U.S. patent application number 17/271462 was filed with the patent office on 2021-06-24 for high-strength and corrosion-resistant magnesium alloy material and method for fabricating same.
This patent application is currently assigned to BAOSHAN IRON & STEEL CO., LTD.. The applicant listed for this patent is BAOSHAN IRON & STEEL CO., LTD.. Invention is credited to Nick BIRBILIS, Ruiliang LIU, Weineng TANG, Shiwei XU, Zhuoran ZENG.
Application Number | 20210189527 17/271462 |
Document ID | / |
Family ID | 1000005445323 |
Filed Date | 2021-06-24 |
United States Patent
Application |
20210189527 |
Kind Code |
A1 |
XU; Shiwei ; et al. |
June 24, 2021 |
HIGH-STRENGTH AND CORROSION-RESISTANT MAGNESIUM ALLOY MATERIAL AND
METHOD FOR FABRICATING SAME
Abstract
A high strength and corrosion-resistant magnesium alloy
material, comprising 0.01-1.2 wt % of Ge and 0.01-1.2 wt % of Zn. A
high strength and corrosion-resistant magnesium alloy material,
comprising the following chemical elements in percentage by weight:
Ge: 0.01-1.2%; Zn: 0.01-1.2%; at least one of Mn, Ca, Zr, Sr, and
Gd, with a total weight percentage of .ltoreq.3%, wherein the
percentage by weight of a single element is .ltoreq.0.8%; and the
balance of Mg and other inevitable impurities. A method for
fabricating the above mentioned high strength and
corrosion-resistant magnesium alloy material, comprising the steps
of: smelting, solid solution heat treatment, and extrusion, wherein
in the extrusion step, the extrusion temperature is 180-350.degree.
C., the extrusion rate is 0.1-10 mm/s, and the extrusion ratio is
10:1-30:1.
Inventors: |
XU; Shiwei; (Shanghai,
CN) ; ZENG; Zhuoran; (Shanghai, CN) ; TANG;
Weineng; (Shanghai, CN) ; LIU; Ruiliang;
(Shanghai, CN) ; BIRBILIS; Nick; (Shanghai,
CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
BAOSHAN IRON & STEEL CO., LTD. |
Shanghai |
|
CN |
|
|
Assignee: |
BAOSHAN IRON & STEEL CO.,
LTD.
Shanghai
CN
|
Family ID: |
1000005445323 |
Appl. No.: |
17/271462 |
Filed: |
October 25, 2019 |
PCT Filed: |
October 25, 2019 |
PCT NO: |
PCT/CN2019/113375 |
371 Date: |
February 25, 2021 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C22F 1/06 20130101; C22C
23/04 20130101 |
International
Class: |
C22C 23/04 20060101
C22C023/04; C22F 1/06 20060101 C22F001/06 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 26, 2018 |
CN |
201811257872.0 |
Claims
1. A high strength and corrosion-resistant magnesium alloy
material, comprising 0.01-1.2 wt % of Ge and 0.01-1.2 wt % of
Zn.
2. The high strength and corrosion-resistant magnesium alloy
material of claim 1, wherein the magnesium alloy material has a
microstructure including an .alpha.-Mg phase and a column-shaped
Mg.sub.2Ge intermetallic compound phase.
3. The high strength and corrosion-resistant magnesium alloy
material of claim 1, wherein the magnesium alloy material has a
yield strength of higher than 260 MPa, and a corrosion weight loss
of less than 0.8 mg/(cm.sup.2 day).
4. A high strength and corrosion-resistant magnesium alloy
material, comprising the following chemical elements in percentage
by weight: Ge: 0.01.about.1.2%; Zn: 0.01.about.1.2%; at least one
of Mn, Ca, Zr, Sr, and Gd with a total weight percentage of
.ltoreq.3%, wherein the percentage by weight of a single element is
.ltoreq.0.8%; and the balance of Mg and other inevitable
impurities.
5. The high strength and corrosion-resistant magnesium alloy
material of claim 4, further comprising at least one of Al, Cu, Si
and Fe in a total weight percentage of .ltoreq.2%, wherein the
percentage by weight of a single element is .ltoreq.0.5%.
6. The high strength and corrosion-resistant magnesium alloy
material of claim 4, wherein the total amount of the inevitable
impurities is less than 100 ppm.
7. The high strength and corrosion-resistant magnesium alloy
material of claim 4, wherein the magnesium alloy material has a
microstructure including an .alpha.-Mg phase and a column-shaped
Mg.sub.2Ge intermetallic compound phase.
8. The high strength and corrosion-resistant magnesium alloy
material of claim 4, wherein the magnesium alloy material has a
yield strength of higher than 260 MPa, and a corrosion weight loss
of less than 0.8 mg/(cm.sup.2 day).
9. A method for fabricating the high strength and
corrosion-resistant magnesium alloy material of claim 1, comprising
the steps of: smelting, solid solution heat treatment and
extrusion, wherein in the extrusion step, the extrusion temperature
is 180-350.degree. C., the extrusion rate is 0.1-10 mm/s, and the
extrusion ratio is 10:1-30:1.
10. The method for fabricating the high strength and
corrosion-resistant magnesium alloy material of claim 9, wherein in
the solid solution heat treatment step, the solid solution heat
treatment temperature is 350-450.degree. C., and the treatment time
is 10-24 h.
11. A method for fabricating the high strength and
corrosion-resistant magnesium alloy material of claim 4, comprising
the steps of: smelting, solid solution heat treatment and
extrusion, wherein in the extrusion step, the extrusion temperature
is 180-350.degree. C., the extrusion rate is 0.1-10 mm/s, and the
extrusion ratio is 10:1-30:1.
12. The method for fabricating the high strength and
corrosion-resistant magnesium alloy material of claim 11, wherein
in the solid solution heat treatment step, the solid solution heat
treatment temperature is 350-450.degree. C., and the treatment time
is 10-24 h.
Description
TECHNICAL FIELD
[0001] The present disclosure relates to a magnesium alloy material
and method for fabricating the same, and in particular relates to a
high strength and corrosion-resistant magnesium alloy material and
method for fabricating the same.
BACKGROUND
[0002] Magnesium is one of the most abundant elements on the Earth.
Commercially available pure magnesium can reach a purity of more
than 99.8%. Magnesium has a low density, and is 35% lighter than
aluminum and 78% lighter than steel. In the age of pursuit of
lightweight, magnesium and its alloys have become increasingly
attractive engineering materials.
[0003] Due to the unstable chemical properties of magnesium, pure
magnesium cannot meet the requirements of most engineering
applications. In order to improve the comprehensive properties of
magnesium, many attempts have been made to add various alloying
elements to magnesium for the production of magnesium alloy
products. Through the addition of alloying elements, the mechanical
properties of magnesium have been significantly improved.
[0004] However, despite the improvement in mechanical properties,
alloying elements usually lead to an increase in corrosion rate of
magnesium alloys. The main reasons are: first, magnesium is a metal
with highly active chemical properties, and the addition of
alloying elements usually leads to the formation of some second
phases in its microstructure, resulting in the formation of
microscopic cathodes, which accelerates the corrosion of the
magnesium alloy matrix. Secondly, magnesium has a limited ability
to support the cathode reaction (hydrogen evolution reaction, HER).
Among all metal elements, magnesium has one of the lowest density
of current exchange in hydrogen evolution reaction. Therefore, when
there are other inerter metal alloying elements or impurities (such
as copper, nickel, iron) present, the corrosion rate of magnesium
alloy will be greatly accelerated.
[0005] In addition, unlike other alloy systems such as some
aluminum alloys and stainless steel systems with good corrosion
properties, magnesium alloys cannot be passivated by incorporating
sufficient alloying elements to form a dense oxide layer. The basic
reason is that many alloying elements have limited solid solubility
in magnesium. Although some elements (such as lithium and yttrium)
have certain solubility in magnesium, the addition of such elements
cannot result in the formation of a more corrosion-resistant inert
oxide film on the surface of the magnesium alloy. On the contrary,
the addition of such elements usually results in the formation of
an even more active oxide layer.
[0006] Based on above, the addition of alloying elements usually
leads to an increase in the corrosion rate of magnesium. Although
alloying elements can enhance mechanical properties, the negative
effects thereof on corrosion properties limit the application of
magnesium alloys.
[0007] In view of the foregoing, it is desired to obtain a
magnesium alloy material that not only has high strength, but also
has strong corrosion resistance.
SUMMARY
[0008] One of the objectives of the present disclosure is to
provide a high strength and corrosion-resistant magnesium alloy
material, which not only has high strength, but also has strong
corrosion resistance.
[0009] In order to achieve the above objective, the present
disclosure provides a high strength and corrosion-resistant
magnesium alloy material, which comprises 0.01-1.2 wt % of Ge and
0.01-1.2 wt % of Zn.
[0010] In some embodiments of the present disclosure, the design
principle of adding Ge and Zn is as follows.
[0011] Germanium (Ge): Pure germanium is a shiny, hard metal with a
grey-white color, and belongs to the carbon group. The chemical
properties of germanium are similar to that of tin and silicon of
the same group. Germanium is insoluble in water, hydrochloric acid,
or diluted caustic alkali solution, but is soluble in aqua regia,
concentrated nitric acid or sulfuric acid. Germanium is amphoteric,
and is therefore soluble in molten alkali, peroxide alkali, alkali
metal nitrate or carbonate. Germanium is rather stable in the air
and reacts with oxygen to form GeO.sub.2 at 700.degree. C. or
higher, and reacts with hydrogen at 1000.degree. C. or higher. When
germanium is added to magnesium, an Mg.sub.2Ge intermetallic
compound phase with column-shaped morphology is formed. This second
phase can strengthen the magnesium alloy and affect the corrosion
resistance of the magnesium alloy. When the content of Ge is low,
the formed second phase can delay corrosion and strengthen the
alloy, significantly improving the corrosion resistance and the
strength of the alloy. However, due to the very low solubility of
Ge in Mg, the addition of excess Ge may embrittle the alloy. When
the Ge content exceeds 1.18%, coarse bulk Mg.sub.2Ge second phase
aggregates at the grain boundary and also occurs inside the grain
and significantly deteriorates the corrosion resistance, mechanical
strength and plasticity of the alloy. Therefore, in the high
strength and corrosion-resistant magnesium alloy material according
to the present disclosure, the percentage by weight of Ge is
limited to 0.01-1.2 wt %. Preferably, the percentage by weight of
Ge is 0.02-1.18 wt %.
[0012] Zinc (Zn): Zinc has both solid solution strengthening and
aging strengthening effects. By adding an appropriate amount of Zn
to the magnesium alloy, a variety of Mg--Zn phases can be formed,
thereby improving the strength (such as yield strength and tensile
strength), plasticity, ductility, melt fluidity, and casting
performance of the magnesium alloy. However, if excessive amount of
Zn is added, the fluidity of the Zn alloy will be greatly reduced
and microporosity or hot cracking tend to occur in the magnesium
alloy. Therefore, in the high strength and corrosion-resistant
magnesium alloy material according to the present disclosure, the
percentage by weight of Zn is limited to 0.01-1.2 wt %. Preferably,
the percentage by weight of Zn is 0.02-1.2 wt %.
[0013] Further, the high strength and corrosion-resistant magnesium
alloy material according to the present disclosure has a
microstructure including an a-Mg phase and a column-shaped
Mg.sub.2Ge intermetallic compound phase.
[0014] Further, the high strength and corrosion-resistant magnesium
alloy material according to the present disclosure has a yield
strength of more than 260 MPa and a corrosion weight loss of less
than 0.8 mg/(cm.sup.2 day).
[0015] Another objective of the present disclosure is to provide a
high strength and corrosion-resistant magnesium alloy material,
which not only has high strength, but also has strong corrosion
resistance.
[0016] In order to achieve the above objective, the present
disclosure provides a high strength corrosion-resistant magnesium
alloy material, comprising the following chemical elements in
percentage by weight:
Ge: 0.01.about.1.2%;
Zn: 0.01.about.1.2%;
[0017] at least one of Mn, Ca, Zr, Sr, and Gd with a total weight
percentage of .ltoreq.3%, wherein the percentage by weight of a
single element is .ltoreq.0.8%; and the balance of Mg and other
inevitable impurities.
[0018] The high strength and corrosion-resistant magnesium alloy
material according to the present disclosure comprises at least one
of Mn, Ca, Zr, Sr, and Gd in addition to the aforementioned
0.01-1.2 wt % of Ge and 0.01-1.2 wt % of Zn. The main design
principle of the material is as follows. Mn, Ca, Zr, Sr, and Gd can
all affect the grain size and the strength and type of crystal
texture in the microstructure of the alloy, and improve the
ductility and formability of magnesium alloy deformable materials.
However, when these alloying elements are excessive, a large amount
of second phases will form and coarsen into large-sized second
phases in the alloy, thereby reducing the plasticity and the
strength of the alloy, and causing intensified microcell corrosion.
In addition, as the solubility of calcium in magnesium is less than
1%, the addition of a large amount of calcium will embrittle the
grain boundaries and reduce the corrosion resistance of magnesium
alloys. Therefore, in the high strength and corrosion-resistant
magnesium alloy material according to the present disclosure, the
total percentage by weight of Mn, Ca, Zr, Sr, and Gd is limited to
.ltoreq.3%, and the percentage by weight of a single element is
limited to .ltoreq.0.8%. In addition, it should be noted that the
design principles of adding Ge and Zn herein are the same as
described above, and is not repeated herein.
[0019] Further, the high strength and corrosion-resistant magnesium
alloy material according to the present disclosure further
comprises at least one of Al, Cu, Si and Fe in a total weight
percentage of .ltoreq.2%, wherein the percentage by weight of a
single element is .ltoreq.0.5%, and the percentage by weight of a
single element is .ltoreq.0.5%.
[0020] The high strength and corrosion-resistant magnesium alloy
material according to the present disclosure further comprises at
least one of Al, Cu, Si and Fe. The design principle is that Al,
Cu, Si and Fe can all improve the ductility and formability of
magnesium alloy sheets. However, when these alloying elements are
excessive, a large amount of second phases will form and coarsen
into large-sized second phases in the alloy, thereby reducing the
plasticity and the strength of the alloy, and causing intensified
microcell corrosion. Therefore, in the high strength and
corrosion-resistant magnesium alloy material according to the
present disclosure, the total percentage by weight of Al, Cu, Si
and Fe is limited to .ltoreq.2%, and the percentage by weight of a
single element is limited to .ltoreq.0.5%. Preferably, the total
percentage by weight of Al, Cu, Si and Fe is .ltoreq.0.5%, and the
percentage by weight of a single element is .ltoreq.0.05%. Within
the above ranges, the plasticity and the mechanical properties of
the magnesium alloy will be significantly improved, and the
corrosion resistance will also be significantly enhanced.
[0021] Further, in the high strength and corrosion-resistant
magnesium alloy material according to the present disclosure, the
total amount of the inevitable impurities is less than 100 ppm.
[0022] Further, the high strength and corrosion-resistant magnesium
alloy material according to the present disclosure has a
microstructure including an a-Mg phase and a column-shaped
Mg.sub.2Ge intermetallic compound phase.
[0023] In an embodiment of the present disclosure, in addition to
the a-Mg phase and the column-shaped Mg.sub.2Ge intermetallic
compound phase, the microstructure of the high strength and
corrosion-resistant magnesium alloy material further comprises
other intermetallic compound phase formed by magnesium and other
alloying elements (e.g. Mn, Ca, Zr, Sr, Gd, etc.) added in small
amounts.
[0024] Further, the high strength and corrosion-resistant magnesium
alloy material according to the present disclosure has a yield
strength of more than 260 MPa and a corrosion weight loss of less
than 0.8 mg/(cm.sup.2 day).
[0025] Correspondingly, another objective of the present disclosure
is to provide a method for fabricating the above-mentioned high
strength and corrosion-resistant magnesium alloy material. The high
strength and corrosion-resistant magnesium alloy material
fabricated by the method not only has high strength, but also has
strong corrosion resistance.
[0026] In order to achieve the above objective, the present
disclosure provides a method for fabricating the high strength and
corrosion-resistant magnesium alloy material, comprising the steps
of: smelting, solid solution heat treatment and extrusion, wherein
in the extrusion step, the extrusion temperature is 180-350.degree.
C., the extrusion rate is 0.1-10 mm/s, and the extrusion ratio is
10:1-30:1. When the extrusion temperature is lower than 180.degree.
C., the mold wears a lot, the spindle is difficult to squeeze, and
cracks appear on the surface of the profile. When the extrusion
temperature is higher than 350.degree. C., the grains become
significantly larger, resulting in a significant decrease in
strength. When the extrusion speed is too fast or the extrusion
ratio is too high, the surface of the material cracks easily. When
the extrusion speed is too slow or the extrusion ratio is too low,
the production efficiency is too low.
[0027] In the fabricating method according to the present
disclosure, during the smelting step, in some embodiments, the raw
material is heated and melted in an SF.sub.6 protective atmosphere,
and the molten magnesium alloy liquid is poured into a preheated
mold to cool. The fabricating method according to the present
disclosure allows the microstructure of the prepared high strength
and corrosion-resistant magnesium alloy material to include an
.alpha.-Mg phase, a Mg.sub.2Ge intermetallic compound phase, and
other intermetallic compound phases formed by other added alloying
elements and magnesium.
[0028] Further, in the method for fabricating the high strength and
corrosion-resistant magnesium alloy material according to the
present disclosure, in the solid solution heat treatment step, the
solid solution heat treatment temperature is 350-450.degree. C.,
and the treatment time is 10-24 h.
[0029] Compared with the prior art, the high strength and
corrosion-resistant magnesium alloy material and the fabricating
method thereof according to the present disclosure have the
following beneficial effects:
[0030] (1) The mechanical properties and corrosion resistance of
the high strength and corrosion-resistant magnesium alloy material
according to the disclosure is significantly improved by the
addition of Zn, Ge and other alloying elements.
[0031] (2) The high strength and corrosion-resistant magnesium
alloy material according to the present disclosure has a yield
strength of more than 260 MPa and a corrosion weight loss of less
than 0.8 mg/(cm.sup.2 day).
[0032] (3) The method for fabricating the high strength and
corrosion-resistant magnesium alloy material according to the
present disclosure significantly improves the strength and
corrosion resistance of the high strength and corrosion-resistant
magnesium alloy material according to the present disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] FIG. 1 shows a scanning electron microscope image in
backscattered electron (BSE) mode of Comparative Example 2.
[0034] FIG. 2 shows a scanning electron microscope image in
backscattered electron (BSE) mode of the high strength and
corrosion-resistant magnesium alloy material of Example 3.
[0035] FIG. 3 shows a scanning electron microscope image in
backscattered electron (BSE) mode of the high strength and
corrosion-resistant magnesium alloy material of Example 4.
[0036] FIG. 4 shows an energy spectrum analysis image of
Comparative Example 2.
[0037] FIG. 5 shows an energy spectrum analysis image of the high
strength and corrosion-resistant magnesium alloy material of
Example 3.
[0038] FIG. 6 shows an energy spectrum analysis image of the high
strength and corrosion-resistant magnesium alloy material of
Example 4.
[0039] FIG. 7 shows an electron backscatter diffraction image of
Comparative Example 2.
[0040] FIG. 8 shows an electron backscatter diffraction image of
the high strength and corrosion-resistant magnesium alloy material
of Example 3.
[0041] FIG. 9 shows an electron backscatter diffraction image of
the high strength and corrosion-resistant magnesium alloy material
of Example 4.
[0042] FIG. 10 shows the grain size distribution of the high
strength and corrosion-resistant magnesium alloy materials of
Examples 3 and 4, and Comparative Example 2.
[0043] FIG. 11 shows the potentiodynamic polarization measurement
results of the high strength and corrosion-resistant magnesium
alloy materials of Examples 3-4 and Comparative Examples 1-2 in a
0.1 M sodium chloride solution.
[0044] FIG. 12 shows the cathodic polarization measurement results
of the high strength and corrosion-resistant magnesium alloy
materials of Examples 3-4 and Comparative Examples 1-2.
[0045] FIG. 13 shows the results of weight loss and hydrogen
evolution measurements of the high strength and corrosion-resistant
magnesium alloy materials of Examples 3-4, Comparative Examples
1-2, and commercial AZ91 magnesium alloy.
[0046] FIG. 14 shows a scanning electron microscope image (at low
magnification) in the secondary electron (SE) mode of Comparative
Example 1 after immersion.
[0047] FIG. 15 shows a scanning electron microscope image (at high
magnification) in the secondary electron (SE) mode of Comparative
Example 1 after immersion.
[0048] FIG. 16 shows a scanning electron microscope image (at low
magnification) in the secondary electron (SE) mode of Comparative
Example 2 after immersion.
[0049] FIG. 17 shows a scanning electron microscope image (at high
magnification) in the secondary electron (SE) mode of Comparative
Example 2 after immersion.
[0050] FIG. 18 shows a scanning electron microscope image (at low
magnification) in the secondary electron (SE) mode of the high
strength and corrosion-resistant magnesium alloy material of
Example 3 after immersion.
[0051] FIG. 19 shows a scanning electron microscope image (at high
magnification) in the secondary electron (SE) mode of the high
strength and corrosion-resistant magnesium alloy material of
Example 3 after immersion.
[0052] FIG. 20 shows a scanning electron microscope image (at low
magnification) in the secondary electron (SE) mode of the high
strength and corrosion-resistant magnesium alloy material of
Example 4 after immersion.
[0053] FIG. 21 shows a scanning electron microscope image (at high
magnification) in the secondary electron (SE) mode of the high
strength and corrosion-resistant magnesium alloy material of
Example 4 after immersion.
[0054] FIG. 22 shows the cathode current density measurement
results of the high strength and corrosion-resistant magnesium
alloy materials of Examples 3-4 and Comparative Examples 1-2 when
the anode current density is 0.025-2.5 mA/cm.sup.2.
[0055] FIG. 23 shows the cathode current density measurement
results of the high strength and corrosion-resistant magnesium
alloy materials of Examples 3-4 and Comparative Examples 1-2 when
the anode current density is 2-24 mA/cm.sup.2.
[0056] FIG. 24 shows the anode dissolution current density of the
high strength and corrosion-resistant magnesium alloy materials of
Examples 3-4 and Comparative Examples 1-2 in 0.1 M sodium chloride
during open circuit potential (OCP) and potentiodynamic
polarization (PDP) by inductively coupled plasma optical emission
spectrometer (ICP-OES).
[0057] FIG. 25 shows the relationship between the anode dissolution
current density and the anode potential of the high strength and
corrosion-resistant magnesium alloy materials of Examples 3-4 and
Comparative Examples 1-2.
[0058] FIG. 26 shows the microhardness measurement results of the
high strength and corrosion-resistant magnesium alloy materials of
Examples 3-4 and Comparative Example 2.
[0059] FIG. 27 shows the engineering stress-strain curves of the
high strength and corrosion-resistant magnesium alloy materials of
Examples 3-4 and Comparative Example 2.
DETAILED DESCRIPTION
[0060] The embodiments of the present invention will be further
described below in conjunction with the drawings and examples.
However, the explanation and description are not intended to unduly
limit the technical solutions of the present invention.
Examples 1-17 and Comparative Examples 1-2
[0061] Table 1-1 and Table 1-2 list the percentage by weight (wt %)
of each element in Examples 1-17 and Comparative Examples 1-2.
TABLE-US-00001 TABLE 1-1 (wt %, and the balance is Mg and other
inevitable impurities) Mn, Ca, Zr, Sr, and Gd No. Ge Zn Mn Ca Zr Sr
Gd in total E1 0.30 1.00 0.01 0.05 -- -- -- 0.06 E2 0.50 1.00 0.02
0.01 -- -- 0.01 0.04 E3 0.30 1.00 0.02 0.8 -- -- -- 0.82 E4 0.50
1.00 0.05 0.5 -- -- -- 0.55 E5 0.03 1.2 0.02 -- 0.5 -- 0.8 1.32 E6
0.21 0.05 0.8 0.2 0.5 -- 0.4 1.9 E7 0.75 0.2 0.8 0.7 0.7 -- 0.8 3
E8 0.86 0.5 0.02 0.2 -- -- -- 0.22 E9 0.27 0.08 0.8 0.5 0.01 -- --
1.31 E10 0.08 1.0 0.02 0.5 0.5 -- -- 1.02 E11 0.05 1.2 0.02 0.5 0.5
0.1 -- 1.12 E12 0.52 0.2 0.1 0.8 -- -- -- 0.9 E13 0.02 0.4 0.02 0.8
-- -- 0.4 1.22 E14 0.66 0.5 0.02 0.8 0.5 -- -- 1.32 E15 1.16 0.04
0.02 0.8 0.8 0.8 -- 2.42 E16 1.06 0.4 0.02 0.8 0.8 -- 0.01 1.63 E17
1.18 0.02 0.02 0.8 0.5 0.01 0.4 1.73 CE1 0.002 0.005 0.01 0.001 --
-- -- 0.011 CE2 0.002 1 0.02 0.001 -- -- -- 0.021
TABLE-US-00002 TABLE 1-2 (wt %, and the balance is Mg and other
inevitable impurities) Al, Cu, Inevitable Si, Fe impurities in in
total Micro- No. Al Cu Si Fe total (ppm) structure E1 0.011 0.001
0.02 0.004 0.036 90 .alpha.-Mg, Mg.sub.2Ge and Mg.sub.2Ca phases E2
0.011 0.001 0.02 0.004 0.036 80 .alpha.-Mg, Mg.sub.2Ge and
Mg.sub.2Ca phases E3 0.011 0.001 0.02 0.005 0.037 90 .alpha.-Mg,
Mg.sub.2Ge and Mg.sub.2Ca phases E4 0.011 0.001 0.02 0.004 0.036 90
.alpha.-Mg, Mg.sub.2Ge and Mg.sub.2Ca phases E5 0.007 0.002 0.02
0.004 0.033 80 .alpha.-Mg, Mg.sub.2Ge and MgZr phases E6 0.010
0.002 0.02 0.004 0.036 90 .alpha.-Mg, Mg.sub.2Ge, Mg.sub.2Ca and
MgZr phases E7 0.010 0.002 0.02 0.004 0.036 60 .alpha.-Mg,
Mg.sub.2Ge, Mg.sub.2Ca, MgGd and MgZr phases E8 0.010 0.002 0.02
0.005 0.037 90 .alpha.-Mg, Mg.sub.2Ge and Mg.sub.2Ca phases E9
0.007 0.002 0.02 0.004 0.033 60 .alpha.-Mg, Mg.sub.2Ge and
Mg.sub.2Ca phases E10 0.012 0.002 0.02 0.004 0.038 70 .alpha.-Mg,
Mg.sub.2Ge, Mg.sub.2Ca, MgZr phases E11 0.013 0.002 0.02 0.005 0.04
90 .alpha.-Mg, Mg.sub.2Ge, Mg.sub.2Ca, MgZr and Mg.sub.2Sr phases
E12 0.011 0.002 0.02 0.004 0.037 60 .alpha.-Mg, Mg.sub.2Ge and
Mg.sub.2Ca phases, etc. E13 0.010 0.002 0.02 0.005 0.037 90
.alpha.-Mg, Mg.sub.2Ge, Mg.sub.2Ca, and Mg.sub.2Gd phases, etc. E14
0.015 0.002 0.02 0.004 0.041 60 .alpha.-Mg, Mg.sub.2Ge, MgZr, and
Mg.sub.2Ca phases, etc. E15 0.013 0.002 0.02 0.004 0.039 70
.alpha.-Mg, Mg.sub.2Ge, Mg.sub.2Ca and Mg.sub.2Sr phases E16 0.013
0.002 0.02 0.005 0.04 90 .alpha.-Mg, Mg.sub.2Ge and Mg.sub.2Ca
phases E17 0.008 0.002 0.02 0.004 0.034 60 .alpha.-Mg, Mg.sub.2Ge,
Mg.sub.2Ca, Mg.sub.2Gd and Mg.sub.2Sr phases CE1 0.005 0.002 0.02
0.006 0.033 70 .alpha.-Mg phase CE2 0.013 0.001 0.02 0.005 0.039 80
.alpha.-Mg, and MgZn phases
[0062] The fabrication method of Examples 1-17 and Comparative
Examples 1-2 is as follows (specific process parameters are listed
in Table 2):
[0063] 1) Mixing the raw materials uniformly in a steel crucible
according to the ratio of elements in Table 1-1 and Table 1-2.
[0064] 2) Smelting: heating and melting the mixture in SF.sub.6
protective atmosphere, and pouring the molten magnesium alloy
liquid into a preheated mold to cool.
[0065] 3) Solid solution heat treatment.
[0066] 4) Extrusion.
TABLE-US-00003 TABLE 2 Specific process parameters in the
fabrication method of Examples 1-17 and Comparative Examples 1-2.
Extrusion Solid solution treatment Extrusion Extrusion Temperature
Time Temperature Extrusion rate No. (.degree. C.) (h) (.degree. C.)
ratio (mm/s) E1 400 24 320 20:1 0.1 E2 400 24 340 26:1 0.9 E3 400
24 300 12:1 0.8 E4 400 24 330 16:1 0.6 E5 450 10 300 20:1 6 E6 400
10 200 25:1 8 E7 420 20 250 28:1 5 E8 400 18 2320 18:1 2 E9 420 12
250 16:1 1 E10 440 22 350 12:1 0.5 E11 380 20 320 15:1 0.2 E12 360
22 300 20:1 0.1 E13 370 20 340 18:1 10 E14 360 18 250 15:1 0.2 E15
390 16 190 20:1 0.6 E16 400 14 180 10:1 5.5 E17 420 12 350 30:1 8.0
CE1 400 24 300 12:1 0.8 CE2 400 24 330 16:1 0.6
[0067] Performance tests were conducted on the high strength and
corrosion-resistant magnesium alloy materials of Examples 1-17 and
Comparative Examples 1-2. Their yield strength and corrosion weight
loss value in 0.1 M NaCl solution in 24 hours were measured.
[0068] The yield strength is measured by a tensile test in
accordance with ASTM E-8 standard. The yield strength is the stress
corresponding to 0.2% strain. The experimental platform is Instron
4505. The stretching rate is 10.sup.-3/s. The initial length of the
extensometer is 10 mm. The length of the parallel part of the
stretched sample is 22 mm.
[0069] The corrosion weight loss is measured according to
ASTM-G1-03 standard. The sample is a cube with a side length of 5
cm. The surface of the sample is polished with a 1200 grid
sandpaper, then the sample is immersed in a 0.1 M NaCl solution at
25.degree. C. for 24 hours. After immersion, the sample surface is
cleaned to remove the corrosion. The sample is weighed after
drying. The results are listed in Table 3.
TABLE-US-00004 TABLE 3 Yield strength (MPa) Corrosion weight loss
(mg/cm.sup.2/day) E1 285 0.72 E2 310 0.78 E3 288 0.60 E4 320 0.70
E5 328 0.69 E6 316 0.75 E7 320 0.73 E8 306 0.77 E9 270 0.78 E10 280
0.75 E11 265 0.63 E12 295 0.58 E13 279 0.68 E14 286 0.65 E15 275
0.60 E16 266 0.62 E17 265 0.72 CE1 70 10.5 CE2 255 1.8
[0070] It can be seen from Table 3 that, the high strength and
corrosion-resistant magnesium alloy material of Examples 1-17 with
a yield strength of higher than 260 MPa and a corrosion weight loss
of less than 0.8 mg/(cm.sup.2 day) has superior mechanical
properties and corrosion resistance compared to Comparative
Examples 1-2. Thus, the high strength and corrosion-resistant
magnesium alloy material has a wide range of application
prospects.
[0071] As can be seen from FIGS. 1 to 6, the microstructure of
Comparative Example 2 consists of a single .alpha.-Mg phase. In
contrast, column-shaped Mg.sub.2Ge intermetallic compound phase and
small amount of Mg.sub.2Ca compound are observed in the
microstructure of the high strength and corrosion-resistant
magnesium alloy materials of Examples 3-4
[0072] As can be seen from FIGS. 7 to 9, the electron backscatter
diffraction measures the grain size of the prepared alloy. The
grain structure of Comparative Example 2 has uniform size and
shape, with an average grain size of 1.2 .mu.m. A bimodal particle
size distribution is observed in the high strength and
corrosion-resistant magnesium alloy materials of Examples 3 and 4,
and the microstructures thereof comprises column-shaped grains with
an average grain size of 10-22 .mu.m.
[0073] FIG. 10 shows the grain size distribution of the high
strength and corrosion-resistant magnesium alloy materials of
Examples 3-4 and Comparative Example 2, wherein Mg-1Zn represents
Comparative Example 2, Mg-1Zn-0.3Ge represents Example 3, and
Mg-1Zn-0.5Ge represents Example 4.
[0074] It can be seen from FIG. 10 that when the content of
germanium in the alloy increases from about 0.3% to about 0.5%, the
proportion of column-shaped grains with large size increases
significantly, which indicates that the content of germanium in the
alloy can affect the formation of column-shaped grains with large
size.
[0075] In order to reveal the influence of the addition of alloying
elements on the electrochemical performances of the magnesium
alloy, potentiodynamic polarization measurement and cathode
polarization measurement are conducted on Comparative Examples 1-2
and the high strength and corrosion-resistant magnesium alloy
materials of Examples 3-4. The specific results are shown in FIGS.
11 and 12, wherein Mg represents Comparative Example 1 (where the
trace amounts of Ge and Zn can be ignored), Mg-1Zn represents
Comparative Example 2, Mg-1Zn-0.3Ge represents Example 3, and
Mg-1Zn-0.5Ge represents Example 4.
[0076] As can be seen from FIG. 11, due to the increase of Zn
content, the corrosion potential of the high strength and
corrosion-resistant magnesium alloy material of Comparative Example
2 increases by about 50 mV compared with Comparative Example 1. In
addition, due to the increase of germanium content, the corrosion
potentials of the high strength and corrosion-resistant magnesium
alloy materials of Examples 3 and 4 is reduced to about -1.67
V.sub.SCE.
[0077] As can be seen from FIG. 12, the cathode reaction rate of
Comparative Example 2 is higher than that of Comparative Example 1,
indicating that the increase of Zn improves the cathode kinetics.
On the contrary, the increase of Ge leads to a decrease in the
cathode current density of the high strength and
corrosion-resistant magnesium alloy materials of Example 3 and
Example 4, indicating that Ge alloying offsets the effect of Zn
alloying and significantly reduces the potential dynamics of the
cathode.
[0078] By incorporating FIG. 11 and FIG. 12, it can be seen that
the high strength and corrosion-resistant magnesium alloy materials
of Example 3 and Example 4 show an anode kinetics similar to that
of Comparative Example 1. The change of corrosion potential of
Example 3 and Example 4 are mainly due to the change of cathode
kinetics.
[0079] In order to verify the long-term corrosion performance of
magnesium alloys, long-term (24 h) immersion test is conducted on
Comparative Examples 1-2 and Examples 3-4 and commercial AZ91
magnesium alloy at open circuit potential in a 0.1 M sodium
chloride solution. The results are shown in FIG. 13, wherein Mg
represents Comparative Example 1, AZ91 represents commercial AZ91
magnesium alloy, Mg-1Zn represents Comparative Example 2,
Mg-1Zn-0.3Ge represents Example 3, and Mg-1Zn-0.5Ge represents
Example 4 in the x-coordinate.
[0080] As can be seen from FIG. 13, under the conditions of
immersion test, the weight loss and hydrogen evolution rate of the
high strength and corrosion-resistant magnesium alloy materials of
Example 3 and Example 4 are about an order of magnitude smaller
than those of Comparative Example 1 and commercial AZ91 magnesium
alloy, which proves that the addition of Zn and Ge can reduce the
corrosion rate of Mg.
[0081] After long-term (24 h) immersion test of Comparative
Examples 1-2 and Examples 3-4 at open circuit potential in a 0.1 M
sodium chloride solution, the corrosion products were washed with a
chromic acid solution (i.e., 200 g/L chromium trioxide, 10 g/L
silver nitrate and 20 g/L barium nitrate) to show the degree of
corrosion, and then the surface morphology was observed.
[0082] As can be seen from FIGS. 14 to 21, after the immersion
test, the corrosion morphology of the high strength and
corrosion-resistant magnesium alloy materials of Examples 3 and 4
are different from that of Comparative Example 1 and Comparative
Example 2. Discrete surface corrosion sites were observed in
Example 3 and Example 4, while widespread "filamentous" corrosion
was observed in Comparative Example 1 and Comparative Example 2.
Thus, Zn and Ge enhance the anti-corrosion ability of magnesium
alloys and inhibit the rate of cathode reaction (i.e., hydrogen
evolution reaction).
[0083] The influence of alloying on cathode activation (difference
effect) of magnesium is further evaluated by constant current
potential experiment. As shown in FIG. 22, the sample is anodic
polarized in a gradual increment of 0.025-2.5 mA/cm.sup.2 cycle,
and a fixed negative potential (-2 V.sub.SCE) is kept in each
anodic polarization period to measure the cathode current density
maintained on the anodic polarized surface (i.e., applied
dissolution current density). As shown in FIG. 23, the sample is
anodic polarized in a gradual increment of 2-24 mA/cm.sup.2 cycle,
and a fixed negative potential (-2 V.sub.SCE) is kept in each
anodic polarization period to measure the cathode current density
maintained on the anodic polarized surface (i.e., applied
dissolution current density). In FIG. 22 and FIG. 23, Mg represents
Comparative Example 1, Mg-1Zn represents Comparative Example 2,
Mg-1Zn-0.3Ge represents Example 3, and Mg-1Zn-0.5Ge represents
Example 4.
[0084] As can be seen from FIG. 22, the cathode current density
measured in Example 3 and Example 4 are 2-3 times lower than those
of Comparative Example 1 and Comparative Example 2, indicating that
the addition of Ge inhibits the activation of magnesium
cathode.
[0085] As can be seen from FIG. 23, a similar trend can be observed
when the experiment is repeated with a higher anode polarization
current density (2-24 mA/cm.sup.2). Thus, the high strength and
corrosion-resistant magnesium alloy materials of Example 3 and
Example 4 show the potential as fine electrode materials due to
their good corrosion resistance performance, low self-reaction
(corrosion) rate, and little hydrogen evolution.
[0086] FIG. 24 shows the anode dissolution current density of the
high strength and corrosion-resistant magnesium alloy materials of
Examples 3-4 and Comparative Examples 1-2 in 0.1 M sodium chloride
during open circuit potential (OCP) and potentiodynamic
polarization (PDP) by inductively coupled plasma optical emission
spectrometer (ICP-OES), wherein Mg represents Comparative Example
1, Mg-1Zn represents Comparative Example 2, Mg-1Zn-0.3Ge represents
Example 3, and Mg-1Zn-0.5Ge represents Example 4.
[0087] It can be seen from FIG. 24 that Example 3 and Example 4
exhibit the lowest anode dissolution current density during both
OCP and potentiodynamic polarization.
[0088] FIG. 25 shows the relationship between the anode dissolution
current density and the anode potential of the high strength and
corrosion-resistant magnesium alloy materials of Examples 3-4 and
Comparative Examples 1-2, wherein Mg represents Comparative Example
1, Mg-1Zn represents Comparative Example 2, Mg-1Zn-0.3Ge represents
Example 3, and Mg-1Zn-0.5 Ge represents Example 4.
[0089] As can be seen from FIG. 25, for Comparative Examples 1-2
and Examples 3-4, the anode dissolution current density increases
logarithmically as the anode potential increases. It shall be noted
that the kinetics of the anode reaction of Examples 3-4 is lower
than those of Comparative Examples 1-2. The slopes of curves
derived from ICP-OES polarization analysis are listed in Table
4.
TABLE-US-00005 TABLE 4 No. Slope (V/.mu.A cm.sup.2) E3 0.0168 E4
0.0234 CE1 0.0114 CE2 0.0106
[0090] It can be seen from Table 4 that the addition of small
amount of the above-mentioned alloying elements inhibits the
kinetics of the magnesium anode.
[0091] FIG. 26 shows the microhardness measurement results of
Comparative Example 2 and Examples 3-4. FIG. 27 shows the
engineering stress-strain curves of Comparative Example 2 and
Examples 3-4. In FIG. 26 and FIG. 27, Mg-1Zn represents Comparative
Example 2, Mg-1Zn-0.3Ge represents Example 3, and Mg-1Zn-0.5Ge
represents Example 4.
[0092] It can be seen from FIG. 26 that as the Ge content
increases, the hardness of the alloy increases from 50HV1 in
Comparative Example 2 to 83HV1 in Example 4.
[0093] It can be seen from FIG. 27 that as the Ge content
increases, the yield strength of the alloy increases from about 255
MPa in Comparative Example 2 to about 320 MPa in Example 4.
[0094] It should be noted that the portion of prior art in the
protection scope of the present invention is not limited to the
embodiments given herein. All prior art that does not contradict
the solutions of the present invention, including but not limited
to the previous patent documents, prior publications, prior
applications, etc., can all be included in the protection scope of
the present invention.
[0095] In addition, the combination of the technical features in
the present disclosure is not limited to the combination described
in the claims or the combination described in the specific
examples. All technical features described herein can be freely
combined in any way, unless contradicts between each other.
[0096] It should also be noted that the above-listed embodiments
are only specific examples of the present invention. Obviously, the
present invention should not be unduly limited to such specific
embodiments. Changes or modifications that can be directly or
easily derived from the present disclosure by those skilled in the
art are intended to be within the protection scope of the present
invention.
* * * * *