Mg alloy
Mg alloys with 13.5-14.5% Li and 4.0-6.0% Zn or Ca achieve superplasticity at lower temperatures with coarser grains, simplifying manufacturing and maintaining strength, thus addressing the complexity and cost issues of conventional alloys.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- HIROSAKI UNIVERSITY
- Filing Date
- 2024-11-29
- Publication Date
- 2026-06-10
AI Technical Summary
Conventional Mg alloys requiring superplasticity necessitate a complex manufacturing process to refine crystal grain size to 5 μm or less and are processed at high temperatures (300°C or higher).
Mg alloys with compositions of 13.5-14.5% Li and 4.0-6.0% Zn or Ca, with average crystal grain sizes of 100-500 μm, allowing simpler manufacturing and superplasticity at lower temperatures (200°C) by maintaining sufficient strength and workability.
The alloys exhibit elongation at break of 150% or more at 200°C, demonstrating superplasticity with coarser grains, reducing manufacturing complexity and cost while maintaining performance.
Smart Images
Figure 2026095146000001_ABST
Abstract
Description
Technical Field
[0001] The present disclosure relates to Mg alloys.
Background Art
[0002] As disclosed in Patent Documents 1 to 3, Mg alloys exhibiting superplasticity are known. In addition, Non-Patent Document 1 discloses a Mg-Li-Zn ternary alloy containing 13.2% by mass of Li and 4.8% by mass of Zn.
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
Patent Document 2
Patent Document 3
Non-Patent Documents
[0004]
Non-Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0005] The inventor has found the following problems with Mg alloys exhibiting superplasticity. In order to utilize superplasticity in conventional Mg alloys, a complicated manufacturing process is required to refine the average crystal grain size to, for example, 5 μm or less, and the Mg alloy needs to be heated to, for example, 300 °C or higher during processing using superplasticity.
Means for Solving the Problems
[0006] According to one embodiment, the Mg alloy is 13.5-14.5 mass% Li, It contains 4.0 to 6.0 mass% of Zn, The remainder consists of Mg and unavoidable impurities. The average crystal grain size is 100 μm or larger.
[0007] According to one embodiment, the Mg alloy is 13.5-14.5 mass% Li, It contains 4.0 to 6.0% by mass of Ca, The remainder consists of Mg and unavoidable impurities. The average crystal grain size is 50 μm or larger. [Effects of the Invention]
[0008] According to one embodiment, it is possible to provide an Mg alloy that can be manufactured using a simpler manufacturing process and that can exhibit superplasticity at lower temperatures. [Brief explanation of the drawing]
[0009] [Figure 1] This is an optical microscope image of Example E1-1. [Figure 2] This graph shows the relationship between heating temperature (°C) and elongation at break (%) for Examples E1-1, E1-2, and E2. [Figure 3] This is a macro photograph of the specimen from Example E1-1 after a tensile creep test at a temperature of 240°C. [Modes for carrying out the invention]
[0010] The following describes specific embodiments in detail with reference to the drawings. However, the embodiments are not limited to those described below. Also, for clarity, the following descriptions and drawings have been simplified as appropriate.
[0011] (First Embodiment) First, the composition of the Mg alloy according to the first embodiment will be described. The Mg alloy according to this embodiment contains 13.5 to 14.5% by mass of Li and 4.0 to 6.0% by mass of Zn, and the balance is a Mg-Li-Zn ternary alloy composed of Mg and unavoidable impurities. The use of the Mg alloy according to this embodiment is not limited in any way. However, since the Mg alloy is lightweight and has excellent workability, it can be applied to, for example, automobile members, aircraft members, various housing members such as PCs (Personal Computers), and biomedical implant members.
[0012] <Regarding Li> This Mg alloy contains 13.5 to 14.5% by mass of Li. Since Li has a lower specific gravity than Mg, by setting the addition amount of Li to 13.5% by mass or more, the specific gravity can be reduced compared to Mg, and weight reduction can be achieved. In addition, due to the addition of Li, the crystal structure changes from the hexagonal close-packed structure of pure Mg to the body-centered cubic structure. Therefore, the specific gravity can be further reduced to achieve weight reduction, and the workability can also be improved.
[0013] On the other hand, the strength decreases due to the addition of Li. Also, Li is more expensive than Mg. Therefore, by setting the addition amount of Li to 14.5% by mass or less, the decrease in strength can be suppressed, and the raw material cost can be suppressed.
[0014] <Regarding Zn> This Mg alloy contains 4.0 to 6.0% by mass of Zn. The addition of Zn improves the strength but decreases the workability. Therefore, by setting the addition amount of Zn to 4.0% by mass or more, sufficient strength can be obtained. On the other hand, by setting the addition amount of Zn to 6.0% by mass or less, the decrease in workability can be suppressed. The Zn content is preferably 4.5 to 5.5% by mass. Here, the contents of Li and Zn are measured by, for example, ICP (Inductively Coupled Plasma) emission spectrometry.
[0015] <Characteristics of the Mg alloy> As described above, in order to utilize superplasticity in conventional Mg alloys, a complicated manufacturing process has been required to refine the average crystal grain size to, for example, 5 μm or less, and it has been necessary to heat the Mg alloy to, for example, 300°C or higher during processing using superplasticity.
[0016] On the other hand, the Mg alloy according to the present embodiment shows an elongation at break of 150% or more at, for example, 200°C, despite having coarse crystal grains with an average crystal grain size of 100 μm or more. Thus, since the Mg alloy according to the present embodiment has coarse crystal grains with an average crystal grain size of 100 μm or more, it can be manufactured by a simpler manufacturing process than Mg alloys with an average crystal grain size of 5 μm or less. In addition, it shows an elongation at break of 150% or more at 200°C, and can exhibit superplasticity at a lower temperature than before. In the present specification, an elongation at break of 150% or more is referred to as superplasticity.
[0017] Although not particularly limited, the average crystal grain size is, for example, 500 μm or less. Even with a coarser average crystal grain size, superplasticity can be exhibited in a low temperature range of about 200°C, but the manufacturing process becomes rather complicated in order to obtain coarse crystal grains. That is, the average crystal grain size is preferably 100 to 500 μm, and more preferably 200 to 400 μm. Here, the average crystal grain size is measured, for example, by a sectioning method using an optical microscope tissue photograph.
[0018] The elongation at break at 200°C is more preferably 200% or more. Further, it is more preferable that the elongation at break at 180°C, which is a lower temperature, is 150% or more, and it is even more preferable that it is 200% or more.
[0019] <Manufacturing method of Mg alloy> This Mg alloy can be manufactured by a known manufacturing method. Although not particularly limited, this Mg alloy can obtain an ingot by melting raw materials, for example, in a vacuum atmosphere, an inert atmosphere, or the like.
[0020] Although not particularly limited, by subjecting the ingot to simple hot working processes such as hot forging or hot rolling using, for example, general-purpose presses, hammers, rolls, etc., an average crystal grain size of 100 μm or more can be obtained. Generally, the higher the heating temperature and the longer the heating time, the easier the hot working becomes and the coarser the crystal grains become. If necessary, further heat treatment may be performed.
[0021] (Second Embodiment) Next, the Mg alloy according to the second embodiment will be described. First, the composition of the Mg alloy according to this embodiment will be described. The Mg alloy according to this embodiment contains 13.5 to 14.5 mass% of Li and 4.0 to 6.0 mass% of Ca, and the balance is a Mg-Li-Ca ternary alloy composed of Mg and unavoidable impurities.
[0022] Regarding the addition of Li, since it is the same as the Mg alloy according to the first embodiment, the description will be omitted. Also, the uses of the Mg alloy according to this embodiment are the same as those of the Mg alloy according to the first embodiment.
[0023] <Regarding Ca> This Mg alloy contains 4.0 to 6.0 mass% of Ca. By adding Ca, the strength is improved, but the workability is decreased. Therefore, by setting the addition amount of Ca to 4.0 mass% or more, sufficient strength can be obtained. On the other hand, by setting the addition amount of Ca to 6.0 mass% or less, the decrease in workability can be suppressed. The Ca content is preferably 4.5 to 5.5 mass%. Here, the Ca content is measured, for example, by ICP emission spectrometry.
[0024] <Properties of the Mg Alloy> The Mg alloy according to this embodiment exhibits a fracture elongation of 150% or more at 200°C, despite having coarse crystal grains with an average grain size of 50 μm or more. Thus, because the Mg alloy according to this embodiment has coarse crystal grains with an average grain size of 50 μm or more, it can be manufactured using a simpler manufacturing process than Mg alloys with an average grain size of 5 μm or less. Furthermore, it exhibits a fracture elongation of 150% or more at 200°C, enabling it to exhibit superplasticity at lower temperatures than before.
[0025] While not particularly limited, the average grain size is, for example, 500 μm or less. Superplasticity can be exhibited even with coarser average grain sizes in the low-temperature range of around 200°C, but the manufacturing process becomes more complicated in order to produce coarser grains. The average grain size is preferably 100 to 500 μm, and more preferably 200 to 400 μm. Here, the average grain size is measured, for example, by sectioning using optical microscope images.
[0026] A fracture elongation of 200% or more at 200°C is more preferable. Furthermore, a fracture elongation of 150% or more at a lower temperature of 180°C is more preferable, and even more preferable if it is 200% or more.
[0027] The method for manufacturing the Mg alloy according to this embodiment is the same as the method for manufacturing the Mg alloy according to the first embodiment. The other components are the same as those of the Mg alloy according to the first embodiment, so a detailed explanation will be omitted. [Examples]
[0028] Examples of the Mg alloy (Mg-Li-Zn alloy) according to the first embodiment and the Mg alloy (Mg-Li-Ca alloy) according to the second embodiment will be described below. However, the Mg alloys according to the first and second embodiments are not limited to the following examples. Table 1 summarizes the results of the tensile creep test at each heating temperature for Examples E1-1 and E1-2, which are Mg-Li-Zn alloys, and Example E2, which is a Mg-Li-Ca alloy. Blank spaces in Table 1 indicate that the tensile creep test was not performed.
[0029] [Table 1]
[0030] <Test Conditions> First, let me explain the test conditions. Examples E1-1 and E1-2, which are Mg-Li-Zn alloys, were prepared by melting a ternary alloy ingot having a composition of Mg-14.1 mass% Li-5.0 mass% Zn in an inert gas atmosphere. The Li and Zn content was measured by the ICP emission spectrometry method described above.
[0031] Next, the ingot was heated to 250°C and hot-rolled to produce a rolled plate from which several I-shaped test specimens with a thickness of 2 mm and a gauge length of 3 mm were prepared. For Example E1-1, each test specimen prepared from the rolled plate was heat-treated in an Ar atmosphere at 300°C for 1 hour, and then water-cooled.
[0032] Here, Figure 1 is an optical microscope image of Example E1-1. The average grain size of Example E1-1 was measured using the sectioning method with optical microscope images and was found to be 305 μm. Using such specimens, a tensile creep test was performed at temperatures of 180 to 280°C as shown in Table 1, while maintaining a true stress of 10 MPa.
[0033] For Example E1-2, no heat treatment was performed on the test specimens prepared from the rolled plates; they were used as is. The average grain size of Example E1-2 was measured using the section method with optical microscope images and found to be 157 μm, which was smaller than that of Example E1-1. Using these test specimens, tensile creep tests were performed at temperatures of 200°C, 240°C, and 260°C, as shown in Table 1, while maintaining a true stress of 10 MPa.
[0034] On the other hand, Example E2, which is an Mg-Li-Ca alloy, was prepared by melting a ternary alloy ingot having a composition of Mg-13.6 mass% Li-4.8 mass% Ca in an inert gas atmosphere. The Li and Ca content was measured by ICP emission spectrometry.
[0035] Next, the ingot was heated to 250°C and hot-rolled to produce a rolled plate from which several I-shaped test specimens with a thickness of 2 mm and a gauge length of 3 mm were prepared. Each test specimen prepared from the rolled plate was heat-treated in an Ar atmosphere at 300°C for 1 hour, and then water-cooled.
[0036] The average grain size of Example E2 was measured using the sectioning method with optical microscope images and found to be 123 μm, which was smaller than that of Example E1-1. Using these specimens, tensile creep tests were performed at temperatures of 200°C and 240°C, as shown in Table 1, while maintaining a true stress of 10 MPa.
[0037] <Test Results> Next, the test results will be explained with reference to Table 1 and Figure 2. Figure 2 is a graph showing the relationship between heating temperature (°C) and elongation at break (%) for Examples E1-1, E1-2, and E2. In Figure 2, the horizontal axis represents the heating temperature (°C) in the tensile creep test, and the vertical axis represents the elongation at break (%).
[0038] As shown in Table 1 and Figure 2, for Example E1-1, an Mg-Li-Zn alloy with an average grain size of 305 μm, the elongation at break was 200% or more at temperatures ranging from 180 to 280°C.
[0039] Here, Figure 3 is a macro photograph of the specimen of Example E1-1 after a tensile creep test at 240°C. In Example E1-1 shown in Figure 3, the elongation at break was a maximum of 303% in the tensile creep test at 240°C.
[0040] Furthermore, for Example E1-2, which is an Mg-Li-Zn alloy with an average grain size of 157 μm, the elongation at break at temperatures of 200°C, 240°C, and 260°C was 294%, 269%, and 281%, respectively, all of which were above 200%.
[0041] Furthermore, as shown in Table 1 and Figure 2, for Example E2, an Mg-Li-Ca alloy with an average grain size of 123 μm, the elongation at break at 200°C was 178%, which was below 200% but above 150%. On the other hand, at 240°C, the elongation at break was 226%, which was above 200%.
[0042] As shown in Examples E1-1, E1-2, and E2 described above, the Mg alloys according to the first and second embodiments exhibited, for example, a fracture elongation of 150% or more at 200°C, despite having coarse crystal grains with an average crystal grain size of 100 μm or more.
[0043] Thus, because the Mg alloys according to the first and second embodiments have coarse crystal grains, they can be manufactured using a simpler manufacturing process than Mg alloys with an average crystal grain size of 5 μm or less. Furthermore, they exhibit a fracture elongation of 150% or more at 200°C, and can exhibit superplasticity at lower temperatures than before.
[0044] The present invention has been described in detail above based on embodiments, but it goes without saying that the present invention is not limited to the embodiments already described, and various modifications are possible without departing from the spirit of the invention.
Claims
1. 13.5 to 14.5 mass% of Li, It contains 4.0 to 6.0% by mass of Zn, The remainder consists of Mg and unavoidable impurities. The average crystal grain size is 100 μm or more. Mg alloy.
2. The average crystal grain size is 500 μm or less. The Mg alloy according to claim 1.
3. 13.5 to 14.5 mass% of Li, It contains 4.0 to 6.0% by mass of Ca, The remainder consists of Mg and unavoidable impurities. The average crystal grain size is 50 μm or more. Mg alloy.
4. The average crystal grain size is 500 μm or less. The Mg alloy according to claim 3.