METHOD FOR PRODUCING Mg ALLOY MATERIAL, METHOD FOR PRODUCING Mg ALLOY MEMBER, Mg ALLOY MATERIAL, AND Mg ALLOY MEMBER

Abstract

To provide a method for producing a Mg alloy material having excellent heat resistance and mechanical strength.SOLUTION: A method for producing a Mg alloy material comprises: a preparation step of preparing a processing alloy material containing first particles of Mg2Si; a refining step of refining the processing alloy material to yield alloy fragments; and a Mg alloy material production step of molding the alloy fragments using a hot press method to produce a Mg alloy material containing second particles of Mg2Si by .SELECTED DRAWING: Figure 1A

Description

[Technical field]

[0001] The present invention relates to a method for producing an Mg alloy material, a method for producing an Mg alloy part, an Mg alloy material, and an Mg alloy part. [Background technology]

[0002] Mg alloys are lightweight materials and are being considered for various applications. For example, Mg alloys are used in transportation equipment, and it is expected that their fuel efficiency will be improved by their application to engine parts. Various manufacturing methods for Mg alloys have been proposed to obtain the desired properties.

[0003] Patent Document 1 describes a method for producing a magnesium alloy containing 1 to 18% by weight of silicon, 12% by weight or less of at least one of aluminum, zinc, and silver, and the remainder being magnesium, by rapidly solidifying a molten alloy. 2 A Mg-Si alloy chip with Si is described.

[0004] Patent Document 2 describes a method for manufacturing a magnesium alloy in which additive components for improving the material are added during the manufacturing process, which includes a silicon addition step of adding silicon as an additive component to a specified magnesium alloy, and a method for producing Mg 2 Si compounds are mixed with Mg 2 The method described includes a particle dispersion step of dispersing silicon particles into Si particles, the specified magnesium alloy being a flame-retardant magnesium alloy AM602, the amount of silicon added in the silicon addition step being adjusted in the range of 5.0 to 15.0 mass%, converted into the silicon content relative to the mass of the magnesium alloy to be produced, the silicon addition step being performed using a casting method, and the particle dispersion step being performed in the temperature range of 200 to 400°C using an extrusion method as a plastic processing treatment. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2011-074469 [Patent Document 2] Japanese Patent Application Publication No. 8-120390 Summary of the Invention [Problem to be solved by the invention]

[0006] For example, when Mg alloys are used in engine parts, it is expected that fuel efficiency will improve. However, it is difficult for Mg alloys containing Mg, which has low heat resistance, to have heat resistance sufficient to withstand the high temperatures inside the engine. Adding rare earth elements is thought to be effective in improving the heat resistance of Mg alloys, but rare earth elements are often expensive, and even if rare earth elements are added to the alloy and used to cast engine pistons, the pistons often do not have sufficient mechanical strength to withstand the high temperatures inside the engine. The present inventors have investigated a method for using as few rare earth metals as possible and have found that adding Si is effective. Addition of Si increases Mg 2 It is expected that the formation of Si particles will improve the heat resistance of the Mg alloy. However, in order to obtain sufficient heat resistance, Mg 2 It is necessary to make the silicon particles extremely fine and to disperse them very uniformly. Furthermore, in the case of Mg alloys containing Si, the viscosity of the molten metal increases due to the presence of Si in the casting process, so the upper limit of the amount of Si that can be added is often about 1 mass%, and as a result, the mechanical strength of the resulting Mg alloy is often insufficient.

[0007] An object of the present invention is to provide a method for producing an Mg alloy material and a method for producing an Mg alloy part that are excellent in heat resistance and mechanical strength. [Means for solving the problem]

[0008] The present invention includes the following aspects. <1> Mg 2A preparation step of preparing a processing alloy material containing first particles of Si; a refinement step of refining the processing alloy material to obtain alloy flakes; and a hot press method to mold the alloy flakes to obtain Mg 2 and producing an Mg alloy material containing second particles of Si. <2> The Mg alloy material production process includes a step of forming a preform by molding the alloy flakes by a hot press method, and a step of extruding the preform at 300° C. or higher to produce an Mg alloy material. <1> A method for producing the Mg alloy material according to claim 1. <3> The pressure in the hot pressing method is 50 MPa to 300 MPa. <1> or <2> A method for producing the Mg alloy material according to claim 1. <4> The temperature in the hot pressing method is 300°C to 700°C. <1> ~ <3> 13. A method for producing an Mg alloy material according to any one of the preceding claims. <5> The Mg 2 The average particle size of the secondary particles of Si is 1.0 μm to 50.0 μm. <1> ~ <4> 13. A method for producing an Mg alloy material according to any one of the preceding claims. <6> The Mg alloy material includes a matrix, and the crystal grain size of the matrix is ​​2.0 μm to 80.0 μm. <1> ~ <5> 13. A method for producing an Mg alloy material according to any one of the preceding claims. <7> The Mg alloy material has a thermal conductivity of 100 W / m K or less at 300°C. <1> ~ <6> 13. A method for producing an Mg alloy material according to any one of the preceding claims. <8> Mg 2 A preparation step of preparing a processing alloy material containing first particles of Si; a refinement step of refining the processing alloy material to obtain alloy flakes; and a hot press method to mold the alloy flakes to obtain Mg 2 A method for producing an Mg alloy part, comprising: a Mg alloy material production step of producing an Mg alloy material containing second particles of Si; and a forging step of forging the Mg alloy material to obtain an Mg alloy part. <9> Mg 2 The alloy flakes are formed from finely divided alloy material containing primary particles of Si, and Mg 2 Mg alloy material containing secondary particles of Si. <10> <9> 2. A Mg alloy part which is a forging of the Mg alloy material according to claim 1. Effect of the Invention

[0009] According to the present invention, it is possible to provide a method for producing an Mg alloy material and a method for producing an Mg alloy part that are excellent in heat resistance and mechanical strength. [Brief description of the drawings]

[0010] [Figure 1A] 1 is a schematic diagram showing a working alloy material before undergoing a refinement process in this embodiment. FIG. [Figure 1B] 2 is a schematic diagram showing the alloy material for processing and the alloy flakes after the refinement process in this embodiment. FIG. [Figure 2A] FIG. 2 is an optical microscope diagram of the Mg alloy material of Comparative Example 1. [Figure 2B] FIG. 2 is an optical microscope diagram of the Mg alloy material of Example 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present invention (hereinafter, referred to as "the present embodiment") will be described in detail. It should be noted that the following embodiment is merely an example for explaining the present invention, and the present invention is not limited to the following embodiment. The present invention can be practiced with appropriate modifications within the scope of the gist of the present invention. In this embodiment, the numerical range indicated using "to" means a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In the numerical ranges described in this embodiment, the upper limit or lower limit of a certain numerical range may be replaced with the upper limit or lower limit of another numerical range described in a stepwise manner. In addition, in the numerical ranges described in this disclosure, the upper limit or lower limit of a certain numerical range may be replaced with a value shown in the examples. In this embodiment, a combination of two or more preferred aspects is a more preferred aspect. In this embodiment, when there are multiple substances corresponding to each component, the amount of each component means the total amount of the multiple substances, unless otherwise specified.

[0012] <Manufacturing method of Mg alloy material> The manufacturing method of the Mg alloy material of this embodiment (also referred to simply as the manufacturing method of this embodiment in this specification) is 2 A preparation step of preparing a processing alloy material containing first particles of Si; a refinement step of refining the processing alloy material to obtain alloy flakes; and a hot press method to mold the alloy flakes to obtain Mg 2 and producing an Mg alloy material containing second particles of Si.

[0013] The manufacturing method of this embodiment is as follows: Mg 2 The alloy material for processing containing the first particles of Si is refined to obtain alloy flakes, which are then solidified and molded by hot pressing to produce fine Mg 2 It is possible to produce an Mg alloy material in which the secondary particles of Si are uniformly dispersed, and as a result, the obtained Mg alloy material has excellent heat resistance and mechanical strength. The Mg alloy material in this embodiment can be suitably used as a precursor for producing a member by a forging method.

[0014] Furthermore, with the manufacturing method of this embodiment, the amount of Si added can be set to a relatively large amount. In Mg alloy materials obtained by casting, the addition of a large amount of Si makes the material more likely to aggregate and reduce dispersibility, and the mechanical strength of the resulting Mg alloy material is likely to decrease, especially in high temperature regions. Since the manufacturing method of this embodiment includes a refining step, even if a relatively large amount of Si is added, the amount of Mg in the resulting Mg alloy material is relatively large. 2 Silicon particles can be uniformly dispersed, resulting in excellent mechanical strength. Furthermore, when Mg alloy materials are manufactured from quenched powder produced by gas atomization, Mg 2Not only the Si particles but also the crystal grain size of the matrix Mg alloy becomes fine grains of 1 μm or less, which reduces the strength at high temperatures. However, the Mg alloy material produced by the manufacturing method of this embodiment does not have such a drawback and has excellent mechanical strength. In this embodiment, the matrix refers to the base structure that is the main component of the Mg alloy material, and the matrix can affect the properties of the Mg alloy material.

[0015] In addition, the manufacturing method of the present embodiment is excellent in terms of cost since it does not require expensive equipment. Furthermore, although the alloy flakes in the manufacturing method of the present embodiment contain Mg alloy as an active material, there is no risk of explosion, unlike quenched powder produced by gas atomization, and therefore the manufacturing method of the present embodiment is also excellent in safety.

[0016] In addition, since the manufacturing method of this embodiment uses alloy flakes, it can be used in parts of the alloy material to be processed (e.g., billets) that have shrinkage cavities. Furthermore, when cutting is performed to process the Mg alloy material into components such as pistons, the alloy flakes generated at that time can be reused as raw materials for the Mg alloy material, and the yield is excellent. In addition, if used components such as pistons are cut again to produce alloy flakes, they can be molded into components again, and therefore the recyclability is also excellent.

[0017] <Preparation process> The preparation process is Mg 2 A process for preparing an alloy material for processing, the alloy material including first particles of Si. The wrought alloy material may be commercially available or may be manufactured.

[0018] (Method of manufacturing alloy materials for processing) The preparation step is to melt a mixture containing Mg alloy and Si in an inert gas atmosphere, cast the resulting melt, and form a Mg alloy. 2 The process may involve producing a wrought alloy material comprising first particles of Si.

[0019] (mixture) The mixture contains an Mg alloy and Si. The mixture may contain other components as required.

[0020] [Mg alloy] The Mg alloy refers to an alloy containing Mg as the main component. An alloy containing Mg as a main component means an alloy in which the Mg content is 50 mass % or more relative to the total mass of the alloy.

[0021] [Mg] The Mg alloy contains Mg as the main component. The Mg content is preferably 60 mass % to 99 mass % based on the total mass of the Mg alloy. By making the Mg content 60 mass % or more relative to the total mass of the Mg alloy, the mass of the Mg alloy material can be reduced. From the above viewpoints, the Mg content is more preferably 70 mass % or more, and further preferably 80 mass % or more, based on the total mass of the Mg alloy. When the Mg content is 99 mass % or less relative to the total mass of the Mg alloy, the Mg alloy material has excellent heat resistance and mechanical strength. From the above viewpoints, the Mg content is more preferably 97 mass % or less, and further preferably 95 mass % or less, based on the total mass of the Mg alloy.

[0022] [Other elements] The Mg alloy in this embodiment further contains elements other than Mg. As other elements, the Mg alloy preferably further contains at least one element selected from the group consisting of Al, Zn, Ca, Mn, Ag, Cu, B and Ni. More preferably, the Mg alloy further contains at least one element selected from the group consisting of Al, Zn and Ca.

[0023] From the viewpoint of reducing the mass of the Mg alloy material, the content of the above elements other than Mg is preferably 1 mass% to 20 mass%, more preferably 3 mass% to 17 mass%, and even more preferably 7 mass% to 15 mass%, in total relative to the total mass of the Mg alloy. By setting the content of elements other than Mg to the above lower limit or more, the Mg alloy material has excellent heat resistance and mechanical strength, and by setting the content of elements other than Mg to the above upper limit or less, the mass of the Mg alloy material can be reduced.

[0024] When the Mg alloy further contains Al, the Al content is preferably 3 mass% to 20 mass%, more preferably 5 mass% to 15 mass%, and further preferably 7 mass% to 12 mass%, relative to the total mass of the Mg alloy. When the Al content is equal to or more than the lower limit, the strength can be improved, whereas when the Al content is equal to or less than the upper limit, the heat resistance is excellent.

[0025] When the Mg alloy contains Zn, the Zn content is preferably 0.1 mass% to 5 mass%, more preferably 0.3 mass% to 3 mass%, and further preferably 0.5 mass% to 2 mass%, relative to the total mass of the Mg alloy.

[0026] When the Mg alloy contains calcium, the calcium content is preferably 0.1 mass % to 10 mass %, and more preferably 1 mass % to 7 mass %, relative to the total mass of the Mg alloy. When the calcium content is within the above range, the resulting Mg alloy has excellent flame retardancy.

[0027] As the Mg alloy, a ready-made product may be used. Examples of ready-made products include Mg-Al-Zn alloys (AZ series) such as AZ92, AZ91, AZ80, AZ63, AZ61, and AZ31; Mg-Al alloys (AM series) such as AM100, AM60, AM50, and AM20; Mg-Al-Si alloys (AS series) such as AS41 and AS21; Mg-Al-RE alloys (AE series) such as AE42; Mg-Zn-Zr alloys (ZK series) such as ZK51 and ZK61; and ZC63. Mg-Cu-Zn based alloys (ZC type) such as; Mg-Zn-RE-Zr based alloys (ZE type) such as ZE41, ZE61; Mg-Zr-Re-Ag based alloys (QE type) such as QE22; Mg-Y-RE based alloys (WE type) such as WE43, WE54; Mg-Al-Zn-Ca based alloys (AZX type) such as AZX612, AZX912; Mg-Al-Ca based alloys (AMX type) such as AMX602, AMX602, etc. Among the above, AZX912 (Mg-9%Al-1%Zn-2%Ca) is preferable as a ready-made Mg alloy.

[0028] The content of the Mg alloy is preferably 60 mass % to 97 mass %, more preferably 70 mass % to 95 mass %, and further preferably 80 mass % to 93 mass %, based on the total mass of the mixture. By making the content of Mg alloy equal to or more than the lower limit, the mass of the Mg alloy material can be reduced, and by making the content of elements other than Mg equal to or less than the upper limit, the Mg alloy material has excellent heat resistance and mechanical strength.

[0029] As a method for producing an Mg alloy, for example, there is a method in which an alloy ingot is produced from raw materials such as Mg, Zn, Al, and Ca, and the ingot is processed into a desired shape. Specifically, pure metals of various alloy elements are placed in a graphite crucible for melting so as to obtain a desired mass ratio. The graphite crucible for melting is placed inside a high-frequency coil in a high-frequency melting furnace chamber, and a mold is placed in front of the high-frequency coil. The high-frequency melting furnace chamber is then filled with helium gas either at atmospheric pressure or after evacuation, and the graphite crucible is heated to 750°C or higher. After confirming that the metals are completely melted, the molten alloy in the graphite crucible is poured into a copper mold, and after cooling, the Mg alloy is obtained from the mold.

[0030] [Si] The mixture includes Si. The Si content is preferably from 1 mass % to 15 mass %, more preferably from 3 mass % to 12 mass %, and further preferably from 5 mass % to 9 mass %, based on the total mass of the mixture. When the Si content is equal to or more than the lower limit, the heat resistance is excellent, and when the Si content is equal to or less than the upper limit, the dispersibility of Si is excellent, and the mechanical strength of the Mg alloy material is excellent.

[0031] [Sb] The mixture may further include Sb. The Sb content is preferably 0.1% by mass to 5% by mass, and more preferably 1% by mass to 4% by mass, based on the total mass of the mixture.

[0032] As a specific example of a process for producing the above-mentioned alloy material for processing, for example, 7.5 mass % of Si and 2 mass % of Sb are mixed into an Mg alloy, which is then melted and cast in an inert gas atmosphere to produce Mg 2 One example is a process for producing a billet (alloy material for machining) having a diameter of 50 mm and containing first particles of Si.

[0033] <Refining process> The grain refinement step is a step of refinement of the alloy material to be processed to obtain alloy flakes. The method for making the particles fine is not particularly limited, and the particles may be cut using a grinder or may be made fine by lathe processing.

[0034] There is no particular limitation on the size of the alloy piece. The size of the alloy piece is preferably such that the average particle diameter of the second Mg 2 Si particles in the obtained Mg alloy material falls within the range described below. For example, when the alloy material for processing is refined using a lathe, it is preferable to obtain alloy pieces by cutting the end face of the alloy material for processing on the lathe preferably by 10 μm to 100 μm, more preferably by 20 μm to 80 μm, and even more preferably by 30 μm to 60 μm at a time.

[0035] The refinement process in this embodiment will be described with reference to FIGS. 1A and 1B. FIG. 1A is a schematic diagram showing the alloy material for processing before the refinement process in this embodiment, and FIG. 1B is a schematic diagram showing the alloy material for processing and the alloy pieces after the refinement process in this embodiment. As shown in FIG. 1A, the alloy material for processing before the refinement process contains relatively large first Mg 2 Si particles. By applying a desired refinement means to this alloy material for processing, alloy pieces as shown in FIG. 1B can be obtained. In the obtained alloy pieces, the Mg 2 Si particles are also refined, and smaller-sized Mg 2 Si particles can be obtained.

[0036] <Mg alloy material manufacturing process> The Mg alloy material manufacturing process is a process of manufacturing a Mg alloy material containing second Mg 2 Si particles by forming alloy pieces by a hot pressing method. The hot pressing method is a method of sintering while applying pressure in an atmosphere such as vacuum, air, or inert gas.

[0037] The pressure in the hot pressing method is not particularly limited, but is preferably 50 MPa to 300 MPa, more preferably 70 MPa to 200 MPa, and even more preferably 100 MPa to 150 MPa. In the hot press method, excellent forgeability is achieved when the pressure is equal to or higher than the above lower limit value. Also, excellent life of the press jig is achieved when the pressure in the hot press method is equal to or lower than the above upper limit value.

[0038] In the hot press method, the temperature is preferably 300°C to 700°C, more preferably 320°C to 500°C, and even more preferably 350°C to 400°C. Although the above temperature range is relatively high, since the Mg alloy material of the present embodiment has excellent heat resistance, it can be hot pressed well even within the above temperature range.

[0039] In the hot press method, the time is preferably 1 minute to 60 minutes, more preferably 5 minutes to 45 minutes, and even more preferably 10 minutes to 30 minutes.

[0040] The Mg alloy material manufacturing process preferably includes a process of forming a preform by shaping an alloy piece by the hot press method (also referred to as the preform forming process), and a process of manufacturing the Mg alloy material by extruding the preform at 300°C or higher (also referred to as the extrusion process).

[0041] (Preform Forming Process) The preform forming process is a process of forming a preform by shaping an alloy piece by the hot press method. By the preform forming process, a preform of the Mg alloy material can be obtained before performing the extrusion process. In the preform forming process, the preferable ranges of the pressure, temperature, and time in the hot press method are the same as the preferable ranges of the pressure, temperature, and time in the hot press method in the above <Mg alloy material manufacturing process>.

[0042] (Extrusion Process) The extrusion process is a process of manufacturing the Mg alloy material by extruding the preform at 300°C or higher.

[0043] The temperature in the extrusion process is preferably 330 °C or higher, more preferably 350 °C or higher, from the viewpoint of ease of extrusion. The temperature in the extrusion process is preferably 500 °C or lower, more preferably 450 °C or lower, from the viewpoint of reducing damage to the properties due to coarsening of the structure of the preform.

[0044] As an example of the Mg alloy material manufacturing process, in the atmosphere, under the conditions of 150 MPa, 400 °C, and 30 minutes, the above alloy pieces may be hot-pressed to produce a preform with a diameter of φ44 mm and a height of 40 mm, and then extruded at 400 °C to produce an Mg alloy material.

[0045] <Mg alloy material> The Mg alloy material of this embodiment contains Mg 2 and second particles of Si. In the Mg alloy material, the second particles of Mg 2 and Si are uniformly dispersed. As a result, the Mg alloy material is excellent in heat resistance and mechanical strength.

[0046] The Mg alloy material of this embodiment is a molded body of alloy pieces that are refined products of a processing alloy material containing first particles of Mg 2 and Si, and may contain second particles of Mg 2 and Si.

[0047] In the manufacturing method of this embodiment, since it includes a refinement step of refining the processing alloy material, the average particle size of the second particles of Mg 2 and Si in the obtained Mg alloy material is preferably smaller than the average particle size of the first particles of Mg 2 and Si in the processing alloy material.

[0048] Mg 2 The average particle size of the second particles of Si is preferably 1.0 μm to 50.0 μm. Mg 2 Since the average particle size of the second particles of Si is 50.0 μm or less, the dispersibility of the second particles of Mg 2 and Si is excellent, and the mechanical strength of the Mg alloy material is excellent. From the above perspective, Mg 2 The average particle size of the second particles of Si is more preferably 40.0 μm or less, further preferably 30.0 μm or less, particularly preferably 20.0 μm or less, and even more preferably 10.0 μm or less. Mg 2 When the average particle size of the secondary Si particles is 1.0 μm or more, the Mg alloy material has excellent mechanical strength. From the above perspective, Mg 2 The average particle size of the second particles of Si is more preferably 2.0 μm or more, and further preferably 3.0 μm or more.

[0049] Mg 2 The average particle size of the first Si particles may be 30.0 μm to 100.0 μm, or 50.0 μm to 80.0 μm.

[0050] The Mg alloy material may include a matrix. In this case, the crystal grain size of the matrix is ​​preferably 2.0 μm to 80.0 μm. The matrix grain size is 80.0 μm or less, so Mg 2 The excellent dispersibility of the secondary Si particles provides the Mg alloy material with excellent mechanical strength. From the above viewpoints, the crystal grain size of the matrix is ​​more preferably 60.0 μm or less, further preferably 40.0 μm or less, particularly preferably 20.0 μm or less, and even more preferably 10.0 μm or less. A matrix crystal grain size of 2.0 μm or more provides the Mg alloy material with excellent mechanical strength at high temperatures. From the above viewpoints, the crystal grain size of the matrix is ​​more preferably 3.0 μm or more, further preferably 4.0 μm or more, and particularly preferably 5.0 μm or more.

[0051] Mg 2 The average grain size of the silicon particles and the crystal grain size of the matrix are measured by an intercept method in accordance with ASTM E112-60T. Specifically, five straight lines with a total length L are drawn on the cross section of the sample observed under an optical microscope, the number n of crystal grains that cross these lines is calculated, and the average grain size d is calculated using the following formula. The average of the five ds obtained is taken as Mg 2 The average grain size of the Si particles and the crystal grain size of the matrix are taken as the average grain size. d=L / n

[0052] The Mg alloy material preferably has a thermal conductivity of 100 W / m K or less at 300°C. Since the thermal conductivity at 300°C is 100 W / m K or less, the Mg alloy material can be suitably used for pistons of engines that use fuels such as bio-methanol and hydrogen. The thermal conductivity of the Mg alloy material at 300°C is preferably 90 W / m·K or less, more preferably 80 W / m·K or less, and even more preferably 70 W / m·K or less. Although there is no particular restriction on the lower limit of the thermal conductivity at 300°C, the thermal conductivity of the Mg alloy material at 300°C is preferably 10 W / m K or more, more preferably 20 W / m K or more, and even more preferably 40 W / m K or more.

[0053] The thermal conductivity at each given temperature is calculated from the following formula. Thermal conductivity at each temperature = λT CpT dT (formula) λT: Thermal diffusivity at each temperature measured by the laser flash method CpT: specific heat capacity dT: Room temperature density (d0) measured by Archimedes method, and density at each temperature obtained from the volume change at each temperature measured by a thermal dilatometer

[0054] <Manufacturing method of Mg alloy components> The method for producing the Mg alloy member of this embodiment includes the steps of: 2 A preparation step of preparing a processing alloy material containing first particles of Si; a refinement step of refining the processing alloy material to obtain alloy flakes; and a hot press method to mold the alloy flakes to obtain Mg 2A Mg alloy material manufacturing process for manufacturing a Mg alloy material containing second particles of Si, and a forging process for forging the Mg alloy material to obtain a Mg alloy member are included.

[0055] The method for manufacturing a Mg alloy member of the present embodiment is a method for manufacturing a Mg alloy member using the Mg alloy material of the present embodiment by performing a forging process following the method for manufacturing the Mg alloy material of the present embodiment. Therefore, the details such as the specific aspects and preferred aspects of each process in the method for manufacturing a Mg alloy member are the same as the details such as the specific aspects and preferred aspects of each process described in the section of ≪Method for Manufacturing Mg Alloy Material≫ above.

[0056] <Mg alloy member> The Mg alloy member of the present embodiment is a forged product of the Mg alloy material of the present embodiment. The Mg alloy material in the present embodiment can be suitably used for forging. As a result, the obtained Mg alloy member contains a Mg alloy material containing uniformly dispersed second particles of Si, and thus is excellent in heat resistance and mechanical strength. 2 Since it contains a Mg alloy material containing second particles of Si, it is excellent in heat resistance and mechanical strength.

Example

[0057] Hereinafter, the present embodiment will be described in more detail by giving specific examples and comparative examples, but the present invention is not limited to the following examples and comparative examples.

[0058] [Example 1] (Preparation process) After obtaining a mixture in which 7.5% by mass of Si and 2% by mass of Sb were mixed with AZX912 (Mg - 9% Al - 1% Zn - 2% Ca), which is a flame - retardant Mg alloy, the mixture was melted and cast in an inert gas atmosphere to produce a φ50 mm billet (casting material).

[0059] (Refinement process) Thereafter, the end face of the billet was machined by turning by 40 μm each time to produce alloy pieces.

[0060] (Mg alloy material manufacturing process) The above alloy pieces were hot pressed in air at 150 MPa, 400°C, and 10 minutes to produce preforms with a diameter of 44 mm and a height of 40 mm, which were then extruded at 400°C to produce Mg alloy materials.

[0061] [Comparative Example 1] A cast material obtained by the method described in (Preparation step) of Example 1 was used as the Mg alloy material. FIG. 2A shows an optical microscope structure diagram of the Mg alloy material of Comparative Example 1, and FIG. 2B shows an optical microscope structure diagram of the Mg alloy material of Example 1.

[0062] (evaluation) [Particle size measurement] In the Mg alloy materials of the examples and comparative examples, the matrix and Mg 2 The particle size of the Si particles was measured by the intercept method in accordance with ASTM E112-60T, and the results are shown in Table 1.

[0063] [Table 1]

[0064] As shown in Table 1, Mg 2 A preparation step of preparing a processing alloy material containing first particles of Si; a refinement step of refining the processing alloy material to obtain alloy flakes; and a hot press method to form the alloy flakes into Mg 2 The Mg alloy material of Example 1 obtained by the Mg alloy material manufacturing method including the step of manufacturing an Mg alloy material containing second particles of Si, is compared with the Mg alloy material of Comparative Example 1 which is a cast material. 2 Si particles (Mg 2 Both the grain size of the Si (secondary particles) and the matrix were small.

[0065] [Thermal Conductivity] The thermal conductivity at each given temperature was calculated from the following formula. Thermal conductivity at each temperature = λT CpT dT (formula) λT: Thermal diffusivity at each temperature measured by the laser flash method CpT: specific heat capacity dT: Room temperature density (d0) measured by Archimedes method, and density at each temperature obtained from the volume change at each temperature measured by a thermal dilatometer The results are shown in Table 2.

[0066] [Table 2]

[0067] As shown in Table 2, the Mg alloy material of Example 1 had a sufficiently low thermal conductivity at 300° C. For this reason, the Mg alloy material of this embodiment can be suitably used for pistons of engines that use fuels such as bio-methanol and hydrogen.

[0068] [Heat resistance and strength] After obtaining the stress-strain curve at each temperature by the compression test, the stress at which the plastic deformation amount reached 0.2% (also called 0.2% yield strength) was measured. The results are shown in Table 3. The higher the 0.2% yield strength, the greater the strength.

[0069] [Table 3]

[0070] As shown in Table 3, the Mg alloy materials of the examples had superior 0.2% yield strength values ​​at 25°C to 300°C compared to the cast Mg alloy material of Comparative Example 1. Therefore, the Mg alloy materials of the examples had superior mechanical strength in the low to high temperature ranges. Furthermore, the Mg alloy material of the embodiment had a superior 0.2% yield strength value at 300°C compared to the Mg alloy material of Comparative Example 1, and therefore had superior mechanical strength in the high temperature range and also superior heat resistance.

Claims

1. Mg 2 A preparation step of preparing an alloy material for processing comprising first particles of Si; a refining step of refining the alloy material to obtain alloy flakes; The alloy pieces are molded by hot pressing to form Mg 2 a Mg alloy material production step of producing an Mg alloy material containing second particles of Si; A method for producing an Mg alloy material comprising the steps of:

2. The Mg alloy material manufacturing process includes: forming the alloy flakes into a preform by hot pressing; extruding the preform at 300° C. or higher to produce an Mg alloy material; The method of claim 1 comprising the steps of:

3. The method for producing an Mg alloy material according to claim 1 or 2, wherein the pressure in the hot pressing method is 50 MPa to 300 MPa.

4. The method for producing an Mg alloy material according to claim 1 or 2, wherein the temperature in the hot pressing method is 300°C to 700°C.

5. The Mg 2 3. The method for producing an Mg alloy material according to claim 1, wherein the average particle size of the second particles of Si is 1.0 μm to 50.0 μm.

6. the Mg alloy material comprises a matrix; The method for producing an Mg alloy material according to claim 1 or 2, wherein the crystal grain size of the matrix is ​​2.0 μm to 80.0 μm.

7. The method for producing an Mg alloy material according to claim 1 or 2, wherein the Mg alloy material has a thermal conductivity of 100 W / m·K or less at 300° C.

8. Mg 2 A preparation step of preparing an alloy material for processing comprising first particles of Si; a refining step of refining the alloy material to obtain alloy flakes; The alloy pieces are molded by hot pressing to form Mg 2 a Mg alloy material production step of producing an Mg alloy material containing second particles of Si; a forging step of forging the Mg alloy material to obtain an Mg alloy part; A method for producing an Mg alloy part comprising the steps of:

9. Mg 2 A compact of alloy flakes which is a finely divided alloy material for processing containing first particles of Si; Mg 2 A Mg alloy material comprising secondary particles of Si.

10. A Mg alloy part which is a forging of the Mg alloy material according to claim 9.

Images