Magnesium alloy and method for producing same

Abstract

Provided is a magnesium alloy having high strength and high thermal conductivity. One embodiment of the present invention is a magnesium alloy which contains a atom% of Zn, b atom% of Y, the remainder comprising Mg and unavoidable impurities, where a and b satisfy the following formulae 1 to 8, and which contains an Mg3Zn3Y2 phase, or simultaneously contains an Mg3Zn3Y2 phase and an Mg3Zn6Y phase without containing a long-period stacking structure phase. (Formula 1) a = 0.5 (0.25 < = b < = 1.2) (Formula 2) b = 1.2 (0.5 < = a < = 1.62) (Formula 3) a = 1.35 b (1.2 < = b < = 3) (Formula 4) b = 3 (4.05 < = a < = 7) (Formula 5) a = 7 (0.25 < = b < = 3) (Formula 6) b = 0.25 (0.5 < = a < = 7) (Formula 7) a = 4.2 b + 0.7 (0.25 < = b < = 1.5) (Formula 8) b = 0.25 (0.5 < = a < = 1.75)

Description

Technical Field

[0001] The invention relates to a magnesium alloy and a method for manufacturing the same. Background Art

[0002] With the trend towards electrification of transportation equipment, there is a growing demand for the development of magnesium alloys that are lightweight, have high heat dissipation, high strength, and high thermal conductivity.

[0003] However, AZ91D (ASTM symbol), a general magnesium alloy, has a thermal conductivity of only about 60 W / m·K, so when used in a high-temperature environment or in a component that generates heat during use, the component may be thermally deformed due to poor heat dissipation (see, for example, paragraph

[0003] in Patent Document 1). In addition, the strength of the component may be insufficient.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Publication No. 2012-197490 Summary of the invention

[0007] Problems to be solved by the invention

[0008] One embodiment of the present invention aims to provide a magnesium alloy having high thermal conductivity or a method for producing the same.

[0009] Another embodiment of the present invention aims to provide a magnesium alloy having high strength and high thermal conductivity or a method for producing the same.

[0010] Another embodiment of the present invention aims to provide a magnesium alloy having high strength, high thermal conductivity, and non-flammability, or a method for producing the same.

[0011] Means of solving problems

[0012] Hereinafter, various embodiments of the present invention will be described.

[0013] [1] A magnesium alloy comprising a atomic % of Zn, b atomic % of Y, and the remainder consisting of Mg and inevitable impurities, characterized in that:

[0014] By using the coordinates (b, a) with a being the vertical axis and b being the horizontal axis, the a atomic % Zn content and the b atomic % Y content are limited to the range enclosed by the straight lines represented by the following (1) to (8),

[0015] The magnesium alloy contains a Mg3Zn3Y2 phase, or contains both a Mg3Zn3Y2 phase and a Mg3Zn6Y phase.

[0016] The magnesium alloy does not contain a long period stacking structure phase.

[0017] (1) When b falls within the range of the following formula 1a, it is the straight line of the following formula 1b,

[0018] (Formula 1a) 0.25 ≤ b ≤ 1.09

[0019] (Formula 1b) a = 0.5

[0020] (2) When b falls within the range of the following formula 2a, it is the straight line of the following formula 2b,

[0021] (Formula 2a) 1.09≤b≤1.2

[0022] (Formula 2b) a = 2.91b - 2.67

[0023] (3) When a falls within the range of the following formula 3a, it is the straight line of the following formula 3b,

[0024] (Formula 3a) 0.82≤a≤1.62

[0025] (Formula 3b) b = 1.2

[0026] (4) When b falls within the range of the following formula 4a, it is the straight line of the following formula 4b,

[0027] (Formula 4a) 1.2≤b≤3

[0028] (Formula 4b) a = 1.35b

[0029] (5) When a falls within the range of the following formula 5a, it is the straight line of the following formula 5b,

[0030] (Formula 5a)4.05≤a≤7

[0031] (Formula 5b) b = 3

[0032] (6) When b falls within the range of the following formula 6a, it is the straight line of the following formula 6b,

[0033] (Formula 6a) 1.5≤b≤3

[0034] (Formula 6b) a=7

[0035] (7) When b falls within the range of the following formula 7a, it is the straight line of the following formula 7b,

[0036] (Formula 7a) 0.25≤b≤1.5

[0037] (Formula 7b) a = 4.2b + 0.7

[0038] (8) When a falls within the range of the following formula 8a, it is the straight line of the following formula 8b,

[0039] (Formula 8a) 0.5≤a≤1.75

[0040] (Formula 8b) b = 0.25

[0041] [2] The magnesium alloy described in [1] above, characterized in that

[0042] The thermal conductivity of the magnesium alloy is 90 W / m·K or more, preferably 100 W / m·K or more, more preferably 110 W / m·K or more, and further preferably 130 W / m·K or more.

[0043] [3] The magnesium alloy described in [1] or [2] above, characterized in that:

[0044] The magnesium alloy contains any one of 0.05 atomic % to 0.6 atomic % of Yb, 0.03 atomic % to 0.3 atomic % of Be, 1.0 atomic % to 2.0 atomic % of Ca, and 0.1 atomic % to 2.0 atomic % of Sr.

[0045] [4] The magnesium alloy described in [1] or [2] above, characterized in that:

[0046] The composition ratio of Zn to Y in the magnesium alloy is Zn / Y in the range of 2 to 5.

[0047] [5] The magnesium alloy described in [1] or [2] above, characterized in that:

[0048] The magnesium alloy has a structure in which the Mg3Zn3Y2 phase does not form a network at the grain boundary (i.e., a structure formed in a network fracture state), or has a structure in which both the Mg3Zn3Y2 phase and the Mg3Zn6Y phase do not form a network at the grain boundary (i.e., a structure formed in a network fracture state).

[0049] [6] The magnesium alloy described in [1] or [2] above, characterized in that:

[0050] The magnesium alloy has a strength of more than 300 MPa and an elongation of more than 5%.

[0051] [7] A method for producing a magnesium alloy, characterized by comprising the steps of: (a) casting a magnesium alloy containing a atomic % of Zn and b atomic % of Y, with the remainder consisting of Mg and inevitable impurities, at a solidification rate of less than 1000 K / s to form a cast material,

[0052] By using the coordinates (b, a) with a being the vertical axis and b being the horizontal axis, the a atomic % Zn content and the b atomic % Y content are limited to the range enclosed by the straight lines represented by the following (1) to (8),

[0053] The casting material contains a Mg3Zn3Y2 phase, or contains both a Mg3Zn3Y2 phase and a Mg3Zn6Y phase.

[0054] The cast material does not contain a long period stacking structure phase.

[0055] (1) When b falls within the range of the following formula 1a, it is the straight line of the following formula 1b,

[0056] (Formula 1a) 0.25 ≤ b ≤ 1.09

[0057] (Formula 1b) a = 0.5

[0058] (2) When b falls within the range of the following formula 2a, it is the straight line of the following formula 2b,

[0059] (Formula 2a) 1.09≤b≤1.2

[0060] (Formula 2b) a = 2.91b - 2.67

[0061] (3) When a falls within the range of the following formula 3a, it is the straight line of the following formula 3b,

[0062] (Formula 3a) 0.82≤a≤1.62

[0063] (Formula 3b) b = 1.2

[0064] (4) When b falls within the range of the following formula 4a, it is the straight line of the following formula 4b,

[0065] (Formula 4a) 1.2≤b≤3

[0066] (Formula 4b) a = 1.35b

[0067] (5) When a falls within the range of the following formula 5a, it is the straight line of the following formula 5b,

[0068] (Formula 5a)4.05≤a≤7

[0069] (Formula 5b) b = 3

[0070] (6) When b falls within the range of the following formula 6a, it is the straight line of the following formula 6b,

[0071] (Formula 6a) 1.5≤b≤3

[0072] (Formula 6b) a=7

[0073] (7) When b falls within the range of the following formula 7a, it is the straight line of the following formula 7b,

[0074] (Formula 7a) 0.25≤b≤1.5

[0075] (Formula 7b) a = 4.2b + 0.7

[0076] (8) When a falls within the range of the following formula 8a, it is the straight line of the following formula 8b,

[0077] (Formula 8a) 0.5≤a≤1.75

[0078] (Formula 8b) b = 0.25

[0079] [8] The method for producing a magnesium alloy as described in [7] above, characterized in that:

[0080] After the step (a), there is a step (b) of subjecting the cast material to a heat treatment to form a heat-treated material.

[0081] The thermal conductivity of the heat-treated material is 90 W / m·K or more, preferably 100 W / m·K or more, more preferably 110 W / m·K or more, and further preferably 130 W / m·K or more.

[0082] The heat-treated material contains a Mg3Zn3Y2 phase, or contains both a Mg3Zn3Y2 phase and a Mg3Zn6Y phase.

[0083] The heat-treated material does not contain a long period stacking structure phase.

[0084] [9] The method for producing a magnesium alloy as described in [8] above, characterized in that:

[0085] The heat treatment is performed under the following conditions: the temperature is 200° C. to 500° C., preferably 300° C. to 450° C., and the heat treatment time is 48 hours or less.

[0086]

[10] The magnesium alloy described in any one of [7] to [9] above, characterized in that:

[0087] The magnesium alloy contains any one of 0.05 atomic % to 0.6 atomic % of Yb, 0.03 atomic % to 0.3 atomic % of Be, 1.0 atomic % to 2.0 atomic % of Ca, and 0.1 atomic % to 2.0 atomic % of Sr.

[0088]

[11] The method for producing a magnesium alloy as described in any one of [7] to [9] above, characterized in that:

[0089] The composition ratio of Zn to Y in the casting material is Zn / Y in the range of 2 to 5.

[0090]

[12] The method for producing a magnesium alloy as described in any one of [7] to [9] above, characterized in that:

[0091] After the above step (a) or the above step (b), there is a step (c): plastic working the heat treated material to form a plastic worked material,

[0092] The plastic processing material has a structure in which the Mg3Zn3Y2 phase does not form a network structure at the grain boundary (i.e., a structure formed in a network fracture state), or has a structure in which both the Mg3Zn3Y2 phase and the Mg3Zn6Y phase do not form a network structure at the grain boundary (i.e., a structure formed in a network fracture state).

[0093]

[13] The manufacturing method described in

[12] above, characterized in that

[0094] The plastic processing material has a strength of more than 300 MPa and an elongation of more than 5%.

[0095] According to one embodiment of the present invention, a magnesium alloy with high thermal conductivity or a method for manufacturing the same can be provided.

[0096] Furthermore, according to one embodiment of the present invention, a magnesium alloy having high strength and high thermal conductivity or a method for manufacturing the same can be provided.

[0097] Furthermore, according to one embodiment of the present invention, a magnesium alloy having high strength, high thermal conductivity, and non-combustibility or a method for producing the same can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0098] Figure 1 (A) is a diagram showing the composition of multiple samples in an embodiment of the present invention, the thermal conductivity of the magnesium alloy casting material corresponding to the composition, and the constituent phases of the casting material; Figure 1 (B) To express Figure 1 (A) is a graph showing the thermal conductivity of heat-treated materials and the constituent phases of the heat-treated materials obtained after heat treatment of cast materials of multiple samples.

[0099] Figure 2 is a graph showing the stress-strain curve of the cast heat-treated material.

[0100] Figure 3 is a graph showing the stress-strain curve of an extruded material.

[0101] Figure 4 Graph showing the non-combustibility of Mg–1.88Zn–0.75Y–xYb alloy and Mg–1.88Zn–0.75Y–xCa alloy.

[0102] Figure 5 It is a graph showing the XRD (X-ray diffraction) measurement results of the Mg-1.88Zn-0.75Y alloy.

[0103] Figure 6Graph showing the characteristics of the Mg-1.88Zn-0.75Y-0.1Yb alloy extruded material in the example. DETAILED DESCRIPTION

[0104] The embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. However, the present invention is not limited to the following description, and those skilled in the art will readily appreciate that various changes may be made to the embodiments and details of the present invention without departing from the spirit and scope of the present invention. Therefore, the present invention should not be construed as being limited to the following embodiments.

[0105] (First Embodiment)

[0106] <Composition of magnesium alloy>

[0107] Figure 1 (A) is a graph showing the thermal conductivity of a cast material of a magnesium alloy according to an embodiment of the present invention and the constituent phases of the cast material; Figure 1 The composition range surrounded by the straight line shown in (A) is a material of the magnesium alloy as cast according to one embodiment of the present invention, and is a composition range of Zn and Y contents that has a thermal conductivity of 90 W / m·K or more. Figure 1 (B) is a graph showing the thermal conductivity and component phases of a heat-treated material of a magnesium alloy after casting according to an embodiment of the present invention. Figure 1 The composition range enclosed by the straight line shown in (B) refers to the casting heat treatment material of the magnesium alloy involved in one embodiment of the present invention, which is the composition range of Zn and Y content with a thermal conductivity of 90 W / m·K or more. In addition, the composition range of the magnesium alloy casting plastic processing material (such as extruded material and extruded material after heat treatment) involved in one embodiment of the present invention can also be used Figure 1 (A) and (B) show the composition range. Figure 1 The thermal conductivity of the cast material shown in (A) and Figure 1 The details of the thermal conductivity of the heat-treated material shown in (B) will be described in the examples described later. In addition, the details of the cast material, the cast heat-treated material, and the cast plastic processing material will be described in the second embodiment.

[0108] Furthermore, the magnesium alloy according to one embodiment of the present invention has a thermal conductivity of 90 W / m·K or more (preferably 100 W / m·K or more, more preferably 110 W / m·K or more, and even more preferably 130 W / m·K or more).

[0109] In addition, in this specification, "casting material" refers to a casting material cast at a solidification rate of less than 1,000K / s, including casting materials produced by casting methods such as mold casting, sand casting, semi-continuous casting, die casting, injection molding, and twin-roll casting.

[0110] In addition, in this specification, "cast heat-treated material" means a heat-treated material obtained by heat-treating the above-mentioned cast material.

[0111] In addition, in this specification, "cast plastic processing material" includes the following two: plastic processing material made by plastic processing such as extrusion, rolling, forging, wire drawing, solidification molding of chip materials, etc. on the above-mentioned heat-treated material, and plastic processing material made by plastic processing such as extrusion, rolling, forging, wire drawing, solidification molding of chip materials, etc. on the above-mentioned cast material without heat treatment.

[0112] The magnesium alloy according to the present embodiment has a composition range in which a atomic % of Zn, b atomic % of Y, and the remainder of the composition is Mg and inevitable impurities.

[0113] like Figure 1 As shown, with the Zn content (atomic %) a as the vertical axis and the Y content (atomic %) b as the horizontal axis, based on such coordinates (b, a), the Zn content a atomic % and the Y content b atomic % are located within the range enclosed by the straight lines represented by the following (1) to (8).

[0114] (1) When b falls within the range of the following formula 1a, it is the straight line of the following formula 1b,

[0115] (Formula 1a) 0.25 ≤ b ≤ 1.09

[0116] (Formula 1b) a = 0.5

[0117] (2) When b falls within the range of the following formula 2a, it is the straight line of the following formula 2b,

[0118] (Formula 2a) 1.09≤b≤1.2

[0119] (Formula 2b) a = 2.91b - 2.67

[0120] (3) When a falls within the range of the following formula 3a, it is the straight line of the following formula 3b,

[0121] (Formula 3a) 0.82≤a≤1.62

[0122] (Formula 3b) b = 1.2

[0123] (4) When b falls within the range of the following formula 4a, it is the straight line of the following formula 4b,

[0124] (Formula 4a) 1.2≤b≤3

[0125] (Formula 4b) a = 1.35b

[0126] (5) When a falls within the range of the following formula 5a, it is the straight line of the following formula 5b,

[0127] (Formula 5a)4.05≤a≤7

[0128] (Formula 5b) b = 3

[0129] (6) When b falls within the range of the following formula 6a, it is the straight line of the following formula 6b,

[0130] (Formula 6a) 1.5≤b≤3

[0131] (Formula 6b) a=7

[0132] (7) When b falls within the range of the following formula 7a, it is the straight line of the following formula 7b,

[0133] (Formula 7a) 0.25≤b≤1.5

[0134] (Formula 7b) a = 4.2b + 0.7

[0135] (8) When a falls within the range of the following formula 8a, it is the straight line of the following formula 8b,

[0136] (Formula 8a) 0.5≤a≤1.75

[0137] (Formula 8b) b = 0.25

[0138] <Phase composition of magnesium alloy>

[0139] like Figure 1 As shown in (A) and (B), it can be seen that the magnesium alloy exhibiting high thermal conductivity must contain W phase (Mg3Zn3Y2 phase), or contain W phase (Mg3Zn3Y2 phase) and I phase (Mg3Zn6Y phase) at the same time, but not X phase (LPSO (Long Period Stacking Order: Long Period Ordered Stacking Structure) phase: Mg 12 ZnY). It can be seen from this that by forming the W phase or the W phase and the I phase simultaneously instead of the LPSO phase, the concentration of the solute element in Mg can be reduced, thereby achieving high thermal conductivity.

[0140] like Figure 1 As shown in (A) and (B), in order to obtain a magnesium alloy with high thermal conductivity, the composition ratio of Zn to Y in the magnesium alloy, Zn / Y, is preferably in the range of 2 or more and 5 or less.

[0141] Through Figure 1The cast materials and cast heat-treated materials of the magnesium alloys shown in (A) and (B) are subjected to plastic processing such as extrusion processing to obtain a magnesium alloy having a structure in which the W phase (Mg3Zn3Y2 phase) is not formed in a network at the grain boundary (i.e., a structure formed in a network fracture state), or having a structure in which both the W phase (Mg3Zn3Y2 phase) and the I phase (Mg3Zn6Y) are not formed in a network at the grain boundary (i.e., a structure formed in a network fracture state). It is believed that the thermal conductivity can be improved.

[0142] Through Figure 1 The high thermal conductivity Mg-Zn-Y alloy shown in (A) and (B) can achieve excellent yield stress and ductility while maintaining high thermal conductivity by applying plastic processing such as extrusion. For example, it can achieve a yield strength of more than 300 MPa and an elongation of more than 5%.

[0143] According to this embodiment, by setting the composition range of Zn and Y with negative and large mixing enthalpy to Figure 1 The ranges shown in (A) and (B) can precipitate Mg3Zn3Y2 phase in the α-Mg matrix phase in the magnesium alloy, or precipitate Mg3Zn3Y2 phase and Mg3Zn6Y phase simultaneously, thereby improving the purity of the α-Mg matrix phase. This can achieve high thermal conductivity of the magnesium alloy.

[0144] Figure 4 This is a graph showing that the Mg-1.88Zn-0.75Y-xYb alloy and the Mg-1.88Zn-0.75Y-xCa alloy exhibit non-combustibility characteristics. Figure 4 In the graph, the vertical axis represents the ignition temperature (T / K), and the horizontal axis represents the content x (at.%) of Yb or Ca.

[0145] according to Figure 4 It has been confirmed that adding 0.1 atomic % or more of Yb or 1.0 atomic % or more of Ca to the Mg-1.88Zn-0.75Y alloy can make the alloy non-combustible. Figure 1 In the magnesium alloy within the composition range encircled by the lines shown in (A) and (B), if 0.05 atomic % or more and 0.6 atomic % of Yb are contained, or 1.0 atomic % or more and 2.0 atomic % or less of Ca are contained, non-combustibility is expected. The reason for setting the lower limit of Yb addition to 0.05 atomic % is that a Yb2O3 film is formed in the outermost layer when the addition amount exceeds this, and the reason for setting the upper limit of Yb to 0.6 atomic % is to suppress the adverse effect on mechanical properties.

[0146] The reason why the lower limit of Ca addition is set to 1.0 atomic % is that a CaO film starts to form in the outermost layer when the addition amount is greater than this, and the reason why the upper limit of Ca is set to 2.0 atomic % is to suppress the adverse effects on mechanical properties.

[0147] Furthermore, in addition to Yb and Ca, adding 0.03 atomic % to 0.3 atomic % of Be, or 0.1 atomic % to 2.0 atomic % of Sr to the above magnesium alloy can also be expected to achieve non-combustibility.

[0148] The reason why Be can also be added to achieve non-flammability is that there are reports that the ignition temperature will increase in alloys containing Y. The reason why the lower limit of Be is set to 0.03 atomic % is that this concentration can improve the oxygen barrier ability of the Y2O3 film, and the reason why the upper limit of Be is set to 0.3 atomic % is that the ignition temperature will not increase significantly above this concentration.

[0149] The reason why adding Sr can also achieve non-flammability is that there are reports that the ignition temperature will increase in alloys containing Y. The reason why the lower limit of Sr is set to 0.1 atomic % is that this concentration can improve the oxygen barrier ability of the Y2O3 film, and the reason why the upper limit of Sr is set to 2.0 atomic % is to avoid increasing the volume fraction of intermetallic compounds.

[0150] Figure 5 It is a graph showing the XRD (X-ray diffraction) measurement results of the Mg-1.88Zn-0.75Y alloy.

[0151] Depend on Figure 5 It can be confirmed that both the cast material and the heat-treated material contain W phase (Mg3Zn3Y2 phase) and I phase (Mg3Zn6Y phase).

[0152] (Second Embodiment)

[0153] <Method for producing magnesium alloy>

[0154] The magnesium alloy having the composition range described in the first embodiment is melted at a predetermined temperature in a flame-retardant gas atmosphere (for example, an Ar atmosphere), and then cast at a solidification rate of less than 1000 K / sec.

[0155] The cast magnesium alloy ingot is cut into a predetermined shape to prepare a casting material, which contains a Mg3Zn3Y2 phase, or contains both a Mg3Zn3Y2 phase and a Mg3Zn6Y phase, but does not contain a long-period stacking structure phase.

[0156] Next, the casting material is heat treated at a temperature of 200°C to 450°C (preferably 300°C to 450°C) for 0 hours to 48 hours to form a casting heat-treated material. The casting heat-treated material has a thermal conductivity of 90W / m·K or more (preferably 100W / m·K or more, more preferably 110W / m·K or more, and further preferably 130W / m·K or more). In addition, the casting heat-treated material contains Mg3Zn3Y2 phase, or contains both Mg3Zn3Y2 phase and Mg3Zn6Y phase, but does not contain a long-period stacking structure phase. In addition, the above heat treatment can also be carried out in an atmospheric atmosphere.

[0157] Next, the cast heat-treated material is subjected to plastic processing, which includes extrusion, rolling, forging, wire drawing, and large strain processing, etc. Among them, large strain processing includes EC-AE (equal-channel-angular-extrusion).

[0158] The plastic processed material obtained by the above plastic processing has a structure in which the Mg3Zn3Y2 phase is not formed in a network shape at the grain boundary (i.e., a structure formed in a network fracture state), or a structure in which both the Mg3Zn3Y2 phase and the Mg3Zn6Y phase are not formed in a network shape at the grain boundary (i.e., a structure formed in a network fracture state). In addition, the plastic processed material has a yield strength of more than 300 MPa and an elongation of more than 5%.

[0159] In addition, in the present embodiment, the cast heat-treated material is subjected to plastic working, but the above-mentioned cast material may also be subjected to plastic working.

[0160] In addition, the plastic processed material obtained by plastic processing the above-mentioned casting material and the casting heat-treated material respectively may also contain the Mg3Zn3Y2 phase, or contain the Mg3Zn3Y2 phase and the Mg3Zn6Y phase at the same time, but not contain the long-period stacking structure phase.

[0161] Furthermore, the above-mentioned cast material and plastic processed material each have high thermal conductivity.

[0162] <Solidification of casting fragments>

[0163] The casting material is prepared by the same method as the casting method. Then, the casting material is mechanically cut to form a fragmented material with a size of, for example, 1 to 2 mm. Then, the fragmented material is press-formed and solidified at room temperature to form a solidified material.

[0164] In addition, before forming the fragment material, the casting material may be subjected to the same heat treatment as the above casting method. In addition, before forming the solidified forming material, the fragment material may be subjected to the same heat treatment as the above casting method. In addition, the solidified forming material may be subjected to the same heat treatment as the above casting method. The solidified forming material after the heat treatment has a thermal conductivity of 90 W / K·m or more (preferably 100 W / m·K or more, more preferably 110 W / m·K or more, and further preferably 130 W / m·K or more).

[0165] In addition, the above-mentioned fragment materials, heat-treated fragment heat-treated materials, heat-treated materials obtained by heat-treating fragment materials, and solidified formed materials each contain Mg3Zn3Y2 phase, or contain Mg3Zn3Y2 phase and Mg3Zn6Y phase at the same time, but do not contain long-period stacking structure phase.

[0166] In addition, the solidified material may be subjected to plastic working, thereby obtaining a plastic working material having a yield strength of 300 MPa or more and an elongation of 5% or more.

[0167] <Injection molding method>

[0168] The magnesium alloy having the composition range described in the first embodiment is heated and melted at a predetermined temperature in a flame-retardant gas atmosphere (e.g., in an Ar atmosphere), and the molten metal of the molten magnesium alloy is injected and poured into a mold, and cooled and solidified to prepare an injection molding material. The cooling speed is preferably less than or equal to 1000K / second.

[0169] Next, the injection molding material is subjected to the same heat treatment as the casting method to form an injection molding heat-treated material having a thermal conductivity of 90 W / m·K or more (preferably 100 W / m·K or more, more preferably 110 W / m·K or more, and further preferably 130 W / m·K or more).

[0170] In addition, the above-mentioned injection molding material and injection molding heat treatment material each contain Mg3Zn3Y2 phase, or contain Mg3Zn3Y2 phase and Mg3Zn6Y phase at the same time, but do not contain long-period stacking structure phase.

[0171] <Die casting method>

[0172] The magnesium alloy having the composition range described in the first embodiment is heated and melted at a specified temperature in a flame-retardant gas atmosphere (for example, in an Ar atmosphere), and then the molten metal of the molten magnesium alloy is pressed into a mold to prepare a die-casting material. The cooling rate at this time is preferably less than 1000K / second. In addition, the die-casting method is a casting method that can mass-produce large-sized, high-precision castings in a short time.

[0173] Next, the die casting material is subjected to the same heat treatment as the casting method to form a die casting heat treated material having a thermal conductivity of 90 W / m·K or more (preferably 100 W / m·K or more, more preferably 110 W / m·K or more, and further preferably 130 W / m·K or more).

[0174] In addition, the above-mentioned die-casting material and die-casting heat-treated material each contain Mg3Zn3Y2 phase, or contain Mg3Zn3Y2 phase and Mg3Zn6Y phase at the same time, but do not contain a long-period stacking structure phase.

[0175] Example

[0176] Figure 1 (A) is a graph showing the compositions of a plurality of samples according to an embodiment of the present invention, the thermal conductivity of a magnesium alloy casting material corresponding to the compositions, and the constituent phases of the casting material. Figure 1 (B) indicates Figure 1 (A) is a schematic diagram of the thermal conductivity and constituent phases of heat-treated materials obtained after heat treatment of cast materials of multiple samples.

[0177] Figure 1 The W phase shown in (A) and (B) represents the Mg3Zn3Y2 phase, the I phase represents the Mg3Zn6Y phase, and the X phase represents the long period stacking structure phase (LPSO phase).

[0178] according to Figure 1 (A) and (B) , by forming the W phase or the W phase and the I phase simultaneously instead of the LPSO phase, the concentration of the solute elements in the Mg phase can be reduced, thereby achieving high thermal conductivity.

[0179] Will Figure 1 After weighing the sample raw materials of the composition shown in (A), the weighed raw materials are melted in an Ar atmosphere using a high-frequency melting furnace, and the molten metal is poured into a mold to form a cast ingot. The thermal conductivity of the casting material was measured, and the results are as follows: Figure 1 (A) is shown. In addition, the thermal conductivity is measured as follows:

[0180] Process the sample into or 5×5×1-3mm 3 After measuring the size and weight of the sample, the surface of the sample is blackened using dry carbon spray. After blackening, the weight is measured again, and the thermal diffusivity of the sample is measured using the laser flash method. The product of the measured thermal diffusivity and the specific gravity and specific heat capacity of the sample is the thermal conductivity.

[0181] Next, the cast material of the sample was heat treated at 360°C for 15 hours to form a cast heat-treated material. The thermal conductivity measurement results of the cast heat-treated material are as follows: Figure 1 (B) The method for measuring the thermal conductivity of the cast heat-treated material is the same as the above method.

[0182] Then, the cast heat-treated material was subjected to extrusion processing to form an extruded material. The extrusion conditions at this time were: extrusion ratio of 15, extrusion temperature of 250°C, and extrusion speed of 1.0 mm / s. In this extruded material, high thermal conductivity can be maintained while excellent yield stress and ductility can be achieved.

[0183] Figure 2 The graph represents the stress-strain curve of the cast heat-treated material. The composition of the cast heat-treated material is Mg-1.88Zn-0.75Y, and the heat treatment condition is heat treatment at 360°C for 15 hours. The thermal conductivity of the cast heat-treated material is 141W / m·K. The results of two tensile tests on the cast heat-treated material are: 0.2% yield σ 0.2 119MPa, elongation ε is 4.4%; 0.2% endurance σ 0.2 The tensile strength is 121 MPa and the elongation is 3.9%. 0.2 The average value is 120 MPa, and the average value of elongation is 4.2%.

[0184] Figure 3 The graph represents the stress-strain curve of the extruded material. The composition of the extruded material is Mg-1.88Zn-0.75Y. The extruded material is obtained by extruding the cast heat-treated material under the above extrusion conditions; the heat treatment condition of the cast heat-treated material is heat treatment at 360°C for 15 hours. The thermal conductivity of the extruded material is 131W / m·K. The extruded material was subjected to three tensile tests, and the results were: 0.2% endurance σ 0.2 361MPa, elongation ε is 10.7%; 0.2% endurance σ 0.2 365MPa, elongation ε is 9.6%; 0.2% endurance σ 0.2 The 0.2% yield strength σ is 358MPa and the elongation ε is 8.8%. 0.2 The average value is 361MPa, and the average value of elongation is 9.7%.

[0185] Figure 4The graph shows the non-combustibility of Mg-1.88Zn-0.75Y-xYb alloy and Mg-1.88Zn-0.75Y-xCa alloy. The results show that adding 0.1 atomic % or more of Yb or 1 atomic % or more of Ca to Mg-1.88Zn-0.75Y alloy can make the alloy non-combustible.

[0186] Figure 6 Graph showing the characteristics of the Mg-1.88Zn-0.75Y-0.1Yb alloy extruded material in the example.

[0187] according to Figure 6 Mg–1.88Zn–0.75Y–0.1Yb alloy extrusion material achieved a high yield strength σ of 383MPa 0.2 、137W·m -1 ·K -1 High thermal conductivity λ and non-flammability T of 1324K ig Therefore, it was confirmed that the thermal conductivity does not decrease even if Yb is added.

Claims

1. A magnesium alloy comprising a atomic % of Zn, b atomic % of Y, and the remainder consisting of Mg and unavoidable impurities, characterized in that: By using the coordinates (b, a) with a being the vertical axis and b being the horizontal axis, the Zn content of a atomic % and the Y content of b atomic % are limited to the range enclosed by the straight lines represented by the following (1) to (8), The magnesium alloy contains a Mg3Zn3Y2 phase, or contains both a Mg3Zn3Y2 phase and a Mg3Zn6Y phase. The magnesium alloy does not contain a long period stacking structure phase, (1) When b falls within the range of the following formula 1a, it is the straight line of the following formula 1b, (Formula 1a) 0.25 ≤ b ≤ 1.09 (Formula 1b) a = 0.5 (2) When b falls within the range of the following formula 2a, it is the straight line of the following formula 2b, (Formula 2a) 1.09≤b≤1.2 (Formula 2b) a = 2.91b - 2.67 (3) When a falls within the range of the following formula 3a, it is the straight line of the following formula 3b, (Formula 3a) 0.82≤a≤1.62 (Formula 3b) b = 1.2 (4) When b falls within the range of the following formula 4a, it is the straight line of the following formula 4b, (Formula 4a) 1.2≤b≤3 (Formula 4b) a = 1.35b (5) When a falls within the range of the following formula 5a, it is the straight line of the following formula 5b, (Formula 5a)4.05≤a≤7 (Formula 5b) b = 3 (6) When b falls within the range of the following formula 6a, it is the straight line of the following formula 6b, (Formula 6a) 1.5≤b≤3 (Formula 6b) a=7 (7) When b falls within the range of the following formula 7a, it is the straight line of the following formula 7b, (Formula 7a) 0.25≤b≤1.5 (Formula 7b) a = 4.2b + 0.7 (8) When a falls within the range of the following formula 8a, it is the straight line of the following formula 8b, (Formula 8a) 0.5≤a≤1.75 (Formula 8b) b = 0.

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2. The magnesium alloy according to claim 1, characterized in that The magnesium alloy has a thermal conductivity of 90 W / (m·K) or more.

3. The magnesium alloy according to claim 1 or 2, characterized in that: The magnesium alloy contains any one of 0.05 atomic % to 0.6 atomic % of Yb, 0.03 atomic % to 0.3 atomic % of Be, 1.0 atomic % to 2.0 atomic % of Ca, and 0.1 atomic % to 2.0 atomic % of Sr.

4. The magnesium alloy according to claim 1 or 2, characterized in that: The composition ratio of Zn to Y in the magnesium alloy is Zn / Y in the range of 2 to 5.

5. The magnesium alloy according to claim 1 or 2, characterized in that: The magnesium alloy has a structure in which the Mg3Zn3Y2 phase does not form a network at the grain boundary, or has a structure in which both the Mg3Zn3Y2 phase and the Mg3Zn6Y phase do not form a network at the grain boundary.

6. The magnesium alloy according to claim 1 or 2, characterized in that: The magnesium alloy has a strength of more than 300 MPa and an elongation of more than 5%.

7. A method for producing a magnesium alloy, characterized in that: The method comprises the steps of: casting a magnesium alloy containing a atomic % of Zn and b atomic % of Y, with the remainder consisting of Mg and inevitable impurities, at a solidification rate of less than 1000 K / s to form a cast material; By using the coordinates (b, a) with a being the vertical axis and b being the horizontal axis, the Zn content of a atomic % and the Y content of b atomic % are limited to the range enclosed by the straight lines represented by the following (1) to (8), The casting material contains a Mg3Zn3Y2 phase, or contains both a Mg3Zn3Y2 phase and a Mg3Zn6Y phase. The casting material does not contain a long-period stacking structure phase, (1) When b falls within the range of the following formula 1a, it is the straight line of the following formula 1b, (Formula 1a) 0.25 ≤ b ≤ 1.09 (Formula 1b) a = 0.5 (2) When b falls within the range of the following formula 2a, it is the straight line of the following formula 2b, (Formula 2a) 1.09≤b≤1.2 (Formula 2b) a = 2.91b - 2.67 (3) When a falls within the range of the following formula 3a, it is the straight line of the following formula 3b, (Formula 3a) 0.82≤a≤1.62 (Formula 3b) b = 1.2 (4) When b falls within the range of the following formula 4a, it is the straight line of the following formula 4b, (Formula 4a) 1.2≤b≤3 (Formula 4b) a = 1.35b (5) When a falls within the range of the following formula 5a, it is the straight line of the following formula 5b, (Formula 5a)4.05≤a≤7 (Formula 5b) b = 3 (6) When b falls within the range of the following formula 6a, it is the straight line of the following formula 6b, (Formula 6a) 1.5≤b≤3 (Formula 6b) a=7 (7) When b falls within the range of the following formula 7a, it is the straight line of the following formula 7b, (Formula 7a) 0.25≤b≤1.5 (Formula 7b) a = 4.2b + 0.7 (8) When a falls within the range of the following formula 8a, it is the straight line of the following formula 8b, (Formula 8a) 0.5≤a≤1.75 (Formula 8b) b = 0.

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8. The method for producing a magnesium alloy according to claim 7, characterized in that: After the step (a), there is a step (b) of subjecting the cast material to a heat treatment to form a heat-treated material. The heat treatment material has a thermal conductivity of 90 W / m·K or more, The heat-treated material contains a Mg3Zn3Y2 phase, or contains both a Mg3Zn3Y2 phase and a Mg3Zn6Y phase. The heat-treated material does not contain a long period stacking structure phase.

9. The method for producing a magnesium alloy according to claim 8, characterized in that: The heat treatment is performed under the following conditions: a temperature of 200° C. to 500° C. and a heat treatment time of 48 hours or less.

10. The method for producing a magnesium alloy according to any one of claims 7 to 9, characterized in that: The magnesium alloy contains any one of 0.05 atomic % to 0.6 atomic % of Yb, 0.03 atomic % to 0.3 atomic % of Be, 1.0 atomic % to 2.0 atomic % of Ca, and 0.1 atomic % to 2.0 atomic % of Sr.

11. The method for producing a magnesium alloy according to any one of claims 7 to 9, characterized in that: The composition ratio of Zn to Y in the casting material is Zn / Y in the range of 2 to 5.

12. The method for producing a magnesium alloy according to any one of claims 7 to 9, characterized in that: After the step (a) or the step (b), there is a step (c): plastic working the heat treated material to form a plastic worked material. The plastic working material has a structure in which the Mg3Zn3Y2 phase does not form a network at the grain boundary, or has a structure in which both the Mg3Zn3Y2 phase and the Mg3Zn6Y phase do not form a network at the grain boundary.

13. The method for producing a magnesium alloy according to claim 12, characterized in that: The plastic processing material has a bearing strength of 300 MPa or more and an elongation of 5% or more.

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