U.S. patent application number 17/672950 was filed with the patent office on 2022-06-02 for calcium-bearing magnesium and rare earth element alloy and method for manufacturing the same.
This patent application is currently assigned to The Boeing Company. The applicant listed for this patent is The Boeing Company. Invention is credited to Peng Dong, Haitao Jiang, Qiang Kang, Chaomin Liu, Peng Liu, Zhe Xu, Yun Zhang.
Application Number | 20220170139 17/672950 |
Document ID | / |
Family ID | |
Filed Date | 2022-06-02 |
United States Patent
Application |
20220170139 |
Kind Code |
A1 |
Jiang; Haitao ; et
al. |
June 2, 2022 |
CALCIUM-BEARING MAGNESIUM AND RARE EARTH ELEMENT ALLOY AND METHOD
FOR MANUFACTURING THE SAME
Abstract
A calcium-bearing magnesium and rare earth element alloy
consists essentially of, in mass percent, zinc (Zn): 1-3%; aluminum
(Al): 1-3%; calcium (Ca): 0.1-0.4%; gadolinium (Gd): 0.1-0.4%;
yttrium (Y): 0-0.4%; manganese (Mn): 0-0.2%; and balance magnesium
(Mg).
Inventors: |
Jiang; Haitao; (Beijing,
CN) ; Kang; Qiang; (Beijing, CN) ; Zhang;
Yun; (Beijing, CN) ; Liu; Peng; (Beijing,
CN) ; Dong; Peng; (Beijing, CN) ; Xu; Zhe;
(Beijing, CN) ; Liu; Chaomin; (Beijing,
CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
The Boeing Company |
Chicago |
IL |
US |
|
|
Assignee: |
The Boeing Company
Chicago
IL
|
Appl. No.: |
17/672950 |
Filed: |
February 16, 2022 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
16471168 |
Jun 19, 2019 |
11286544 |
|
|
PCT/US2017/050913 |
Sep 11, 2017 |
|
|
|
17672950 |
|
|
|
|
International
Class: |
C22C 23/02 20060101
C22C023/02; B21B 1/02 20060101 B21B001/02; B21B 27/02 20060101
B21B027/02; B21J 1/02 20060101 B21J001/02; C22C 1/03 20060101
C22C001/03; C22C 23/04 20060101 C22C023/04; C22F 1/06 20060101
C22F001/06 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 11, 2017 |
CN |
201710020396X |
Claims
1. A magnesium alloy consisting essentially of: about 1 to about 3
percent by weight zinc; about 1 to about 3 percent by weight
aluminum; about 0.1 to about 0.4 percent by weight calcium; about
0.1 to about 0.4 percent by weight gadolinium; zero to about 0.4
percent by weight yttrium; zero to about 0.2 percent by weight
manganese; and balance magnesium.
2. The magnesium alloy of claim 1 wherein the yttrium is present at
a non-zero quantity.
3. The magnesium alloy of claim 1 wherein the manganese is present
at a non-zero quantity.
4. The magnesium alloy of claim 1 wherein the yttrium is present at
a non-zero quantity and the manganese is present at a non-zero
quantity.
5. The magnesium alloy of claim 1 wherein the zinc is present at
about 1 to about 2 percent by weight.
6. The magnesium alloy of claim 1 wherein the aluminum is present
at about 1 to about 2 percent by weight.
7. The magnesium alloy of claim 1 wherein the calcium is present at
about 0.1 to about 0.2 percent by weight.
8. The magnesium alloy of claim 1 wherein the gadolinium is present
at about 0.1 to about 0.2 percent by weight.
9. The magnesium alloy of claim 1 wherein the yttrium is present at
about 0 to about 0.2 percent by weight.
10. The magnesium alloy of claim 1 wherein the manganese is present
at about 0 to about 0.2 percent by weight.
11. The magnesium alloy of claim 1 wherein: the zinc is present at
about 1 to about 2 percent by weight; the aluminum is present at
about 1 to about 2 percent by weight; the calcium is present at
about 0.1 to about 0.2 percent by weight; the gadolinium is present
at about 0.1 to about 0.2 percent by weight; the yttrium is present
at about 0 to about 0.2 percent by weight; and the manganese is
present at about 0 to about 0.2 percent by weight.
12. The magnesium alloy of claim 1 in a form of a sheet.
13. The magnesium alloy of claim 12 wherein the sheet is a solution
treated sheet.
14. The magnesium alloy of claim 13 wherein the sheet is an
annealed solution treated sheet.
15. The magnesium alloy of claim 14 wherein the sheet has a tensile
strength of at least about 245 MPa, an elongation to failure of at
least about 18 percent, and an IE value of at least about 4.5.
16. The magnesium alloy of claim 14 wherein the sheet has a tensile
strength of about 245 to about 280 MPa, an elongation to failure of
about 18 to about 32 percent, and an IE value of about 4.5 to about
7.0.
17. A sheet of magnesium alloy, the magnesium alloy consisting
essentially of: about 1 to about 3 percent by weight zinc; about 1
to about 3 percent by weight aluminum; about 0.1 to about 0.4
percent by weight calcium; about 0.1 to about 0.4 percent by weight
gadolinium; zero to about 0.4 percent by weight yttrium; zero to
about 0.2 percent by weight manganese; and balance magnesium.
18. An alloy sheet formed by a method comprising: weighting raw
materials to yield a magnesium alloy composition consisting
essentially of: about 1 to about 3 percent by weight zinc; about 1
to about 3 percent by weight aluminum; about 0.1 to about 0.4
percent by weight calcium; about 0.1 to about 0.4 percent by weight
gadolinium; zero to about 0.4 percent by weight yttrium; zero to
about 0.2 percent by weight manganese; and balance magnesium;
charging the raw materials into a vacuum induction melting furnace
to obtain a molten mass; casting the molten mass to yield a
magnesium alloy ingot; solid solution treating the magnesium alloy
ingot to yield a treated magnesium alloy ingot; hot rolling the
treated magnesium alloy ingot to yield a rolled material; cutting
defects from the rolled material to obtain an alloy sheet; and
annealing the alloy sheet.
19. The alloy sheet of claim 18 having a tensile strength of at
least about 245 MPa, an elongation to failure of at least about 18
percent, and an IE value of at least about 4.5.
20. The alloy sheet of claim 18 wherein the sheet has a tensile
strength of about 245 to about 280 MPa, an elongation to failure of
about 18 to about 32 percent, and an IE value of about 4.5 to about
7.0.
Description
PRIORITY
[0001] This application is a divisional of U.S. Ser. No. 16/471,168
filed on Jun. 19, 2019, which is the U.S. national phase entry of
Intl. Pat. App. No. PCT/US2017/050913 filed on Sep. 11, 2017, which
claims priority from Chinese Pat. App. No. 201710020396X filed on
Jan. 11, 2017. The entire contents of U.S. Ser. No. 16/471,168,
Intl. Pat. App. No. PCT/US2017/050913, and Chinese Pat. App. No.
201710020396X are incorporated herein by reference.
FIELD
[0002] This application relates to magnesium alloys and, more
particularly, to calcium-bearing magnesium and rare earth element
alloys and, even more particularly, to calcium-bearing magnesium
and rare earth element alloy sheets with superior room temperature
formability.
BACKGROUND
[0003] Magnesium alloys have a series of advantages, such as high
specific strength, high specific stiffness, good damping
performance and good magnetic-shielding performance. Furthermore,
magnesium alloys are readily recyclable and are commonly referred
to as the green engineering material in the 21st century.
Therefore, magnesium alloys may find particular utility in the
aerospace, automobile and electronic industries.
[0004] However, since magnesium alloys have a hexagonal close
packed structure and, therefore, less slip plane, the room
temperature formability of magnesium alloy sheets is poor, and to a
certain extent limits the application of magnesium alloy sheets.
The formability of a sheet is mainly characterized by its Erichsen
index (IE value). The Erichsen cupping test of a metallic sheet,
which combines the process features of tension and bulging, is an
important testing method for measuring the sheet formability and,
therefore, has become a standard test for measuring the formability
of a material. The higher the IE value of a metallic sheet, the
better the formability.
[0005] To a certain extent, some advanced preparation or processing
methods, such as equal channel angular pressing (ECAP), cross
rolling (CR), accumulative roll bonding (ARB), differential speed
rolling (DSR) and the like, could create a weak texture and improve
the formability of magnesium alloys. However, these methods have
low efficiencies in production compared with the conventional
rolling method.
[0006] Accordingly, those skilled in the art continue with research
and development efforts in the field of magnesium alloys.
SUMMARY
[0007] Disclosed are calcium-bearing magnesium and rare earth
element alloys with high formability and method for manufacturing
the same. The disclosed calcium-bearing magnesium and rare earth
element alloys may exhibit higher room temperature formability, as
well as excellent mechanical properties, better anti-flammability
and better corrosion resistance performance.
[0008] In one embodiment, the disclosed calcium-bearing magnesium
and rare earth element alloy consists essentially of, in mass
percent: [0009] Zinc (Zn): 1-3%; [0010] Aluminum (Al): 1-3%; [0011]
Calcium (Ca): 0.1-0.4%; [0012] Gadolinium (Gd): 0.1-0.4%; and
[0013] the balance is essentially magnesium (Mg) and
impurities.
[0014] In another embodiment, the disclosed calcium-bearing
magnesium and rare earth element alloy consists essentially of, in
mass percent: [0015] Zinc (Zn): 1-3%; [0016] Aluminum (Al): 1-3%;
[0017] Calcium (Ca): 0.1-0.4%; [0018] Gadolinium (Gd): 0.1-0.4%;
[0019] Yttrium (Y): 0-0.4%; [0020] Manganese (Mn): 0-0.2%; [0021]
the balance is essentially magnesium (Mg) and impurities.
[0022] In yet another embodiment, the disclosed calcium-bearing
magnesium and rare earth element alloy consists essentially of, in
mass percent: [0023] Zinc (Zn): 1-2%; [0024] Aluminum (Al): 1-2%;
[0025] Calcium (Ca): 0.1-0.2%; [0026] Gadolinium (Gd): 0.1-0.2%;
[0027] Yttrium (Y): 0.1-0.2%; [0028] Manganese (Mn): 0-0.2%; and
[0029] the balance is essentially magnesium (Mg) and
impurities.
[0030] Also disclosed are methods for manufacturing the disclosed
calcium-bearing magnesium and rare earth element alloys. In one
embodiment, the disclosed manufacturing method includes the
following steps:
[0031] Step 1: burdening: weighting raw materials according to the
designed composition, wherein the raw materials are magnesium ingot
of no less than 99.99 mass percent, aluminum ingot of no less than
99.9 mass percent, zinc ingot of no less than 99.99 mass percent,
master alloy of magnesium and calcium, master alloy of magnesium
and gadolinium, master alloy of magnesium and yttrium, and master
alloy of magnesium and manganese;
[0032] Step 2: melting and casting: charging the raw materials into
a vacuum induction melting furnace, and heating up to 750.degree.
C. for 10 to 15 minutes; then magnesium alloy ingot is produced via
semi continuous direct-chill casting or permanent mold casting;
[0033] Step 3: solid solution treatment: keeping the magnesium
alloy ingot obtained in Step 2 at the temperature of 300 to
450.degree. C. for 12 to 24 hours, and then air-cooling to room
temperature;
[0034] Step 4: preparation of sheet: subjecting the magnesium alloy
ingot after the solid solution treatment to hot rolling, or
extrusion followed by hot rolling, or isothermal forging followed
by hot rolling, or the like processes, and then cutting the defects
at the head, tail and edge to obtain a hot rolled magnesium alloy
sheet;
[0035] Step 5: annealing: subjecting the hot rolled sheet obtained
in Step 4 to annealing treatment at 300 to 350.degree. C. for 30 to
60 minutes.
[0036] Further, after the raw materials are completely melted
during melting and casting in Step 2, an electromagnetic,
mechanical or gas stirring is performed for about 5 to 10
minutes.
[0037] Further, the hot rolling process in the Step 4 is: the
magnesium alloy slab is hot rolled at 400 to 450.degree. C. in
multiple passes, wherein the total reduction in thickness by the
hot rolling is 90 percent, and the thickness reductions are within
15 percent for the first two passes, within 10 to 30 percent for
the other passes, and within 8 to 18 percent for the last two
passes. Between each pass, the slab is kept at required temperature
for 5 to 8 minutes.
[0038] Further, the extrusion followed by hot rolling process in
the Step 4 is: magnesium alloy billet is extruded into a magnesium
alloy plates (5 to 20 mm in thickness) or rod (.PHI.20 to 25 mm) at
250 to 350.degree. C., wherein the extrusion ratio is (16-23):1,
and the extrusion rate is 0.5 to 3 mm/s; Further, the extruded
magnesium alloy rod or sheet is hot rolled into a thin sheet with a
thickness of 1 mm at 400 to 450.degree. C., wherein the thickness
reductions are controlled within 20 percent for the first two
passes, within 15 to 35 percent for other passes, and within 10 to
25 percent for the last two passes. Between each pass, the work
piece is kept at required temperature for 5 to 8 minutes.
[0039] Further, the isothermal forging followed by hot rolling
process in the Step 4 is: magnesium alloy billet is isothermally
forged into thin round billet of a certain size at 300 to
350.degree. C., wherein the total reduction in thickness by forging
is about 75 to 85 percent, and the forging rate is 1 to 3 mm/s;
Further, the magnesium alloy billet after isothermal forging is hot
rolled into a thin plate with a thickness of 1 mm at 400 to
450.degree. C., wherein the thickness reductions are controlled
within 20 percent for the first two passes, within 15 to 35 percent
for the other passes, and within 10 to 25 percent for the last two
passes. Between each pass, the work piece is kept at required
temperature for 5 to 8 minutes.
[0040] The addition of Al and Zn may effectively improve the
mechanical properties of the magnesium alloy. The addition of Ca,
Gd and Y may not only improve the mechanical properties of the
magnesium alloy, but may also greatly improve the room temperature
formability of the magnesium alloy. The addition of an appropriate
amount of Mn may eliminate the impurity element Fe, which may
effectively purify the magnesium alloy melt, and improve the
corrosion-resistance of the magnesium alloy. At the same time, the
addition of Ca, Gd and Y may effectively increase the ignition
point of the magnesium alloy and improve the flame resistance
thereof. Finally, the disclosed preparation process, such as
rolling, extrusion followed by rolling, isothermal forging followed
by rolling, and the like, may further improve performance and
reduce costs.
BRIEF DESCRIPTION OF THE DRAWINGS
[0041] FIG. 1 is a microstructure photograph of the rolled and
annealed Mg.sub.96.6Al.sub.2Zn.sub.1Ca.sub.0.2Gd.sub.0.2 magnesium
alloy sheet (1 mm in thickness) of Example 1 disclosed herein;
[0042] FIG. 2 is a microstructure photograph of the rolled and
annealed Mg.sub.96.6Al.sub.2Zn.sub.1Ca.sub.0.2Gd.sub.0.2 magnesium
alloy sheet (5 mm in thickness) of Example 2 disclosed herein;
[0043] FIG. 3 is a microstructure photograph of the isothermally
forged, rolled and annealed
Mg.sub.96.6Al.sub.2Zn.sub.1Ca.sub.0.2Gd.sub.0.2 magnesium alloy
sheet (1 mm in thickness) of Example 3 disclosed herein;
[0044] FIG. 4 is a microstructure photograph of the rolled and
annealed Mg.sub.96.6Zn.sub.2Al.sub.1Ca.sub.0.2Gd.sub.0.2 magnesium
alloy sheet (1 mm in thickness) of Example 4 disclosed herein;
[0045] FIG. 5 is a microstructure photograph of the rolled and
annealed Mg.sub.96.6Zn.sub.2Al.sub.1Ca.sub.0.2Gd.sub.0.2 magnesium
alloy sheet (5 mm in thickness) of Example 5 disclosed herein;
[0046] FIG. 6 is a microstructure photograph of the extruded,
rolled and annealed Mg.sub.96.6Zn.sub.2Al.sub.1Ca.sub.0.2Gd.sub.0.2
magnesium alloy sheet (1 mm in thickness) of Example 6 disclosed
herein;
[0047] FIG. 7 is a microstructure photograph of the isothermally
forged, rolled and annealed
Mg.sub.96.6Zn.sub.2Al.sub.1Ca.sub.0.2Gd.sub.0.2 magnesium alloy
sheet (1 mm in thickness) of Example 7 disclosed herein;
[0048] FIG. 8 is a microstructure photograph of the rolled and
annealed
Mg.sub.96.4Zn.sub.2Al.sub.1Ca.sub.0.2Gd.sub.0.1Y.sub.0.1Mn.sub.0.2
magnesium alloy sheet (1 mm in thickness) of Example 8 disclosed
herein;
[0049] FIG. 9 is a microstructure photograph of the rolled and
annealed Mg.sub.95Al.sub.3Zn.sub.1Ca.sub.0.4Gd.sub.0.4Mn.sub.0.2
magnesium alloy sheet (1 mm in thickness) of Example 9 disclosed
herein;
[0050] FIG. 10 is a microstructure photograph of the rolled and
annealed Mg.sub.95Al.sub.3Zn.sub.1Ca.sub.0.4Y.sub.0.4Mn.sub.0.2
magnesium alloy sheet (1 mm in thickness) of Example 10 disclosed
herein; and
[0051] FIG. 11 is a microstructure photograph of the rolled and
annealed Mg.sub.95Zn.sub.3Al.sub.1Ca.sub.0.3Gd.sub.0.3Mn.sub.0.2
magnesium alloy sheet (1 mm in thickness) of Example 11 disclosed
herein.
DETAILED DESCRIPTION
[0052] It has now been discovered that optimizing a magnesium alloy
composition by adding alkaline earth and rare earth elements that
can weaken the basal plane texture of magnesium alloys, in
combination with conventional rolling, is an economical and
effective way to improve the room temperature formability of
magnesium alloys.
[0053] Furthermore, since magnesium is very reactive with a
standard electrode potential of -2.37V, which is the lowest in all
the structural metals, it acts as an anode relative to other
structural metals and easily reacts with a second phase or impurity
elements to cause galvanic corrosion. The oxidative films naturally
formed on the surfaces of magnesium alloys are porous, which could
not provide sufficient protection for the metal matrix and,
therefore, magnesium alloys are not suitable for most of the
corrosive environments. This poor corrosion resistance seriously
restricts the application of magnesium alloys. However, without
being limited to any particular theory, it is believed that
addition of rare earth elements to magnesium alloys, as disclosed
herein, can effectively improve the corrosion resistance of
magnesium alloys.
[0054] Still furthermore, magnesium alloys can be easy to ignite,
which leads to poor anti-flammability. However, without being
limited to any particular theory, it is believed that addition of
rare earth elements, as disclosed herein, can improve the
anti-flammability of magnesium alloys due to their affinity for
oxygen and the formed REO film could effectively prevent the
continuous burning of magnesium alloys. Additionally, rare earth
elements and alkaline earth metal elements have significant effect
on increasing the ignition point of magnesium alloys.
[0055] Thus, the optimization of alloy composition by the addition
of alkaline earth and rare earth metal elements, further in
combination with the optimized extrusion, rolling, isothermal
forging process, etc., may not only improve the mechanical
properties, the room temperature formability, flame resistance,
corrosion resistance and like properties of magnesium alloys, but
may also have a lower cost compared to equal channel angular
pressing, differential speed rolling and like preparation
processes.
[0056] In one embodiment, the disclosed calcium-bearing magnesium
and rare earth element alloy has the composition shown in Table
1.
TABLE-US-00001 TABLE 1 Element Quantity Zinc 1-3 wt % Aluminum 1-3
wt % Calcium 0.1-0.4 wt % Gadolinium 0.1-0.4 wt % Yttrium 0-0.4 wt
% Manganese 0-0.2 wt % Magnesium Balance
[0057] While magnesium forms the balance (essentially) of the
calcium-bearing magnesium and rare earth element alloy of Table 1,
those skilled in the art will appreciate that impurities may be
present.
[0058] The calcium-bearing magnesium and rare earth element alloy
of Table 1, in sheet form, has a tensile strength of 245.0 to 280.0
MPa, an elongation to failure of 18.0 to 32.0 percent, and an IE
value of 4.5 to 7.0.
[0059] In another embodiment, the disclosed calcium-bearing
magnesium and rare earth element alloy has the composition shown in
Table 2.
TABLE-US-00002 TABLE 2 Element Quantity Zinc 1-2 wt % Aluminum 1-2
wt % Calcium 0.1-0.2 wt % Gadolinium 0.1-0.2 wt % Yttrium 0-0.2 wt
% Manganese 0-0.2 wt % Magnesium Balance
[0060] While magnesium forms the balance (essentially) of the
calcium-bearing magnesium and rare earth element alloy of Table 2,
those skilled in the art will appreciate that impurities may be
present.
[0061] Aluminum at 1 to 2 mass percent may effectively strengthen
the magnesium alloy, improve the rollability and improve the
corrosion resistance. Zinc at 1 to 2 mass percent may have a
function of solid solution strengthening, and may form a second
phase particle with elements Mg, Gd, etc., and may play a role of
precipitation strengthening. Calcium at 0.1 to 0.2 mass percent not
only could refine grain and strengthen the magnesium alloy, but
also may improve the annealed texture of the alloy. Gadolinium at
0.1 to 0.2 mass percent may enhance the strength and ductility of
the magnesium alloy, weaken the basal plane texture, and improve
the formability of the magnesium alloy sheet. Yttrium at 0 to 0.2
mass percent may effectively enhance the strength of the magnesium
alloy sheet. Manganese at 0 to 0.2 mass percent may improve the
corrosion resistance of the magnesium alloy. A low content of alloy
elements, in particular the low content of rare earth elements, in
combination with the conventional preparation process, greatly
reduces the preparation cost of the disclosed magnesium alloy.
[0062] In one embodiment, the disclosed calcium-bearing magnesium
and rare earth element alloys may be manufactured as follows.
[0063] Step 1: burdening: weighting raw materials according to the
designed composition, wherein the raw materials are magnesium ingot
of no less than 99.99 mass percent, aluminum ingot of no less than
99.9 mass percent, zinc ingot of no less than 99.99 mass percent,
master alloy of magnesium and calcium, master alloy of magnesium
and gadolinium, master alloy of magnesium and yttrium, and master
alloy of magnesium and manganese.
[0064] Step 2: melting and casting: charging the raw materials into
a vacuum induction melting furnace, and heating up to 750.degree.
C. for 10 to 15 minutes; then the magnesium alloy ingot is produced
via semi-continuous direct-chill casting or permanent mold
casting.
[0065] Step 3: solid solution treatment: keeping the magnesium
alloy ingot obtained in Step 2 at a temperature of 300 to
450.degree. C. for 12 to 24 hours, and then air-cooling to room
temperature.
[0066] Step 4: preparation of sheet: subjecting the magnesium alloy
ingot after the solid solution treatment to hot rolling, or
extrusion followed by hot rolling, or isothermal forging followed
by hot rolling, or like processes, and then cutting the defects at
the head, tail and edge to obtain a hot rolled magnesium alloy
sheet with good shape.
[0067] Step 5: annealing: subjecting the hot rolled sheet obtained
in Step 4 to annealing treatment at 350.degree. C. for 30 to 60
minutes.
EXAMPLES
Example 1
[0068] Mg.sub.96.6Al.sub.2Zn.sub.1Ca.sub.0.2Gd.sub.0.2 magnesium
alloy sheet (1 mm in thickness): weighting raw materials according
to the designed composition, wherein the raw materials were:
magnesium ingot of 99.99 mass percent, aluminum ingot of 99.9 mass
percent, zinc ingot of 99.99 mass percent, master alloy of
magnesium and calcium of 30 mass percent, and master alloy of
magnesium and gadolinium of 30 mass percent. The burdening was
carried out, according to the nominal composition of the magnesium
alloy, and also in consideration of the thermal loss of
elements.
[0069] Melting and casting of
Mg.sub.96.6Al.sub.2Zn.sub.1Ca.sub.0.2Gd.sub.0.2. The raw materials
were charged into a crucible in a vacuum induction melting furnace
and the melting furnace was vacuumed and heated under inert
atmosphere. The temperature was increased to 750.degree. C. and
maintained for 15 minutes. After the raw materials were completely
melted, the melts were electromagnetically stirred for about 8
minutes. Finally, the melts were poured into the graphite crucible
and placed in the air to cool, giving an ingot.
[0070] Solid solution treatment of
Mg.sub.96.6Al.sub.2Zn.sub.1Ca.sub.0.2Gd.sub.0.2. The magnesium
alloy ingot was placed in a resistance furnace and kept at
450.degree. C. for 12 hours, and then air-cooled to room
temperature.
[0071] Hot rolling of
Mg.sub.96.6Al.sub.2Zn.sub.1Ca.sub.0.2Gd.sub.0.2. The magnesium
alloy ingot after the solid solution treatment was wire-cut into a
slab having a thickness of 10 mm, and then the surface of the slab
was polished for hot rolling. The specific hot rolling process was
as follows: the slab was kept at 450.degree. C. for about 30
minutes and then was hot rolled. The total reduction in thickness
by hot rolling was 90 percent, that is, the final thickness of
sheet was 1 mm. The thickness reductions of the first two passes
was 8 percent and 10 percent, respectively, and the thickness
reductions of other passes were controlled within 10 to 30 percent,
wherein the thickness reductions of the last two passes were 15
percent and 10 percent, respectively. Due to the fast heat
dissipation of the magnesium alloy, in order to stabilize the
temperature during the rolling, the sample was kept at 450.degree.
C. for 5 minutes in the resistance furnace after each rolling pass.
After the hot rolling, the defects at head, tail and edge of the
hot rolled sheet were cut to obtain a hot rolled magnesium alloy
sheet.
[0072] Annealing of the hot rolled
Mg.sub.96.6Al.sub.2Zn.sub.1Ca.sub.0.2Gd.sub.0.2 sheet. The finally
rolled sheet was placed into a resistance furnace and kept at
350.degree. C. for 60 minutes.
[0073] The Mg.sub.96.6Al.sub.2Zn.sub.1Ca.sub.0.2Gd.sub.0.2 sheet
has a yield strength of 231 MPa, a tensile strength of 260 MPa, an
elongation to failure of 21 percent and an IE value of 5.87, and
has an average corrosion rate of 0.2987 mg/cm.sup.2/d after 5 days
salt spray test with 3.5 percent NaCl neutral solution (pH=7) at
25.degree. C. The microstructure photograph of this sheet after
rolling and annealing is shown in FIG. 1.
Example 2
[0074] Mg.sub.96.6Al.sub.2Zn.sub.1Ca.sub.0.2Gd.sub.0.2 magnesium
alloy sheet (5 mm in thickness): the same burdening, melting and
casting, and solid solution treatment processes of
Mg.sub.96.6Al.sub.2Zn.sub.1Ca.sub.0.2Gd.sub.0.2 as in Example 1 was
carried out.
[0075] Hot rolling of
Mg.sub.96.6Al.sub.2Zn.sub.1Ca.sub.0.2Gd.sub.0.2. The magnesium
alloy ingot after the solid solution treatment was wire-cut into a
slab having a thickness of 30 mm, and then the surface of the slab
was polished for hot rolling. The specific hot rolling process was
as follows: the slab was kept at 450.degree. C. for about 50
minutes and then was hot rolled. The total thickness reduction by
hot rolling was 83.3 percent, that is, the final thickness of the
sheet was 5 mm. The thickness reductions of the first two passes
were 8 percent and 10 percent, respectively, and the thickness
reductions of other passes were controlled within 10 to 30 percent,
wherein the thickness reductions of the last two passes were 15
percent and 10 percent, respectively. Due to the fast heat
dissipation of the magnesium alloy, in order to stabilize the
temperature during the rolling, the sample was kept at 450.degree.
C. for 5 to 8 minutes in the resistance furnace after each rolling
pass. After the hot rolling, the defects at head, tail and edges of
the hot rolled sheet were cut to obtain a hot rolled magnesium
alloy sheet with good shape.
[0076] Annealing of the hot rolled
Mg.sub.96.6Al.sub.2Zn.sub.1Ca.sub.0.2Gd.sub.0.2 sheet. The finally
rolled sheet was placed into a resistance furnace and kept at
350.degree. C. for 60 minutes.
[0077] The Mg.sub.96.6Al.sub.2Zn.sub.1Ca.sub.0.2Gd.sub.0.2 sheet
has a yield strength of 167 MPa, a tensile strength of 245 MPa, and
an elongation to failure of 18 percent. The microstructure
photograph of this sheet after rolling and annealing is shown in
FIG. 2.
Example 3
[0078] Mg.sub.96.6Al.sub.2Zn.sub.1Ca.sub.0.2Gd.sub.0.2 magnesium
alloy sheet (1 mm in thickness): the same burdening, melting and
casting, and solid solution treatment processes of
Mg.sub.96.6Al.sub.2Zn.sub.1Ca.sub.0.2Gd.sub.0.2 as in Example 1 was
carried out.
[0079] Isothermal forging of
Mg.sub.96.6Al.sub.2Zn.sub.1Ca.sub.0.2Gd.sub.0.2. The magnesium
ingot after the solid solution treatment was cut into a cylindrical
billet (.PHI. 140 mm.times.110 mm), and then the billet was
isothermally forged into a round billet having a thickness of 20 mm
at 350.degree. C., wherein the forging rate was 1 mm/s, and the
total reduction by forging was about 80 percent.
[0080] Hot rolling of
Mg.sub.96.6Al.sub.2Zn.sub.1Ca.sub.0.2Gd.sub.0.2. The round billet
obtained by isothermal forging was wire-cut into a slab having a
thickness of 10 mm, and then the surface of the slab was polished
for hot rolling. The specific hot rolling process was as follows:
the slab was kept at 400.degree. C. for about 30 minutes and then
was hot rolled. The total reduction in thickness by hot rolling was
95 percent, that is, the final thickness of sheet was 1 mm. The
thickness reductions of the first two passes were 10 percent and 15
percent, respectively, and thickness reductions of other passes
were controlled within 15 to 35 percent, wherein the thickness
reductions of the last two passes were 20 percent and 15 percent,
respectively. Due to the fast heat dissipation of the magnesium
alloy, in order to stabilize the temperature during the rolling,
the sample was kept at 450.degree. C. for 5 minutes in the
resistance furnace after each rolling pass. After the hot rolling,
the defects at head, tail and edges of the hot rolled sheet were
cut in order to obtain a hot rolled magnesium alloy sheet.
[0081] Annealing of the hot rolled
Mg.sub.96.6Al.sub.2Zn.sub.1Ca.sub.0.2Gd.sub.0.2 sheet. Finally, the
rolled sheet was placed into a resistance furnace and kept at
350.degree. C. for 60 minutes.
[0082] Mg.sub.96.6Al.sub.2Zn.sub.1Ca.sub.0.2Gd.sub.0.2 sheet has a
yield strength of 231 MPa, a tensile strength of 249 MPa, an
elongation to failure of 23 percent and an IE value of 5.51. The
microstructure photograph of this sheet after rolling and annealing
is shown in FIG. 3.
Example 4
[0083] Mg.sub.96.6Zn.sub.2Al.sub.1Ca.sub.0.2Gd.sub.0.2 sheet (1 mm
in thickness): weighting raw materials according to the designed
composition, wherein the raw materials were: magnesium ingot of
99.99 mass percent, aluminum ingot of 99.9 mass percent, zinc ingot
of 99.99 mass percent, master alloy of magnesium and calcium of 30
mass percent, and master alloy of magnesium and gadolinium of 30
mass percent. The burdening was carried out, according to the
nominal composition of the magnesium alloy, and also in
consideration of the thermal loss of each of elements.
[0084] Melting and casting of
Mg.sub.96.6Zn.sub.2Al.sub.1Ca.sub.0.2Gd.sub.0.2. The raw materials
were charged into a crucible in a vacuum induction melting furnace
and the melting furnace was vacuumed and heated under inert
atmosphere. The temperature was increased to 750.degree. C. and
maintained for 15 minutes. After the raw materials were completely
melted, the melts were electromagnetically stirred for about 8
minutes. Finally, the melts were poured into the graphite crucible
and placed in the air to cool, giving an ingot.
[0085] Solid solution treatment of
Mg.sub.96.6Zn.sub.2Al.sub.1Ca.sub.0.2Gd.sub.0.2. The magnesium
alloy ingot was placed in a resistance furnace and kept at
300.degree. C. for 20 hours, and then air-cooled to room
temperature.
[0086] Hot rolling of
Mg.sub.96.6Zn.sub.2Al.sub.1Ca.sub.0.2Gd.sub.0.2. The magnesium
alloy ingot after the solid solution treatment was wire-cut into a
slab having a thickness of 10 mm, and then the surface of the slab
was polished for hot rolling. The specific hot rolling process was
as follows: the slab was kept at 400.degree. C. for about 30
minutes and then was hot rolled. The total thickness reduction by
hot rolling was 90 percent, that is, the final thickness of sheet
was 1 mm. The thickness reductions of the first two passes were 8
percent and 10 percent, respectively, and the thickness reductions
of the other passes were controlled within about 10 to 30 percent,
wherein the thickness reductions of the last two passes were 15
percent and 10 percent, respectively. Due to the fast heat
dissipation of the magnesium alloy, in order to stabilize the
rolling temperature, the sample was kept at 400.degree. C. for 5
minutes in the resistance furnace after each rolling pass. After
the hot rolling, the defects at head, tail and edges of the hot
rolled sheet were cut to obtain a hot rolled magnesium alloy sheet
with good shape.
[0087] Annealing of the hot rolled
Mg.sub.96.6Zn.sub.2Al.sub.1Ca.sub.0.2Gd.sub.0.2 sheet. The finally
rolled sheet was placed into a resistance furnace and kept at
350.degree. C. for 45 minutes.
[0088] The Mg.sub.96.6Zn.sub.2Al.sub.1Ca.sub.0.2Gd.sub.0.2 sheet
has a yield strength of 145 MPa, a tensile strength of 245 MPa, an
elongation to failure of 26 percent and an IE value of 6.38. The
microstructure photograph of this sheet after rolling and annealing
is shown in FIG. 4. This sheet has an average corrosion rate of
0.2943 mg/cm.sup.2/d of 5 days, in 3.5 percent NaCl neutral
solution (pH=7) at 25.degree. C. when the salt spray falling rate
is 0.013 ml/cm.sup.2/h.
Example 5
[0089] Mg.sub.96.6Zn.sub.2Al.sub.1Ca.sub.0.2Gd.sub.0.2 sheet (5 mm
in thickness): the same burdening, melting and casting, and solid
solution treatment processes of
Mg.sub.96.6Zn.sub.2Al.sub.1Ca.sub.0.2Gd.sub.0.2 as in Example 4 was
carried out.
[0090] Hot rolling of
Mg.sub.96.6Zn.sub.2Al.sub.1Ca.sub.0.2Gd.sub.0.2. The magnesium
alloy ingot after the solid solution treatment was wire-cut into a
slab having a thickness of 30 mm, and then the surface of the slab
was polished for hot rolling. The specific hot rolling process was
as follows: the slab was kept at 400.degree. C. for about 30
minutes and then was hot rolled. The total thickness reduction by
hot rolling was 83.3 percent, that is, the final thickness of sheet
was 5 mm. The thickness reductions of the first two passes were 8
percent and 10 percent, respectively, and the thickness reductions
of the other passes were controlled within about 10 to 30 percent,
wherein the thickness reductions of the last two passes were 15
percent and 10 percent, respectively. Due to the fast heat
dissipation of the magnesium alloy, in order to stabilize the
temperature during the rolling, the sample was kept at 400.degree.
C. for 5 to 8 minutes in the resistance furnace after each rolling
pass was complete. After the hot rolling was complete, the defects
at head, tail and edges of the hot rolled sheet were cut to obtain
a hot rolled magnesium alloy sheet with good shape.
[0091] Annealing of the hot rolled
Mg.sub.96.6Zn.sub.2Al.sub.1Ca.sub.0.2Gd.sub.0.2 sheet. The finally
rolled sheet was placed into a resistance furnace and kept at
350.degree. C. for 45 minutes.
[0092] The Mg.sub.96.6Zn.sub.2Al.sub.1Ca.sub.0.2Gd.sub.0.2 sheet
has a yield strength of 227 MPa, a tensile strength of 250 MPa, and
an elongation to failure of 23 percent. The microstructure
photograph of this sheet after rolling and annealing is shown in
FIG. 5.
Example 6
[0093] Mg.sub.96.6Zn.sub.2Al.sub.1Ca.sub.0.2Gd.sub.0.2 sheet (1 mm
in thickness): the same burdening, melting and casting, and solid
solution treatment processes of
Mg.sub.96.6Zn.sub.2Al.sub.1Ca.sub.0.2Gd.sub.0.2 as in Example 4 was
carried out.
[0094] Extrusion of
Mg.sub.96.6Zn.sub.2Al.sub.1Ca.sub.0.2Gd.sub.0.2. The magnesium
alloy ingot after the solid solution treatment was wire-cut into a
cylindrical billet (.PHI. 120 mm.times.110 mm), and then the billet
was extruded into a magnesium alloy sheet (90.times.6 mm) at
250.degree. C., wherein the extrusion ratio was about 20:1, and the
extrusion rate was 1 mm/s.
[0095] Hot rolling of
Mg.sub.96.6Zn.sub.2Al.sub.1Ca.sub.0.2Gd.sub.0.2. The magnesium
alloy slab after the extrusion was polished for hot rolling. The
specific hot rolling process was as follows: the slab was kept at
400.degree. C. for about 30 minutes and then was hot rolled. The
total thickness reduction by hot rolling was 83 percent, that is,
the final thickness of sheet was 1 mm. The thickness reductions of
the first two passes were 10 percent and 15 percent, respectively,
and the thickness reductions of other passes were controlled within
about 15 to 30 percent, wherein the thickness reductions of the
last two passes were 20 percent and 15 percent, respectively. Due
to the fast heat dissipation of the magnesium alloy, in order to
stabilize the temperature during the rolling, the sample was kept
at 400.degree. C. for 5 minutes in the resistance furnace after
each rolling pass was complete. After the hot rolling was complete,
the defects at head, tail and edges of the hot rolled sheet were
cut to obtain a hot rolled magnesium alloy sheet with good
shape.
[0096] Annealing of the hot rolled
Mg.sub.96.6Zn.sub.2Al.sub.1Ca.sub.0.2Gd.sub.0.2 sheet. The finally
rolled sheet was placed into a resistance furnace and kept at
350.degree. C. for 60 minutes.
[0097] The Mg.sub.96.6Zn.sub.2Al.sub.1Ca.sub.0.2Gd.sub.0.2 sheet
has a yield strength of 184.8 MPa, a tensile strength of 252.6 MPa,
an elongation to failure of 31.4 percent. The microstructure
photograph of this sheet after rolling and annealing is shown in
FIG. 6.
Example 7
[0098] Mg.sub.96.6Zn.sub.2Al.sub.1Ca.sub.0.2Gd.sub.0.2 sheet (1 mm
in thickness): the same burdening, melting and casting, and solid
solution treatment processes of
Mg.sub.96.6Zn.sub.2Al.sub.1Ca.sub.0.2Gd.sub.0.2 as in Example 4 was
carried out.
[0099] Isothermal forging of
Mg.sub.96.6Zn.sub.2Al.sub.1Ca.sub.0.2Gd.sub.0.2. The magnesium
ingot after the solid solution treatment was cut into a cylindrical
billet (.PHI. 140 mm.times.110 mm), and then the billet was
isothermally forged into a round billet having a thickness of 20 mm
at 350.degree. C., wherein the forging rate was 1 mm/s, and the
total reduction by forging was about 80 percent.
[0100] Hot rolling of
Mg.sub.96.6Zn.sub.2Al.sub.1Ca.sub.0.2Gd.sub.0.2. The round billet
obtained by isothermal forging was wire-cut into a slab having a
thickness of 10 mm, and then the surface of the slab was polished
for hot rolling. The specific hot rolling process was as follows:
the slab was kept at 400.degree. C. for about 30 minutes and then
was hot rolled. The total thickness reduction by hot rolling was 95
percent, that is, the final thickness of sheet was 1 mm. The
thickness reductions of the first two passes were 15 percent and 20
percent, respectively, and the thickness reductions of other passes
were controlled within 15%-35%, wherein the thickness reductions of
the last two passes were 20 percent and 15 percent, respectively.
Due to the fast heat dissipation of the magnesium alloy, in order
to stabilize the temperature during the rolling, the sample was
kept at 400.degree. C. for 5 minutes in the resistance furnace
after each rolling pass. After the hot rolling, the defects at
head, tail and edges of the hot rolled sheet were cut to obtain a
hot rolled magnesium alloy sheet with good shape.
[0101] Annealing of the hot rolled
Mg.sub.96.6Zn.sub.2Al.sub.1Ca.sub.0.2Gd.sub.0.2 sheet. The finally
rolled sheet was placed into a resistance furnace and kept at
350.degree. C. for 60 minutes.
[0102] The Mg.sub.96.6Zn.sub.2Al.sub.1Ca.sub.0.2Gd.sub.0.2 sheet
has a yield strength of 170 MPa, a tensile strength of 255 MPa, an
elongation to failure of 24 percent and an IE value of 5.62. The
microstructure photograph of this sheet after rolling and annealing
is shown in FIG. 7.
Example 8
[0103]
Mg.sub.96.4Zn.sub.2Al.sub.1Ca.sub.0.2Gd.sub.0.1Y.sub.0.1Mn.sub.0.2
magnesium alloy sheet (1 mm in thickness): weighting raw materials
according to the mass percent of composition, wherein the raw
materials were: magnesium ingot of 99.99 mass percent, aluminum
ingot of 99.9 mass percent, zinc ingot of 99.99 mass percent,
master alloy of magnesium and calcium of 30 mass percent, and
master alloy of magnesium and gadolinium of 30 mass percent, master
alloy of magnesium and manganese of 30 mass percent. The burdening
was carried out, according to the nominal composition of the
magnesium alloy, and also in consideration of the thermal loss of
each of elements.
[0104] Melting and casting of
Mg.sub.96.4Zn.sub.2Al.sub.1Ca.sub.0.2Gd.sub.0.1Y.sub.0.1Mn.sub.0.2.
The raw materials were charged into a crucible in a vacuum
induction melting furnace and the melting furnace was vacuumed and
heated under inert atmosphere. The temperature was increased to
750.degree. C. and maintained for 15 minutes. After the raw
materials were completely melted, the melts were
electromagnetically stirred for about 8 minutes. Finally, the melts
were poured into the graphite crucible and placed in the air to
cool, giving an ingot.
[0105] Solid solution treatment of
Mg.sub.96.4Zn.sub.2Al.sub.1Ca.sub.0.2Gd.sub.0.1Y.sub.0.1Mn.sub.0.2.
The magnesium alloy ingot was placed in a resistance furnace and
kept at 300.degree. C. for 12 hours, and then air-cooled to room
temperature.
[0106] Hot rolling of
Mg.sub.96.4Zn.sub.2Al.sub.1Ca.sub.0.2Gd.sub.0.1Y.sub.0.1Mn.sub.0.2.
The magnesium alloy ingot after the solid solution treatment was
wire-cut into a slab having a thickness of 10 mm, and then the
surface of the slab was polished for hot rolling. The specific hot
rolling process was as follows: the slab was kept at 400.degree. C.
for about 30 minutes and then was hot rolled. The total thickness
reduction by hot rolling was 90 percent, that is, the final
thickness of sheet was 1 mm. The thickness reductions of the first
two passes were 8 percent and 10 percent, respectively, and the
thickness reductions of other passes were controlled within 10 to
30 percent, wherein the thickness reductions of the last two passes
were 15 percent and 10 percent, respectively. Due to the fast heat
dissipation of the magnesium alloy, in order to stabilize the
temperature during the rolling, the sample was kept at 400.degree.
C. for 5 minutes in the resistance further after each rolling pass.
After the hot rolling, the defects at head, tail and edges of the
hot rolled sheet were cut to obtain a hot rolled magnesium alloy
sheet with good shape.
[0107] Annealing of the hot rolled
Mg.sub.96.4Zn.sub.2Al.sub.1Ca.sub.0.2Gd.sub.0.1Y.sub.0.1Mn.sub.0.2
sheet. The finally rolled sheet was placed into a resistance
furnace and kept at 350.degree. C. for 60 minutes.
[0108] The
Mg.sub.96.4Zn.sub.2Al.sub.1Ca.sub.0.2Gd.sub.0.1Y.sub.0.1Mn.sub.-
0.2 has a yield strength of 202.8 MPa, a tensile strength of 265.6
MPa, an elongation to failure of 26.6 percent and an IE value of
5.10. The microstructure photograph of this sheet after rolling and
annealing is shown in FIG. 8.
Example 9
[0109] Mg.sub.95Al.sub.3Zn.sub.1Ca.sub.0.4Gd.sub.0.4Mn.sub.0.2
magnesium alloy sheet (1 mm in thickness): weighting raw materials
according to the mass percent of composition, wherein the raw
materials were: magnesium ingot of 99.99 mass percent, aluminum
ingot of 99.9 mass percent, zinc ingot of 99.99 mass percent,
master alloy of magnesium and calcium of 30 mass percent, master
alloy of magnesium and gadolinium of 30 mass percent, and master
alloy of magnesium and manganese of 30 mass percent. The burdening
was carried out, according to the nominal composition of the
magnesium alloy, and also in consideration of the thermal loss of
each of elements.
[0110] Melting and casting of
Mg.sub.95Al.sub.3Zn.sub.1Ca.sub.0.4Gd.sub.0.4Mn.sub.0.2. The raw
materials were charged into a crucible in a vacuum induction
melting furnace and the melting furnace was vacuumed and heated
under inert atmosphere. The temperature was increased to
750.degree. C. and maintained for 15 minutes. After the raw
materials were completely melted, the melts were
electromagnetically stirred for about 10 minutes. Finally, the
melts were poured into the graphite crucible and placed in the air
to cool, giving an ingot.
[0111] Solid solution treatment of
Mg.sub.95Al.sub.3Zn.sub.1Ca.sub.0.4Gd.sub.0.4Mn.sub.0.2. The
magnesium alloy ingot was placed in a resistance furnace and kept
at 450.degree. C. for 12 hours, and then air-cooled to room
temperature.
[0112] Hot rolling of
Mg.sub.95Al.sub.3Zn.sub.1Ca.sub.0.4Gd.sub.0.4Mn.sub.0.2. The
magnesium alloy ingot after the solid solution treatment was
wire-cut into a slab having a thickness of 10 mm, and then the
surface of the slab was polished for hot rolling. The specific hot
rolling process was as follows: the slab was kept at 400.degree. C.
for about 30 minutes and then was hot rolled. The total thickness
reduction by hot rolling was 90 percent, that is, the final
thickness of sheet was 1 mm. The thickness reductions of the first
two passes were 8 percent and 10 percent, respectively, and the
thickness reductions of other passes were controlled within 10 to
30 percent, wherein thickness reductions of the last two passes
were 15 percent and 10 percent, respectively. Due to the fast heat
dissipation of the magnesium alloy, in order to stabilize the
temperature during the rolling, the sample was kept at 400.degree.
C. for 8 minutes in the resistance further after each rolling pass.
After the hot rolling, the defects at head, tail and edges of the
hot rolled sheet were cut to obtain a hot rolled magnesium alloy
sheet with good shape.
[0113] Annealing of the hot rolled
Mg.sub.95Al.sub.3Zn.sub.1Ca.sub.0.4Gd.sub.0.4Mn.sub.0.2 sheet. The
finally rolled sheet was placed into a resistance furnace and kept
at 350.degree. C. for 60 minutes.
[0114] The Mg.sub.95Al.sub.3Zn.sub.1Ca.sub.0.4Gd.sub.0.4Mn.sub.0.2
sheet has a yield strength of 200 MPa, a tensile strength of 275
MPa, an elongation to failure of 20 percent and an IE value of 5.0.
The microstructure photograph of this sheet after rolling and
annealing is shown in FIG. 9.
Example 10
[0115] Mg.sub.95Al.sub.3Zn.sub.1Ca.sub.0.4Y.sub.0.4Mn.sub.0.2
magnesium alloy sheet (1 mm in thickness): weighting raw materials
according to the mass percent of composition, wherein the raw
materials were: magnesium ingot of 99.99 mass percent, aluminum
ingot of 99.9 mass percent, zinc ingot of 99.99 mass percent,
master alloy of magnesium and calcium of 30 mass percent, master
alloy of magnesium and yttrium of 30 mass percent, and master alloy
of magnesium and manganese of 30 mass percent. The burdening was
carried out, according to the nominal composition of the magnesium
alloy, and also in consideration of the thermal loss of each of
elements.
[0116] Melting and casting of
Mg.sub.95Al.sub.3Zn.sub.1Ca.sub.0.4Y.sub.0.4Mn.sub.0.2. The raw
materials were charged into a crucible in a vacuum induction
melting furnace and the melting furnace was vacuumed and heated
under inert atmosphere. The temperature was increased to
750.degree. C. and maintained for 15 minutes. After the raw
materials were completely melted, the melts were
electromagnetically stirred for about 10 minutes. Finally, the
melts were poured into the graphite crucible and placed in the air
to cool, giving an ingot.
[0117] Solid solution treatment of
Mg.sub.95Al.sub.3Zn.sub.1Ca.sub.0.4Y.sub.0.4Mn.sub.0.2. The
magnesium alloy ingot was placed in a resistance furnace and kept
at 450.degree. C. for 15 hours, and then air-cooled to room
temperature.
[0118] Hot rolling of
Mg.sub.95Al.sub.3Zn.sub.1Ca.sub.0.4Y.sub.0.4Mn.sub.0.2. The
magnesium alloy ingot after the solid solution treatment was
wire-cut into a slab having a thickness of 10 mm, and then the
surface of the slab was polished for hot rolling. The specific hot
rolling process was as follows: the slab was kept at 400.degree. C.
for about 30 minutes and then was hot rolled. The total thickness
reduction by hot rolling was 90 percent, that is, the final
thickness of sheet was 1 mm. The thickness reductions of the first
two passes were 8 percent and 10 percent, respectively, and the
thickness reductions of the other passes were controlled within 10
to 30 percent, wherein the thickness reductions of the last two
passes were 15 percent and 10 percent, respectively. Due to the
fast heat dissipation of the magnesium alloy, in order to stabilize
the rolling temperature, the sample was kept at 400.degree. C. for
8 minutes in the resistance further after each rolling pass. After
the hot rolling, the defects at head, tail and edges of the hot
rolled sheet were cut to obtain a hot rolled magnesium alloy sheet
with good shape.
[0119] Annealing of the hot rolled
Mg.sub.95Al.sub.3Zn.sub.1Ca.sub.0.4Y.sub.0.4Mn.sub.0.2 sheet. The
finally rolled sheet was placed into a resistance furnace and kept
at 350.degree. C. for 60 minutes.
[0120] The Mg.sub.95Al.sub.3Zn.sub.1Ca.sub.0.4Y.sub.0.4Mn.sub.0.2
sheet has a yield strength of 205 MPa, a tensile strength of 280
MPa, an elongation to failure of 18 percent and an IE value of 4.5.
The microstructure photograph of this sheet after rolling and
annealing is shown in FIG. 10.
Example 11
[0121] Mg.sub.95.2Zn.sub.3Al.sub.1Ca.sub.0.3Gd.sub.0.3Mn.sub.0.2
magnesium alloy sheet (1 mm in thickness): weighting raw materials
according to the mass percent of composition, wherein the raw
materials were: magnesium ingot of 99.99 mass percent, aluminum
ingot of 99.9 mass percent, zinc ingot of 99.99 mass percent,
master alloy of magnesium and calcium of 30 mass percent, master
alloy of magnesium and gadolinium of 30 mass percent, and master
alloy of magnesium and manganese of 30 mass percent. The burdening
was carried out, according to the nominal composition of the
magnesium alloy, and also in consideration of the thermal loss of
each of elements.
[0122] Melting and casting of
Mg.sub.95.2Zn.sub.3Al.sub.1Ca.sub.0.3Gd.sub.0.3Mn.sub.0.2. The raw
materials were charged into a crucible in a vacuum induction
melting furnace and the melting furnace was vacuumed and heated
under inert atmosphere. The temperature was increased to
750.degree. C. and maintained for 15 minutes. After the raw
materials were completely melted, the melts were
electromagnetically stirred for about 10 minutes. Finally, the
melts were poured into the graphite crucible and placed in the air
to cool, giving an ingot.
[0123] Solid solution treatment of
Mg.sub.95.2Zn.sub.3Al.sub.1Ca.sub.0.3Gd.sub.0.3Mn.sub.0.2. The
magnesium alloy ingot was placed in a resistance furnace and kept
at 300.degree. C. for 20 hours, and then air-cooled to room
temperature.
[0124] Hot rolling of
Mg.sub.95.2Zn.sub.3Al.sub.1Ca.sub.0.3Gd.sub.0.3Mn.sub.0.2. The
magnesium alloy ingot after the solid solution treatment was
wire-cut into a slab having a thickness of 10 mm, and then the
surface of the slab was polished for hot rolling. The specific hot
rolling process was as follows: the slab was kept at 400.degree. C.
for about 30 minutes and then was hot rolled. The total thickness
reduction by hot rolling was 90 percent, that is, the final
thickness of sheet was 1 mm. The thickness reductions of the first
two passes were 8 percent and 10 percent, respectively, and the
thickness reductions of other passes were controlled within 10 to
30 percent, wherein the thickness reductions of the last two passes
were 15 percent and 10 percent, respectively. Due to the fast heat
dissipation of the magnesium alloy, in order to stabilize the
temperature during the rolling, the sample was kept at 400.degree.
C. for 8 minutes in the resistance furnace after each rolling pass.
After the hot rolling, the defects at head, tail and edges of the
hot rolled sheet were cut to obtain a hot rolled magnesium alloy
sheet with good shape.
[0125] Annealing of the hot rolled
Mg.sub.95.2Zn.sub.3Al.sub.1Ca.sub.0.3Gd.sub.0.3Mn.sub.0.2 sheet.
The finally rolled sheet was placed into a resistance furnace and
kept at 350.degree. C. for 60 minutes.
[0126] The
Mg.sub.95.2Zn.sub.3Al.sub.1Ca.sub.0.3Gd.sub.0.3Mn.sub.0.2 sheet has
a yield strength of 210 MPa, a tensile strength of 275 MPa, an
elongation to failure of 22 percent and an IE value of 5. The
microstructure photograph of this sheet after rolling and annealing
is shown in FIG. 11.
[0127] Compared with the prior art, the tensile strength, the
ductility and IE value of the present invention are significantly
improved. As shown in Table 3, the commonly rolled AZ31 (NR) only
has an IE value of 3.45 (prior art 1), and even using differential
speed rolling (DSR), its IE value is only increased to 3.73 (prior
art 2). As disclosed herein, the chemical composition has been
modified and adds 0.2 wt % Ca and 0.2 wt % Gd on the basis of AZ21,
and the tensile strength thereof is increased to 260 MPa, the
elongation to failure to 21 percent, and the IE value to 5.87
(Example 1). Further, the content of Al is reduced and the
strengthening element Zn is added so as to obtain
Mg.sub.96.6Zn.sub.2Al.sub.1Ca.sub.0.2Gd.sub.0.2, the IE value of
which is increased to 6.67 (Example 4). Further, on the basis of
Mg.sub.96.6Zn.sub.2Al.sub.1Ca.sub.0.2Gd.sub.0.2, 0.1 wt % Gd is
reduced and 0.1 wt % Y is added, so as to obtain
Mg.sub.96.4Zn.sub.2Al.sub.1Ca.sub.0.2Gd.sub.0.1Y.sub.0.1Mn.sub.0.2,
the tensile-strength of which is increased to 265.6 MPa. On the
other hand, in order to further increase mechanical properties,
more Al/Zn, Ca, Gd/Y and Mn elements were added based on
Mg.sub.96.6Al.sub.2Zn.sub.1Ca.sub.0.2Gd.sub.0.2 (Example 1) and
Mg.sub.96.6Zn.sub.2Al.sub.1Ca.sub.0.2Gd.sub.0.2 (Example 4) to
obtain Mg.sub.95Al.sub.3Zn.sub.1Ca.sub.0.4Gd.sub.0.4Mn.sub.0.2
(Example 9), Mg.sub.95Al.sub.3Zn.sub.1Ca.sub.0.4Y.sub.0.4Mn.sub.0.2
(Example 10) and
Mg.sub.95.2Zn.sub.3Al.sub.1Ca.sub.0.3Gd.sub.0.3Mn.sub.0.2 (Example
11). In addition, the disclosed magnesium alloys contain a lower
content of rare earth elements, have a better processability, and
have a higher yield during the whole preparation process including
melting, extruding, rolling, etc. Therefore, the disclosed
magnesium alloy not only has a high room temperature formability,
better mechanical properties, and anti-flammability and
corrosion-resistance performance, but also has a low cost in
preparation, and may be an ideal material for forming
non-structural parts in the aerospace field and the like.
TABLE-US-00003 TABLE 3 Yield Tensile Elongation strength/ strength/
to failure/ IE Alloy MPa MPa % value Illustration AZ31 (NR) -- --
-- 3.45 Prior art 1 AZ31 (DSR) -- -- -- 3.73 Prior art 2
Mg.sub.96.6Al.sub.2Zn.sub.1Ca.sub.0.2Gd.sub.0.2 231.0 260.0 21.0
5.87 Example 1 Mg.sub.96.6Al.sub.2Zn.sub.1Ca.sub.0.2Gd.sub.0.2
167.0 245.0 19.0 -- Example 2
Mg.sub.96.6Al.sub.2Zn.sub.1Ca.sub.0.2Gd.sub.0.2 231.0 249.0 23.0
5.51 Example 3 Mg.sub.96.6Zn.sub.2Al.sub.1Ca.sub.0.2Gd.sub.0.2
145.0 245.0 26.0 6.67 Example 4
Mg.sub.96.6Zn.sub.2Al.sub.1Ca.sub.0.2Gd.sub.0.2 227.0 250.0 23.0 --
Example 5 Mg.sub.96.6Zn.sub.2Al.sub.1Ca.sub.0.2Gd.sub.0.2 184.8
252.6 31.4 5.93 Example 6
Mg.sub.96.6Zn.sub.2Al.sub.1Ca.sub.0.2Gd.sub.0.2 170.0 255.0 24.0
5.63 Example 7
Mg.sub.96.4Zn.sub.2Al.sub.1Ca.sub.0.2Gd.sub.0.1Y.sub.0.1Mn.sub.0.2
202.8 265.6 26.6 5.10 Example 8
Mg.sub.95Al.sub.3Zn.sub.1Ca.sub.0.4Gd.sub.0.4Mn.sub.0.2 200.0 275.0
20.0 5.00 Example 9
Mg.sub.95Al.sub.3Zn.sub.1Ca.sub.0.4Y.sub.0.4Mn.sub.0.2 205.0 280.0
18.0 4.50 Example 10
Mg.sub.95Zn.sub.3Al.sub.1Ca.sub.0.3Gd.sub.0.3Mn.sub.0.2 210.0 275.0
22.0 5.00 Example 11
[0128] Table 1 shows the mechanical properties and IE values for
alloys AZ31 (NR) (prior art 1), AZ31 (DSR) (prior art 2),
Mg.sub.96.6Al.sub.2Zn.sub.1Ca.sub.0.2Gd.sub.0.2 (Examples 1-3),
Mg.sub.96.6Zn.sub.2Al.sub.1Ca.sub.0.2Gd.sub.0.2 (Examples 4-7),
Mg.sub.96.4Zn.sub.2Al.sub.1Ca.sub.0.2Gd.sub.0.1Y.sub.0.1Mn.sub.0.2
(Example 8), Mg.sub.95Al.sub.3Zn.sub.1Ca.sub.0.4Y.sub.0.4Mn.sub.0.2
(Example 9), Mg.sub.95Al.sub.3Zn.sub.1Ca.sub.0.4Y.sub.0.4Mn.sub.0.2
(Example 10) and
Mg.sub.95Zn.sub.3Al.sub.1Ca.sub.0.3Gd.sub.0.3Mn.sub.0.2 (Example
11).
[0129] Although various embodiments of the disclosed
calcium-bearing magnesium and rare earth element alloys and methods
have been shown and described, modifications may occur to those
skilled in the art upon reading the specification. The present
application includes such modifications and is limited only by the
scope of the claims.
* * * * *