WO2008016150A1 - Magnesium alloy and method for producing the same - Google Patents

Abstract

Disclosed is a novel magnesium alloy expanded material having a structure wherein second-phase particles containing zinc or quasicrystal particle phases, respectively having a nanosized spherical shape with an average particle diameter of not more than 500 nm, are deposited in a magnesium matrix. The magnesium alloy expanded material has high strength, high ductility, high compression strength and high fracture toughness.

Description

 Specification

 Magnesium alloy and manufacturing method thereof

 Technical field

 The present invention relates to a new magnesium alloy having good strength and toughness and a method for producing the same.

 Background art

 [0002] Magnesium alloys are expected to be applied to various structural members because they are lightweight! And the improvement of the characteristic for practical use is also advanced. In particular, in order to put magnesium alloy into practical use as a mechanical structure material, it is a challenge to have high strength and toughness as well as the feature of being lightweight.

 In order to solve this problem, various studies and ideas have been attempted so far.

 [0004] For example, conventionally, as a means for realizing the high strength and high toughness characteristics of a magnesium alloy, a powdered foil strip or the like is mainly used to produce a solidified molded body, and then a warm strain is produced. It is generally attempted to introduce processing. The feature of this method is that the second-phase particles such as intermetallic compounds are uniformly and finely dispersed in the magnesium matrix simultaneously with the refinement of the crystal grain structure.

 [0005] However, in these conventional methods, there is a possibility that oxygen taken in at the time of solidification molding exists as an oxide compound on the grain boundary, which may cause deterioration of characteristics. Also, since supersaturated alloy powder foil strips are used, the second phase particles easily precipitate during warm working, making it difficult to control the volume fraction of the particles (especially on the low concentration side)! / Therefore, it has been difficult to improve the strength and toughness of the magnesium alloy beyond a certain level.

[0006] For example, in the method of Patent Document 1 (Japanese Patent Application Laid-Open No. 2006-2184), a powder solidified alloy of Mg — ;! ~ 8RE (RE: rare earth element) 1-6Ca is prepared, and then warm extrusion is performed. Force to be used When creating a powder solidified body, it is difficult to improve fracture toughness due to oxide incorporation at the interface between the parent phase and the parent phase. In addition, since rare earth metals are used, it is difficult to expect significant improvements in properties and functions to meet such an increased burden because the price of the substrate is expected to increase. Patent Document 2 (Japanese Patent Application Laid-Open No. 2004-149862) relates to a high-strength, high-toughness magnesium alloy using an Mg—Zn—RE alloy. However, the molten metal added with a high concentration of different elements is used as a rapidly solidified powder and solidified and formed to uniformly disperse the precipitates with a high volume fraction, which depends on the dispersion strengthening of the intermetallic compound. Therefore, there is a problem that the fracture easily progresses at the interface between the high volume fraction dispersion and the matrix phase, and the toughness and the high ductility cannot be achieved. In addition, since rare earth metals are used, the price of the substrate becomes expensive, but it is difficult to expect significant improvements in properties and functions to meet such an increased burden.

 [0008] Patent Document 3 (Japanese Patent Laid-Open No. 5-70880) and Patent Document 4 (Japanese Patent Laid-Open No. 7-3375) describe a rapidly solidified foil body using a molten metal added with a high concentration of different elements, and then extrusion-solidified. It relates to the manufacturing method.

 However, since this method relies on dispersion strengthening of the intermetallic compound, fracture easily progresses at the interface between the high volume fraction dispersion and the parent phase, resulting in high toughness and high ductility. Cannot be achieved. In addition, since it is performed in a deoxygenated atmosphere until solidified molding is obtained, there is a problem that it is impossible to simplify the work! /, And! /.

 Patent Document 5 (Japanese Patent Laid-Open No. 5-306424) relates to a method for producing a high hardness / strength / toughness magnesium alloy using an Mg—RE alloy.

 [0011] The method and problems thereof are the same as in Patent Documents 3 and 4.

 On the other hand, Patent Document 6 (Japanese Unexamined Patent Application Publication No. 2003-277899) relates to a manufacturing method in which a pre-strain of 0.4 or less is applied to a forged magnesium alloy and then warm strain processing is performed.

 [0013] In this method, pre-strain is applied before warm working to introduce uniform precipitation nucleation sites.

 This makes it possible to form a finely dispersed particle phase in the magnesium matrix.

 [0014] Although the method of Patent Document 6 is more practically rational in that it uses a forged magnesium alloy that is not a solidified molded body such as a powdery foil body, the method is practically practical. It is not always easy to control and reproduce. For this reason, there is a great difficulty in improving the strength-toughness due to the structure of fine particle dispersion in the magnesium matrix.

[0015] In addition, as a method using a forged material, in Non-Patent Document 1 (Materials Transactions, 47 (2006), 1066-1077), manufacturing a high toughness alloy using Mg-RE-Zn-Zr alloy Is disclosed. In this method, the forged material is expanded by warm strain processing and then heated. A treatment is applied to disperse precipitates such as second phase particles in the parent phase.

 [0016] However, since the heat treatment is performed after the processing in the warm strain, there is a problem that the crystal grains of the parent phase are coarsened and high strength cannot be achieved. In addition, since rare earth elements are used as additive elements, it is difficult to expect improvements in properties and functions to meet such an increased burden.

 [0017] In the conventional technology as described above, the force S, which is noted in terms of the structure configuration in which fine particles are dispersed in the magnesium matrix to improve the strength-toughness characteristics. Therefore, it is difficult to develop such structural features to improve strength and toughness. Therefore, it is necessary to develop new technical means for this purpose. At that time, the following should be considered.

 [0018] 1) Presenting new developmental knowledge as the structure of the magnesium alloy.

 [0019] 2) Realize more simply and practically.

 [0020] 3) A magnesium alloy that uses a relatively inexpensive additive element rather than a rare earth element.

 [0021] 4) When using rare earth elements, remarkable characteristics and functions should be improved to meet the economic burden.

 [0022] With regard to such a viewpoint, the applicant of the present invention also uses high-strength and good ductility as in the case of using the rare earth element of viewpoint 4), as in Patent Document 7 (Japanese Patent Laid-Open No. 2005-113235). In particular, we have already developed a high-strength, high-strength magnesium alloy wrought material!

 [0023] This wrought magnesium alloy has a composition represented by the composition formula Mg Zn Y (where a and b are atomic%, and a / 12≤b≤a / 3, 1.5≤a≤10). And a quasicrystal represented by the composition formula Mg Zn Y crystallizes at the grain boundary of the magnesium parent phase (a-Mg), and a quasicrystal having a particle diameter of 100 nm or less and its approximate crystal are the magnesium parent phase. It has a uniformly dispersed structure in the crystal grains! Quasicrystals and approximate crystals are stable without causing phase transformation at temperatures below 250 ° C, and the strength is remarkably increased by strong interaction with dislocations. Slip is suppressed, and these effects synergistically improve the high-temperature strength.

[0024] The above-mentioned magnesium alloy wrought material has strength and ductility during tensile deformation and high strength. It was developed with an emphasis on improving the temperature and other characteristics are not clear. Considering application to structural members for moving bodies such as vehicles, it is necessary to ensure safety and reliability against contact, collision, etc. For that purpose, it must have high compressive deformability and excellent fracture toughness performance. Is very important.

 [0025] The magnesium alloy is subjected to strain processing such as rolling and extrusion due to the crystal structure peculiar to magnesium, so that the texture oriented in the bottom surface formed during strain processing remains in the material as it is. For this reason, commercially available wrought magnesium alloy materials so far show high tensile strength at room temperature, while compressive strength remains at about 50% to 80% of tensile strength. Therefore, when a general magnesium alloy wrought material is applied to a structural member for a moving body, it is difficult to maintain a shape with low strength at a location where compressive strain occurs. In addition, if quasicrystals and approximate crystals are excessively precipitated in the magnesium matrix, the quasicrystals and approximate crystals may be the starting point of fracture, which may reduce fracture toughness.

 [0026] Further, since the magnesium alloy wrought material is subjected to hot working of a magnesium alloy forged material at 230 ° C to 420 ° C with a working rate of 50% or more in order to form the above structure. Hold at 370 ° C to 420 ° C for 10 minutes to 10 hours, then cool to room temperature at a cooling rate of 20 ° C / sec or more, then 150 ° C to 250 ° C for 1 hour It is produced by applying a heat treatment consisting of a second stage of cooling to room temperature after holding for ~ 15 hours. Thus, it is undeniable that the process is complicated to perform the heat treatment consisting of two stages after the hot working. Simplification of the process is desired for practical technology!

 Disclosure of the invention

 Problems to be solved by the invention

[0027] The present invention solves the problems of the prior art from the background as described above,

 1) Presenting new and advanced knowledge about the structure of magnesium alloys,

 2) It can be realized more easily and practically,

 3) As a magnesium alloy using a relatively inexpensive additive element that is not a rare earth element, it is an object to provide a new magnesium alloy with high strength and high toughness and a method for producing the same.

4) When using rare earth elements, remarkable characteristics just enough to meet the increased economic burden, Function improvement is planned,

 In view of the above, a new magnesium alloy having high strength and high ductility, high compressive strength and high fracture toughness, and a production method capable of easily producing this magnesium alloy are provided as an issue. RU

 Means for solving the problem

[0028] The magnesium alloy of the present invention is characterized by the following in order to solve the above problems.

 [0029] First: a magnesium alloy containing magnesium and zinc, or a non-rare earth element in the alloy composition, wherein a second phase particle containing at least zinc is included in a magnesium matrix. The biphasic particles are spherical and the average particle size is nano-sized.

 [0030] Second: Alloy composition is the following formula:

 Mg Zn M

 100- (a + b) a b

 (M represents one or more non-rare earth elements, a and b represent atomic%, and b = 0, 1.6 ≤ a ≤ 8.0, and 0 <b ≤ 5.7, 0. 3≤a≤8.5 It is the above magnesium alloy represented by).

[0031] Third: The ratio K between the average particle size of the second phase particles represented by the following formula and the average crystal particle size of the magnesium matrix is 0.005 or more and 0.2 or less.

 A

 [0032] K = average particle diameter of second phase particles / magnesium parent phase

 A

 Average crystal particle size

 Fourth: Zinc content is in the range of 1.6≤a≤3.5.

[0033] Fifth: The magnesium alloy according to any one of the above! /, Wherein the non-rare earth element is at least one of an alkaline earth metal and a transition metal.

[0034] Sixth: A magnesium alloy that contains magnesium and zinc, and further contains a non-rare earth element in the alloy composition, and the quasicrystalline particle phase is folded only in the magnesium matrix crystals, and the quasicrystalline particle phase is It is spherical and its average particle size is nano-sized.

[0035] Seventh: The alloy composition is:

 Mg Zn RE

 100- (y + x) y x

(RE represents one or more of rare earth elements, y and x represent atomic%, 0.2≤x≤l .5, 5 Indicates x≤y≤7x. )

 It is said magnesium alloy represented by these.

[0036] Eighth: The ratio K between the average particle size of the quasicrystalline particle phase represented by the following formula and the average crystal particle size of the magnesium parent phase is 0.01 or more and 0.2 or less.

 B

 [0037] K = average particle diameter of quasicrystalline particle phase / magnesium matrix phase

 B

 Average grain size

 Ninth: The average grain size of the magnesium parent phase is 511 m or less, and the average grain size of the quasicrystalline grain phase is 0.2 m or less.

[0038] Tenth: The magnesium alloy according to any one of the above, wherein the rare earth element is at least one of Y, Gd, Tb, Dy, Ho, and Er.

[0039] The present invention provides a method for producing a magnesium alloy according to the first to tenth inventions described above.

It is characterized by homogenization after melting and then straining in the warm temperature range.

 [0040] Further, the present invention provides a method for producing a magnesium alloy in which the ninth or tenth quasicrystalline particle phase is precipitated, and a homogenization treatment is performed at 460 ° C or lower for 4 hours or longer after melting. It is also characterized by strain processing with a processing ratio of 8: 1 or more in the warm temperature range. The invention's effect

 [0041] In the magnesium alloys of the first to fifth inventions, the second phase particles containing zinc are precipitated in the magnesium matrix without using rare earth elements as additive elements, and the second phase particles are spherical. It has a nano-sized average particle size! /, And the composition and the composition of the structure make it possible to significantly improve strength and toughness as an alloy based on completely different knowledge.

 [0042] The precipitated particles of the second phase act as dispersion-strengthened particles, and it is possible to further increase the strength simply by improving the strength due to the refinement of the crystal grains of the magnesium matrix. The spherical second-phase precipitated particles can fix more dislocation movements that occur during deformation, and can achieve high strength and high toughness.

 [0043] The refinement of the crystal grains of the magnesium matrix can suppress the generation of deformation twins that are the starting points of fracture, and as a result, high ductility and high fracture toughness can also be obtained.

[0044] Further, the magnesium alloys of the sixth to tenth inventions are used when a rare earth element is used. The alloy is based on the composition and the structure of the structure that the quasicrystalline phase is precipitated only in the crystal grains of the magnesium matrix and is spherical and the average grain size is nano-sized. As a result, the strength and toughness can be remarkably improved. For example, a magnesium matrix with an average grain size of 5 m or less is represented by the composition formula Mg Zn RE.

 The quasicrystalline particle phase with an average particle size of 0.2 πι or less within the matrix crystal grains has a uniform interface with a consistent interface, and has a tensile strength at room temperature. The room temperature compressive strength can be significantly increased. By reducing the crystal grain size of the magnesium matrix, non-bottom dislocations can be activated in the deformation process, and the generation of deformation twins that can be the starting point of fracture can be suppressed. High ductility and high fracture toughness can be obtained. In particular, since the quasicrystalline particle phase has an interface that is consistent with the magnesium matrix phase, it is possible to maintain good deformation continuity, relax stress concentration at the interface, and achieve high ductility and high fracture toughness. It becomes possible. Therefore, the application of the magnesium alloy wrought material to the structural member for a moving body becomes more realistic.

 [0045] In addition, excellent warm formability (secondary processing such as superplasticity) is expected due to the formation of fine crystal grains in the matrix. According to the eleventh and twelfth inventions, the magnesium alloy of the present invention as described above is manufactured by a simple and practically reasonable method. That is, strain processing is introduced in the warm temperature range after homogenizing the forged magnesium alloy to refine the crystal grains of the magnesium matrix, and at the same time, fine precipitate particles of the second phase having a nano-sized spherical shape are formed. This can be achieved by uniformly dispersing in the magnesium matrix or by dispersing the quasicrystalline grain phase in the crystal grains of the magnesium matrix. Brief Description of Drawings

 [0046] FIG. 1 is a TEM observation image of the spherical precipitated particle structure of ZK60 in Experiment No. 1.

 [Fig. 2] A TEM observation of the ZK60 acicular precipitate grain structure in Experiment No. 2 (comparative example).

FIG. 3 is a structure observation photograph of an extruded completion part of a Mg—Zn binary magnesium alloy.

 FIG. 4 is a structure observation photograph of the part during extrusion deformation compared with FIG.

 [Fig. 5] SEM fracture surface observation photograph of Experiment No. 5.

[Fig.6] TEM observation of ZK60 alloy extruded material extruded at 200 ° C in Experiment No. 11 It is.

 [Fig. 7] This is a TEM microstructure observation photograph of ZK60 alloy extruded material extruded at 220 ° C in Experiment No. 12.

 8] Relationship between specific strength and plane strain fracture toughness of aluminum and magnesium alloys

FIG. 9 is a transmission electron microscope (TEM) photograph showing the structure of a Mg-6at.% Zn-lat.% Ho alloy wrought material extruded at 230 ° C (503K).

 [Fig. 10] (a) and (b) are the structure of Mg— 2 · 7 at.% Zn 0.4 at.% Ho alloy wrought material extruded at 210 ° C (483K) and the quasicrystalline particle phase, respectively. 2 is an enlarged transmission electron microscope (TEM) photograph. (C) is a high-resolution TEM photograph showing the interface between the magnesium matrix and the quasicrystalline particle phase of the wrought alloy.

 [Fig.11] Scanning electron microscope after fracture toughness test of Mg— 2.7 at.% Zn 0.4 at.% Ho alloy stretched at 210 ° C (483K) at an extrusion ratio of 18: 1 ( SEM) Photo.

 BEST MODE FOR CARRYING OUT THE INVENTION

 [0047] The magnesium alloy containing no rare earth element of the present invention is specified as a composition comprising magnesium and zinc, or magnesium and zinc, and further a non-rare earth element. In this magnesium alloy, as described above, second-phase particles containing at least zinc are precipitated in the magnesium matrix, the second-phase particles are spherical, and the average particle system is nano-sized.

 [0048] Here, the second phase particles are considered as being in an intermetallic compound of an alloy constituent element, or in an alloy or mixed phase. In any case, at least one elemental species constituting the second phase particle is zinc. In the present invention, such second phase particles are “spherical”. In the present invention, the aspect ratio force between the major axis and the minor axis of a crystal particle that is not only a true sphere is the major axis length: the minor axis length. Defined as being in the range of 10: 1 or less. The average particle size force S “nanosize” is defined as being less than Ιπι, more specifically 500 nm or less.

[0049] If there are precipitated particles of 1 micron or more in the magnesium matrix, Stress concentration occurs and tends to be the starting point of fracture. The same applies to needle-shaped or columnar products with an aspect ratio of 10: 1 or more. For this reason, it is difficult to achieve higher toughness and higher ductility than just expecting higher strength.

 [0050] There is a possibility that precipitated particles of the second phase are present on the grain boundaries of the magnesium matrix.

 [0051] Precipitated particles existing on the grain boundaries can be expected to increase in strength, which makes it difficult to maintain continuity of deformation, but it is difficult to achieve high toughness and high ductility as their presence increases. It is desirable that the number of precipitated particles existing on the grain boundary is as small as possible.

 [0052] In the present invention, it is considered that the aspect ratio is more preferably 5: 1 or less, and the nano-sized average particle diameter is preferably lOOnm or less.

 [0053] The volume fraction related to the density of precipitation of the second phase particles is generally 10% or less as the maximum volume fraction, and the center-to-center spacing of the particles is generally in the range of 100 to 300 nm. It is preferably taken into account.

 [0054] The magnesium matrix may be a solid solution of force or other alloying elements that are mainly composed of magnesium. Such a magnesium matrix preferably has a fine crystal grain size. Normally, the average grain size is 15 m or less, and more preferably 5 πι or less in view of alloy characteristics. Is done. An increase in tensile strength can be expected due to the refinement of crystal grains. In addition, non-bottom dislocations and grain boundary sliding can be performed in the deformation process, which leads to the suppression of the generation of deformation twins, which are the starting points of fracture, and dramatically improves tensile ductility.

 [0055] The ratio between the average particle size of the second phase particles and the average particle size of the magnesium matrix is preferably in the range of 0.005 to 0.2 as a mean value in the above formula.

 A

 [0056] As the composition of the alloy, for example, as described above, the alloy composition is represented by the following formula:

 Mg Zn M

 100 (+ b) b

(M represents one or more of non-rare earth elements, a and b represent atomic%, and b = 0, 1.6 ≤ a ≤ 8.0, and 0 <b ≤ 5.7, 0. 3≤a≤8.5 indicates that it is expressed as). This is considered as the case where the maximum volume fraction of the second matrix particles having an average particle diameter of 500 nm or less is 10% or less. Furthermore, the zinc content is preferably in the range of 1.6≤a≤3.5. [0057] When the amount of zinc added is 1.6 at.% Or less, the formation of precipitates tends to be difficult.

[0058] Further, if it exceeds 3.5 at.% Or more, a large amount of precipitates composed of Mg—Zn are present, and the effect of the present invention and the high ductility can be expected to be a starting point of fracture. # 1 is getting harder.

 [0059] When a non-rare earth atom other than zinc is added, it is selected from elements that can be dissolved in magnesium as a parent phase. The range can be one or more of alkaline earth metals and transition metals. For example, examples of such non-rare earth elements include Zr, Ca, Sr, Ba, and Al.

 [0060] The addition of these non-rare earth elements is considered to have the effect of quickly dispersing and dispersing the second phase particles at a high density in a short time.

 [0061] In the magnesium alloy of the present invention containing a rare earth element together with zinc in its synthetic composition, the quasicrystalline phase is precipitated and dispersed only in the crystal grains of the magnesium matrix. The quasicrystalline particle phase is spherical and the average particle size is nano-sized.

 Here, the definition of the magnesium matrix, “spherical”, and “nanosize” in the present invention is the same as in the case of the magnesium alloy of the non-rare earth element. The “quasicrystalline particle phase” is a force S whose composition is already known as Mg Zn RE, the present invention.

 3 6

 In this case, an approximate stable phase may be included.

[0063] The quasicrystalline particle phase in the present invention exists substantially only in the crystal grains of the magnesium matrix, and does not exist in the grain boundary. This is the largest and extremely important feature of the present invention and is an essential component of the invention.

[0064] More preferably, the magnesium alloy wrought material of the present invention containing a rare earth element has the composition formula Mg Zn RE (wherein RE is any one of Y, Gd, Tb, Dy, Ho, Er) Rare earth

100- (y + x) y x

 X, y are atomic% each, and have a composition represented by 0.2≤x≤l.5, 5x≤y≤7x), and an average crystal grain size of 5 m or less In the composition formula Mg Zn RE

 3 6 It has a composition as shown, and has a structure in which a quasicrystalline particle phase having an average particle diameter of 0.2 πι or less in the matrix crystal grains is uniformly dispersed with a consistent interface.

[0065] The magnesium alloy of the present invention in this case has a ternary alloy composition of Mg-Zn-RE, and RE includes rare earths including Y, Gd, Tb, Dy, Ho, and Er. Any one of the elements Is preferably selected.

[0066] The atom ⁰ / ox of RE is common to Y, Gd, Tb, Dy, Ho, and Er, and preferably 0 · 2≤χ ≤1.5. When the RE atomic degree / is less than 0.2 atomic%, the crystallization of the quasicrystalline particle phase is so small that it is difficult to achieve high strength and high toughness. 1. If it exceeds 5 atomic%, the crystallization of the quasicrystalline particle phase becomes excessive, and the quasicrystalline particle phase becomes the starting point of fracture, and the ductility and fracture toughness tend to decrease.

 [0067] The atomic% of η is determined based on the atomic degree / of RE, and preferably 5x≤y≤7χ.原子 If the atomic% of η is less than 5χ, it is difficult to form a quasicrystalline particle phase composed of Mg Zn RE. If it exceeds 7χ, a large number of quasicrystalline particle phases and other intermetallic compounds (for example, MgZn) crystallize, and they become the starting point of the deformation process, which is easy to cause characteristic deterioration.

 [0068] The structure of the magnesium alloy of the present invention has a composition represented by the composition formula Mg Zn RE in the magnesium matrix having an average crystal grain size of 5 m or less, and the average grain size is 0 in the matrix crystal grains.

. A structure in which quasicrystalline particle phases of 2πι or less are uniformly dispersed with a consistent interface. Such a structure increases the room temperature compressive strength as well as the room temperature tensile strength. Compressive yield strength

(σ) can be 80% or more of the tensile yield strength (σ) (σ ≥0.8 σ). Also

In the deformation process, the activity of non-bottom dislocations becomes possible, and the generation of deformation twins, which are the starting points of fracture, can be suppressed. As a result, high ductility and high fracture toughness can be obtained. In particular, since the quasicrystalline particle phase has an interface that is consistent with the magnesium matrix phase, the continuity of deformation can be maintained well, stress concentration at the interface is relaxed, and high ductility and toughness can be achieved. Become.

[0069] Planar strain fracture toughness values of 25 MPa'm ^1/2 or more equivalent to commercial high-strength aluminum alloys are possible. Therefore, safety and reliability in the case of application to a moving structural member is ensured, and application of the magnesium alloy wrought material to the moving structural member becomes more realistic. Can be a candidate for alternative materials for commercial high-strength aluminum alloy materials.

[0070] When the average particle size of the magnesium matrix exceeds 5 am, it is difficult to suppress the generation of deformation twins, and it becomes difficult to achieve high ductility and high toughness. [0071] The quasicrystalline particle phase having an average particle diameter of 0.2 μm or less and uniformly dispersed in the magnesium matrix acts as a dispersion strengthened particle, and further enhances the strength of the magnesium alloy wrought material. .

 [0072] When the average particle diameter of the quasicrystalline particle phase exceeds 0.2 µm, the quasicrystalline particle phase is easily cracked during the deformation process and tends to be a starting point of fracture. Preferably, the ratio of the average particle size of the fine particle phase to the average crystal particle size of the magnesium mother phase, ie, the straight K force determined by the above formula.

 B

 κ = average particle size of quasicrystalline particle phase / average crystal particle size of magnesium matrix phase 0

B

 .01 or more and 0.2 or less. If it is within this range, the force S can sufficiently suppress cracks in the deformation process.

 [0073] The volume ratio of the quasicrystalline particle phase and the center-to-center spacing can be considered in the same manner as in the case of the non-rare earth element alloy.

[0074] As described above, the quasicrystalline particle phase of the present invention has an interface consistent with the magnesium matrix phase. By having a consistent interface, it is possible to maintain good deformation continuity, and to relieve stress concentration on the interface. This contributes to high ductility and high fracture toughness. A high plane strain fracture toughness value of 25 MPa 'm ¹⁷² or higher is obtained. If the interface between the quasicrystalline particle phase and the magnesium matrix phase is inconsistent, deformation is easily cut off at the interface between the magnesium matrix phase and the quasicrystalline phase, and continuity cannot be maintained. Stress concentration occurs and becomes the starting point of fracture. Ductility and fracture toughness are reduced.

 [0075] With regard to the magnesium alloy of the present invention as described above, in both the non-rare earth system and the rare earth system, the magnesium alloy having the above composition is dissolved and solidified. After homogenization, it is manufactured by straining in the warm temperature range.

[0076] Here, a homogenization treatment for the base material after melting (forging) is essential for the method of the present invention. The purpose of this homogenization treatment is to prevent the solidified structure after melting (forging) from remaining in the subsequent warm strain processing, and to form second-phase particles or quasicrystalline particle phases. . This homogenization treatment is performed by heating the base material, and the heating temperature at this time is usually lower than the recrystallization temperature of the base material, and the second phase particles or quasicrystalline particles are not heated. Can be determined taking into account the degree of formation and the time for heating [0077] The heating temperature and the heating time for the homogenization treatment are the force S that can be determined in consideration of the alloy composition, and the predetermined structure and characteristic level, and a general guideline is 200 ° C to 500 ° C. In the temperature range of ° C, it ranges from 2 to 50 hours.

 [0078] When the homogenization treatment as described above is not performed, it is difficult to realize the magnesium alloy of the present invention. The second-phase particles and the quasicrystalline particle phase are mixed with spherical or nano-sized particles that are needle-like or plate-like particles. Is difficult to achieve.

 [0079] Further, in the production method of the present invention, strain processing in the warm temperature region after the homogenization treatment is indispensable.

 [0080] The temperature range of the “warm temperature range” here! /, V, the deformation resistance positively, like the processing at the recrystallization temperature or higher in the so-called “hot working”. It does not mean the temperature range that would cause work hardening at a lower value. In other words, by heating, the crystal grain size of the magnesium matrix is within the required range, and strain processing is performed to make the second phase particles with a sphere-like average particle size of sphere size or the quasicrystalline particle phase into the required range. It is defined as the heating temperature range for Specifically, a general guideline is a temperature lower than the recrystallization temperature. However, depending on the composition of the alloy and the predetermined characteristics, it is also considered that it is more than that.

 [0081] In general, a temperature range of 150 ° C to 400 ° C is considered.

 [0082] With regard to strain processing, it is desirable to perform strain processing after holding (heat treatment) for a required time at a temperature equivalent to the processing temperature in advance. The holding time here is considered as the time required for the processing temperature to reach the entire base material. The force that varies depending on the composition and size of the base material is generally 10 minutes to 2 hours.

 [0083] The degree of processing at the time of strain processing is considered as a range for obtaining a predetermined alloy structure. Generally, it is 5: 1 or more. For example, 5:;! ~ 30: 1 is considered as a guide.

 [0084] A force that can be appropriately determined depending on the composition and characteristics of the alloy. For example, the following practical process conditions can be considered as a guideline.

[0085] <1> Maintaining the temperature range of 300 ° C to 500 ° C in the heating furnace to homogenize the molten material Do.

 [0086] <2> Quenching is performed to freeze the structure once and stabilize it.

<3> A billet for strain processing is formed by machining.

 [0088] <4> Extrusion at a temperature range of 150 ° C to 400 ° C, and perform strain processing such as rolling and swaging.

 Of course, the present invention is not limited to the above form.

 [0090] In the present invention, as a rare earth element-containing alloy, more preferably, after melting, homogenization treatment is performed under conditions of 460 ° C or less and 4 hours or more, and after strain processing, magnesium is applied. Hold the time required for the entire base metal to reach the temperature at a temperature at which the size of the parent matrix reaches 5 m or less, and then perform strain processing at a processing ratio of 8: 1 or more above the warm temperature.

 [0091] Production of the base material is not particularly limited. For example, it is possible to use Mg, Zn and RE as raw materials in the above composition range, and after melting, solidify by forging etc. to produce a base material.

 [0092] The base material is first subjected to a homogenization treatment under conditions of 460 ° C or lower and 4 hours or longer. By this homogenization treatment, a dendrite structure formed at the time of fabrication is reduced! /, A magnesium phase and a quasicrystalline particle phase are formed. When the temperature exceeds 460 ° C, the quasicrystalline particle phase dissolves in the magnesium matrix and the desired effect cannot be obtained. If it is less than 4 hours, the homogenization process is insufficient and a forged structure remains.

 [0093] After the homogenization treatment, quenching can be performed. The ability to freeze the tissue once by quenching can stabilize the tissue.

 [0094] Next, at a temperature at which the size of the magnesium matrix becomes 5 m or less after strain processing, the time required for the entire matrix to reach the temperature is maintained. The heat treatment temperature is equivalent to the temperature during strain application. If the heat treatment temperature is higher than the strain processing temperature, a fine magnesium matrix with an average crystal grain size of 5 in or less will not be formed.If the heat treatment temperature is lower than the strain processing temperature, cracks will occur during heating, and a healthy extruded material will be Can't get. Even when heat treatment is not performed, cracks and the like occur during strain processing, and a sound extruded material cannot be obtained. The heat treatment time can be set as a rough guide for 15 minutes to 90 minutes.

[0095] Then, a strain processing of 8: 1 or more is performed at a temperature equal to or higher than the same temperature as the heat treatment. Hi Scumming can be performed by rolling, extruding, forging, or the like. Due to the applied strain, recrystallization occurs and a fine magnesium matrix with an average grain size of 5 m or less is formed, and dislocations are introduced, and the average grain size is 0.2 to 111 or less within the parent phase crystal grains. The quasicrystalline particle phase is formed, and the quasicrystalline particle phase has a consistent interface and is uniformly dispersed in the magnesium matrix. If the processing ratio is less than 8: 1, the applied strain is insufficient, a fine magnesium matrix with an average grain size of 5 m or less is not formed, and the quasicrystal with a low density of dislocations to be introduced. A uniform dispersion of the particle phase cannot be obtained.

 As described above, the method for producing a magnesium alloy wrought material according to the present invention includes a simplified process suitable for a practical application technique of homogenization, heat treatment, and strain processing in a warm temperature range. . A magnesium alloy wrought material having high strength and high ductility, as well as high compressive strength and high fracture toughness can be easily produced.

 [0097] In order to set the ratio of the average particle size of the quasicrystalline particle phase and the average crystal particle size of the magnesium matrix to 0.01 or more and 0.2 or less, the processing temperature and strain in strain processing

B

 What is necessary is just to control quantity.

 Example

 [0098] In the following examples, the average diameter of the crystal grains and particles of the alloy structure was determined using a commercially available image software (PhotoShop: registered trademark), with a strong contrast! It is regarded as particles, and the average value is obtained by measuring more than 250 crystal grains and particles.

 [0099] The tensile 'compressive strength is obtained from a stress-strain curve. Specifically, the stress value with a strain of 0.2% is measured.

[0100] Elongation! / After joining the test pieces after rupture, obtain them from the original length! /. The plane strain fracture toughness test conforms to ASTM E399.

 <1> Magnesium alloy with ZK60 composition

 This is an example in which spherical particles were precipitated on a commercial magnesium alloy (Mg—6 wt.% Zn-0. 5 wt.% Zr: material name ZK60).

 (Experiment No. 1)

ZK60 was kept in a furnace at 500 ° C for 2 hours and homogenized. After removal from the furnace The tissue was frozen by water quenching.

 [0101] Thereafter, an extruded billet was prepared by machining. Next, the billet was heated to 380 ° C. and held for about 0.5 hour, and extrusion was performed at an extrusion ratio of 18: 1 to obtain an extruded material.

 [0102] As a result of the structure observation (see Fig. 1), as shown in Table 1, the average crystal grain size of the magnesium matrix is about 13.5 m, and the second phase has an average particle size of 35-50 nm. It was confirmed to show a structure of spherical precipitated particles.

 [0103] The maximum volume fraction of the second phase particles reached about 5%, and the center-to-center spacing was 100 to 200 nm.

 (Experiment No. 2: Comparative example)

500 for commercial magnesium alloy (Mg—6wt.% Zn-0.5wt.% Zr: ZK60). C was kept in the furnace for 2 hours and homogenized. After removal from the furnace, the tissue was frozen by water quenching. Thereafter, an extruded billet was prepared by machining. After raising the billet to 380 ° C., the billet was held for about 0.5 hour and extruded at an extrusion ratio of 18: 1 to obtain an extruded material. The extruded material was further homogenized at 360 ° C for 24 hours, then water-quenched and aged at 175 ° C at 1 X 10 ⁵ seconds.

[0104] As a result of the structure observation (see Fig. 2), as shown in Table 1, the average crystal grain size was about 13.5 m, and needle-like precipitated particles of about 75 nm were confirmed. It was possible to create samples with the same force S and different precipitation particle morphology.

 (Characteristic contrast)

 Table 1 shows the measurement results of elongation at break, yield strength, and plane strain fracture toughness for each of the above samples.

 [0105] The plane strain fracture toughness values were obtained from the fracture zone analysis of the fracture toughness specimens collected from each sample. That is, three-point bending fracture toughness specimens having a shape of 5 x 10 x 40 mm in accordance with ASTE-E399 were collected from each extruded material, and plane strain fracture toughness values were obtained by stretch zone fracture surface analysis. .

[0106] Experiment No. ² with spherical precipitated particles was found as 22.4 and 21.0MPam ^1/2 , respectively.

Sample 1 showed higher plane strain fracture toughness values. <2> Mg—Zn binary magnesium alloy

 (Formation of spherical precipitated particles)

 2.4 atomic% zinc was dissolved and cast in commercial pure magnesium (purity 99. 95%) to prepare a master alloy (material name: Mg—2.4Zn).

[0107] This mother alloy was held in a furnace at 300 ° C or higher for 48 hours, and homogenized. After removal from the furnace, the tissue was frozen by water quenching. Thereafter, an extruded billet was prepared by machining.

 [0108] Next, the billet was heated to about 210 ° C, held for about 0.5 hours, and extruded at an extrusion ratio of about 20: 1 to obtain an extruded material.

[0109] Observation of the transmission electron microscope (TEM) structure confirmed the presence of second-phase spherical precipitated particles at the site where the extrusion process was completed (see Fig. 3). Precipitated particles with a mixture of needles were confirmed at the site during extrusion (see Fig. 4).

[0110] From Fig. 3, the average crystal grain size (d) of the magnesium matrix (the dark-contrast part in the figure) is about 1 μm, and the average grain size of the magnesium matrix is about 0.1 m. The formation of spherical precipitates (indicated by arrows) can be confirmed.

[0111] It is understood that spherical precipitate particles are formed by introducing strain processing such as extrusion into the forged magnesium alloy.

 (Experiment Νο · 3〜; 10)

 In commercial pure magnesium (purity 99 · 95%), 1 · 9 2. 4 3. 0 or 3 · 4 atomic%, is dissolved and forged, and the master alloy (material name Mg—l. 9Zn Mg—2.4Zn Mg — 3. 0Zn Mg—3.4Zn) was prepared.

 [0112] As shown in Table 1, the master alloy was kept in a furnace at various temperatures (300 ° C, 400 ° C) for 24 48 hours and homogenized. After removal from the furnace, the tissue is frozen by water quenching.

 [0113] Thereafter, an extruded billet was prepared by machining. Next, the billet was heated to various temperatures (200 230 ° C.) and held for about 0.5 hours, and extrusion was performed at an extrusion ratio of 18: 1 to obtain an extruded material.

[0114] All Mg—Xat.% Zn (X = l. 9, 2. 4, 3. 0, 3.4) Table 1 summarizes the relationship between the average crystal grain size and the precipitated particle size.

[0115] Three-point bending fracture toughness specimens with a shape of 5 X 10 X 40 mm conforming to ASTE-E399 were taken from each extruded material, and the plane strain fracture toughness value was obtained by stretch zone fracture surface analysis. Asked. Then, a test piece having a parallel portion f2.5 X 10 mm was taken from the extruded material and subjected to a tensile test.

[0116] SEM observation results of typical stretch zone fracture surface analysis for Experiment No. 5 are shown in Fig. 5, and the results of fracture toughness test and tensile test are shown in Table 1.

 <3> Plane strain fracture toughness of ZK60 alloy

 (Experiment Νο · 11〜; 12)

 Commercial magnesium alloy (Mg— 6wt.% Zn-0. 5wt.% Zr: material name ZK60), 5

It was kept in the furnace at 00 ° C for 2 hours and homogenized. After removal from the furnace, the tissue was frozen by water quenching.

[0117] Thereafter, an extruded billet was prepared by machining. Next, the billet was heated to 200 ° C (Experiment No. 11) and 220 ° C (Experiment No. 12) and held for about 0.5 hours.

Extrusion was performed at an extrusion ratio of 1 to obtain an extruded material.

[0118] The results of TEM observation are shown in Fig. 6 (Experiment No. 11) and Fig. 7 (Experiment No. 12).

[0119] In the case of 220 ° C extruded material (Experiment No. 12), as shown in Table 1, as a result of structural observation, the average crystal grain size of the mother phase was about 1.5 m, about 25-50 nm. It was confirmed to show a structure of spherical second-phase precipitated particles uniformly and finely dispersed. On the other hand, extruded material at 200 ° C: Experiment No.

In No. 11, the average crystal grain size of the parent phase was about 0.δπι. Tensile specimens and fracture toughness specimens were sampled from the extruded materials and tested.

[0120] Extruded material at 220 ° C: As a result of the tensile test of Experiment No. 12, high strength and high ductility of 286 MPa in tensile yield strength and 27% elongation at break were confirmed. From the results of the fracture toughness test, the plane strain fracture toughness value was found to be 34.8 MPa ^1/2, and high toughness was achieved by introducing strain processing in the warm temperature range.

[0121] Fig. 8 shows this magnesium alloy, a general commercial magnesium alloy (Cast Mg, wrough Mg), and an anoremium alloy (J. R. Davis, Aluminum and

Aluminum Alloys, ASM Specialty Handbook, ASM International, Materials Park, OH , 1993) showed the relationship between toughness and life and specific strength.

[0122] It can be seen that the magnesium alloy of the present invention has the same strength-toughness characteristics as commercial high-strength aluminum alloys.

 <4> Mg- l. 8at.% Zn- 0.3 at.% Ca alloy and its plane strain fracture toughness value

 (Experiment No. 13)

 A master alloy was prepared by dissolving and forging 1.8 atomic% zinc and 0.3 atomic% calcium in commercial pure magnesium (purity 99. 95%). Next, the master alloy was stored in a furnace at 500 ° C. for 2 hours and homogenized. After removal from the furnace, the tissue was frozen by water quenching. Then, the extrusion billet was created by machining. The billet was heated to about 250 ° C., held for about 0.5 hour, and extruded at an extrusion ratio of about 18: 1 to obtain an extruded material.

 [0123] As a result of the structure observation, as shown in Table 1, it was confirmed that the average crystal grain size of the magnesium matrix was about 1 µm, and spherical precipitated particles with uniform fine dispersion of about 25 to 50 nm were confirmed.

[0124] Tensile test pieces and fracture toughness test pieces were sampled from the extruded material, and each test was performed.

 [0125] As shown in Table 1, as a result of the tensile test, high strength and high ductility were confirmed with a tensile yield strength of 310 MPa and a breaking elongation of 16%.

[0126] From the results of the fracture toughness test, the plane strain fracture toughness value was found to be 28. lMPam ^1/2, and high strength was achieved by introducing strain processing to the magnesium alloy forged material in the warm temperature range.

• High toughness was achieved.

[0127] [Table 1]

Homogenization treatment _{ι |} , _{Β | ίΡ} Spherical particles, Yield strength PPJS ^ ^ Extrusion ≤ Degree Extrusion 破 断 Breaking elongation Tensile composition 1¾ degree Holding ¾ Size W (¾ Maximum volume ratio 5I3S pressure i

 One

 Time in seconds: needle shape

 One

 ;

 One, one

 ;

 One,

 ;

 One by one

 ;

 ;

 ;

 One

 : Average crystal grain size of magnesium S phase * (): Average value obtained by transmission S microscope observation

 : Average particle in quasicrystalline particle phase $ []: Volume ratio calculated from average particle diameter and average particle spacing

: Plane strain fracture toughness value

One

Nanana Nanana Nanana Nanana

Shishi Shishi Shishi Shishi

[0128] <5> Mg-6at.% Zn-lat.% Ho alloy

 (Experiment No. 14-15)

 6 atom% zinc (Zn) and 1 atom% holonium (Ho) were dissolved in commercial pure magnesium (Mg, purity 99 · 95%) according to a conventional method, and fabricated to prepare an ingot. The ingot was kept in a furnace at 400 ° C for 24 hours and homogenized. The tissue was removed from the furnace and water quenched. Thereafter, an extruded billet of φ 40 X 50 mm was produced by machining.

 [0129] Extrude billet bowl 230. C (503K): Experiment No. 14 or 300. C (573K): The temperature was raised to Experiment No. 15, and held for 30 minutes. After that, extrusion at an extrusion ratio of 25: 1 was performed at the same temperature to obtain an extruded material having a diameter of more than φ8 X 1000 mm.

 [0130] 230 ° C (503K): The extruded material extruded in Experiment No. 14 was observed for structure using a transmission electron microscope (TEM). As shown in Fig. 9, the quasicrystalline phase (the part indicated by the white arrow in the figure) with an average grain size of 0.1 am is uniformly formed on the magnesium matrix with an average grain size d of about 1.5 m. It was confirmed that a dispersed structure was formed. The ratio between the average particle size of the quasicrystalline particle phase and the average crystal particle size of the magnesium matrix obtained by the above equation was 0.07.

 B

[0131] Tensile test pieces having a parallel part Φ 3 Χ 15 mm and compression test pieces having Φ 4 Χ 8 mm were collected from the extruded material, and subjected to a tensile test and a compression test at room temperature. The tensile test was performed at a strain rate of 10-^- ¹ using a universal testing machine. For the compression test, a universal testing machine was used, and the strain rate was IX lO ^ s ¹ in the same way.

 [0132] The results of the tensile test and the compression test are shown in Table 2. Table 2 also shows the extrusion temperature, the average grain size of the magnesium matrix and the average grain size of the quasicrystalline grain phase.

[0133] With respect to the sample extruded at 230 ° C (503K) (Experiment No. 14), high strength and high ductility were confirmed with a tensile yield strength of 280 MPa and a breaking elongation of 16%. In addition, a compressive yield strength of 300 MPa was confirmed, and the ratio of compressive strength / tensile strength was 1.06. It was confirmed that the compressive yield strength was equivalent to the tensile strength. It can be seen that it is a magnesium alloy with high strength and high ductility and high compressive strength. [0134] For the sample extruded at 300 ° C (573K) (Experiment No. 15), as shown in Table 2, the average crystal grain size of the magnesium matrix is about 3πι, The average particle size is 0.2 111, which is slightly larger than the sample extruded at 230 ° (5031 (Experiment No. 14). Also, as shown in Table 2, the tensile strength is 265 MPa and the fracture An elongation of 13% and a compressive strength of 248 MPa were confirmed, indicating that it is a wrought magnesium alloy with high strength, high ductility, and high compressive strength, while 230 ° C (503K) (Experiment No. 14 ), The ratio of compressive strength / tensile strength is 0.94, and it can be seen that the compressive strength decreases slightly as the heat treatment temperature and extrusion temperature increase.

 <6> Mg- 2. 7at.% Zn-0. 4at.% Ho alloy

 (Experiment No. 16-18)

Commercial pure magnesium (Mg, 99 - 95%), 2-7 atomic% of zinc (Zn) and 0 · 4 atoms _^0/0 Horoniumu the (Ho) was dissolved according to a conventional method, producing an ingot with铸造did. The ingot was held in a furnace at 400 ° C for 24 hours and homogenized. The tissue was removed from the furnace and water quenched. Thereafter, an extruded billet of φ 40 X 50 mm was produced by machining.

 [0135] Extrude billet to 210 ° C (483K) (Experiment No. 16), 260 ° C (533K) (Experiment No. 17) or 300 ° C (573K) (Experiment No. 18: Comparative Example) After raising the temperature, it was held for 30 minutes, and then subjected to extrusion at an extrusion ratio of 18: 1 or 25: 1 at the same temperature to obtain an extruded material of more than 8Χ1 000 mm.

 [0136] The structure of the extruded material extruded at 210 ° C (483K) (Experiment No. 16) was observed using a transmission electron microscope (TEM). As shown in Fig. 10 (a), the average grain size is 0.1 m as shown in Fig. 10 (b). It was confirmed that a structure in which am quasicrystals were uniformly dispersed was formed. Ki Nao was 0.1. In addition, the white frame shown in Fig. 10 (b)

 B

 Resolution Observed using TEM. As a result, as shown in Fig. 10 (c), it was confirmed that the interface between the magnesium matrix phase and the quasicrystalline particle phase was more than 90% aligned.

[0137] Tensile test pieces and compression test pieces similar to the above Mg-6at.% Zn-lat.% Ho alloy were collected from the extruded material, and subjected to tensile tests and compression tests at room temperature. [0138] Table 2 shows the results of the tensile test and the compression test.

 [0139] 210 ° C (483K): The sample extruded in Experiment No. 16 was confirmed to have high strength and high ductility with a tensile yield strength of 30 4MPa and an elongation at break of 18%. In addition, a compressive yield strength of 290 MPa was confirmed, and the ratio of compressive strength / tensile strength was 0.95, confirming that the compressive strength was equivalent to the tensile strength. It can be seen that this is a magnesium alloy with high strength and high ductility and high compressive strength.

 [0140] 260 ° C (533K): Experiment No. 17, 300 ° C (573K): The microstructure observation results and the tensile and compression test results for the samples extruded in Experiment No. 18 are also shown in Table 2. Showed.

 [0141] It can be seen that as the extrusion temperature rises, the average grain size of the magnesium matrix and the average grain size of the quasi-crystalline grain phase increase, and the compressive strength tends to decrease. 300 ° C (573 K): In the sample extruded in Experiment No. 18, the average crystal grain size of the magnesium matrix is about 15 m, which is not substantially applicable to the magnesium alloy of the present invention. The ratio of compressive strength / tensile strength of this sample is as low as 0.76. It is estimated that the heat treatment temperature and extrusion temperature were high.

 [0142] Next, the plane strain fracture toughness value was determined.

[0143] Three-point bending fracture toughness test specimens of 5 x 10 x 40 mm were taken from Extruded No. 16 and subjected to fracture toughness tests using the universal testing machine under the conditions specified in ASTM-E399. It was. Figure 11 shows an image of the fracture surface after the fracture toughness test observed using a scanning electron microscope (SEM). The plane strain fracture toughness value was obtained by stretch zone analysis using the fracture surface after fracture toughness. The plane strain fracture toughness value was 32. IMPa 'm ¹⁷² , confirming high toughness.

 <7> Mg- 2.6 at.% Zn-0. 4 at.% Y Alloy Exhibition

 (Experiment No. 19)

Commercial pure magnesium (Mg, 99 - 95%), 2.6 atomic% of zinc (Zn) and 0 · 4 atoms _^0/0 of yttrium (Y) was dissolved in a conventional manner, producing an ingot with铸造did. The ingot was held in a furnace at 400 ° C for 24 hours and homogenized. The tissue was removed from the furnace, water quenched, and frozen. After that, extruded billet of φ 40 X 50mm by machining Was made.

 [0144] After raising the temperature of the extrusion billet to 210 ° C (483K), hold it for 30 minutes, and then perform extrusion at an extrusion ratio of 18: 1 at the same temperature, exceeding φ 8 X 1000mm Obtained extrusion material

[0145] The structure was observed using a transmission electron microscope (TEM). It was confirmed that a structure in which quasicrystals with an average particle size of 0.1 am were uniformly dispersed was formed in a magnesium matrix having an average crystal size of about 1111 m. The K value was 0.1.

 B

 [0146] Tensile test pieces and compression test pieces similar to the above Mg-6at.% Zn-lat.% Ho alloy were collected from the extruded material, and subjected to tensile tests and compression tests at room temperature. The test conditions were also the same as the test conditions for the Mg-6at.% Zn-lat.% Ho alloy wrought material.

 [0147] Table 2 shows the results of the tensile test and the compression test.

[0148] It was confirmed that the tensile yield strength was 303 MPa and the elongation at break was 20%. In addition, a compression yield strength of 290 MPa was confirmed, and it was confirmed that the compressive yield strength was equivalent to the tensile strength. And has a high ductility at high strength, it forces ^s Wakakaru a high magnesium alloy wrought compression strength.

[0149] The fracture toughness value was determined. A three-point bending specimen was also taken from the extruded material and a fracture toughness test was conducted. The plane strain fracture toughness value was found to be 32.5 MPa 'm ^1/2 , confirming high toughness.

 <8> Mg-2. 6at% Zn-0. 4at% (Dy, Gd, Tb, Er) alloy

 (Experiment No. 20-23)

 7) Same as the alloy of Mg—Zn—Y, but with the same or the same extrusion ratio, Mg—Zn—Dy (Experiment No. 20), Mg—Zn—Gd (Experiment No. 21), Mg— Extruded materials of Zn—Tb (Experiment No. 22) and Mg—Zn—Er (Experiment No. 23) were obtained. Table 2 shows the microstructure, observation results, and measurement results of elongation at break, yield strength, and plane strain fracture toughness.

 [0150] It was confirmed to have high strength, high ductility, and high toughness.

[0151] [Table 2] Homogenization Mg-2η spherical particles Yield strength

Experiment Extrusion temperature Extrusion ratio I) 2) Elongation at break Compression / tension

 Να Composition Temperature Holding time Size Center-to-center spacing Maximum volume ratio Tension Compression

 (K) (hrs) (K), u m) m) (%) m) (%) (MPa) (MPa)

 14 Mg-6Zn-lHo 673 24 503 25 L 1. 5 25— 50 100 -200 One 6. 5 0. 1 16 280 300 1, 06

 15 Mg-6Zn-lHo 673 24 573 25 1 3 25—50 100- -200 —6. 5 0. 2 13 265 248 0. 94

 16 g-2. 7Zn-0. 4Ho 673 24 483 18 1 1 25—50 100- -200 One 6. 5 0. 1 18 304 290 0. 95 32. 1

17 g-2. 7Zn-0. 4Ho 673 24 533 25 1 5 25— 50 100 -200 -6. 5 0. 2 19 205 190 0. 93

 18 Mg-2. 7Zn-0. 4Ho 673 24 573 25 1 15 25—50 100- -200 One 6. 5 0. 2 18 210 160 0. 76 Comparative Example

19 Mg-2. 62n-0. 4Y 673 24 483 18 1 1 25—50 100 -200 —6. 5 0. 1 17 303 290 0. 96 32. 5

20 Mg-2. 6Zn-0, 4Dy 673 24 478 18 1 1 25-50 100- -200 —6. 5 0. 1 18 305 290 0. 95 28. 3

21 Mg-2. 6Zn-0. 4Gd 673 24 483 18 1 1 25— 50 100 -200 -6. 5 0. 1 15 317 277 0. 87 28. 9

22 Mg-2. 6Zn- 0. 4Tb 673 24 488 18 1 1 25—50 100- -200 —6. 5 0. 1 13 315 277 0. 88 29. 5

23 Mg ~ 2. 6Zn-0. 4Er 673 24 483 18 1 1 25—50 100- -200 —6. 5 0. 1 17 305 268 0. 88 28. 6

 Average grain size of the magnesium matrix

 Average particle size of quasicrystalline particle phase

 Plane strain toughness value

What

Claims

The scope of the claims

 [1] The alloy composition contains magnesium and zinc, or further non-rare earth elements.

A magnesium alloy in which second phase particles containing at least zinc in a magnesium matrix are folded out, wherein the second phase particles are spherical and the average particle size is nano-sized. Magnesium alloy.

 [2] The alloy composition is:

 Mg Zn M

 100— (a + b) a b

 (M represents one or more non-rare earth elements, a and b represent atomic%, and b = 0, 1.6 ≤ a ≤ 8.0, and 0 <b ≤ 5.7, 0. The magnesium alloy according to claim 1, characterized in that 3≤a≤8.5.

[3] The ratio K between the average particle size of the second phase particles represented by the following formula and the average crystal particle size of the magnesium matrix is 0.005 or more and 0.2 or less, Described in

 A

 Magnesium alloy.

 κ = average particle size of second phase particles / magnesium matrix phase

 A

 Average crystal particle size

 [4] The magnesium alloy according to claim 2 or 3, wherein the zinc content is in the range of 1.6≤a≤3.5.

[5] The magnesium alloy according to any one of [1] to [4], wherein the non-rare earth element is at least one of an alkaline earth metal and a transition metal.

[6] Magnesium alloy that contains magnesium, zinc, and non-rare earth elements in the alloy composition, and the quasicrystalline particle phase is folded only in the magnesium matrix crystals, the quasicrystalline particle phase is spherical. A magnesium alloy characterized in that its average particle size is nano-sized.

[7] The alloy composition is:

 Mg Zn RE

 100- (y + x) y x

 (RE indicates one or more rare earth elements, y and x indicate atomic%, and 0.2≤x≤l.5, 5 x≤y≤7x.)

The magnesium alloy according to claim 6, which is represented by:

[8] The ratio K between the average particle size of the quasicrystalline particle phase represented by the following formula and the average crystal particle size of the magnesium parent phase is 0.01 or more and 0.2 or less, Or 7

 B

 Magnesium alloy.

 K = average particle size of quasicrystalline particle phase / magnesium matrix phase

 B

 Average grain size

 [9] The difference between! / In claim 6 and 8, characterized in that the average grain size of the magnesium matrix is 511 m or less and the average grain size of the quasicrystalline grain phase is 0.2 or 1 m or less. Magnesium alloy described in 1.

 [10] The magnesium alloy according to any one of [6] to [9], wherein the rare earth element is at least one of Y, Gd, Tb, Dy, Ho, and Er.

[11] A method for producing a magnesium alloy according to any one of claims 1 to 10, wherein the magnesium alloy is homogenized after melting and then subjected to strain processing in a warm temperature range. A method for producing a gnesium alloy.

[12] A method for producing a magnesium alloy according to claim 9 or 10, wherein

A method for producing a magnesium alloy, characterized in that homogenization is performed at a temperature of ° C or lower for 4 hours or longer, and strain processing is performed at a processing ratio of 8: 1 or higher in a warm temperature range.