Magnesium alloy aging treatment material, its manufacturing method, and office automation equipment, transportation equipment and parts using the same

Abstract

Provided is a highly-versatile magnesium alloy aging treatment material that is capable of providing compatibility between strength and large thermal conductivity in a temperature range that includes room temperature. The magnesium alloy aging treatment material contains 1 mass% or less of Ca and 3 mass% of less of Zn, with the remainder comprising Mg and unavoidable impurities. Precipitates of a Guinier-Preston (GP) zone or the like comprising Mg, Ca and Zn are dispersed on the (0001) surface of a magnesium parent phase. The longitudinal direction of the GP zone on the (0001) surface is from 4.0 to 5.0 nm, and the number density of the GP zone is in the range of 1 × 10 20 to 1 × 10 24m-3.

Description

[Technical Field]

[0001] The present invention relates to an aged magnesium alloy material and a method for producing the same, and further relates to office automation equipment, transportation equipment, and parts thereof that use the aged magnesium alloy material. [Background technology]

[0002] Magnesium alloys are known as the lightest metals among practical metals, and their lightweight properties can be utilized in applications such as laptop computer housings and structural materials for transportation equipment. For these applications, wrought materials such as plates and rods produced by rolling or extrusion are used. When using plates as laptop computer housings, they require excellent heat dissipation properties in addition to sufficient mechanical properties for the application.

[0003] Until now, commercially available wrought magnesium alloys have mainly been strengthened by solid solution strengthening, a method of strengthening by introducing lattice strain into the matrix by dissolving elements with atomic radii different from those of the matrix. The greater the amount of solute elements, the greater the amount of solid solution strengthening that can be achieved.

[0004] However, in general, in metallic materials where thermal conductivity is largely due to conduction electrons, the thermal conductivity decreases when alloying elements are dissolved. For example, Patent Document 1 discloses a magnesium alloy in which Al (aluminum) and rare earth metals are added to magnesium, resulting in a thermal conductivity of 80 W / (m·K) or more and a tensile strength of 200 MPa or more. The thermal conductivity of pure Mg (magnesium) is 158 W / (m·K) at room temperature, but its yield strength is very low at less than 100 MPa (see Non-Patent Document 1). Therefore, it has been difficult to simultaneously improve both strength and thermal conductivity using this approach.

[0005] In magnesium alloy castings that require heat resistance, such as automobile engine blocks, a few atomic percent of calcium (Ca) has been added to Mg-Al alloys to form thermally stable intermetallic compounds along the grain boundaries, primarily on the grain boundaries, thereby achieving excellent high-temperature strength. The intermetallic compounds formed on the grain boundaries by adding calcium are compounds such as Al2Ca, which contains the alloying element Al. The formation of intermetallic compounds by adding calcium can reduce the concentration of solute elements in the matrix, which is also effective in improving thermal conductivity.

[0006] A common feature of methods for imparting excellent thermal conductivity and creep properties to magnesium alloy casting alloys is that alloy elements are crystallized as precipitates within grains or along grain boundaries. When alloy elements form precipitates, the concentration of the alloy elements in the matrix decreases, making it possible to impart excellent thermal conductivity. Forming precipitates on grain boundaries to form a three-dimensional mesh network (see Patent Document 2) has the advantage of being usable as a strength member, but there is a risk of significant loss of ductility. Furthermore, magnesium alloys that can achieve both workability and strength have been disclosed (see Patent Document 3, Non-Patent Documents 3 and 4). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-1921 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-1927490 [Patent Document 3] Japanese Patent Application Publication No. 2019-143206 [Non-patent literature]

[0008] [Non-Patent Document 1] X. Tong, GQ You, YH Ding,HS Xue, YC Wang, W. Guo,Mater. Lett. 229 (2018) 261-264 [Non-patent document 2] X. Gao, BC Muddle, JF Nie, Philos. Mag. Lett. 89 (2009) 33 - 43 [Non-patent document 3] Bian et al., Magnesium Technology 2018, 361-364 [Non-patent document 4] BC Suh et al., Magnesium Technology 2018, 373-377 Summary of the Invention [Problem to be solved by the invention]

[0009] However, the intermetallic compounds formed by adding Ca are very coarse, and therefore, even if these alloys are wrought to produce sheets or bars, they do not have good ductility, making them unsuitable for sheets that require further processing into the final shape after wrought processing.

[0010] In the prior art, the difficulty of strengthening commercially available wrought materials or recently reported cast materials lies in the difficulty of improving both mechanical properties and thermal conductivity. Solid-solution strengthening has traditionally been used as a strengthening method for wrought magnesium alloys. However, in metallic materials, where thermal conductivity is generally largely due to conduction electrons, the thermal conductivity generally decreases when alloying elements are solid-solved. Therefore, it is difficult to simultaneously improve both strength and thermal conductivity through solid-solution strengthening.

[0011] There have been examples where excellent high-temperature strength has been achieved by adding a few atomic percent of Ca to Mg-Al-based casting alloys, which form thermally stable intermetallic compounds along the grain boundaries. However, because the intermetallic compounds formed by adding Ca are very coarse, even when the alloys obtained in this way are wrought to produce plates or bars, they do not achieve good ductility or formability. Therefore, they are not suitable for use as plates that require processing into the final shape after wrought processing.

[0012] Incidentally, the housings and panels of office automation equipment require alloys with mechanical properties and thermal conductivity of approximately 120 W / (m·K) or more for heat dissipation. In many applications, there is a strong demand for alloys that exhibit both strength and excellent thermal conductivity at room temperature. However, conventional magnesium alloy manufacturing methods have not been able to produce versatile magnesium alloys that adequately combine strength and thermal conductivity at room temperature.

[0013] The first object of the present invention is to provide a versatile aged magnesium alloy material that can achieve both high thermal conductivity and strength over a temperature range including room temperature, a second object is to provide a method for manufacturing the aged magnesium alloy material, a third object is to provide office automation equipment using the aged magnesium alloy material, and a fourth object is to provide transportation equipment using the aged magnesium alloy material. [Means for solving the problem]

[0014] The present inventors have come up with the idea of ​​the present invention based on the discovery that, instead of the conventional solid solution strengthening of magnesium alloys, magnesium alloys can be strengthened by a new precipitation strengthening method in which GP zones are precipitated at high density from the magnesium matrix by aging treatment, thereby achieving high thermal conductivity and improved mechanical strength.

[0015] In order to achieve the first object, the present invention provides an aged magnesium alloy material containing 1 mass % or less of Ca and 3 mass % or less of Zn, with the remainder being Mg and unavoidable impurities, wherein GP zones consisting of Mg, Ca, and Zn are dispersed on the (0001) plane of the magnesium matrix, and the GP zones are oriented along the (0001) plane in a longitudinal direction of 4.0°. nm and the number density is 1×10 20 From 1×10 24 m -3 and the thermal conductivity of the aged magnesium alloy is 120 W / (m·K) or more.

[0016] The aged magnesium alloy preferably contains 0.5% by mass to 1% by mass of Ca, 0.8% by mass to 3% by mass of Zn, and the balance being Mg and unavoidable impurities. The aged magnesium alloy preferably has a tensile yield strength of 171±1 MPa. a from 227±2MP a This magnesium alloy aging treatment material further has the following properties: 0.4% by mass or less Zirconium or 0.5% by mass or less may contain manganese, 0.3% by mass or less Gadolinium or 0.2% by mass or less It may also contain cerium.

[0017] In order to achieve the second object, the method for producing an aged magnesium alloy material of the present invention comprises: melting Mg, Zn and Ca to obtain a cast solid; homogenizing the cast solid to obtain a homogenized material; a step of aging the homogenized material to obtain an aged magnesium alloy material; Including, The magnesium alloy aging material has a composition containing 1 mass % or less of Ca, 3 mass % or less of Zn, and the balance being Mg and inevitable impurities; The aging treatment is carried out in the temperature range of 140°C to 250°C until the thermal conductivity of the aged magnesium alloy material reaches 120 W / (m·K) or more. At the same time, the GP zone consisting of Mg, Ca, and Zn dispersed on the (0001) plane of the magnesium matrix is ​​formed into a zone having a longitudinal length of 4.0 nm or more on the (0001) plane and a number density of 1×10 20 From 1×1024 m -3 The range is .

[0018] The aging treatment is preferably carried out at a temperature in the range of 140°C to 250°C. 4 hours, 6 hours, 10 hours, 16 hours, or 500 hours . Preferably, a step of subjecting the homogenized material to solution treatment to obtain a solution-treated material is inserted between the step of obtaining the homogenized material and the step of obtaining the aged magnesium alloy material. Preferably, a process of wrought processing the homogenized material is inserted between the process of obtaining the homogenized material and the process of obtaining the solution-treated material. The homogenization process is preferably carried out at a temperature of 300°C or higher and 500°C or lower for a predetermined period of time.

[0019] The office automation equipment of the present invention, which achieves the third object, has a housing or panel material using the aged magnesium alloy material.

[0020] The transportation equipment and parts thereof of the present invention, which achieve the fourth object, use the above-mentioned aged magnesium alloy material or use it as a part thereof. [Effects of the Invention]

[0021] The present invention can provide a highly versatile aged magnesium alloy material that can achieve both high strength and thermal conductivity over a temperature range including room temperature, a method for manufacturing the same, and office automation equipment, transportation equipment, and parts thereof that use the same. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a flow chart showing a method for producing an aged magnesium alloy according to the present invention. [Figure 2] Bright-field transmission electron microscope images of the magnesium alloy in Example 6, where (a) is a solution-treated material, (b) is an aged material aged for 4 hours, (c) is an aged material aged for 120 hours, and (d) is an aged material aged for 1000 hours. [Figure 3]High-angle annular dark-field scanning transmission electron microscope (HAADF-STEM) images of the aged material of Example 6, where (a) is a material aged for 4 hours, (b) is a material aged for 1000 hours, (c) is an enlarged view of (a), and (d) is an enlarged view of (b). [Figure 4] 10 shows three-dimensional atom maps of the magnesium alloy of Example 6, where (a) is a solution-treated material, (b) is a material aged at 170°C for 4 hours, (c) is a material aged for 1000 hours, (d) is the concentration distribution of Zn, Ca, and Zr atoms in the aged material shown in (b), and (e) is the concentration distribution of Zn, Ca, and Zr atoms in the aged material shown in (c). [Figure 5] FIG. 10 is a graph showing the relationship between aging time during isothermal aging at 170° C. and Vickers hardness and thermal conductivity in Example 6. [Figure 6] FIG. 10 is a diagram showing the tensile stress-strain curve of the magnesium alloy of Example 6. [Figure 7] FIG. 10 is a graph showing the relationship between tensile yield strength and thermal conductivity in the aged material subjected to 4-hour aging treatment in Example 6 and other commercially available forged alloys. DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, embodiments of the present invention will be described in detail. The aged magnesium alloy material of the present invention is an alloy containing 1 mass% or less of Ca (calcium) and 3 mass% or less of Zn (zinc), with the balance being Mg (magnesium) and unavoidable impurities. Here, 1 mass% or less of Ca means more than 0 mass% but not more than 1 mass% of Ca. 3 mass% or less of Ca means more than 0 mass% but not more than 3 mass% of Zn. More preferably, the alloy contains 0.5 mass% to 1 mass% of Ca and 0.8 mass% to 3 mass% of Zn, with the balance being Mg and unavoidable impurities. In the aged magnesium alloy of the present invention, Guinier Preston zones (hereinafter referred to as GP zones) consisting of Mg, Ca, and Zn are dispersed and precipitated as second phases on the (0001) plane of the magnesium matrix. The GP zones have a size of 4.0 to 5.0 nm or more and a number density of 1×1020 From 1×10 24 m -3 Here, the number density of the GP zone is in the range of 1 m 3 The number density of GP zones is defined as the number of GP zones present per unit area. The number density of GP zones can be measured by 3DAP analysis using an atom probe (3DAP) as described below. The thermal conductivity of aged magnesium alloys is 120 W / (m·K) or higher, and they may further contain Zr (zirconium) or Mn (manganese) as constituent elements. They may also contain Gd (gadolinium) or Ce (cerium). The alloy composition and other details are described below.

[0024] (Upper limit of added element amount) To obtain excellent thermal conductivity, the lower the concentration of alloying elements added to Mg, the better. Therefore, there is no lower limit to the alloying element concentration; an upper limit can be set. The upper limit for Ca is preferably 1% by mass or less. Adding more than 1% by mass of Ca is undesirable because it has been empirically shown that the sample may crack during water quenching after solution treatment, i.e., during rapid cooling.

[0025] To obtain excellent thermal conductivity, the lower the concentration of Zn added to Mg, the better; therefore, there is no lower limit to the Zn concentration; an upper limit may be set. The Zn concentration is preferably greater than 0 mass% and equal to or less than 3 mass%. Based on Comparative Example 1 described below, the upper limit of the Zn concentration is preferably less than 3 mass% in order to obtain a thermal conductivity of 120 W / (m K).

[0026] (Lower limit of added element amount) To obtain a thermal conductivity of 130 W / (m K) or more in an Mg-Zn-Ca alloy, which is a more preferred embodiment, aging treatment is required. Comparison of Example 1 with Examples 2 and 3 described below reveals that the addition of more than 0 mass% of Ca, for example, 0.5 mass% or more, is required to precipitate a second phase by aging treatment. Furthermore, as shown in Example 2, the Zn concentration is preferably 0.8 mass% or more. From this perspective, the aged magnesium alloy material of the present invention is preferably an alloy containing 0.5 mass% to 1 mass% of Ca and 0.8 mass% to 3 mass% of Zn, with the remainder consisting of Mg and unavoidable impurities.

[0027] (Addition of other alloying elements) Furthermore, to increase the strength by refining the grains, Zr or Mn may be added as a grain refiner. From a comparison between Examples 3 and 5, or Examples 6 and 7, which will be described later, it is desirable to add Zr or Mn as a grain refiner. Furthermore, it is preferable to add Zr as a grain refiner.

[0028] It is preferable to add Ce or Gd as an additive element for improving age hardenability and controlling texture during rolling. As shown in Examples 5 and 8 described below, the addition of alloying elements reduces thermal conductivity, so it is preferable to minimize the amount of addition. When a magnesium alloy is expressed as an alloy of the general formula Mg-Ca-X (X is Zn or Al), a comparison of Comparative Examples 1 and 2 described below with Example 6 shows that adding Zn as the X element is more suitable than Al.

[0029] Next, a method for producing an aged magnesium alloy will be described. Fig. 1 is a flow diagram showing a method for producing an aged magnesium alloy material of the present invention. The method for producing a magnesium alloy of the present invention includes the following steps: Step 1, in which raw materials such as Mg, Zn, and Ca are melted and then cast to obtain a cast solid; Step 2, in which the cast solid is homogenized to obtain a homogenized material (also called T4 treatment); Step 3, in which the homogenized material is wrought, as needed, to obtain a worked material; Step 4, in which the worked material is solution treated to obtain a solution treated material; and Step 5, in which the solution treated material is aged to obtain an aged magnesium alloy material (also called T6 treatment).

[0030] (Process 1: Casting) In step 1, alloy components containing more than 0% by mass but not more than 1% by mass of Ca, more than 0% by mass but not more than 3% by mass of Zn, with the remainder consisting of Mg and unavoidable impurities, are melted, and then a cast solid is produced. In step 1, Zr, etc., may be further added to the magnesium alloy as needed. Any method may be used for melting, as long as an alloy of the desired composition can be produced. For example, the alloy components can be melted by melting an alloy of the desired composition in an argon atmosphere using a high-frequency induction melting furnace, pouring the melt into a mold made of iron, etc., and cooling it to produce a cast. The melting furnace used for melting and the dimensions of the cast solid are not particularly limited, as long as a cast solid of the desired composition can be produced.

[0031] (Step 2: Homogenization) In step 2, a heat treatment is performed as a homogenization treatment to dissolve the segregation of alloying elements present in the cast alloy and compounds formed during cooling of the molten alloy into the matrix, thereby homogenizing the distribution of alloying elements. The cast solid is homogenized for a predetermined time at a temperature ranging from 300°C to 500°C, more preferably from 350°C to 450°C, to produce a homogenized solid. Detailed conditions are listed in Table 1 below. In regions where alloying elements are highly macrosegregated, high-temperature heat treatment will cause melting. Therefore, a low-temperature heat treatment may be performed before the heat treatment at the predetermined temperature. For example, in regions where Zn is highly macrosegregated, starting heat treatment at 450°C may cause localized melting of the alloy, i.e., incipient melting. Therefore, by first performing heat treatment in the range of 300°C to 350°C to suppress the initial melting of the Mg-Zn phase formed during casting and disperse Zn, the distribution of Zn can be homogenized to obtain a homogenized solid by performing heat treatment for a predetermined time at 400°C or higher and 500°C or lower.

[0032] (Process 3: Stretching) In step 3, which is inserted between the homogenization treatment step 2 and the solution treatment step 4 as needed, the cast material is wrought by, for example, rolling or extrusion, and processed into a worked material such as a plate or a bar. This step 3 is not necessarily required for improving thermal conductivity. For example, the homogenized solid is processed into a plate by hot or warm rolling, etc., to produce a plate-shaped worked material. The production of plate materials by wrought processing is not limited to hot or warm processing, particularly rolling, and other processing methods that can produce a fine structure may be used.

[0033] (Step 4: Solution treatment) In step 4, the plate-shaped tangible solid obtained by rolling or other processes is solution-treated and then cooled to produce a solution-treated material. This process is performed to dissolve fine precipitates formed during rolling into the magnesium matrix and form a recrystallized microstructure. If rolling is not performed, this process can be performed in conjunction with the homogenization treatment in step 2, and the solution treatment can be omitted. In this case, step 5 is performed after step 2 to obtain the homogenized material, in which the homogenized material is aged to obtain an aged magnesium alloy. In solution treatment, the processed material is heat-treated to dissolve fine precipitates formed during hot or warm working into the matrix and recrystallize them to form a microstructure. Solution treatment is performed at a temperature between 350°C and 500°C for 15 minutes to 24 hours. However, longer heat treatment times increase production costs, so longer treatment times are not necessary. Various temperature conditions can be used; the details of the conditions are listed in Table 1 below. By carrying out a solution treatment after hot or warm working, the orientation of the crystal grains can be made random, and excellent formability can be imparted.

[0034] (Step 5: Aging treatment) In step 5, the solution-treated material is aged by heat treatment, dispersing the precipitates in the solution-treated material and imparting strength, thereby producing the aged magnesium alloy of the present invention. In the present invention, significant strengthening and high thermal conductivity of the magnesium alloy can be achieved by using an aging treatment not previously used in commercial magnesium alloys. The aging treatment is performed at a temperature ranging from 140°C to 250°C for a specified period of time. The aging treatment is performed for a period of time that increases the thermal conductivity of the magnesium alloy, preferably for a period of time that reaches or exceeds 120 W / (m·K). For example, the aging treatment is performed in an oil bath at 170°C.

[0035] The aged magnesium alloy material of the present invention produced in this manner is an alloy containing more than 0% by mass and not more than 1% by mass of Ca, more than 0% by mass and not more than 3% by mass of Zn, with the remainder being Mg and unavoidable impurities, in which nanometer-order precipitates (GP zones) consisting of Mg, Ca, and Zn are dispersed on the (0001) plane of the magnesium matrix.

[0036] According to the present invention, by adding Ca and Zn to Mg and then performing aging treatment, it is possible to form a high density of nano-precipitates, called GP zones, which have interfaces that are coherent with the magnesium matrix, thereby providing an aged material that can improve thermal conductivity and mechanical strength without significantly impairing ductility.

[0037] The aged magnesium alloy material of the present invention can achieve high density dispersion of coherent nanoscale precipitates as GP zones, which are nanoscale precipitates that are coherent with the magnesium matrix, by combining a solution treatment with a low-temperature heat treatment called aging treatment. This allows for the production of aged magnesium alloy material that combines excellent thermal conductivity and mechanical properties at low cost without using expensive elements.

[0038] (OA equipment) Office automation equipment (referred to as OA equipment) has a housing or panel material using the aged magnesium alloy material of the present invention. OA equipment is a general term for equipment necessary for office automation in companies, offices, etc., and can be applied to OA equipment according to purpose without any particular restrictions. Examples include computers such as laptop computers and desktop computers, mobile phones (smartphones), personal digital assistants (also called PDAs), copiers, various printers, and facsimiles (FAX machines).

[0039] In OA equipment, the housings and panel materials processed by wrought processing of the aged magnesium alloy material of the present invention are used, for example, as housings and panel materials for OA equipment.

[0040] (Transportation equipment and its parts) The aged magnesium alloy panel material of the present invention may be used for transportation equipment and its parts, such as automobiles, aircraft, flying objects such as drones, and railroad cars, and is not particularly limited and can be used as appropriate depending on the purpose.

[0041] Parts for transportation equipment include parts using the aged magnesium alloy material of the present invention. Furthermore, panel materials processed by wrought processing such as rolling are parts such as luggage retainers used as panel materials or rear seat parts for automobiles. [Example]

[0042] The embodiments of the present invention will now be described in more detail. The measurements of the samples in the examples and comparative examples were carried out by the following methods. (Measurement of thermal conductivity) A sample with a length x width of 10 x 10 mm and a thickness of 1 mm was prepared and measured using the laser flash method. The thermal conductivity λ (W / (m K)) was calculated using the formula (a x Cp x ρ), where the thermal diffusivity a (m / s) was measured at 298 K using a thermal conductivity measuring device (Linseis LFA 1000 laser flash analyzer). The density ρ (g / cm) at room temperature was 3 ) was measured by the Archimedes method (Mettler, Toledo AG285). The specific heat capacity Cp (J / g K) was estimated by the Neumann-Kopf law.

[0043] (Transmission electron microscope image) Transmission electron microscopy images for microstructural characterization were obtained using a transmission electron microscope (FEI Tecnai 20 and Titan G). 2 Thin foil specimens for TEM or STEM observation were prepared by punching out 3 mm diameter disks and twin-jet electropolishing at a voltage of 90 V at approximately −50°C.

[0044] (3DAP analysis) Three-dimensional atom probe (3DAP) is a method for measuring three-dimensional atomic distribution by applying a high voltage to a needle-shaped sample, detecting ions that are field-evaporated from the sample surface with a mass spectrometer, and sequentially detecting each ion in the depth direction. 3DAP analysis was performed using a local electrode atom probe (CAMECA, LEAP5000XS) in voltage pulse mode at a temperature of 30 K. The sharp needle-shaped sample used for field evaporation in 3DAP analysis was prepared by lift-out and annular milling techniques using a SEM-focused ion beam (FIB, FEI Helios G4UX). The number density of the GP zone was measured using the data analysis software of the mass spectrometer (CAMECA) used for 3DAP analysis. First, the volume of the sample was calculated from the measured sample data. The data analysis software used was IVAS (CAMECA). Next, the locations of the GP zones in the sample were detected using the isodensity surface of the data, and the number of GP zones was counted. The number of GP zones was then divided by the volume initially obtained to calculate the number density of the GP zones.

[0045] (Age hardening response) The age-hardening response was measured by a micro-Vickers hardness tester (Mitutoyo HM-101) under a load of 300 g.

[0046] (Tensile properties) The tensile properties are -3 s -1 The specimens were evaluated at room temperature using a tensile testing machine (Instron, 5567) with an initial strain rate of 1.5 mm. Tensile specimens with a gauge length of 12.5 mm and a width of 5 mm were machined from the solute-treated and aged materials.

[0047] (Eriksen value) The Erichsen value (IE value), which evaluates workability at room temperature, was measured using an Erichsen test in which a thin plate with a fixed outer periphery was deformed by pressing a ball-headed punch at a constant speed, and the height of the indentation until the material broke was measured. The Erichsen value was evaluated using a testing machine (Erichsen, Model 111).

[0048] Example 1 (1) Alloy composition: Mg-1.0Zn-0.3Ca-0.3Zr (2) Homogenization treatment: After holding at 300°C for 4 hours, the temperature was increased at 7.5°C / h, held at 450°C for 6 hours, and then water-cooled. (3) Solution treatment: 450°C for 2 hours (4) Aging treatment: 170°C for 6 hours, 500 hours A sample was prepared according to the experimental procedure described above, and as shown in Table 1, the sample was held at 300°C for 4 hours as a homogenization treatment, then heated at a rate of 7.5°C / h (1 h = 1 hour), and further held at 450°C for 6 hours, followed by water cooling.

[0049] [Table 1]

[0050] Plate samples were then prepared and solution-treated at 450°C for two hours. The thermal conductivity of each sample was measured: the solution-treated material, the aging-treated material obtained by aging the solution-treated material at 170°C for six hours, and the aging-treated material obtained by aging for 500 hours. Table 2 summarizes the detailed aging conditions and thermal conductivity.

[0051] [Table 2]

[0052] The thermal conductivity of each sample was measured using the method described above and was found to be 125.2 W / (m·K), 127.7 W / (m·K), and 134.8 W / (m·K), respectively, indicating a slight increase in thermal conductivity due to aging treatment.

[0053] Example 2 (1) Alloy composition: Mg-0.8Zn-0.5Ca-0.4Zr (2) Homogenization treatment: After holding at 300°C for 4 hours, the temperature was increased at 7.5°C / h, held at 450°C for 6 hours, and then water-cooled. (3) Solution treatment: 1 hour at 450°C (4) Aging treatment: 10 hours at 170°C, 500 hours Samples were prepared according to the experimental procedure described above, and as a homogenization treatment, they were held at 300°C for 4 hours, then heated at a rate of 7.5°C / h, and further held at 450°C for 6 hours, followed by water quenching, as shown in Table 1. Plate-shaped samples were then prepared and subjected to solution treatment at 450°C for 1 hour. The thermal conductivity of each sample was measured: a solution-treated material, an aged material obtained by aging the solution-treated material at 170°C for 10 hours, and an aged material obtained by aging for 500 hours. The thermal conductivities of the samples were 123.8 W / (m·K), 130.9 W / (m·K), and 135.1 W / (m·K), respectively, indicating an increase in thermal conductivity due to aging. In Example 2, the amount of Ca added was increased compared to Example 1. It was found that an addition of approximately 0.5% Ca was necessary to increase thermal conductivity through aging.

[0054] Example 3 (1) Alloy composition: Mg-0.8Zn-0.8Ca-0.4Zr (2) Homogenization treatment: After holding at 300°C for 4 hours, the temperature was increased at 7.5°C / h, held at 450°C for 6 hours, and then water-cooled. (3) Solution treatment: 1 hour at 450°C (4) Aging treatment: 170°C for 16 hours, 500 hours Samples were prepared according to the experimental procedure described above, and as a homogenization treatment, they were held at 300°C for 4 hours, then heated at a rate of 7.5°C / h, and further held at 450°C for 6 hours, followed by water quenching, as shown in Table 1. Plate-shaped samples were then prepared and subjected to solution treatment at 450°C for 1 hour. The thermal conductivity of each sample was measured: a solution-treated material, an aged material obtained by aging the solution-treated material at 170°C for 16 hours, and an aged material obtained by aging for 500 hours. The thermal conductivities of the samples were 126.8 W / (m·K), 130.7 W / (m·K), and 130.2 W / (m·K), respectively, indicating that the aging treatment increased the thermal conductivity. In Example 3, the amount of Ca added was even greater than in Example 2, but the thermal conductivity was lower than in Example 2. This indicates that the addition of approximately 0.5% Ca is necessary to increase the thermal conductivity through aging.

[0055] Example 4 (1) Alloy composition: Mg-0.8Zn-0.8Ca-0.3Mn (2) Homogenization treatment: After holding at 300°C for 4 hours, the temperature was increased at 7.5°C / h, held at 450°C for 6 hours, and then water-cooled. (3) Solution treatment: 1 hour at 450°C (4) Aging treatment: 170°C for 16 hours, 500 hours Samples were prepared according to the experimental procedure described above, and as a homogenization treatment, they were held at 300°C for 4 hours, then heated at a rate of 7.5°C / h, and further held at 450°C for 6 hours, followed by water quenching, as shown in Table 1. Plate-shaped samples were then prepared and subjected to solution treatment at 450°C for 1 hour. The thermal conductivity of each sample was measured: a solution-treated material, an aged material obtained by aging the solution-treated material at 170°C for 16 hours, and an aged material obtained by aging for 500 hours. The thermal conductivities of the samples were 121.0 W / (m·K), 129.5 W / (m·K), and 129.5 W / (m·K), respectively, indicating an increase in thermal conductivity due to aging. Example 4 had an alloy composition in which Zr in Example 3 was replaced with Mn. Although a thermal conductivity exceeding 120 W / (m·K) was achieved even with the substitution of Mn, the thermal conductivity was lower than that of Example 3. This indicates that adding Zr as a refiner is preferable to Mn in order to achieve a thermal conductivity exceeding 130 W / (m·K).

[0056] Example 5 (1) Alloy composition: Mg-1.6Zn-0.5Ca-0.5Mn-0.2Ce (2) Homogenization treatment: After holding at 300°C for 4 hours, the temperature was increased at 7.5°C / h, held at 450°C for 6 hours, and then water-cooled. (3) Solution treatment: 1 hour at 450°C (4) Aging treatment: 170°C for 4 hours, 500 hours Samples were prepared according to the experimental procedure described above, and as a homogenization treatment, they were held at 300°C for 4 hours, then heated at a rate of 7.5°C / h, and further held at 450°C for 6 hours, followed by water quenching, as shown in Table 1. Plate-shaped samples were then prepared and subjected to solution treatment at 450°C for 1 hour. The thermal conductivity of each sample was measured: a solution-treated material, an aged material obtained by aging the solution-treated material at 170°C for 4 hours, and an aged material obtained by aging for 500 hours. The thermal conductivities of the samples were 113.2 W / (m·K), 115.9 W / (m·K), and 121.1 W / (m·K), respectively. The alloy composition of Example 5 was the same as that of Example 4, with Ce added. Although a thermal conductivity exceeding 120 W / (m·K) was achieved, the thermal conductivity was lower than that of Example 4. This indicates that to achieve a thermal conductivity exceeding 130 W / (m·K), the composition of Examples 3 or 4 is sufficient, and it is better not to add any additional elements.

[0057] Example 6 (1) Alloy composition: Mg-1.6Zn-0.5Ca-0.4Zr (2) Homogenization treatment: After holding at 300°C for 4 hours, the temperature was increased at 7.5°C / h, held at 450°C for 6 hours, air-cooled to 300°C, and then water-cooled. (3) Solution treatment: 1 hour at 450°C (4) Aging treatment: 170°C for 6 hours, 500 hours Samples were prepared according to the experimental procedure described above, and as shown in Table 1, the homogenization treatment consisted of holding the sample at 300°C for 4 hours, then increasing the temperature at a rate of 7.5°C / h, holding the sample at 450°C for 6 hours, air-cooling to 300°C, and water-cooling. Plate samples were then prepared and solution-treated at 450°C for 2 hours. The thermal conductivity of each sample was measured: a solution-treated material, a material that had been aged at 170°C for 6 hours, and a material that had been aged for 500 hours. The thermal conductivity of each sample was 122.6 W / (m·K), 128.3 W / (m·K), and 135.8 W / (m·K), respectively, indicating that the aging treatment increased the thermal conductivity.

[0058] Figure 2 shows bright-field transmission electron microscope (BEM) images of the magnesium alloy in Example 6. (a) shows a solution-treated material, (b) shows a material aged at 170°C for 4 hours, (c) shows a material aged at 170°C for 120 hours, and (d) shows a material aged at 170°C for 1000 hours. Each BEM image was taken along the [112 bar 0] zone axis. The corresponding selected area electron diffraction (SAED) patterns are shown at the bottom, taken along the [101 bar 0]α and

[0001] α directions. As shown in Figure 2(a), the solution-treated material contains rod-like, agglomerated particles along the grain boundaries and inside the grains, suggesting that these particles suppressed the growth of recrystallized grains during the solution treatment. According to Gao et al. (see Non-Patent Document 2), these particles are presumed to be the Zn2Zr3 phase.

[0059] As shown in Figure 2(b), the contrast of the SAED pattern for the 4-hour aged specimen reveals the dense distribution of nm-scale platelet precipitates on the basal plane of the Mg matrix. The corresponding SAED patterns for [011bar0]α and

[0001] α show streaks along the

[0001] α direction and extra diffraction spots at 1 / 3{2bar110} and 2 / 3{2bar110} compared to the positions in the solution-treated specimen. Analysis of the SAED pattern reveals that fine precipitates, known as the GP zone (Guinier-Preston zone), are distributed on the basal plane of the Mg matrix, i.e., on the (0001)α plane of the magnesium matrix.

[0060] As shown in Figure 2(c), pairs of large plate-like GP zones with lengths of 10-50 nm precipitate on the (0001) α-plane in the 120-hour aged material.

[0061] As shown in Figure 2(d), the SAED pattern for the 1000-hour aged specimen is similar to that for the 4-hour aged specimen, with the presence of aligned GP zones.

[0062] The aged material of Example 6 was observed by high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) using a transmission electron microscope. Figure 3 shows HAADF-STEM images of the aged material of Example 6. (a) shows the aged material aged for 4 hours, (b) shows the aged material aged for 1000 hours, (c) shows an enlarged view of (a), and (d) shows an enlarged view of (b). Each HAADF-STEM image was taken from the [112 bar 0] zone axis. As shown in Figures 3(a) and 3(b), in the low-magnification HAADF-STEM images of the aged material of Example 6, the GP zone is observed as a bright linear contrast along the basal plane, i.e., the (0001) α-plane of the magnesium matrix. According to the 3D atom map described below, this precipitate is rich in Ca and / or Zn.

[0063] As shown in Figure 3(a), the average size of the GP zone in the 4-hour aged specimen was approximately 3.2 ± 0.4 nm. As shown in Figure 3(c), it was found to consist of a single-layer of bright atomic columns arranged on the (0001) α plane. On the other hand, as shown in Figure 3(b), the average size of the GP precipitate in the 1000-hour aged specimen was 35 ± 10 nm. As shown in Figure 3(d), it was found to consist of two bright atomic columns spaced approximately 1.3 nm apart. The precipitates observed in the 1000-hour aged specimen differed from the GP zones observed in the shorter aged specimens, and some precipitates may not be considered GP zones. Therefore, to distinguish them from GP zones, we refer to them as GP precipitates. The average size of the GP precipitates on the (0001) α plane increased with increasing aging time.

[0064] As shown in Figure 3, no misfit dislocations were observed on the surface or edge of the GP precipitates in both 4-hour and 1000-hour aged specimens, and the GP zones in both specimens were found to be perfectly aligned with the magnesium matrix. However, the misfit displacement between the GP zones and the magnesium matrix in the 1000-hour aged specimen was found to decrease from 4.1% in the 4-hour aged specimen to 1.8%.

[0065] Figure 4 shows three-dimensional atom maps of the magnesium alloy of Example 6, where (a) shows a solution-treated material, (b) shows an aged material aged at 170°C for 4 hours, and (c) shows an aged material aged for 1000 hours. Figure 4(d) shows the concentration distribution of Zn, Ca, and Zr atoms in the aged material of (b), and (e) shows the concentration distribution of Zn, Ca, and Zr atoms in (c). The three-dimensional atom maps of Figures 4(a) to (c) are obtained by plotting the concentration distribution of Zn, Ca, and Zr atoms in a selected 40 × 40 × 200 nm 3 The volume of the sample was collected and analyzed in the direction parallel to the <0001> Mg. Table 3 summarizes the solute concentration, planar spacing, and number density of GP zones in the magnesium matrix measured in the 3D atom maps shown in Figures 4(a) to 4(c).

[0066] [Table 3]

[0067] The Zn, Ca, and Zr atoms in the solution-treated material shown in Figure 4(a) have concentrations of 0.412, 0.241, and 0.001 atomic percent, respectively, indicating a uniform distribution and a chemically uniform solid solution.

[0068] In the case of the aged material aged for 4 hours shown in Figure 4(b), numerous fine plate-like precipitates enriched in Ca and Zn, i.e., GP zones, were observed to form in the magnesium matrix. As shown in Table 4, the number density and effective planar spacing of the GP zones were approximately 9.9 × 10 23 m -3 The calculated values ​​were 8.9 nm and 8.9 nm. The solute concentrations of Zn and Ca atoms in the magnesium matrix were reduced to 0.195 and 0.111 at.% compared to the solution-treated material.

[0069] In Figures 4(c) and 4(e), the aged material after 1000 hours of aging has a pair of large plate-like GP precipitates located close to each other on the (0001)α plane. As shown in Table 4, the number density of GP precipitates is approximately 1.5 × 10 23 m -3 The effective interplanar spacing was calculated to be 95.1 nm, which is significantly greater than that of the 4-hour aged material. The solute concentrations of Zn and Ca atoms in the magnesium matrix further decreased to 0.071 and 0.003 atomic %, respectively. The Zr concentration was barely detectable in the magnesium matrix due to the formation of Zn-Zr particles.

[0070] From the above results, it can be seen that the concentration of solute elements in the magnesium matrix tends to decrease with the aging time. After 4 hours of aging, the number density was 9.9 × 10 23 m -3 , that is, 1 × 10 24 m -3However, as the aging time progresses, the GP zones become coarser, so their number density decreases and the particle spacing also increases.

[0071] Figure 5 shows the relationship between aging time and Vickers hardness and thermal conductivity during isothermal aging at 170°C in Example 6. The horizontal axis of Figure 5 represents aging time (hours), the left vertical axis represents Vickers hardness (HV), and the right vertical axis represents thermal conductivity (W / (m·K)). As shown in Figure 5, the Vickers hardness of the solution-treated material is 52.8±1.6 HV, and it can be seen that after 4 hours of aging, rapid age hardening is observed, reaching a peak Vickers hardness of 66.1±1.5 HV. After 1000 hours of aging, the Vickers hardness decreases to 52.3±1.3 HV.

[0072] On the other hand, the thermal conductivity of the solution-treated material (T4) was 123.3±0.8 W / (m·K), and that of the aged material (T6) after 4 hours of aging increased to 128.6±0.5 W / (m·K), and the thermal conductivity of the aged material (T6) after 1000 hours of aging reached a maximum of 132.7±0.6 W / (m·K).

[0073] Figure 6 is a diagram showing the tensile stress-strain curve of the magnesium alloy of Example 6. The horizontal axis of the diagram is strain (%), and the vertical axis is tensile stress (MPa). The tensile yield strength, ultimate tensile yield strength, elongation, and thermal conductivity obtained from the stress-strain curve are shown in Table 4. As shown in Figure 6 and Table 4, the tensile yield strength of the solution-treated material was 181 MPa, the ultimate tensile yield strength was 265 MPa, and the elongation was 28.2%. In addition, the Erichsen value measured at room temperature was 8.11 mm. The 4-hour aging treatment yielded a tensile yield strength of 227 MPa and an ultimate tensile yield strength of 291 MPa, demonstrating a strength increase over that of the solution-treated material. The elongation was 22.6%, slightly lower than that of the solution-treated material. The 1000-hour aging treatment yielded a tensile yield strength of 171 MPa, an ultimate tensile yield strength of 242 MPa, and an elongation of 23.8%.

[0074] [Table 4]

[0075] Figure 7 shows the relationship between tensile yield strength and thermal conductivity for the aged material aged for 4 hours in Example 6 and other commercially available wrought alloys. As shown in Figure 7, it was found that the aged material (T6) aged for 4 hours has a better balance between tensile yield strength and thermal conductivity than the other commercially available wrought alloys. Example 6 is the case where the Zn concentration in Example 3 was increased from 0.8 mass% to 1.6 mass%. This example shows that although the thermal conductivity after solution treatment was approximately 120 W / (m K), aging treatment can achieve a thermal conductivity of over 130 W / (m K).

[0076] In the magnesium alloys of the present invention, including Example 6, the parent material is solution-treated and then rapidly cooled to form a supersaturated solid solution. The subsequent aging treatment causes the supersaturated solute elements to precipitate as densely dispersed fine GP zone precipitates or GP precipitates, thereby increasing the mechanical strength of the aged material (T6). Furthermore, the formation of GP precipitates reduces the amount of solute elements, such as Ca, Zn, and Zr, dissolved in the magnesium parent phase, thereby reducing the amount of solute elements that contribute to reduced thermal conductivity. As a result, age hardening through aging treatment can improve both strength and thermal conductivity. This principle has already been used in aluminum alloys, and the present invention has been found to be applicable to magnesium alloys.

[0077] Example 7 (1) Alloy composition: Mg-1.6Zn-0.5Ca-0.4Mn (2) Homogenization treatment: After holding at 300°C for 4 hours, the temperature was increased at 7.5°C / h, held at 450°C for 6 hours, air-cooled to 300°C, and then water-cooled. (3) Solution treatment: 400°C for 1 hour (4) Aging treatment: 170°C for 16 hours, 500 hours Samples were prepared according to the experimental procedure described above. As shown in Table 1, the homogenization treatment consisted of holding the sample at 300°C for 4 hours, then increasing the temperature at a rate of 7.5°C / h, holding the sample at 450°C for 6 hours, and then air-cooling to 300°C and water-cooling. Plate samples were then prepared and solution-treated at 450°C for 2 hours. The thermal conductivity of each sample was measured: the solution-treated sample, the aging-treated sample at 170°C for 16 hours, and the aging-treated sample for 500 hours. The thermal conductivities of the samples were 112.6 W / (m·K), 117.2 W / (m·K), and 124.7 W / (m·K), respectively, indicating an increase in thermal conductivity due to the aging treatment. The alloy composition of Example 7 is an example in which Zr in Example 6 was replaced with Mn. Although the thermal conductivity value decreased when Zr was replaced with Mn, a thermal conductivity of over 120 W / (m K) was achieved after aging treatment. However, it was found that it is preferable to add Zr rather than Mn as a grain refiner.

[0078] Example 8 (1) Alloy composition: Mg-1.6Zn-0.5Ca-0.4Zr-0.3Gd (2) Homogenization treatment: After holding at 300°C for 4 hours, the temperature was increased at 7.5°C / h, held at 450°C for 6 hours, air-cooled to 300°C, and then water-cooled. (3) Solution treatment: 400°C for 1 hour (4) Aging treatment: 170°C for 16 hours, 500 hours Samples were prepared according to the experimental procedure described above, and as shown in Table 1, the homogenization treatment consisted of holding the sample at 300°C for 4 hours, then increasing the temperature at a rate of 7.5°C / h, holding the sample at 450°C for 6 hours, air-cooling to 300°C, and water-cooling. Plate samples were then prepared and solution-treated at 450°C for 2 hours. The thermal conductivity of each sample was measured: a solution-treated material, an aged material that had been aged at 170°C for 16 hours, and a material that had been aged for 500 hours. The thermal conductivity of each sample was found to be 112.6 W / (m K), 117.2 W / (m K), and 124.7 W / (m K), respectively. The alloy composition of Example 7 is the same as that of Example 6, but with the addition of Gd. Aging treatment can achieve a thermal conductivity of over 120 W / (m K), but it was found that adding no additional elements is better in order to achieve a thermal conductivity of over 130 W / (m K).

[0079] Example 9 (1) Alloy composition: Mg-1.6Zn-0.5Ca-0.4Zr (2) Homogenization treatment: After holding at 300°C for 4 hours, the temperature was increased at 7.5°C / h, held at 450°C for 6 hours, air-cooled to 300°C, and then water-cooled. (3) Solution treatment: 400°C for 1 hour (4) Aging treatment: 170°C for 6 hours, 500 hours Samples were prepared according to the experimental procedure described above, and as shown in Table 1, the homogenization treatment consisted of holding the sample at 300°C for 4 hours, then increasing the temperature at a rate of 7.5°C / h, holding the sample at 450°C for 6 hours, air-cooling to 300°C, and water-cooling. The homogenized sample was then solution-treated at 450°C for 2 hours. The thermal conductivity of each sample was measured: a solution-treated material, an aged material that had been aged at 170°C for 6 hours, and an aged material that had been aged for 500 hours. The thermal conductivity of each sample was found to be 110.7 W / (m K), 126.5 W / (m K), and 135.7 W / (m K), respectively. Example 9 has the same composition as Example 6, but was homogenized without being made into a plate-shaped sample. Example 9 is an example that shows that the thermal conductivity is not affected even when a rolling process or the like is not performed to prepare a plate-shaped sample.

[0080] (Comparative Example 1) (1) Alloy composition: Mg-3.0Zn-0.5Ca-0.4Zr (2) Homogenization treatment: After holding at 300°C for 4 hours, the temperature was increased at a rate of 7.5°C / h and held at 450°C for 6 hours. (3) Solution treatment: 400°C for 2 hours (4) Aging treatment: 10 hours at 170°C, 500 hours Samples were prepared according to the experimental procedure described above, and as a homogenization treatment, they were held at 300°C for 4 hours, then heated at a rate of 7.5°C / h, held at 450°C for 6 hours, and water-cooled, as shown in Table 1. Plate-shaped samples were then prepared and subjected to solution treatment at 400°C for 2 hours. The thermal conductivity of each sample was measured: a solution-treated material, an aged material that had been aged at 170°C for 10 hours, and a material that had been aged for 500 hours. The thermal conductivity of each sample was found to be 115.3 W / (m K), 116.8 W / (m K), and 129.5 W / (m K), respectively. Comparative Example 1 is an example showing the upper limit of the Zn concentration, and is a case in which the amount of Zn added was increased compared to Example 6. When 3 mass% Zn was added, the thermal conductivity could be improved by aging treatment, but a value higher than 120 W / (m K) could not be obtained after aging treatment at 170°C for 10 hours.

[0081] (Comparative Example 2) (1) Alloy composition: Mg-3.0Al-0.7Zn-0.4Ca-0.3Mn (2) Solution treatment: 1 hour at 400°C A sample was prepared according to the experimental procedure described above and subjected to solution treatment at 400°C for 1 hour. Thermal conductivity was measured on the solution-treated material. The resulting thermal conductivity value was 85.6 W / (m·K). Comparative Example 2 is a case in which 90% of the Zn in Comparative Example 1 was replaced with Al. Substituting Zn with Al significantly reduces thermal conductivity, indicating that Zn is more preferable than Al as an alloying element.

[0082] (Comparative Example 3) (1) Alloy composition: Mg-4.0Zn-0.5Ca-0.4Zr (2) Homogenization treatment: After holding at 300°C for 4 hours, the temperature was increased at a rate of 7.5°C / h and held at 350°C for 20 hours. (3) Solution treatment: 400°C for 1 hour (4) Aging treatment: 10 hours at 170°C, 500 hours Samples were prepared according to the experimental procedure described above, and as a homogenization treatment, they were held at 300°C for 4 hours, then heated at a rate of 7.5°C / h, held at 350°C for 20 hours, and water-cooled, as shown in Table 1. Plate-shaped samples were then prepared and subjected to solution treatment at 450°C for 2 hours. The thermal conductivity of each sample was measured: a solution-treated material, an aged material obtained by aging the solution-treated material at 170°C for 10 hours, and an aged material obtained by aging for 500 hours. The thermal conductivity of each sample was 114.6 W / (m·K), 119.5 W / (m·K), and 124.1 W / (m·K), respectively. Comparative Example 3 is an example that demonstrates the upper limit of the Zn concentration, and the amount of Zn added was greater than in the examples and comparative example 1. Although the addition of 4 mass% Zn improved the thermal conductivity through aging, a value higher than 120 W / (m·K) was not obtained after aging at 170°C for 10 hours.

[0083] The present invention is not limited to the above-described embodiment, and various modifications are possible within the scope of the invention described in the claims, and it goes without saying that these modifications are also included within the scope of the present invention.

Claims

1. Magnesium alloy aging treatment material, containing 1 mass% or less of Ca and 3 mass% or less of Zn, with the balance being Mg and inevitable impurities; The thermal conductivity of the magnesium alloy aging treatment material is 120 W / (m K) or more, G.P. zones consisting of Mg, Ca, and Zn are dispersed on the (0001) plane of the magnesium matrix, The GP zone has a longitudinal length of 4.0 nm or more on the (0001) plane and a number density of 1×10 ２０ From 1 x 10 ２４ m －３ Magnesium alloy aging treatment material in the range.

2. 2. The aged magnesium alloy material according to claim 1, comprising 0.5% by mass or more and 1% by mass or less of Ca, 0.8% by mass or more and 3% by mass or less of Zn, with the balance consisting of Mg and inevitable impurities.

3. 2. The aged magnesium alloy according to claim 1, wherein the tensile yield strength of the aged magnesium alloy is 171±1 MPa or 227±2 MPa.

4. 4. The aged magnesium alloy material according to claim 1, further comprising 0.4 mass % or less of zirconium or 0.5 mass % or less of manganese.

5. 5. The aged magnesium alloy material according to claim 1, further comprising 0.3 mass % or less of gadolinium or 0.2 mass % or less of cerium.

6. Melting Mg, Zn and Ca to obtain a cast solid; homogenizing the cast solid to obtain a homogenized material; a step of aging the homogenized material to obtain an aged magnesium alloy material; Including, the magnesium alloy aging material has a composition containing 1 mass % or less of Ca, 3 mass % or less of Zn, and the balance being Mg and inevitable impurities; The aging treatment is carried out in a temperature range of 140°C to 250°C until the thermal conductivity of the magnesium alloy aged material reaches 120 W / (m·K) or more, and a G.P. zone consisting of Mg, Ca, and Zn dispersed on the (0001) plane of the magnesium matrix has a longitudinal length of 4.0 nm or more on the (0001) plane and a number density in the range of 1×10 20 to 1×10 24 m −3 .

7. 7. The method for producing an aged magnesium alloy material according to claim 6, wherein the aging treatment is carried out in the temperature range of 140°C to 250°C for any one of 4 hours, 6 hours, 10 hours, 16 hours, and 500 hours.

8. 8. The method for producing an aged magnesium alloy material according to claim 6 or 7, further comprising the step of subjecting the homogenized material to solution treatment to obtain a solution treated material, inserted between the step of obtaining the homogenized material and the step of obtaining the aged magnesium alloy material.

9. 9. The method for producing an aged magnesium alloy material according to claim 8, further comprising the step of wrought processing the homogenized material between the step of obtaining the homogenized material and the step of obtaining the solution heat treated material.

10. The method for producing an aged magnesium alloy material according to claim 6, wherein the homogenization treatment is carried out at a temperature of 300°C or higher and 500°C or lower for a predetermined time.

11. 10. Office automation equipment having a housing or panel material made of the aged magnesium alloy material according to claim 1.

12. 2. A transportation device and a part thereof, which uses the aged magnesium alloy material according to claim 1.

Images