U.S. patent application number 13/511891 was filed with the patent office on 2012-10-25 for magnesium alloy.
Invention is credited to Sung-Youn Cho, Jong-Tack Kim, Yu-Chan Kim, Ja-Kyo Koo, Hyun-Kwang Seok, Seok-Jo Yang.
Application Number | 20120269673 13/511891 |
Document ID | / |
Family ID | 44146044 |
Filed Date | 2012-10-25 |
United States Patent
Application |
20120269673 |
Kind Code |
A1 |
Koo; Ja-Kyo ; et
al. |
October 25, 2012 |
MAGNESIUM ALLOY
Abstract
The present invention relates to a magnesium alloy having
controlled corrosion resistance properties, which comprises
magnesium (Mg) and an alloying element and includes a magnesium
phase and a phase composed of magnesium and the alloying element,
wherein the difference in electrical potential between the
magnesium phase and the phase composed of magnesium and the
alloying element is greater than 0 V but not greater than 0.2
V.
Inventors: |
Koo; Ja-Kyo; (Seoul, KR)
; Seok; Hyun-Kwang; (Seoul, KR) ; Yang;
Seok-Jo; (Daejeon, KR) ; Kim; Yu-Chan; (Seoul,
KR) ; Cho; Sung-Youn; (Uijeongbu-si, KR) ;
Kim; Jong-Tack; (Jeonju-si, KR) |
Family ID: |
44146044 |
Appl. No.: |
13/511891 |
Filed: |
December 7, 2010 |
PCT Filed: |
December 7, 2010 |
PCT NO: |
PCT/KR2010/008725 |
371 Date: |
May 24, 2012 |
Current U.S.
Class: |
420/403 ;
420/402; 420/411; 420/413; 420/414 |
Current CPC
Class: |
A61L 27/50 20130101;
C22C 23/00 20130101; C22C 23/04 20130101; A61L 27/047 20130101;
C22C 1/02 20130101; C22C 23/06 20130101 |
Class at
Publication: |
420/403 ;
420/402; 420/411; 420/413; 420/414 |
International
Class: |
C22C 23/04 20060101
C22C023/04; C22C 23/00 20060101 C22C023/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 7, 2009 |
KR |
10-2009-0120356 |
Claims
1. A magnesium alloy having controlled corrosion resistance
properties, which comprises magnesium (Mg) and an alloying element
and includes a magnesium phase and a phase composed of magnesium
and the alloying element, wherein the difference in electrical
potential between the magnesium phase and the phase composed of
magnesium and the alloying element is greater than 0 V but not
greater than 0.2 V.
2. The magnesium alloy of claim 1, wherein the magnesium alloy
contains no aluminum.
3. The magnesium alloy of claim 1, wherein the magnesium alloy
contains no rare earth element.
4. The magnesium alloy of claim 1, wherein the alloying element is
one or more selected from among calcium (Ca), iron (Fe), manganese
(Mn), cobalt (Co), nickel (Ni), chromium (Cr), copper (Cu), cadmium
(Cd), zirconium (Zr), silver (Ag), gold (Au), palladium (Pd),
platinum (Pt), rhenium (Re), iron (Fe), zinc (Zn), molybdenum (Mo),
niobium (Nb), tantalum (Ta), titanium (Ti), strontium (Sr), silicon
(Si), phosphorus (P) and selenium (Se).
5. The magnesium alloy of claim 1, wherein the magnesium alloy is
represented by the following formula 1: Mg.sub.aCa.sub.bX.sub.c
[Formula 1] wherein a, b and c represent the molar fractions of the
respective components, a+b+c=1, 0.5.ltoreq.a<1,
0.ltoreq.b.ltoreq.0.4, and 0.ltoreq.c.ltoreq.0.4; if at least one
of b and c is greater than 0 and c is 0, the content of Ca is 5-33
wt % based on the total weight of the magnesium alloy; and X is one
or more selected from among zirconium (Zr), molybdenum (Mo),
niobium (Nb), tantalum (Ta), titanium (Ti), strontium (Sr),
chromium (Cr), manganese (Mn), zinc (Zn), silicon (Si), phosphorus
(P), nickel (Ni) and iron (Fe).
6. The magnesium alloy of claim 1, wherein the magnesium alloy is
represented by the following formula 2 and comprises, based on the
total weight thereof, greater than 0 wt % but not greater than 23
wt % of calcium (Ca), greater than 0 wt % but not greater than 10
wt % of Y, and a balance of magnesium (Mg): Mg--Ca--Y [Formula 2]
wherein Y is Mn or Zn.
7. The magnesium alloy of claim 1, wherein the magnesium alloy is
represented by the following formula 3 and comprises, based on the
total weight thereof, greater than 0 wt % but not greater than 40
wt % of Z and a balance of magnesium (Mg): Mg--Z [Formula 3]
wherein Z is one or more selected from among manganese (Mn), cobalt
(Co), nickel (Ni), chromium (Cr), copper (Cu), cadmium (Cd),
zirconium (Zr), silver (Ag), gold (Au), palladium (Pd), platinum
(Pt), rhenium (Re), iron (Fe), zinc (Zn), molybdenum (Mo), niobium
(Nb), tantalum (Ta), titanium (Ti), strontium (Sr), silicon (Si),
phosphorus (P) and selenium (Se).
8. The magnesium alloy of claim 1, wherein the magnesium alloy is
surface-treated.
9. A method for preparing a magnesium alloy having controlled
corrosion resistance properties, the method comprising adding, to a
magnesium alloy comprised of magnesium and an alloying element, a
third element, thereby reducing the difference in electrical
potential between a magnesium phase and a phase composed of
magnesium and the alloying element to greater than 0 V but not
greater than 0.2 V.
10. The method of claim 9, wherein the magnesium alloy comprises
magnesium and calcium, and the third element is zinc.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of priority of Korean
Patent Application No. 10-2009-0120356, filed with the Korean
Intellectual Property Office on Dec. 7, 2009, the disclosure of
which is incorporated herein by reference in its entirety.
TECHNICAL FIELD
[0002] The present invention relates to a magnesium alloy.
BACKGROUND ART
[0003] Magnesium alloys are easily shaped, but have disadvantages
of poor corrosion resistance and poor strength. Studies are
continually performed with the aim of suitably changing the
composition of magnesium alloys in order to improve the corrosion
resistance and strength of magnesium alloys. In addition, studies
have demonstrated that an increase in the amount of alloying
elements in the magnesium alloy leads to an increase in the
mechanical strength of the magnesium alloy. However, as the amount
of alloying elements increases, several phases are formed, and an
increase in the difference in electrical potential between these
phases results in conditions such that a galvanic circuit, which
increases the rate of corrosion of the alloy, is likely to be
formed.
[0004] Therefore, there is a need for studies on a magnesium alloy,
the corrosion resistance properties of which can be controlled and
which has excellent corrosion resistance and strength.
DISCLOSURE
Technical Problem
[0005] It is an object of the present invention to provide a
magnesium alloy whose corrosion resistance properties are
controlled by adding an alloying element having an electrical
potential different from that of magnesium, depending on the
intended use of the magnesium alloy.
[0006] Another object of the present invention is to provide a
magnesium alloy, the corrosion resistance and strength properties
of which can be controlled through post-treatment processing.
Technical Solution
[0007] In order to accomplish the above objects, the present
invention provides a magnesium alloy having controlled corrosion
resistance properties, which comprises magnesium (Mg) and an
alloying element and includes a magnesium phase and a phase
composed of magnesium and the alloying element, wherein the
difference in electrical potential between the magnesium phase and
the phase composed of magnesium and the alloying element is greater
than 0 V but not greater than 0.2 V.
[0008] The present invention also provides a method for preparing a
magnesium alloy having controlled corrosion resistance properties,
the method comprising adding, to a magnesium alloy comprised of
magnesium and an alloying element, a third element, thereby
reducing the difference in electrical potential between a magnesium
phase and a phase composed of magnesium and the alloying element to
greater than 0 V but not greater than 0.2 V.
Advantageous Effects
[0009] The corrosion resistance properties of the magnesium alloy
according to the present invention can be controlled using the
difference in electrical potential between the magnesium and the
alloying element. In addition, the corrosion resistance and
strength properties of the magnesium alloy of the present invention
can also be controlled through post-treatment processing.
Furthermore, due to these effects, the magnesium alloy can be used
in the industrial and medical fields.
DESCRIPTION OF DRAWINGS
[0010] FIG. 1 is a graphic diagram showing the corrosion rates of
the magnesium alloys of Examples 1 to 4 and Comparative Examples 1
and 2.
[0011] FIG. 2 is a graphic diagram showing the results of
measurement of the strengths of the magnesium alloys of Example 1,
Example 2 and Comparative Example 1.
[0012] FIG. 3 is a graphic diagram showing the results of
measurement of the strengths of the magnesium alloys of Example 3,
Example 4 and Comparative Example 2.
[0013] FIG. 4 is a photograph showing the alloy of Example 2 before
and after surface treatment.
[0014] FIG. 5 is a graphic diagram showing the open circuit
potentials of the magnesium alloys of Examples 5 to 9 and
Comparative Example 1 as a function of time.
[0015] FIG. 6 is a graphic diagram showing the rate of generation
of hydrogen as a function of the content of zinc.
[0016] FIG. 7 is a graphic diagram showing open circuit potential
(electrical potential) as a function of the content of zinc.
[0017] FIG. 8 is a graphic diagram showing the rate of degradation
as a function of the difference in open circuit potential
(electrical potential).
BEST MODE
[0018] Hereinafter, the present invention will be described in
detail.
[0019] I. Magnesium Alloy
[0020] The present invention is directed to a magnesium alloy
having controlled corrosion resistance properties, which comprises
magnesium (Mg) and an alloying element and includes a magnesium
phase and a phase composed of magnesium and the alloying
element.
[0021] Herein, the difference in electrical potential between the
magnesium phase and the phase composed of magnesium and the
alloying element is greater than 0 V but not greater than 0.2 V,
and is preferably close to 0. If the magnesium alloy satisfies the
above-described range, it has a very low rate of degradation, and
thus can be effectively used in the industrial and medical fields.
In addition, the magnesium alloy has excellent corrosion resistance
and strength.
[0022] The alloying element is not specifically limited, as long as
the difference in electrical potential between the magnesium phase
and the phase composed of magnesium and the alloying element falls
within the above-described range. Examples of the alloying element
include calcium (Ca), iron (Fe), manganese (Mn), cobalt (Co),
nickel (Ni), chromium (Cr), copper (Cu), cadmium (Cd), zirconium
(Zr), silver (Ag), gold (Au), palladium (Pd), platinum (Pt),
rhenium (Re), iron (Fe), zinc (Zn), molybdenum (Mo), niobium (Nb),
tantalum (Ta), titanium (Ti), strontium (Sr), silicon (Si),
phosphorus (P) and selenium (Se).
[0023] Meanwhile, the magnesium alloy that realizes the difference
in electrical potential between the magnesium phase and the phase
composed of magnesium and the alloying element is preferably
represented by the following formula 1:
Mg.sub.aCa.sub.bX.sub.c [Formula 1]
wherein a, b and c represent the molar fractions of the respective
components, a+b+c=1, 0.5.ltoreq.a<1, 0.ltoreq.b.ltoreq.0.4, and
0.ltoreq.c.ltoreq.0.4; if at least one of b and c is greater than
0, and c is 0, the content of Ca is 5-33 wt % based on the total
weight of the magnesium alloy; and X is one or more selected from
among zirconium (Zr), molybdenum (Mo), niobium (Nb), tantalum (Ta),
titanium (Ti), strontium (Sr), chromium (Cr), manganese (Mn), zinc
(Zn), silicon (Si), phosphorus (P), nickel (Ni) and iron (Fe).
[0024] Even if X represents two or more elements, the total molar
fraction of the elements of X satisfies the range of c. As the
contents of Ca and X increase, the strength of the magnesium alloy
increases while the rate of degradation thereof also increases.
Thus, the amounts of Ca and X in the magnesium alloy of the present
invention can be determined within the above-described ranges by
taking into consideration the required strength of the alloy and
the rates of degradation of the additional metals.
[0025] When nickel (Ni) is included in X, nickel reduces the
toxicity of the magnesium alloy and makes it possible to control
the rate of corrosion of the magnesium alloy. Herein, the content
of nickel is preferably 100 ppm or less, and more preferably 50 ppm
or less. In addition, when iron (Fe) is included in X, iron
significantly influences the increase in the rate of corrosion of
the magnesium, and for this reason, the content of iron is
preferably 1,000 ppm or less, and more preferably 500 ppm or less.
If iron is contained in an amount exceeding the upper limit of the
above range, iron will be present as an independent factor, without
being fixed to magnesium, thus increasing the rate of corrosion of
the magnesium alloy.
[0026] The magnesium alloy that realizes the difference in
electrical potential between the magnesium phase and the phase
composed of magnesium and the alloying element is preferably
represented by the following formula 2.
[0027] The magnesium alloy represented by formula 2 comprises,
based on the total weight thereof, greater than 0 wt % but not
greater than 23 wt % of calcium (Ca), greater than 0 wt % but not
greater than 10 wt % of Y, and the balance of magnesium (Mg).
Mg--Ca--Y [Formula 2]
wherein Y is Mn or Zn.
[0028] When the composition of the magnesium alloy represented by
formula 2 falls within the above-described ranges, it has not only
improved mechanical properties, but also improved corrosion
resistance, and does not undergo brittle fracture.
[0029] The magnesium alloy represented by formula 2 preferably
comprises, based on the total weight thereof, greater than 0 wt %
but not greater than 23 wt % of calcium (Ca), 0.1-5 wt % of Y, and
the balance of magnesium (Mg). More preferably, the magnesium alloy
represented by formula 2 comprises greater than 0 wt % but not
greater than 23 wt % of calcium (Ca), 0.1-3 wt % of Y, and the
balance of Mg. The reason for this is that when the same corrosion
rate is realized, taking into consideration the possible side
effects of impurities, the contents of the impurities should
preferably be low.
[0030] The magnesium alloy that realizes the difference in
electrical potential between the magnesium phase and the phase
composed of magnesium and the alloying element is preferably
represented by the following formula 3. The magnesium alloy
represented by formula 3 comprises, based on the total weight
thereof, greater than 0 wt % but no greater than 40 wt % of Z and
the balance of magnesium (Mg).
Mg--Z [Formula 3]
wherein Z is one or more selected from among manganese (Mn), cobalt
(Co), nickel (Ni), chromium (Cr), copper (Cu), cadmium (Cd),
zirconium (Zr), silver (Ag), gold (Au), palladium (Pd), platinum
(Pt), rhenium (Re), iron (Fe), zinc (Zn), molybdenum (Mo), niobium
(Nb), tantalum (Ta), titanium (Ti), strontium (Sr), silicon (Si),
phosphorus (P) and selenium (Se). The magnesium alloy is preferably
subjected to surface treatment. The surface treatment is preferably
shot peening.
[0031] The magnesium alloy which is included in an implant of the
present invention may be subjected to surface coating. When the
surface coating is performed, a corrosion-resistant product can be
produced on the surface of the magnesium alloy, whereby the rate of
degradation of the magnesium alloy can be delayed.
[0032] The surface coating may be performed with a ceramic and/or
polymer material.
[0033] Hereinafter, the coating of the magnesium alloy surface with
a ceramic material will be described. When the magnesium is
immersed in a biomimetic solution or physiological saline, the
surface of the magnesium alloy can be coated with a
corrosion-resistant product. Herein, the corrosion-resistant
product may be a ceramic material, in which the ceramic material
may be magnesium oxide or calcium phosphate. In addition, after the
surface of the biodegradable magnesium alloy is coated with the
corrosion-resistant product, it may further be coated with a
polymer. Examples of the polymer which may be used in the present
invention are as described below.
[0034] The polymer that is used to coat the surface of the
magnesium alloy is not specifically limited, as long as it is one
that is conventionally used in the art. Preferred examples of the
polymer for use in the present invention include poly(L-lactide),
poly(glycolide), poly(DL-lactide), poly(dioxanone),
poly(DL-lactide-co-L-lactide), poly(DL-lactide-co-glycolide),
poly(glycolide-co-trimethylene carbonate),
poly(L-lactide-co-glycolide), poly(e-caprolactone), and
combinations thereof.
[0035] The magnesium alloy according to the present invention can
be used in various ways. For example, it may be coated on the
surface of ceramic, metal and polymer materials. In addition, the
magnesium alloy according to the present invention may be used in
combination with a ceramic or polymeric material.
[0036] II. Preparation Method
[0037] The present invention also provides a method for preparing a
magnesium alloy having controlled corrosion resistance properties,
the method comprising adding, to a magnesium alloy comprised of
magnesium and an alloying element, a third element, thereby
reducing the difference in electrical potential between the
magnesium phase and the phase composed of magnesium and the
alloying element to greater than 0 V, but not greater than 0.2 V.
Herein, the magnesium alloy is preferably an alloy comprising
magnesium and calcium. In addition, the third element is preferably
zinc.
[0038] III. Method for Preparing Magnesium Alloy
[0039] The inventive method for preparing the magnesium alloy
having controlled corrosion resistance properties may comprise the
steps of: a) providing the magnesium alloy; and b) shaping the
magnesium alloy.
[0040] Step a) of the method is preferably performed by melting the
magnesium.
[0041] More specifically, step a) may be performed by melting the
magnesium in a vacuum atmosphere or in an atmosphere of inert gas
such as argon (Ar), which does not react with magnesium. In
addition, step a) may be performed by melting the magnesium using
various methods, such as a resistance heating method, in which heat
is generated by electrically heating a resistive material, an
induction heating method, in which a current is allowed to flow
through an induction coil, or a method that uses a laser or focused
light. Among these melting methods, the resistance heating method
is the most economical method. In addition, the melted alloy
(hereinafter referred to as the "melt") is preferably stirred
during the melting of magnesium such that impurities can be mixed
well.
[0042] Step b) of the inventive method for preparing the magnesium
alloy may be performed by shaping the molten magnesium alloy using
one or more selected from the group consisting of a quenching
method, an extrusion method, and a metal processing method.
[0043] The quenching method can be used in order to improve the
mechanical strength of the magnesium alloy. More specifically, if
magnesium is melted in step a), a method of immersing a crucible
containing the molten magnesium in water may be used. In addition,
a quenching method of spraying inert gas such as argon onto the
molten magnesium may also be used. This spray-quenching method can
quench the molten magnesium at a very high quenching rate, thereby
realizing a very fine structure. However, in the case in which
magnesium is cast in a small size, it should be noted that a
plurality of pores (black portions) can also be formed.
[0044] The extrusion method is used to make the structure of the
magnesium uniform and enhance the mechanical performance of the
magnesium. The extrusion method can control the strength and
corrosion resistance properties of the magnesium alloy of the
present invention.
[0045] The extrusion method is preferably performed at
300.about.450.degree. C. Furthermore, the extrusion of magnesium
may be carried out at a ratio of reduction in the cross-sectional
area before and after extrusion (an extrusion ratio) of 10:1 to
30:1. As the extrusion ratio increases, the fine structure of the
extruded material becomes more uniform, and defects formed during
casting are easily removed. In this case, it is preferred to
increase the capacity of the extrusion system.
[0046] The metal processing method is not particularly limited so
long as it is known in the art. Examples of the metal processing
method include a method in which the molten magnesium is poured and
cast in a mold that is processed such that it has a shape close to
the shape of a final product; a method in which the molten
magnesium is prepared into an intermediate material such as a rod
or a sheet and is then subjected to turning or milling; and a
method in which the magnesium alloy is forged at a higher pressure,
thus obtaining a final product.
MODE FOR INVENTION
[0047] Hereinafter, the preparation of magnesium alloys will be
described in further detail with reference to examples. It is to be
understood, however, that these examples are provided for
illustrative purposes only, and are not intended to limit the scope
of the present invention.
Examples 1 to 4 and Comparative Examples 1 and 2
Preparation of Magnesium Alloys
Examples 1 and 2 and Comparative Example
[0048] Elements were mixed to have the compositions shown in Table
1 below, and were charged into a stainless steel (SUS 410) crucible
having an inner diameter of 50 mm. Then, while argon (Ar) gas was
allowed to flow around the crucible so that the magnesium in the
crucible did not come into contact with air, the temperature of the
crucible was increased to about 700.about.750.degree. C. using a
resistance heating furnace, thereby melting the magnesium. The
crucible was shaken so that the molten magnesium could be mixed
well with the impurities. The completely molted Mg alloy was
quenched, thus preparing solid-state magnesium. Also, upon
quenching, the crucible was immersed in water (20.degree. C.) to
enhance the mechanical strength of magnesium such that the molten
magnesium was rapidly quenched, thereby preparing a magnesium
alloy.
TABLE-US-00001 TABLE 1 Difference in Mg Ca Zn electrical (parts by
(parts by (parts by potential (V) weight) weight) weight) Mg vs.
Mg--Ca--Zn Example 1 95 5 0 -- (due to the absence of Zn) Example 2
95 5 6.35 0.20 Comparative 100 -- -- -- Example 1 Mg: Ultrahigh
purity (99.98%) for reagents
Examples 3 and 4 and Comparative Example 2
[0049] The magnesium alloys of Examples 1 and 2 and Comparative
Example 1 were extruded. The extrusion was performed at
370-375.degree. C., and the ratio of reduction in the
cross-sectional area before and after extrusion (the extrusion
ratio) was set at 15:1. Herein, the extruded alloy of Example 2
corresponds to the magnesium alloy of Example 1; the extruded alloy
of Example 4 corresponds to the magnesium alloy of Example 2; and
the extruded alloy of Comparative Example 2 corresponds to the
magnesium alloy of Comparative Example 1.
Test Example 1
Evaluation of Rate of Corrosion of Magnesium Alloy
[0050] In general, the rate of corrosion of magnesium alloys is
determined by measuring the amount of hydrogen generated when the
magnesium alloy is immersed in the solution shown in Table 2 below.
This is because the biodegradation of magnesium results in the
generation of hydrogen and the solution shown in Table 2 is a
biomimetic solution.
TABLE-US-00002 TABLE 2 Molar concentration (mM/L) Mass (g)
CaCl.sub.22H.sub.2O 1.26 0.185 KCl 5.37 0.400 KH.sub.2PO.sub.4 0.44
0.060 MgSO.sub.47H.sub.2O 0.81 0.200 NaCl 136.89 8.000
Na.sub.2HPO.sub.42H.sub.2O 0.34 0.060 NaHCO.sub.3 4.17 0.350
D-Glucose 5.55 1.000
[0051] FIG. 1 is a graphic diagram showing the rates of corrosion
of the magnesium alloys of Examples 1 to 4 and Comparative Examples
1 and 2.
[0052] As can be seen in FIG. 1, the corrosion resistance
properties of the magnesium alloys were significantly improved when
the alloying element was added and extrusion was performed. This
suggests that the rate of degradation of magnesium alloys can be
controlled to various levels using an alloying element and a
post-treatment process.
Test Example 2
Evaluation of Strength of Magnesium Alloys
[0053] The magnesium alloys of Examples 1 to 4 and Comparative
Examples 1 and 2 were electric-discharge-machined into specimens
having a diameter of 3 mm and a length of 6 mm. The upper and lower
surfaces of the specimens were polished with #1000 emery paper to
adjust the level of the surface. The specimens were horizontally
placed on a jig made of tungsten carbide, and then a force was
vertically applied to the specimens using the head of a compression
tester with a maximum load of 20 tons. At this time, the vertical
speed of the head was 10.sup.-4/s. During the test, the changes in
strain and compressive stress were recorded in real time using an
extensometer and a load cell provided in the compression tester. At
this time, the size of the specimen was too small to place the
extensometer in the specimen, so the extensometer was placed in the
jig of the tester that was used to press the specimen. Therefore,
the strain of the specimen was measured as higher than its actual
strain.
[0054] FIG. 2 is a graphic diagram showing the results of
measurement of the strengths of the magnesium alloys of Examples 1
and 2 and Comparative Example 1. FIG. 3 is a graphic diagram
showing the results of measurement of the strengths of the
magnesium alloys of Examples 3 and 4 and Comparative Example 2.
[0055] In addition, Table 3 below shows the strengths of the
magnesium alloys of Examples 1 to 4 and Comparative Examples 1 and
2. In Table 3, Y.S indicates yield strength, and UCS indicates
ultimate compression strength.
TABLE-US-00003 TABLE 3 Comp. Comp. Example Example Example Example
Example Example 1 2 3 4 1 2 Strength Y.S 87 100 155 165 47 48 (MPa)
UCS 180 230 365 400 146 208
[0056] As can be seen in FIGS. 2 and 3 and Table 3, the strength
properties of the magnesium alloys were significantly improved when
the alloying element was added and physical treatment was
performed. The magnesium alloy of Example 4 showed the best
results.
[0057] From the results in FIGS. 1 to 3, it can be seen that the
magnesium alloys of Examples 1 to 4 according to the present
invention can be controlled to have corrosion resistance properties
ranging from 2-3 days to 2 years and strengths of 87 MPa to 400 MPa
by controlling the composition of the alloy and performing the
post-treatment processing (extrusion). Thus, it can be seen that a
magnesium alloy that can maintain its strength for a required
period of time can be prepared based on the above findings.
Test Example 3
Evaluation of Properties Caused by Surface Treatment
[0058] The alloy of Example 2 was subjected to surface treatment
(shot peening), and the results of the treatment are shown in FIG.
4. The upper portion of FIG. 4 shows the alloy before surface
treatment, and the lower portion shows the alloy after surface
treatment.
[0059] As can be seen in FIG. 4, before surface treatment, the
magnesium was bright, but after surface treatment, the brightness
disappeared.
[0060] In addition, after surface treatment, plastic deformation of
the surface occurred, thus reducing the rate of degradation of the
alloy and increasing the strength thereof. Furthermore, it will
reflect less light in an operating room so as not to interfere with
vision, and gives an elegant feel. In addition, when the surface of
the magnesium becomes rough, the adhesion of bone to the surface
can be improved.
Examples 5 to 9
Preparation of Magnesium Alloys
[0061] Magnesium alloys of Examples 5 to 9 were prepared using the
compositions shown in Table 4 below according to the method of
Example 1.
TABLE-US-00004 TABLE 4 Example 5 Example 6 Example 7 Example 8
Example 9 Mg.sub.2Ca 93.65 95.78 97.89 99.58 100 (wt %) Zn (wt %)
6.35 4.22 2.11 0.42 0
Test Example 4
Evaluation of Open Circuit Potentials
[0062] FIG. 5 is a graphic diagram showing the open circuit
potentials of the magnesium alloys of Examples 5 to 9 and
Comparative Example 1 as a function of time.
[0063] As can be seen in FIG. 5, the magnesium alloys of
Comparative Example 1 and Example 5 showed the smallest difference
in open circuit potential, indicating the best corrosion
resistance, but the magnesium alloys of Comparative Example 1 and
Example 9 showed a great difference in open circuit potential,
indicating the highest corrosion rate.
Test Example 5
Evaluation of Rate of Biodegradation by Difference in Electrical
Potential
[0064] The corrosion rates of the magnesium alloys were determined
by measuring the amount of hydrogen that was generated when the
magnesium alloys were immersed in the solution of Table 2
above.
[0065] FIG. 6 is a graphic diagram showing the rate of generation
of hydrogen as a function of the content of zinc. In FIG. 6, the
x-axis indicates the Zn (at %) content in magnesium alloy
containing Mg.sub.2Ca.
[0066] As can be seen in FIG. 6, as the content of zinc increased,
the rate of corrosion of the magnesium alloys increased.
[0067] FIG. 7 is a graphic diagram showing the open circuit
potential (electrical potential) as a function of the content of
zinc. In FIG. 7, the x-axis indicates the Zn (at %) content in
magnesium alloy containing Mg.sub.2Ca.
[0068] As can be seen in FIG. 7, as the content of zinc increased,
the difference in open circuit potential from Comparative Example 1
decreased.
[0069] FIG. 8 shows the rate of degradation of a magnesium alloy as
a function of the difference in open circuit potential.
[0070] As can be seen in FIG. 8, when the difference in open
circuit potential was greater than 0.2 V, the rate of degradation
of the magnesium alloy rapidly increased. In FIG. 8, the rate of
degradation is expressed as hydrogen generation rate.
* * * * *