JP2023174228A - Alloy, alloy member, apparatus and manufacturing method of alloy - Google Patents

Abstract

To provide a magnesium-lithium based alloy having an α phase and a β phase excellent in machinability.SOLUTION: An alloy includes Mg, Li and O, and a sum of a content of the Mg and a content of the Li is 90 mass% or more, with respect to a mass excluding the O. The alloy has an α phase and a β phase at 25°C. On a surface of the alloy, if a ratio of a present amount of the α phase with respect to a present amount of the α phase and the β phase measured by X-ray diffraction (XRD) is αr and a ratio of a present amount of the O with respect to a present amount of the Mg, the Li and the O measured by X-ray photoelectron spectroscopy (XPS) is Or, a ratio Or/αr of the Or with respect to αr is 0.11 or more.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to a Mg-Li alloy, an alloy member, a device, and a method for manufacturing the alloy member.

Alloy members made of magnesium-based alloys are lightweight and have excellent vibration damping properties and specific strength, so they are used in various devices. In recent years, there has been a demand for further weight reduction of equipment, and magnesium-lithium alloys (Mg-Li alloys), which have a lower specific gravity than magnesium alloys, are attracting attention. Patent Document 1 discloses a magnesium-lithium alloy having an α phase and a β phase.

Japanese Patent Application Publication No. 2004-156089

The larger the Li content, the lighter the magnesium-lithium alloy becomes. However, when the Li content increases and the material has a β phase, long chips are generated during cutting, and the chips become wrapped around a processing machine, making it difficult to cut.

A first aspect of solving the above problem contains Mg, Li, and O, and the sum of the Mg content and the Li content is 90% by mass or more with respect to the mass excluding the O. , an alloy having an α phase and a β phase at 25° C., the amount of the α phase relative to the amount of the α phase and the β phase measured by X-ray diffraction (XRD) on the surface of the alloy. αr is the ratio of O, and Or is the ratio of the O abundance to the Mg, Li, and O abundances measured by X-ray photoelectron spectroscopy (XPS) on the surface of the alloy. The alloy is characterized in that Or/αr, which is the ratio of Or to αr, is 0.11 or more.

A second aspect of solving the above problem includes a preparation step of preparing a raw material containing Mg and Li, in which the sum of the Mg content and the Li content is 90% by mass or more, and 1×10 ^- An alloy characterized by having a heating step of heating the raw material to 600° C. or higher to melt it at a degree of vacuum in a range of ⁴ Pa or more and 1 Pa or less, and a cooling step of cooling and solidifying the molten raw material. This is a manufacturing method.

According to the present disclosure, it is possible to provide a magnesium-lithium alloy having an α phase and a β phase with excellent machinability.

FIG. 1 is a schematic diagram of an alloy member according to a first embodiment. FIG. 2 is a schematic diagram of a device according to a second embodiment. FIG. 3 is a schematic diagram of a device according to a third embodiment. A schematic diagram of a device according to a fourth embodiment. FIG. 3 is a diagram showing a backscattered electron image of Example 1. FIG. 3 is a diagram showing the distribution of O in Example 1. FIG. 3 is a diagram showing an X-ray diffraction pattern of Example 2. FIG. 3 is a diagram showing an O1s spectrum of Example 2.

Embodiments of the present disclosure will be described below.

(First embodiment

[Alloy member]
FIG. 1 is a schematic diagram of an alloy member according to a first embodiment, and is a sectional view taken from the stacking direction.

The alloy member 100 is a magnesium-lithium alloy member (Mg-Li alloy member). The alloy member includes a base material 102 and a coating 101 provided on the base material 102. The coating 101 is provided to improve the corrosion resistance of the first surface 102A of the base material, and may be made of, for example, a material containing magnesium phosphate or magnesium fluoride. Further, a coating film such as a primer or an overcoat layer may be provided on the coating 101 depending on the purpose of the user. Examples of the coating film include a heat shielding film having a heat shielding function. However, depending on the purpose of use, the coating 101 may be omitted. Therefore, in the present disclosure, an embodiment without the coating 101 is also referred to as an Mg-Li alloy member.

The base material 102 has a first surface 102A. Moreover, the shape is not particularly limited. The shape is not limited to a hexahedron such as a rectangular parallelepiped or a cube shown in FIG. 1, but may be a cylinder, a sphere, a prism, a pyramid, or a cylinder. Moreover, since the first surface 102A is an arbitrary surface, its location is not particularly limited. In this specification, the surface refers to a position from the outermost surface in contact with the atmosphere to a depth of 1 mm. The base material 102 includes a magnesium-lithium alloy (Mg-Li alloy). In the present disclosure, the Mg-Li alloy refers to an alloy that contains Mg and Li, and the sum of the Mg content and the Li content is 90% by mass or more based on the mass excluding O. When the sum of the Mg content and the Li content is 90% by mass or more, it becomes easy to reduce the specific gravity to 1.60 or less. Mg-Li alloys are lightweight metal materials, and are superior in weight, vibration damping properties, and specific strength compared to Mg alloys that do not contain Li. Having excellent vibration damping properties means that vibrations can be quickly converged by quickly converting vibration energy into thermal energy. Further, the specific strength is the tensile strength per density, and the higher the specific strength, the lighter the member can be. On the other hand, if the sum of the contents of Mg and Li is less than 90% by mass, the specific gravity will exceed 1.60, making it difficult to reduce the weight. A more preferable specific gravity is 1.50 or less.

It is known that Mg--Li alloys have different crystal structures depending on the Li content. Its structure is based on the phase diagram described in the document “Binary Alloy State Diagram Collection”, edited by Seizo Nagasaki and Makoto Hirabayashi, publisher: Agne Gijutsu Center, ISBN-13:978-4900041882, release date: January 2001. According to this phase diagram, the Mg-Li alloy has a single phase region of α phase, a single phase region of β phase, and a eutectic region having both α phase and β phase. I understand. The α phase contains a lot of Mg and is also called a close-packed hexagonal phase, and its crystal structure is an hcp (Hexagonal Close-Packed) structure. The β phase contains a lot of Li and is also called a body-centered cubic phase, and its crystal structure is has a bcc (Body-Centered Cubic) structure. At 25° C., if the Li content is lower than 5.34% by mass with respect to the sum of the Mg content and the Li content, only the α phase is present. In addition, at 25°C, if Li is 5.34% by mass or more and 11% by mass or less, a mixed phase of α phase and β phase will be formed.Also, if Li exceeds 11% by mass at 25°C, only β phase will be formed. However, since this phase diagram is a binary alloy, one or more elements selected from the first group consisting of Ge, Mn, and Si may be included, or the Li content in the eutectic region may be within the range mentioned above depending on the manufacturing method. Changes from

However, when the Mg-Li alloy has an increased Li content and has a β phase, there is a problem that long chips are generated during cutting, and the chips become wrapped around the processing machine, making it difficult to process. This is because the β phase is a body-centered cubic crystal, and therefore has more slip planes than the α phase, and is therefore more ductile than the α phase. In general, high ductility and ease of plastic deformation are advantageous when controlling the shape using methods such as extrusion, rolling, and forging, but the presence of the β phase can result in long chips during cutting.

Therefore, as a result of intensive studies, the inventor of the present application found that by increasing the proportion of α phase contained in the Mg-Li alloy and the proportion of O (oxygen) contained in the Mg-Li alloy, the β It has been found that it is possible to shorten the length of chips of an Mg-Li alloy having a phase. Specifically, the ratio of the abundance of α phase to the abundance of α phase and β phase on the surface such as the first surface 102A is αr, and the ratio of the abundance of Mg, Li, and O on the surface such as the first surface 102A is It has been found that when the ratio of the amount of O present is Or, when Or/αr is set to 0.11 or more, the chips become shorter.

The inventor of this application considers this mechanism as follows. When an Mg-Li alloy having an α phase and a β phase contains O, O is preferentially incorporated into the β phase, which is a dense hexagonal system, rather than the β phase, which is a body-centered cubic system. This is because the c-axis length of the α phase is 0.517 nm, which is longer than the c-axis length of the β phase, which is 0.303 nm, and there is more room for O to enter the unit cell or form a solid solution in the α phase than in the β phase. It's for a reason. By incorporating O into the alpha phase in this way, the lattice becomes more strained and brittle than the prior art alpha phase in which no O is incorporated. As the α phase becomes brittle, the chips generated during cutting become shorter.

It is preferable that Or/αr is 0.15 or more. As the value of Or/αr increases, O is not only taken into the α phase, but also forms oxides with Mg and/or Li and precipitates at the grain boundaries of crystal grains. If cutting is performed with the oxide precipitated at the grain boundaries of the crystal grains, the precipitated location becomes a stress concentration source, and the chips can be further shortened. Note that the precipitated oxide is preferably a Li oxide. This is because when Mg oxide precipitates, the Mg component in the α phase decreases, making the α phase less likely to become brittle.

Or/αr is preferably 7.4 or less. Within this range, the lightweight effect of Li in the Mg-Li alloy can be obtained. On the other hand, if Or/αr exceeds 7.4, the proportion of O, which is heavier than Li, in the alloy will increase, and the lightweight effect of Li will become smaller.

More preferably, Or/αr is 3.0 or less. Within this range, sufficient corrosion resistance can be obtained. More preferably, it is 0.70 or less.

That is, Or/αr is preferably in the range of 0.15 or more and 7.4 or less, more preferably in the range of 0.15 or more and 3.0 or less. More preferably, it is in the range of 0.15 or more and 0.70 or less.

It is preferable that αr is in the range of 2% or more and 85% or less. Within this range, the Mg-Li alloy has excellent machinability. More preferably, it is in the range of 5% or more and 60% or less. More preferably, it is in the range of 8% or more and 40% or less.

αr, which is the ratio of the amount of α phase present to the amounts of α phase and β phase, can be measured by X-ray diffraction (XRD). Specifically, for example, it is possible to measure by the following procedure. First, a diffraction pattern is obtained using the 2θ-θ method for a Mg-Li alloy in a range where 2θ is 20° or more and 100° or less, and the background is removed. Next, each peak of the diffraction pattern from which the background has been removed is divided into a peak derived from the α phase and a peak derived from the β phase. Using the cps (Count per Second) value of each diffraction peak, calculate (sum of all cps showing α phase)/{(sum of all cps showing α phase) + (sum of all cps showing β phase)} Calculate αr from the formula. Identification of each peak in the diffraction pattern as a peak derived from the α phase and a peak derived from the β phase can be performed with reference to known powder X-ray diffraction data.

Or, which is the ratio of the amount of O present to the amounts of Mg, Li, and O, can be measured by X-ray photoelectron spectroscopy (XPS). For example, it can be measured using the following procedure. First, Ar sputtering is performed on a Mg--Li alloy to a depth of 750 nm, and spectra of Mg2p, Li1s, and O1s are obtained. The order of measurement is preferably O1s, Mg2p, and Li1s. If O1s is measured later, oxidation progresses in vacuum, making it difficult to accurately measure the amount of O present. After that, Ar sputtering is further performed until the depth reaches 1000 nm, and spectra of Mg2p, Li1s, and O1s are obtained. Spectra are acquired at multiple locations. The abundances of Mg, Li, and O are calculated from the acquired spectra, and an average value is calculated from the abundances at multiple locations at each of the two depths. Then, using the average value, Or is calculated from the formula (abundance of O)/{(abundance of O)+(abundance of Mg)+(abundance of Li)}.

Whether or not the Mg-Li alloy contains oxides can be determined by X-ray photoelectron spectroscopy (XPS). Specifically, it can be determined from the O1s spectrum. In addition, it can be determined from the backscattered electron image of a scanning electron microscope (SEM) and energy dispersive X-ray analysis (EDX) that the oxide is Li oxide and that Li oxide exists at the grain boundaries of crystal grains. is possible.

The Mg--Li alloy preferably contains one or more elements selected from the first group consisting of Ge, Mn, and Si. Although the detailed mechanism has not been completely elucidated, based on experimental results including the examples described below, it is believed that these first group elements play a role in generating the α phase.

The content of Ge in the Mg-Li alloy is preferably 0.3% by mass or less based on the mass excluding O. When the Ge content is 0.3% by mass or less, corrosion resistance is particularly good. On the other hand, if the Ge content exceeds 0.3% by mass, there is a risk that Ge oxides will segregate at the grain boundaries of the Mg-Li alloy. From the viewpoint of improving toughness, the more preferable Ge content is in the range of 0.01% by mass or more and 0.3% by mass or less.

The content of Mn in the Mg-Li alloy is preferably 2% by mass or less based on the mass excluding O. When the Mn content is 2% by mass or less, the toughness is good. On the other hand, when the Mn content exceeds 2% by mass, the corrosion resistance may be the same as when no Mn is contained. A more preferable Mn content is 1.5% by mass or less. A more preferable Mn content is 0.09% by mass and 1.1% by mass or less.

The content of Si in the Mg-Li alloy is preferably 0.5% by mass or less based on the mass excluding O. When the Si content is 0.5% by mass or less, corrosion resistance is particularly good. On the other hand, when the Si content exceeds 0.5% by mass, the corrosion resistance may be the same as when no Si is contained. A more preferable Si content is less than 0.1% by mass. More preferably, the Si content is in the range of 0.01% by mass or more and 0.03% by mass or less.

In addition, in the Mg-Li alloy of the first embodiment, it is preferable that two or more types of elements of the first group are contained from the viewpoint of facilitating the formation of the α phase. More preferably, all three types are contained. Moreover, from the same viewpoint, it is preferable that the content of Ge is the highest among these three types. Further, from the same viewpoint, it is preferable that the content of Si is the smallest among these three types.

Preferably, the Mg-Li alloy of the first embodiment further contains one or more elements selected from the second group consisting of Al, Zn, Zr, Ca, and Be. These elements of the second group are elements that the inventor has experimentally confirmed that even if they exist in the Mg-Li alloy, they do not easily inhibit the formation of the α phase. Here, it is preferable that the sum of the contents of one or more elements selected from the second group is 0.01% by mass or more and 7% by mass or less. When the sum of the contents of one or more elements selected from the second group is within the above range, at least one of corrosion resistance, fracture strength, ductility, and toughness will be good.

The content of Al in the Mg-Li alloy is preferably 5% by mass or less based on the mass excluding O. When the Al content is 5% by mass or less, the fracture strength will be good. On the other hand, if the Al content exceeds 5% by mass, the process window becomes narrower, although the mechanism is unknown, and there is a risk that the effect of the first group elements to generate the α phase may be inhibited. A more preferable Al content is in the range of 0.1% by mass or more and 4% by mass or less.

The content of Zn in the Mg-Li alloy is preferably 4% by mass or less based on the mass excluding O. When the Zn content is 4% by mass or less, ductility becomes good. On the other hand, if the Zn content exceeds 4% by mass, the process window becomes narrower, although the mechanism is unknown, and there is a risk that the effect of the first group elements to generate the α phase may be inhibited. A more preferable Zn content is 0.1% by mass or more and 3% by mass or less.

The content of Zr in the Mg-Li alloy is preferably 0.7% by mass or less based on the mass excluding O. When the Zr content is 0.7% by mass or less, the toughness will be good. On the other hand, when the Zr content exceeds 0.7% by mass, the toughness may be comparable to that when Zr is not contained. A more preferable Zr content is in the range of 0.1% by mass to 0.5% by mass.

The content of Ca in the Mg-Li alloy is preferably 0.3% by mass or less based on the mass excluding O. When the Ca content is 0.3% by mass or less, corrosion resistance is good. On the other hand, when the content of Ca exceeds 0.3% by mass, the corrosion resistance may be the same as when no Ca is contained. A more preferable Ca content is in the range of 0.01% by mass or more and 0.15% by mass or less.

The Be content in the Mg-Li alloy is preferably 0.1% by mass or less based on the mass excluding O. When the Be content is 0.1% by mass or less, the toughness is good. On the other hand, when the Be content exceeds 0.1% by mass, the toughness may be comparable to that when Be is not contained. A more preferable Be content is in the range of 0.01% by mass or more and 0.05% by mass or less.

Further, the Mg--Li alloy of the first embodiment may contain metal elements other than the elements exemplified above as long as the characteristics do not change. These metal elements also include unavoidable impurities that cannot be avoided during manufacturing. Examples of unavoidable impurities include Fe and Cu. The content of unavoidable impurities in the Mg-Li alloy is 1% by mass or less.

[Method for manufacturing alloy members]
The method for producing the alloy of the first embodiment is not particularly limited as long as it can be synthesized to include oxygen so that Or/αr is 0.11 or more. An example of a preferred manufacturing method will be described below.

First, a raw material for an Mg-Li alloy is prepared (preparation step). Specifically, a raw material containing Mg and Li and having a sum of Mg content and Li content of 90% by mass or more is prepared so as to have a desired composition. The purity of the raw material is, for example, 2N, 3N, and 4N, and commercially available high-purity metals can be used. From the viewpoint of increasing the value of Or/αr, it is preferable to use a raw material with a purity of 2N, and it is more preferable that the purity of the raw material containing Li is 2N. The form of the metal is not particularly limited, and a desired form can be selected from, for example, ingot, chip, flake, powder, shot, and pellet. As for the metal, not only a single metal element but also an alloy made of a plurality of metal elements may be used.

Next, these raw materials are heated and melted (heating step). Specifically, these raw materials are placed in a crucible and heated to 600° C. or higher to melt them. The temperature may be any temperature higher than the melting point of these raw materials, but preferably 700°C or higher. More preferably, the temperature is 800°C or higher. The means for heating is not particularly limited, but for example, high frequency induction heating or electromagnetic induction stirring can be employed. In the heating step, it is preferable that the degree of vacuum in the furnace is in the range of 1×10 ⁻⁴ Pa or more and 1 Pa or less. This is to increase the value of Or/αr. From the viewpoint of increasing the value of Or/αr, the range is more preferably 1×10 ⁻³ or more and 1 Pa or less. The means for maintaining the degree of vacuum is not limited, and for example, it can be adjusted with a pump such as an oil diffusion pump or a turbomolecular pump, or a throttle can be provided between the pump and the furnace. From the viewpoint of setting the value of Or/αr to 7.4 or less, the atmosphere during heating is preferably a reducing atmosphere, for example, an argon gas atmosphere is preferable. Note that the rate of temperature increase to the melting temperature is not particularly limited. Further, the temperature may be maintained for a certain period of time during heating and melting, but the holding time can be appropriately selected depending on the desired amount of oxygen.

Next, the molten raw material is cooled and solidified (cooling step). The temperature decreasing rate in the cooling step is not particularly limited, but it is preferable to control the cooling rate so that the cooling rate from the time when the molten raw material begins to solidify to 100° C., which is just below the recrystallization temperature, is 100° C./min or less. This is to facilitate the development of α phase in the alloy. Note that the cooling rate mentioned above is the average cooling rate when the molten raw material is cooled to 100° C., which is just below the recrystallization temperature, after it begins to solidify. By going through the above steps, the Mg--Li alloy of the first embodiment can be obtained.

In addition, from the viewpoint of making it easier to express the α phase, a more preferable cooling rate in the cooling step is 50° C./min or less, and an even more preferable cooling rate is 25° C./min or less. Moreover, it is preferable to cool at a rate of 100° C./min or less throughout the entire cooling process in which the molten raw material is cooled down to 100° C. after it begins to solidify. Further, the cooling rate at temperatures below 200°C is preferably slower than the cooling rate at temperatures higher than 200°C.

Further, the obtained Mg-Li alloy may be machined to form a desired shape. The machining process may be lapping, cutting, barrel polishing, etc., and can be selected as needed. Further, the obtained Mg-Li alloy may be cleaned. Cleaning can remove metal scraps, dust, oil stains, altered layers, etc. caused by machining such as cutting. Therefore, it is possible to use general cleaning methods such as acid or alkali cleaning, surfactant cleaning, brush cleaning, and ultrasonic cleaning. After washing, drying may be performed if necessary.

Alternatively, the obtained Mg-Li alloy may be used as a base material and a coating may be provided on the base material. The means for providing the coating is not particularly limited, and can be appropriately selected depending on the coating to be provided. When the film is made of magnesium fluoride, a known anodic oxidation process or a chemical conversion treatment using a known treatment liquid can be used. Further, when the film is made of magnesium phosphate, a chemical conversion treatment using a known treatment liquid can be used.

As described above, according to the Mg-Li alloy of the first embodiment, since Or/αr is 0.11 or more and the oxygen content is higher than that of the conventional technology, it has an α phase and a β phase with excellent machinability. A Mg-Li based alloy can be provided.

(Second embodiment

[Optical equipment/imaging device]
FIG. 2 shows the configuration of a single-lens reflex digital camera 600, which is an imaging device that is an example of a device according to a second embodiment of the present disclosure. In FIG. 2, a camera body 602 and a lens barrel 601, which is an optical device, are combined, but the lens barrel 601 is a so-called interchangeable lens that can be attached to and detached from the camera body 602.

Light from the subject passes through an optical system consisting of a plurality of lenses 603 and 605, which are examples of parts arranged on the optical axis of the photographing optical system within the housing of the lens barrel 601, and is received by the image sensor. It is photographed by this. Here, the lens 605 is supported by an inner tube 604 and movably supported relative to the outer tube of the lens barrel 601 for focusing and zooming. During the observation period before photographing, light from the subject is reflected by the main mirror 607, which is an example of a component inside the housing 621 of the camera body, and after passing through the prism 611, the photographed image is projected to the photographer through the finder lens 612. It will be done. The main mirror 607 is, for example, a half mirror, and the light transmitted through the main mirror is reflected by a submirror 608 in the direction of an AF (autofocus) unit 613, and this reflected light is used, for example, for distance measurement. Further, the main mirror 607 is mounted and supported by a main mirror holder 640 by adhesive or the like. During photographing, the main mirror 607 and sub mirror 608 are moved out of the optical path through a drive mechanism (not shown), the shutter 609 is opened, and a photographic light image incident from the lens barrel 601 is formed on the image sensor 610. Further, the diaphragm 606 is configured so that brightness and depth of focus during photographing can be changed by changing the aperture area.

The alloy member 100 can be used for at least a portion of the housings 620 and 621. Note that the casings 620 and 621 may be made of only an Mg-Li alloy member, or the alloy member 100 may be provided with a coating film. Since the Mg-Li alloy of the present disclosure has excellent machinability, it is possible to provide an imaging device that is easier to manufacture than conventional imaging devices.

Note that although the imaging device has been described using a single-lens reflex digital camera as an example, the present disclosure is not limited thereto, and may be a smartphone or a compact digital camera.

(Third embodiment

[Electronics]
FIG. 3 shows the configuration of a personal computer, which is an electronic device that is an example of a device according to a third embodiment of the present disclosure. In FIG. 3, a personal computer 800 includes a display section 801 and a main body section 802. An electronic component 830, which is an example of a component provided within the housing, is provided inside the housing 820 of the main body portion 802. The alloy member 100 can be used for at least a portion of the casing 820 of the main body portion 802. The housing 820 may be made of only a Mg-Li alloy member, or the alloy member 100 may be provided with a coating film. Since the Mg-Li alloy of the present disclosure has excellent machinability, it is possible to provide a personal computer that is easier to manufacture than conventional personal computers.

Note that although the electronic device has been described using the personal computer 800 as an example, the present disclosure is not limited thereto, and may be a smartphone or a tablet.

(Fourth embodiment

[Mobile object]
FIG. 4 shows a drone that is an example of a mobile object according to the fourth embodiment of the present disclosure. The drone 700 includes a plurality of drive units 701 and a main body 702 connected to the drive units 701. Inside the main body portion 702, there is a drive circuit (not shown) that is an example of a component. The drive unit 701 includes, for example, a propeller. As shown in FIG. 4, a leg 703 may be connected to the main body 702, or a camera 704 may be connected. The alloy member 100 can be used for at least a portion of the housing 710 of the main body portion 702 and the leg portions 703. The casing 710 may be made of only a Mg-Li alloy member, or the alloy member 100 may be provided with a coating film. Since the Mg-Li alloy of the present disclosure has excellent machinability, it is possible to provide a drone that is easier to manufacture than conventional drones.

Note that although the mobile object has been described using the drone 700 as an example, the present disclosure is not limited thereto, and may be a car or an airplane.

Examples will be described below. First, a method for evaluating alloys will be explained.

[Alloy evaluation method

(Measurement and calculation of αr)
αr, which is the ratio of the amount of α phase to the amounts of α phase and β phase, was measured using an X-ray diffraction (XRD) method in an environment of 25° C. (±2° C.). The X-ray diffraction device used was Ultima IV manufactured by Rigaku Corporation. A Cu tube was used as the tube, and the measurement wavelength λ was 1.5418 Å. Further, the tube voltage was 40 kV, and the tube current was 40 mA. First, a diffraction pattern was obtained using the 2θ-θ method for a range in which 2θ is 20° or more and 100° or less. The step width was 0.02°, and the scanning speed was 2°/min (accumulated twice). Next, the background was removed from the obtained diffraction pattern. Then, each peak of the diffraction pattern from which the background was removed was divided into a peak derived from the α phase and a peak derived from the β phase. Using the cps (Count per Second) value of each diffraction peak, calculate (sum of all cps showing α phase)/{(sum of all cps showing α phase) + (sum of all cps showing β phase)} αr was calculated from the formula.

For the measurements, samples were used in which a cylindrical billet with a diameter of 160 mm was cut into a plate shape of 20 mm x 50 mm x 2 mm in size. A 20 mm x 50 mm surface, which is the measurement surface (first surface 102A) of the sample, was finished polished to #2000 using a polishing machine, and then X-rays were irradiated.

(Measurement/calculation of Or)
Or, which is the ratio of the amount of O to the amounts of Mg, Li, and O, was measured using X-ray photoelectron spectroscopy (XPS) in an environment of 25° C. (±2° C.). The X-ray photoelectron spectrometer used was PHI Quantera II manufactured by ULVAC-PHI. Depth direction analysis was performed using AlKα rays as the X-ray source and Ar sputtering. The X-ray irradiation conditions were a beam diameter of 200 μm, an X-ray output of 50 W, and an accelerating voltage of 15 kV. The detector conditions were a pass energy of 112 eV and a time per step of 10 ms. The conditions for Ar sputtering were to process an area of 2 mm x 2 mm at an accelerating voltage of 4 kV. For depth conversion, an etching rate using SiO ₂ was applied.

Measurements were performed at two points: a point where the depth reached 750 nm and a point where the depth reached 1000 nm. To evaluate O1s, a range from 523.0 eV to 543.0 eV was measured, and to evaluate Mg2p and Li1s, a range from 44.0 eV to 72.0 eV was measured. In order to avoid surface distortion during the measurement, measurements in the range from 523.0 eV to 543.0 eV were first performed, and measurements were repeated 15 times and integrated. Thereafter, the measurement was repeated 30 times in the range from 44.0 eV to 72.0 eV and integrated.

Next, the intensity of each element was obtained using the obtained spectrum. The Mg intensity was obtained by multiplying the integrated intensity of the spectrum from 45 eV to 51 eV by the sensitivity coefficient of Mg2p. The Li intensity was obtained by multiplying the integrated intensity of the spectrum from 51 eV to 55 eV by the Li1s sensitivity coefficient. The O intensity was obtained by multiplying the integrated intensity of the spectrum from 525 eV to 535 eV by the sensitivity coefficient of O1s. The Shirley method was used for background setting when acquiring the integrated intensity of the spectrum. (Intensity of O)/{(Intensity of O)+(Intensity of Mg)+(Intensity of Li)} was defined as Or.

For the measurement, a sample was used in which the prepared cylindrical billet with a diameter of 160 mm was cut into a plate shape of 20 mm x 50 mm x 2 mm in size. A surface of 20 mm x 50 mm, which is the measurement surface of the sample, was polished using a polishing machine using #400, #800, #1200, and #2000 polishing sheets until the previous polishing marks were removed. As a final polish, a mirror surface was created using colloidal silica. Furthermore, the sample with a mirror surface was immersed in a 3% ethanol nital solution for 30 seconds, and further immersed in an ethanol solution for 3 minutes of ultrasonic cleaning. The polisher used was IS-POLISHER manufactured by Ikegami Seiki Co., Ltd. The sample was placed into an X-ray photoelectron spectrometer within 5 minutes after ultrasonic cleaning.

(cutting performance)
The machinability was evaluated by cutting a cylindrical billet of φ110 mm×100 mm. The device used was CR-253 manufactured by DMG Mori Seiki. Cutting was performed using a carbide tip as a blade, with a feed rate of 0.1 mm/rev, a depth of cut of 0.5 mm, and a rotational speed of 400 rpm, using denatured ethyl alcohol as a cooling solvent. The quality was judged using chips with eight turns of chips. Ten chips were randomly picked up and their average length was determined. Those with an average length of 40 mm or less were evaluated as A (good), and those with an average length longer than 40 mm were evaluated as B (bad).

[Manufacture and evaluation of alloy parts

(Example 1)
First, the raw materials were adjusted so that the composition was Mg-12.3wt%Li-2.9wt%Al-0.09wt%Mn-0.15wt%Ca-0.29wt%Ge-0.02wt%Si. Metal pieces of each element with a purity of 4N were prepared.

Subsequently, these raw materials were placed in a ceramic crucible. The crucible was placed in a chamber, the chamber was evacuated to 0.1 Pa, and the crucible was heated at a maximum temperature of 800° C. in an argon gas atmosphere to melt the raw materials. After holding at 800° C. for 1 hour, it was cooled. Cooling was slow cooling, and the cooling rate from 594°C, when solidification started, to 100°C was 15°C/min. After cooling was completed, the alloy member of Example 1, which was a cylindrical billet with a diameter of 160 mm, was obtained. The composition of the obtained alloy was evaluated using ICP-AES (Inductively Coupled Plasma Emission Spectroscopy).

Subsequently, samples were prepared from the obtained cylindrical billet in order to perform each measurement, and each measurement was performed. As a result, αr of the alloy of Example 1 was 22.2%, Or was 3.5 at%, and the calculated Or/αr was 0.16. Moreover, the average chip length was 6 mm, and the machinability was evaluated as A.

(Example 2)
Example 2 differs from Example 1 in composition. The composition of Example 2 is Mg-11.5wt%Li-3.4wt%Al-0.18wt%Mn-0.25wt%Ge-0.04wt%Be-0.02wt%Si. An alloy of Example 2 was obtained in the same manner as in Example 1 except for the above. The composition of the obtained alloy was evaluated using ICP-AES (Inductively Coupled Plasma Emission Spectroscopy).

The αr of the alloy of Example 2 was 35.4%, the Or was 8.4 at%, and the calculated Or/αr was 0.24. Further, the average chip length was 11 mm, and the machinability was evaluated as A.

(Example 3)
Example 3 differs from Example 1 in composition and grade of raw materials. The composition of Example 3-1 is Mg-12.2wt%Li-3.0wt%Zn-0.41wt%Zr-0.01wt%Si. As raw materials, metal pieces of Mg with a purity of 4N, LiMg with a purity of 2N, and Zn, Zr, and Si with a purity of 4N were prepared. An alloy of Example 3 was obtained in the same manner as in Example 1 except for the above.

The αr of the alloy of Example 3 was 8.1%, the Or was 5.6 at%, and the calculated Or/αr was 0.69. Moreover, the average chip length was 6 mm, and the machinability was evaluated as A.

(Comparative example 1)
The alloy of Comparative Example 1 is manufactured by Anri Materials Technology Co., Ltd. and has the product name LAZ-Ares. The composition of the alloy was evaluated using ICP-AES (inductively coupled plasma emission spectrometry). The composition was Mg-9.0wt%Li-4.1wt%Al-1.1wt%Zn-0.01wt%Mn-0.02wt%Si.

Subsequently, samples were prepared and various measurements were performed. As a result, αr of the alloy of Comparative Example 1 was 47.0%, Or was 1.3 at%, and the calculated Or/αr was 0.03. Further, the average chip length was 186 mm, and the machinability was evaluated as B.

(Comparative example 2)
The alloy of Comparative Example 2 is a magnesium-lithium-aluminum alloy manufactured by Santoku Corporation. The composition of the alloy was evaluated using ICP-AES (inductively coupled plasma emission spectrometry). The composition was Mg-14.7wt%Li-6.0wt%Al-0.3wt%Ca-0.02wt%Si.

Subsequently, samples were prepared and various measurements were performed. As a result, αr of the alloy of Comparative Example 2 was 32.0%, Or was 3.1 at%, and the calculated Or/αr was 0.10. Further, the average chip length was 433 mm, and the machinability was evaluated as B.

The above evaluation results are shown in Table 1.

表１より、切屑性の評価がＡだった実施例１～３はいずれもＯｒ／αｒが０．１１以上であった。一方、Ｏｒ／αｒが０．１１に満たなかった比較例１及び２は切削性の評価がＢだった。

From Table 1, all of Examples 1 to 3 in which the evaluation of chipping property was A were Or/αr of 0.11 or more. On the other hand, Comparative Examples 1 and 2 in which Or/αr was less than 0.11 were evaluated as B in machinability.

FIG. 5A is a backscattered electron image taken by a scanning electron microscope in Example 1, and FIG. 5B is a diagram showing the distribution of O in energy dispersive X-ray analysis. 5A and 5B were obtained by measuring the same surface. The backscattered electron image was obtained using Sigma 500VP manufactured by Carl Zeiss under conditions of an accelerating voltage of 10 kV and an aperture size of 60 μm. The O distribution map was obtained using X-MAXN80 manufactured by OXFORD. A backscattered electron image can be obtained that corresponds to the element distribution, with parts displayed in black containing substances with small atomic numbers, and parts displayed in white containing substances with large atomic numbers. In FIG. 5A, a black precipitate was observed within the measurement surface of Example 1. Since the area around the precipitate is Mg-Li, it can be seen that the black part contains a large amount of Li. FIG. 5B shows the distribution of O, and shows that there are many O in the white portion. In FIG. 5B, the portions shown in black in FIG. 5A are shown in white, indicating that the precipitates are oxides. From these results, it can be said that in Example 1, Li oxide was precipitated at the grain boundaries of the crystal grains.

FIG. 6 is an X-ray diffraction pattern obtained by 2θ-θ measurement in Example 2, and it can be seen that α phase and β phase were observed, respectively.

FIG. 7 is a diagram showing the spectrum of O1s of Example 2, in which a solid solution O peak was observed at a binding energy of around 530 eV. Further, an oxide peak was observed at a binding energy of around 527 eV. From the peak around 530 eV, it is considered that O is dissolved in the α phase. Moreover, since an oxide peak was also observed, it is considered that O is not only dissolved in the α phase but also precipitated at the grain boundaries of the crystal grains.

As described above, according to the present disclosure, it is possible to provide an Mg-Li alloy having an α phase and a β phase at 25° C., which has excellent machinability and good chip breaking properties.

The disclosure of this embodiment includes the following configuration and method.

(Configuration 1)
Contains Mg, Li and O, the sum of the Mg content and the Li content is 90% by mass or more with respect to the mass excluding the O, and the α phase and the β phase are formed at 25°C. An alloy having
αr is the ratio of the abundance of the α phase to the abundance of the α phase and the β phase, which is measured by X-ray diffraction (XRD) on the surface of the alloy;
When the ratio of the amount of O to the amounts of Mg, Li and O measured by X-ray photoelectron spectroscopy (XPS) on the surface of the alloy is Or,
An alloy characterized in that Or/αr, which is the ratio of the Or to the αr, is 0.11 or more.

(Configuration 2)
The alloy according to configuration 1, wherein the alloy includes Li oxide.

(Configuration 3)
The alloy according to configuration 2, wherein the Li oxide is precipitated from grain boundaries of the alloy.

(Configuration 4)
The alloy according to any one of configurations 1 to 3, wherein the Or/αr is 7.4 or less

(Configuration 5)
The alloy according to any one of configurations 1 to 3, wherein the Or/αr is 3.0 or less.

(Configuration 6)
The alloy according to any one of configurations 1 to 3, wherein the Or/αr is in a range of 0.15 or more and 0.70 or less.

(Configuration 7)
The alloy according to any one of configurations 1 to 6, wherein the αr is in a range of 2% or more and 85% or less.

(Configuration 8)
The alloy according to configuration 7, wherein the αr is in a range of 5% or more and 60% or less.

(Configuration 9)
The alloy according to configuration 7, wherein the αr is in a range of 8% or more and 40% or less.

(Configuration 10)
The alloy according to any one of configurations 1 to 9, wherein the alloy further contains one or more elements selected from the first group consisting of Ge, Mn, and Si.

(Configuration 11)
The alloy according to configuration 10, wherein the Ge content is 0.3% by mass or less.

(Configuration 12)
The alloy according to configuration 10 or 11, wherein the Mn content is 2% by mass or less.

(Configuration 13)
The alloy according to any one of configurations 10 to 12, wherein the Si content is 0.5% by mass or less.

(Configuration 14)
The alloy further contains one or more elements selected from the second group consisting of Al, Zn, Zr, Ca and Be,
The alloy according to any one of Structures 1 to 13, wherein the sum of the contents of one or more elements selected from the second group is 0.01% by mass or more and 7% by mass or less.

(Configuration 15)
The content of Al is 5% by mass or less,
The content of Zn is 2% by mass or less,
The content of Zr is 0.7% by mass or less,
The content of Ca is 0.3% by mass or less,
The alloy according to configuration 14, wherein the Be content is 0.1% by mass or less.

(Configuration 16)
base material and
An alloy member comprising a coating provided on the base material,
An alloy member characterized in that the base material contains the alloy according to any one of Structures 1 to 15.

(Configuration 17)
17. The alloy member according to configuration 16, wherein the coating contains magnesium fluoride or magnesium phosphate.

(Configuration 18)
A casing and
A device comprising: a component provided within the housing;
An apparatus characterized in that the casing includes the alloy member according to configuration 16 or 17.

(Method 19)
a preparation step of preparing a raw material containing Mg and Li, the sum of the Mg content and the Li content being 90% by mass or more;
A heating step of heating the raw material to 600° C. or higher to melt it at a degree of vacuum in a range of 1×10 ⁻⁴ Pa or more and 1 Pa or less;
A method for producing an alloy, comprising a cooling step of cooling and solidifying the molten raw material.

(Method 20)
20. The method for producing an alloy according to method 19, wherein in the cooling step, the cooling rate from when the molten raw material starts to solidify to 100°C is 100°C/min or less.

100 Alloy member 101 Coating 102 Base material 600 Single-lens reflex digital camera (equipment)
601 Lens barrel (equipment)
700 Drones (equipment) 800 Computers (equipment)

(First embodiment )

(Second embodiment )

(Third embodiment )

(Fourth embodiment )

[Alloy evaluation method ]

[Manufacture and evaluation of alloy parts ]

The disclosure of this embodiment includes the following configuration and method.

(Configuration 4)
The alloy according to any one of configurations 1 to 3, wherein the Or/αr is 7.4 or less .

Claims (20)

Contains Mg, Li and O, the sum of the Mg content and the Li content is 90% by mass or more with respect to the mass excluding the O, and the α phase and the β phase are formed at 25°C. An alloy having
αr is the ratio of the abundance of the α phase to the abundance of the α phase and the β phase, which is measured by X-ray diffraction (XRD) on the surface of the alloy;
When the ratio of the amount of O to the amounts of Mg, Li and O measured by X-ray photoelectron spectroscopy (XPS) on the surface of the alloy is Or,
An alloy characterized in that Or/αr, which is the ratio of the Or to the αr, is 0.11 or more. The alloy according to claim 1, wherein the alloy includes Li oxide. The alloy according to claim 2, wherein the Li oxide is precipitated from grain boundaries of the alloy. The alloy according to claim 1, wherein the Or/αr is 7.4 or less. The alloy according to claim 1, wherein the Or/αr is 3.0 or less. The alloy according to claim 5, wherein the Or/αr is in a range of 0.15 or more and 0.70 or less. The alloy according to claim 1, wherein the αr is in a range of 2% or more and 85% or less. The alloy according to claim 7, wherein the αr is in a range of 5% or more and 60% or less. The alloy according to claim 7, wherein the αr is in a range of 8% or more and 40% or less. The alloy according to claim 1, wherein the alloy further contains one or more elements selected from the first group consisting of Ge, Mn, and Si. The alloy according to claim 10, wherein the Ge content is 0.3% by mass or less. The alloy according to claim 10, wherein the Mn content is 2% by mass or less. The alloy according to claim 10, wherein the Si content is 0.5% by mass or less. The alloy further contains one or more elements selected from the second group consisting of Al, Zn, Zr, Ca and Be,
The alloy according to claim 1, wherein the sum of the contents of one or more elements selected from the second group is 0.01% by mass or more and 7% by mass or less. The content of Al is 5% by mass or less,
The content of Zn is 2% by mass or less,
The content of Zr is 0.7% by mass or less,
The content of Ca is 0.3% by mass or less,
The alloy according to claim 14, wherein the Be content is 0.1% by mass or less. base material and
An alloy member comprising a coating provided on the base material,
An alloy member characterized in that the base material contains the alloy according to any one of claims 1 to 15. The alloy member according to claim 16, wherein the coating contains magnesium fluoride or magnesium phosphate. A casing and
A device comprising: a component provided within the housing;
An apparatus characterized in that the housing includes the alloy member according to claim 16. a preparation step of preparing a raw material containing Mg and Li, the sum of the Mg content and the Li content being 90% by mass or more;
A heating step of heating the raw material to 600° C. or higher to melt it at a degree of vacuum in a range of 1×10 ⁻⁴ Pa or more and 1 Pa or less;
A method for producing an alloy, comprising a cooling step of cooling and solidifying the molten raw material. 20. The method for manufacturing an alloy according to claim 19, wherein in the cooling step, the cooling rate from when the molten raw material starts to solidify to 100°C is 100°C/min or less.

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