Feo.7 particles). Of the hydrogen
trapping
energies of the microstructures in the aluminum alloy material, that of
Al7Cu2Fe
particles is 0.56 eV. However, preferred second phase particles or
microstructures
other than Al7Cu2Fe particles having hydrogen trapping energies that are
higher than
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that of a semi-coherent precipitate interface (0.55 eV) are not yet known.
[0027] The shape of the second phase particles includes a variety of shapes,
such as
spherical, elliptical, square cylinder-shaped, cylindrical, cubic, rectangular
parallelepiped-shaped and scaly, but is preferably spherical or elliptical.
[0028] The volume ratio of the second phase particles is preferably 0.05 to
10.0%,
more preferably 0.1 to 5.0%, and particularly preferably 0.5 to 2.0%. The
volume ratio
of the second phase particles can be calculated as the volume of the second
phase
particles relative to the volume of the aluminum alloy material by means of,
for
example, 3D analysis using X-Ray tomography (CT).
[0029] The number density of the second phase particles is preferably
6.5x1012/m3 to
100x1012/m3, more preferably 10x1012/m3 to 50x1012/m3, and particularly
preferably
20x1012/m3 to 40x1012/m3. The number density of the second phase particles can
be
calculated by means of, for example, 3D analysis using high resolution X-Ray
tomography (CT) having a spatial resolution of up to 1 pm.
[0030] The average particle diameter of the second phase particles is
preferably 0.5 to
20 pm. The upper limit of the average particle diameter of the second phase
particles
is preferably 10 pm or less, and particularly preferably 5.0 pm or less. The
average
particle diameter of the second phase particles can be calculated as an
arithmetic
mean value by means of, for example, 3D analysis using X-Ray tomography (CT).
[0031] <Method for producing aluminum alloy material>
The method for producing the aluminum alloy material is not particularity
limited.
By forming the hydrogen embrittlement inhibitor for aluminum alloy materials,
which comprises Al7Cu2Fe particles, inside a raw material aluminum alloy
material, it is
possible to prevent hydrogen embrittlement in the aluminum alloy material.
It is possible to add Al7Cu2Fe particles to the raw material aluminum alloy
material, or to add Fe at the time of production to form Al7Cu2Fe particles,
and
ultimately use the Al7Cu2Fe particles as a hydrogen embrittlement inhibitor.
The raw material aluminum alloy material may be a raw material mixture before
a metal such as Al or a metal compound is alloyed.
[0032] The aluminum alloy material can be produced by subjecting the raw
material
aluminum alloy material (which may be a raw material mixture) to a well-known
process such as a heat treatment, rolling, forging and/or casting. In the
present
invention, it is preferable to cast the raw material aluminum alloy material
to produce
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the aluminum alloy material from the perspective of inhibiting hydrogen
trapping in
precipitates, that is, inhibiting quasi-cleavage creak. In particular, it is
preferable to
actively form Al7Cu2Fe particles by adding Fe at the time of casting to the
raw material
mixture before each metal or metal compound is alloyed, at a higher quantity
than in a
case where a conventional aluminum alloy material is produced. In addition, it
is
possible to not carry out a heat treatment, rolling or forging.
As other production methods, the method described in paragraphs [0034] to
[0042] of Japanese Patent Application Publication No. 2009-221556 can be
appropriated, and the contents of this publication are incorporated herein by
reference.
[0033] [Hydrogen embrittlement inhibitor for aluminum alloy materials]
The hydrogen embrittlement inhibitor for aluminum alloy materials of the
present invention comprises Al7Cu2Fe particles and can prevent hydrogen
embrittlement of aluminum alloy materials.
Al7Cu2Fe particles may be contained in an existing aluminum alloy material,
but
such a product was not known to be a hydrogen embrittlement inhibitor for
aluminum
alloy materials.
[0034] <Raw material aluminum alloy material>
The raw material aluminum alloy material in which hydrogen embrittlement is to
be prevented may be the aluminum alloy material of the present invention or a
conventional aluminum alloy material.
[0035] It is preferable for the hydrogen embrittlement inhibitor for aluminum
alloy
materials of the present invention to be able to prevent hydrogen
embrittlement of an
aluminum alloy material having aluminum alloy composition (A) below.
Aluminum alloy composition (A)
0.40 mass% or less of Si, 2.6 mass% or less of Cu, 0.70 mass% or less of Mn,
3.1 mass% or less of Mg, 0.30 mass% or less of Cr, 7.3 mass% or less of Zn,
and 0.20
mass% or less of Ti, while additionally containing Fe and Al.
[0036] In a case where a raw material aluminum alloy material in which
hydrogen
embrittlement is to be prevented is the aluminum alloy material of the present
invention, it is preferable for the hydrogen embrittlement inhibitor for
aluminum alloy
materials of the present invention to be able to prevent hydrogen
embrittlement in an
aluminum alloy material having any one of aluminum alloy compositions (1) to
(7)
above.
[0037] In a case where a raw material aluminum alloy material in which
hydrogen
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CA 03185880 2022-12-02
embrittlement is to be prevented is a conventional aluminum alloy material, it
is
preferable for the hydrogen embrittlement inhibitor for aluminum alloy
materials of the
present invention to be able to prevent hydrogen embrittlement in an aluminum
alloy
material having any one of aluminum alloy compositions (Al) to (A7) below.
However,
in a case where a raw material aluminum alloy material in which hydrogen
embrittlement is to be prevented is a conventional aluminum alloy material, it
is
preferable to reduce the particle diameter of second phase particles to lower
than in
the past and disperse these second phase particles so as to more readily
prevent
hydrogen embrittlement.
Aluminum alloy composition (Al)
0.30 mass% or less of Si, 0.35 mass% or less of Fe, 0.20 mass% or less of Cu,
0.20 to 0.70 mass% of Mn, 1.0 to 2.0 mass% of Mg, 0.30 mass% or less of Cr,
4.0 to
5.0 mass% of Zn, 0.10 mass% or less of V, 0.25 mass% or less of Zr, and 0.20
mass%
or less of Ti, while additionally containing Al.
Aluminum alloy composition (A2)
0.12 mass% or less of Si, 0.15 mass% or less of Fe, 1.5 to 2.0 mass% of Cu,
0.10 mass% or less of Mn, 2.1 to 2.6 mass% of Mg, 0.05 mass% or less of Cr,
5.7 to
6.7 mass% of Zn, 0.05 mass% or less of Ni, 0.10 to 0.16 mass% of Zr, and 0.06
mass% or less of Ti, while additionally containing Al.
Aluminum alloy composition (A3)
0.12 mass% or less of Si, 0.15 mass% or less of Fe, 2.0 to 2.6 mass% of Cu,
0.10 mass% or less of Mn, 1.9 to 2.6 mass% of Mg, 0.04 mass% or less of Cr,
5.7 to
6.7 mass% of Zn, 0.08 to 0.15 mass% of Zr, and 0.06 mass% or less of Ti, while
additionally containing Al.
Aluminum alloy composition (A4)
0.40 mass% or less of Si, 0.50 mass% or less of Fe, 1.2 to 2.0 mass% of Cu,
0.30 mass% or less of Mn, 2.1 to 2.9 mass% of Mg, 0.18 to 0.26 mass% of Cr,
5.1 to
6.1 mass% of Zn, and 0.20 mass% or less of Ti, while additionally containing
Al.
Aluminum alloy composition (A5)
0.7 mass% or less of Si+Fe, 0.10 mass% or less of Cu, 0.10 mass% or less of
Mn, 0.10 mass% or less of Mg, and 0.8 to 1.3 mass% of Zn, while additionally
containing Al.
Aluminum alloy composition (A6)
0.12 mass% or less of Si, 0.12 mass% or less of Fe, 2.0 to 2.6 mass% of Cu,
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CA 03185880 2022-12-02
0.06 mass% or less of Mn, 1.9 to 2.6 mass% of Mg, 0.04 mass% or less of Cr,
5.7 to
6.7 mass% of Zn, 0.08 to 0.15 mass% of Zr, and 0.05 mass% or less of Ti, while
additionally containing Al.
Aluminum alloy composition (A7)
0.40 mass% or less of Si, 0.50 mass% or less of Fe, 1.6 to 2.4 mass% of Cu,
0.30 mass% or less of Mn, 2.4 to 3.1 mass% of Mg, 0.18 to 0.28 mass% of Cr,
6.3 to
7.3 mass% of Zn, and 0.20 mass% or less of Ti, while additionally containing
Al.
[0038] Aluminum alloy compositions (A1) to (A7) are summarized in Table 1
below.
"Alloy number" in Table 1 means the alloy number in JIS H 4100: 2014 "Aluminum
and
aluminum alloy plates and strips".
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Date Recue/Date Recieved 2022-12-02
[0039]
a
w
Er [Table 1]
x
ai
,
c Alloy Alloy Laminated
Ga, V, Ni, Others
a) Si Fe Cu Mn Mg Cr
Zn Ti Al
0
w Composition
No. sheet B, Zr etc. Each Total
a'
x 7204
V: 0.10,
0
O (Al) 0.30 0.35 0.20
0.20-0/ 1.0-2.0 0.30 4.0-5.0 0.20 0.05 0.15 Balance
0
<
(7N01) Zr: 0.25
0
0_
r.)
Ni: 0.05,
co
r.) (A2) 7010 0.12 0.15 1.5-2.0 0.10 2.1-2.6 0.05
5.7-6.7 0.06 0.05 0.15 Balance
r)
Zr: 0.10-0.16
i -=i
O
r.) (A3) 7050 0.12 0.15 2.0-2.6 0.10 1.9-2.6
0.04 5.7-6.7 Zr: 0.08-0.15 0.06 0.05 0.15 Balance
7075 0.40 0.50 1.2-2.0 0.30 2.1-2.9 0.18-
0.28 5.1-6.1 0.20 0.05 0.15 Balance
P
Core
0
(A4)
,
03
material 0.40 0.50 1.2-2.0 0.30 2.1-2.9 0.18-
0.28 5.1-6.1 - 0.20 0.05 0.15 Balance g
7075
0 3
(7075)
"
Laminated
" IV
Skin
,
IVI-'
sheet
,
(A5) material Si+Fe: 0.7
0.10 0.10 0.10 - 0.8-1.3 - - 0.05
0.15 Balance "
(7072)
(A6) 7475 0.10
0.12 1.2-1.9 0.06 1.9-2.6 0.18-0.25 5.2-6.2 - 0.06
0.05 0.15 Balance
(A7) 7178 0.40
0.50 1.6-2.4 0.30 2.4-3.1 0.18-0.28 6.3-7.3 - 0.20
0.05 0.15 Balance
18
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Working Examples
[0040] The present invention will now be explained in greater detail by means
of
working examples and comparative examples. The materials, usage quantities,
ratios,
treatment details, treatment procedures, and so on, shown in the working
examples
below can be changed as appropriate as long as these do not deviate from the
gist of
the present invention. Therefore, the scope of the present invention should
not be
interpreted as being limited by the specific examples given below.
[0041] [Working Example 1]
Using the method described below, an aluminum alloy material (High Fe) of
Working Example 1, in which content of Fe was 0.30 mass%, was prepared as an
aluminum alloy material that satisfies aluminum alloy composition (3). This
aluminum
alloy material is an Al-Zn-Cu alloy which contains 50 mass% or more of Al as a
primary
component, with the component having the next highest content being Zn,
followed by
Cu.
Fe was further added to a melting column for the composition of Alloy No. 7050
in JIS H 4100: 2014 "Aluminum and Aluminum Alloy Plates and Strips", that is,
a
material for casting an aluminum alloy material that satisfies the aluminum
alloy
composition (A3), and Al7Cu2Fe particles were formed inside the material as
second
phase particles.
[0042] [Reference Examples 1 and 2]
An aluminum alloy (Mid Fe) of Reference Example 1, in which the content of Fe
was 0.05 mass%, and an aluminum alloy material (Low Fe) of Reference Example
2,
in which the content of Fe was 0.01 mass%, were prepared as aluminum alloy
materials that satisfy the composition of Alloy No. 7050 in JIS H 4100: 2014
"Aluminum
and Aluminum Alloy Plates and Strips", that is, aluminum alloy composition
(A3).
[0043] [Evaluations]
<3D analysis>
The aluminum alloy materials of Working Example 1 and Reference Examples
1 and 2 were subjected to 3D analysis by means of X-Ray tomography. The
obtained
results are shown in Table 2 below. In Table 2 below, "Particles" means
Al7Cu2Fe
particles.
[0044]
[Table 2]
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Material Amount of Fe Volume ratio of Number density Particle
(mass%) particles (%) of particles diameter
(pm)
(1012/m3)
High Fe 0.30 1.0 35.2 4.6
Mid Fe 0.05 0.1 6.7 1.7
Low Fe 0.01 0.05 6.3 1.7
[0045] From Table 2 above, it was understood that the volume ratio of Al7Cu2Fe
particles also increased as the amount of Fe increased.
[0046] <Tomographic images>
Next, tomographic images were taken of the aluminum alloy materials of
Working Example 1 and Reference Examples 1 and 2.
Fig. 1 shows a virtual cross section of a tomographic image of a
microstructure
of the (High Fe) aluminum alloy material of Working Example I. In addition,
Fig. 2
shows a virtual cross section of a tomographic image of a fracture surface of
the (High
Fe) aluminum alloy material of Working Example I. In Fig. 2 and Fig. 4, QCF
means
Area fraction of Quasi-cleavage creak.
Fig. 3 shows a virtual cross section of a tomographic image of the (Low Fe)
aluminum alloy material of Reference Example 2. In addition, Fig. 4 shows a
virtual
cross section of a tomographic image of a fracture surface of the (Low Fe)
aluminum
alloy material of Reference Example 2.
Diagrams are not shown for Reference Example I.
[0047] From Fig. 1, it was understood that in the (High Fe) aluminum alloy
material of
Working Example 1, second phase particles, namely Al7Cu2Fe particles, were
formed
inside the material. It was also understood that the Al7Cu2Fe particles were
present at
the micron level, and were dispersed at a high density.
However, in the (Low Fe) aluminum alloy material of Reference Example 2
shown in Fig. 3, it was understood that the second phase particles were hardly
formed
inside the material.
[0048] Furthermore, from Fig. 2 and Fig. 4 and the results of Reference
Example 1
(not shown), the area fraction of quasi-cleavage creak (QCF) at fracture
surfaces was
determined for Working Example 1 (High Fe), Reference Example 1 (Mid Fe) and
Reference Example 2 (Low Fe). The obtained results are shown in Table 3 below.
[0049]
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[Table 3]
Area fraction of
quasi-cleavage creak
QCF (%)
High Fe (0.30 mass%) 8.1
Mid Fe (0.05 mass%) 18.8
Low Fe (0.01 mass%) 22.4
[0050] In view of Table 3 above, hydrogen embrittlement can be reduced. It was
understood that when the amount of Fe increases from 0.01 mass% to 0.3 mass%,
the
area fraction of quasi-cleavage creak (QCF) decreases from 22.4% to 8.1%. The
area
fraction of quasi-cleavage creak QCF corresponds to the hydrogen embrittlement
fracture surface ratio. It was thus understood that hydrogen embrittlement can
be
reduced by increasing the amount of Fe in comparison with conventional
aluminum
alloy materials, to form and disperse at the micron level at a high density
Al7Cu2Fe
particles as second phase particles inside the material. In addition, it was
found that
Al7Cu2Fe particles can effectively prevent or inhibit quasi-cleavage creak of
the
aluminum alloy material, and are extremely effective as a hydrogen
embrittlement
inhibitor for aluminum alloy materials.
[0051] <Analysis of hydrogen distribution state>
For the aluminum alloy materials of Working Example 1, Reference Example 1
and Reference Example 2, the hydrogen amount (H at IMC) in a microstructure
and
the hydrogen amount (H at n2) in a semi-coherent precipitate (-12, semi-
coherent) were
determined using a calculation process.
[0052] (1) Semi-spontaneous separation of semi-coherent precipitate interface
by
hydrogen
Separation of a n/AI interface by hydrogen trapping was calculated using first
principle calculations. The obtained results are shown in Fig. 5.
From Fig. 5, it was understood that when hydrogen was concentrated at a
semi-coherent precipitate interface (-12, semi-coherent), the interface semi-
spontaneously separated, and this separation became a starting point for
hydrogen
embrittlement. This result is a new hydrogen embrittlement mechanism in
aluminum
alloy materials.
21
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[0053] (2) Hydrogen trapping energies of microstructures
The hydrogen trapping energies of microstructures in the aluminum alloy
material were calculated using first principle calculations. The obtained
results are
shown in Fig. 6. In Fig. 6, spiral dislocations (Screw disl.), solute Mg atoms
(Solute
Mg), edge dislocations (Edge disl.), grain boundaries (GB), vacancies (Vac.),
coherent
precipitate interfaces (m, coherent), semi-coherent precipitate interfaces (-
12, semi-
coherent), Al7Cu2Fe particles (IMCp), pore surface (Pore (surface H), and
molecular
hydrogen in the pore (Pore (H2)) are shown in order from the left.
From Fig. 6, it was understood that in the control of hydrogen embrittlement,
microstructure control by heat treatment or rolling is not effective for
inhibiting
hydrogen trapping in precipitates, that is, is not effective for suppressing
quasi-
cleavage creak. It was understood that the binding energy between a
precipitate and
hydrogen was the second highest after a pore, and the trapping site density of
hydrogen was also high. It was understood that in order to inhibit quasi-
cleavage
creak based on hydrogen distribution control, it is necessary to provide a
site in the
material which has a higher binding energy with hydrogen than a precipitate
and a
sufficiently high trapping site density. From Fig. 6, it was understood that
among the
hydrogen trapping energies of the microstructures, that of Al7Cu2Fe particles
was 0.56
eV, which was higher than 0.35 eV for a coherent precipitate interface (ni,
coherent)
and 0.55 eV for a semi-coherent precipitate interface (-12, semi-coherent).
That is, the
Al7Cu2Fe particles have a higher hydrogen trapping energy than that of a semi-
coherent precipitate interface, and this is effective for preventing hydrogen
embrittlement.
The crystal structure (space group P4/mnc) of the Al7Cu2Fe particles is shown
in Fig. 7 (see Bown et al., Acta Cryst., 9(1956), 911). From Fig. 7, it can be
confirmed
that there is a hydrogen trapping site that can strongly trap H inside the
Al7Cu2Fe
particles.
[0054] (3) Calculation of hydrogen distribution state
The hydrogen distribution state in the aluminum alloy material was analyzed.
Based on the relationships of Numerical Formulae 1 to 3 below, the
distribution
state of hydrogen in a state of thermal equilibrium was calculated using
hydrogen
trapping energies determined using first principle calculations. Specific
calculations
were carried out using a method according to Engineering Fracture Mechanics
216
(2019) 106503.
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[0055]
[Math. 1]
Formula 1: Thermal equilibrium
Occupancy
(trapping sites) Binding E
'E hi
____________________ = OLexp _______
1 ¨ RT
OT. õõõ,1161111õ, i
Occupancy (lattices)
[0056]
[Math. 2]
Formula 2: Distribution of hydrogen at trapping sites
Trapping :site density
Surface E
(trapping sites)
4yV
CI; = OLNL OTiNTi + 2NA d RT
Pore surface H
Trapping site density
(lattices)
[0057]
[Math. 3]
Formula 3: Reduction in surface E (surface energy) of pore due to hydrogen
adsorption
A 150 N,
V yo ¨ (Es + RT11(9 L.)) R7'09,41(00 + 11 ¨ 0 õ)11)(1 ¨ 90}
= -NA NA
A A
Surface E Binding E and Configurational entropy of
chemical potential of hydrogen adsorbed hydr'i en
in lattices
[0058] The obtained results are shown in Fig. 8. In Fig. 8, amounts of
hydrogen
trapped in microstructures of lattices (Lattice), solute Mg atoms (Mg), pores
(V), grain
boundaries (1), Al7Cu2Fe particles (IMCp), coherent precipitate interfaces
(coherent),
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Date Recue/Date Recieved 2022-12-02
CA 03185880 2022-12-02
semi-coherent precipitate interfaces (semi-coherent) and pores (Pore),
respectively,
are shown in order from the left. In the two bar charts for each
microstructure, the left
hand bar shows a case where the amount of Fe is 0.30 mass% (High Fe), which
corresponds to Working Example 1, and the right hand bar shows a case where
the
amount of Fe is 0.01 mass% (Low Fe), which corresponds to Reference Example 2.
However, results for a case where the amount of Fe is 0.05 mass% (Mid Fe),
which
corresponds to Reference Example 1, are not shown in Fig. 8.
As shown in Fig. 8, it can be understood that hydrogen in the aluminum alloy
material is distributed at each microstructure according to the trapping
energy thereof.
In an aluminum alloy material having a low Fe amount of 0.01 mass% (Low Fe),
which is similar to that of Reference Example 1, hydrogen is most strongly
distributed
at a semi-coherent precipitate interface (12, semi-coherent). This is a
starting point for
hydrogen embrittlement (see Fig. 5 above).
On the other hand, in an aluminum alloy having a high Fe amount of 0.30
mass% (High Fe), which is similar to Working Example 1, hydrogen is most
strongly
distributed at Al7Cu2Fe particles (IMCp). As a result, it was understood that
the
hydrogen concentration at a precipitate interface such as a semi-coherent
precipitate
(n2, semi-coherent) interface was reduced, and hydrogen embrittlement could be
prevented.
[0059] The evaluation results above are summarized in Fig. 9. Fig. 9 is a
graph that
shows the relationship between hydrogen distribution to IMC (Al7Cu2Fe)
particles (H at
IMC), hydrogen distribution to a semi-coherent precipitate interface (H at
n2), and
hydrogen embrittlement (quasi-cleavage creak) area fraction QCF. The
horizontal axis
shows the amount of Fe in the aluminum alloy materials of Working Example 1,
Reference Example 1 and Reference Example 2.
From Table 1 above, it was understood that the volume ratio of the Al7Cu2Fe
particles increases as the amount of Fe in the aluminum alloy material
increases.
From the results in Table 1 and Fig. 9, it was understood that as the amount
of
Fe in the aluminum alloy material increases, the amount of hydrogen trapped by
Al7Cu2Fe particles increases (dashed line; H at IMC), the amount of hydrogen
in the
precipitate decreases (H at no, and hydrogen embrittlement (quasi-cleavage
creak)
can be effectively prevented or inhibited (QCF).
In addition, it was understood that the aluminum alloy material effectively
functions as a hydrogen brittle inhibitor even in a case where a material for
casting an
24
Date Recue/Date Recieved 2022-12-02
CA 03185880 2022-12-02
aluminum alloy material having a conventional well-known composition specified
in JIS
H 4100: 2014 is used, because Al7Cu2Fe particles are formed inside the
material as
second phase particles.
Date Recue/Date Recieved 2022-12-02
