Note: Descriptions are shown in the official language in which they were submitted.
CA 02729251 2012-09-14
HIGH STRENGTH CASTING ALUMINUM ALLOY MATERIAL
Technical Field
The invention relates to an aluminum alloy material, in particular to a high
strength
casting aluminum alloy material.
Background
The aluminum alloy as a younger metal material was not put into industrial use
until early in the twentieth century. During the World War II, the aluminum
material was
mainly used to manufacture military aircraft. In the post-war years, the sharp
drop in the
demand for the aluminum material in the military industry led the aluminum
industry to
turn to the development of the aluminum alloy for civil use, so as to extend
the applicable
range thereof from aviation industry to various fields of national economy
such as
construction industry, container packaging industry, transportation industry,
power
industry, electronic industry, mechanical manufacturing industry,
petrochemical industry
and so on and apply the aluminum alloy to daily life. Nowadays, owing to high
consumption and wide range, the aluminum material ranks second next to steel
in metal
materials. The aluminum alloy can be dated back to 1906 when Alfred Wilm
Duralumin
discovered the age hardening by chance in Berlin and then the Duralumin was
developed
and applied to the structural parts of aircraft. Various Al-Cu alloys were
developed based
on the Duralumin. Early in the twentieth century, aluminum alloy A-U5GT
((W)Si<0.05%,
(W)Fe<0.10% and tensile strength (T4) > 275MPa according to SAE J452-1989),
which
has been listed in France's national standards and aerospace standards, was
developed and
put into use and production; aluminum alloys 201.0 (1968) and 206.0 (1967)
according to
the Aluminum Association were based on the A-U5GT, and aluminum alloy 204.0
(1974)
was equivalent to A-U5GT; aluminum alloy 201.0 (A1Cu4AgMgMn) containing Ag
(0.4%
to 1.0%) and having high cost is commercially named KO-1 (with the tensile
strength (T7)
thereof being 415MPa and the coefficient of elongation thereof being 3%
according to
ASTM B26/B26(M)-1999); BAJI10 is equivalent to ZL204 for domestic use in the
aspect
of major element components but its trace elements is under secret and it is
only used in
the military field or other fields having high requirements.
ZL204A, ZL205A and other grades of casting aluminum alloy are developed in
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China, wherein the tensile strength of the ZL204A (65>4%) under the T5 state
is 440Mpa,
however, the ZL204A has the poorest fluidity and hot-cracking resistance among
the
Al-Cu based casting alloys; the tensile strengths of ZL205A under the T5 state
and T6
state are 435MPa and 465MPa respectively according to the technical standard
(GB1173-86), and the tensile strength of ZL205A (T6) is 470MPa according to
the
standard (GB/F1173-1995), so the ZL205A is one of casting aluminum alloy
materials
having highest strength worldwide at present.
The plasticity of ZL205A (T5) is good, and the coefficient of elongation
thereof
reaches 7%, so ZL2OSA has been widely applied in the field of aerospace,
however,
ZL205A contains precious metal V as an element and is high in cost; meanwhile,
ZL205A
is based on refined aluminum or high-purity aluminum as a base metal, thus
increasing the
cost and limiting the material supply. Additionally, ZL209, which is made by
adding RE to
ZL205A, is still subject to the limitation of high cost due to the addition of
the element V.
The aluminum alloy developed by LV Jie, BIAM (Beijing Institute of
Aeronautical
Materials) is similar to ZL2O5A in the aspect of main components, however, the
aluminum
alloy contains 0.1% to 0.25% of V in the trace elements, has a tensile
strength of 385MPa
to 405MPa and the coefficient of elongation reaching 19% to 23%, and it is
disclosed only
in document study, the tensile strength of the aluminum alloy is lower, and
the raw
materials include high-cost element V.
In conclusion, the existing research on the field of high-strength casting
aluminum
alloy at home and aboard has the following problems: the strength of the
aluminum alloy
is not high enough, more particularly, few of casting aluminum alloys has the
tensile
strength higher than 450MPa; precious metals and rare elements (Ag, V and Be)
are added
in an amount higher than 1%.3, and high-impurity aluminum is used as the base
metals,
thus increasing the cost, limiting the material source and making the aluminum
alloy
difficult to be popularized and put into civil use; the problem of the ratio
between strength
and plasticity is yet to be solved, and the contradiction between the strength
and castability
of the alloy is serious; and the fatigue life is short, and the resistance to
stress corrosion is
poor.
Summary of the Present Invention
The invention intends to solve the technical problems that the existing
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high-strength casting aluminum alloy has the disadvantages of high formula
cost, low
strength, poor castability, short fatigue life and poor resistance to stress
corrosion and to
develop a high-strength, high-toughness and high-corrosion-resistance casting
aluminum
alloy material for both military and civil uses by optimizing the common
formula and the
processes of casting and purifying.
In order to solve the problems, the invention provides a high-strength casting
aluminum alloy material comprising the following components by weight
percentage:
2.0% to 6.0% of Cu, 0.05% to 1.0% of Mn, 0.01% to 0.5% of Ti, 0.01% to 0.2% of
Cr,
0.01% to 0.4% of Cd, 0.01% to 0.25% of Zr, 0.005% to 0.04% of B, 0.05% to 0.3%
of rare
earth element and the balancing amount of Al and trace impurities.
The rare earth element may be Pr, Ce, La or mixed rare earth elements RE.
The total content of various rare earth elements in the mixed rare earth
elements
RE is not lower than 98% (based on the total weight of the mixed rare earth
elements RE).
The mixed rare earth elements RE may contain 40wt% to 50wt% of Ce (based on
the total weight of the mixed rare earth elements RE).
The method for preparing the high-strength casting aluminum alloy material
comprises the following steps:
(1) adding a proper amount of aluminum ingots or molten aluminum liquid to a
melting furnace, heating until the aluminum ingots or molten aluminum liquid
is melted
down, and holding at 660 to 850 DEG C;
(2) adding the alloying elements of Cu and Mn by formula ratio and evenly
stirring,
and then adding trace elements Ti, Cr, Cd, Zr, B, rare earth element Pr, Ce,
La or rare earth
RE and evenly stirring;
(3) then, refining the alloy melt in the melting furnace, adding a refining
agent
(chlorine gas, hexachloroethane, manganese chloride and the like may be
selected as the
refining agent according to different working conditions) to the alloy melt
and evenly
stirring, wherein the melt should be refined in a closed environment as
possible, in order to
prevent the melt from water absorption and melting loss;
(4) pouring the alloy liquid out of the melting furnace, and carrying out the
online
treatment of filtering, degassing and deslagging;
(5) permanent mold casting; and
(6) finally, carrying out solid-solution precipitation strengthening thermal
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treatment at lower than 620 DEG C within 72 hours.
Compared with the prior art, the invention has the following advantages:
(1) Advanced designs of alloying and micro-alloying. By determining the
reasonable design of micro-alloying elements (Ti, Cr, B, Zr, Pr, Ce, La and
mixed rare
earth elements) and composition range thereof based on the main components of
Al-Cu-Mn, the invention can achieve the effect of substituting for precious
metals, such as
Ag and V and reduce the formula cost by 5% to 10%.
(2) Advanced techniques for melting and impurity removal. The invention can
effectively break through the technical bottleneck in impurity removal and
ensure that the
tensile strength of the material is higher than 450MPa and the coefficient of
elongation is
higher than 5% at the same time.
(3) The invention can maintain the high strength of the material and obviously
increase the plasticity thereof at the same time.
According to the novelty research concluded by the novelty research center of
the
Southwest Information Center, MOST (Ministry of Science and Technology), the
development and industrialization of the novel high-strength casting aluminum
alloy 1, in
which the parameters of the element components can be achieved by using the
project, are
not disclosed in documents or reports at home and abroad. Therefore, the
disputes and
conflicts can be avoided in the intellectual property and research achievement
of the
project.
The characterization of the composition and performance parameters of the
novel
materials: the comparison of mechanical properties between some Al-Cu alloys
and the
high-strength casting aluminum alloy material based on national standards is
listed in the
following table.
Comparison of mechanical properties between Al-Cu alloys and high-strength
casting
aluminum alloy material 1 based on national standards
Alloy Grade Alloy Code Thermal Tensile
Elongation after
Treatment Strength
Fracture Sc(%)
Conditions cyb/MPa
ZA1Cu5Mn ZL201 T5 335 4
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ZA1Cu5MnA ZL201A T5 390 8
ZAICu10 ZL202 T6 163
ZA1Cu4 ZL203 T5 225 3
ZA1Cu5MnCdA ZL204A T5 440 4
T5 440 7
ZA1Cu5MnCdVA ZL205A T6 470 3
T7 460 2
ZA1RE5Cu3Si2 ZL207 T1 175
A1Cu4AgMgMn (US) 201.0 T7 415 3
A1Cu4MgTi (US) 206.0 T4 275 8
Unknown components (RUS) BAJI10 Maximum
Worst 4 (corr.
except Al and Cu 500, minimum MINGb),
T4-T7
320
Optimum 12
(corr. MAXab )
Novel < 620
AlCuMnTiCrCdZrBRE high-toughness DEG C 450 5
1 < 72h
Detailed Description
Example: the high-strength casting aluminum alloy material comprises the
following components by weight percentage: 2.0% to 6.0% of Cu, 0.05% to 1.0%
of Mn,
0.01% to 0.5% of Ti, 0.01% to 0.2% of Cr, 0.01% to 0.4% of Cd, 0.01% to 0.25%
of Zr,
0.005% to 0.04% of B, 0.05% to 0.3% of Pr, Ce, La or mixed rare earth elements
RE and
the balancing amount of Al and trace impurities.
The total content of various rare earth elements in the mixed rare earth
elements
RE is not lower than 98%, and the content of Ce in the mixed rare earth
elements is 45%
by weight percentage. (Because the ionic radius and oxidation state of the
rare earth
elements are similar to those of other elements, the rare earth elements
generally coexist
with other elements in minerals.)
(1) adding a proper amount of aluminum ingots or molten aluminum liquid to a
melting furnace, heating until the aluminum ingots or molten aluminum liquid
is melted
down, and holding at 660 to 850 DEG C.
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(2) adding the alloying elements of Cu and Mn by formula ratio and evenly
stirring,
and then adding trace elements Ti, Cr, Cd, Zr, B, rare earth elements Pr, Ce,
La or RE and
evenly stirring.
(3) then, refining the alloy melt in the melting furnace, adding a refining
agent
(chlorine gas, hexachloroethane, manganese chloride and the like may be
selected as the
refining agent according to different working conditions) to the alloy melt
and evenly
stirring, wherein the melt should be refined in a closed environment as
possible, in order to
prevent the melt from water absorption and melting loss.
(4) pouring the alloy liquid out of the melting furnace, and carrying out the
online
treatment of filtering, degassing and deslagging.
(5) permanent mold casting.
(6) finally, carrying out solid-solution precipitation strengthening thermal
treatment at lower than 620 DEG C within 72 hours.
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