JPWO2020012890A1 - Magnesium-based metal members, their manufacturing methods, and decorative articles using them. - Google Patents

Abstract

Provided are Mg-based metal members having excellent design and corrosion resistance, manufacturing methods thereof, and decorative articles using the same. In the embodiment of the present invention, the Mg-based metal member includes a substrate of Mg or Mg alloy and an oxide layer covering the surface of the substrate, and the oxide layer is at least magnesium (Mg) and scandium (Sc). ) And oxygen (O). It is obtained by thermal oxidation or anodizing an Mg alloy containing magnesium as a main component and scandium in a range of 0.1 at% or more and less than 50 at%.

Description

The present invention relates to a magnesium (hereinafter referred to as "Mg")-based metal member having corrosion resistance and excellent design, a method for producing the same, and a decorative article using the same.

Mg alloys are attracting attention as structural materials because they are the lightest of all practical alloys. Recently, Mg alloys having high strength and high ductility and having a shape memory effect have been developed (for example, Patent Document 1 and Non-Patent Document 1).

According to Patent Document 1 and Non-Patent Document 1, for example, an Mg alloy having a Bcc (body-centered cubic structure) (β) phase in which 20 at% of Sc is added exhibits superelasticity and shape memory effect at low temperature. It has been reported that Mg alloys are expected to be put into practical use.

Since such Mg alloys are easily oxidized in the atmosphere, corrosion resistance is usually imparted, and in some cases, designability / designability is enhanced by dyeing or the like (for example, Patent Document 2). 3). According to Patent Document 2, the surface of the Mg material is roughened, a coating film layer is formed on the surface by chemical conversion treatment or anodizing treatment, and a coating film layer is formed on the coating film layer by electrodeposition coating, spray coating, immersion coating or the like. Is provided. According to Patent Document 3, it is disclosed that a dense film is formed on the Mg-based metal member and has a metallic luster by carefully examining the conditions of anodization. Further, according to Patent Document 3, by adding a dye to the electrolytic solution, dyeing can be performed at the same time as anodizing.

However, in order to improve not only the metallic luster of Mg-based metals but also the designability, it is currently necessary to paint with paints and dyes. It is desirable to provide an Mg-based metal member with improved design without using paint or dye.

International Publication No. 2017/065208 Japanese Unexamined Patent Publication No. 2001-192854 Japanese Unexamined Patent Publication No. 2009-270190

Y. Ogawa et al., Shape Memory and Superiorastity, Vol. 4, Issue 1, pp. 163-173, 2018

From the above, an object of the present invention is to provide an Mg-based metal member having corrosion resistance and excellent design, a method for producing the same, and a decorative article using the same.

In the embodiment of the present invention, the Mg-based metal member includes a substrate of Mg or Mg alloy and an oxide layer covering the surface of the substrate, and the oxide layer is at least magnesium (Mg) and scandium (Mg). It contains Sc) and / or yttrium (Y) and oxygen (O), thereby solving the above problems.
The oxide _layer, Mg _x M y _{O z} (provided that, x + y + z = 1 , M is Sc and / or Y) is represented by the parameters x, y and z,
0.003 ≤ x ≤ 0.8
0.03 ≤ y ≤ 0.65
0.005 ≤ z ≤ 0.95
May be satisfied.
The parameters x, y and z are
0.2 ≤ x ≤ 0.75
0.2 ≤ y ≤ 0.4
0.005 ≤ z ≤ 0.45
May be satisfied.
The oxide layer may be polycrystalline.
The coverage of the oxide layer on the substrate may be 70% or more.
The oxide layer may have a thickness in the range of 50 nm or more and 1 μm or less.
The oxide layer may have a thickness in the range of 100 nm or more and 350 nm or less.
The Mg alloy may contain magnesium as a main component and scandium and / or yttrium in a range of 0.1 at% or more and less than 50 at%.
The Mg alloy may contain magnesium as a main component and scandium and / or yttrium in the range of 0.3 at% or more and 40 at% or less.
The thickness of the oxide layer may be uniform.
The thickness of the oxide layer may be non-uniform.
The oxide layer may have a step in the range of 5 nm or more and 15 nm or less on the surface.
In the embodiment of the present invention, the method for producing the above-mentioned Mg-based metal member comprises a surface-polished Mg alloy containing magnesium as a main component and scandium and / or yttrium in a range of 0.1 at% or more and less than 50 at%. Includes the step of thermal oxidation in a temperature range above 50 ° C. and below 800 ° C. in an atmosphere containing at least oxygen. Then, the above problem is solved.
The thermal oxidation step may be performed in a temperature range of 300 ° C. or higher and 700 ° C. or lower.
The thermal oxidation step may be carried out for 5 minutes or more and 100 days or less.
In the embodiment of the present invention, the method for producing the above-mentioned Mg-based metal member comprises a surface-polished Mg alloy containing magnesium as a main component and scandium and / or yttrium in a range of 0.1 at% or more and less than 50 at%. Includes the step of anodizing in an electrolytic solution. Then, the above problem is solved.
In the anodizing step, a voltage of 2 V or more and 40 V or less may be applied.
The step of anodizing may be carried out for 5 minutes or more and 20 minutes or less.
In the decorative article using the Mg-based metal in the embodiment of the present invention, the Mg-based metal is the above-mentioned Mg-based metal member, thereby solving the above-mentioned problem.
The decorative article may be selected from the group consisting of watches, eyeglasses, tableware, and housings of portable electronic devices.

In the embodiment of the present invention, the Mg-based metal member includes a Mg or Mg alloy substrate and an oxide layer covering the surface of the substrate. The oxide layer contains at least scandium (Sc) and / or yttrium (Y), magnesium (Mg) and oxygen (O). Since the oxide layer contains scandium and / or yttrium, oxidation is promoted more than magnesium, resulting in a dense oxide layer. This makes it possible to provide an Mg-based metal member that is colored not only by metallic luster but also by interference of an oxide layer. Moreover, such an oxide layer is excellent in corrosion resistance. In the embodiment of the present invention, since the Mg-based metal member is excellent in design, it is lightweight when used in a case of a watch, eyeglasses, tableware, or a portable electronic device such as a notebook computer, a smartphone, or a digital camera. Along with the change, the design can be enhanced.

In the embodiment of the present invention, the Mg-based metal member contains a surface-polished Mg alloy containing magnesium as a main component and scandium and / or yttrium in a range of 0.1 at% or more and less than 50 at% in an electrolytic solution. The above-mentioned oxide layer is formed by anodizing with or by thermally oxidizing in the air in a temperature range of more than 50 ° C. and less than 800 ° C. It is advantageous because it enables coloring by simply performing thermal oxidation or anodizing without using a paint or dye.

The figure which shows typically the Mg-based metal member of the Example of this invention. The figure which shows typically another Mg-based metal member of the Example of this invention. A flowchart showing a manufacturing process of the Mg-based metal member according to the embodiment of the present invention. A flowchart showing another manufacturing process of the Mg-based metal member according to the embodiment of the present invention. The figure which shows the TEM image of the cross section of the sample of Example 40 The figure which shows the enlarged TEM image of the cross section of the sample of Example 40 The figure which shows the electron diffraction pattern of the region shown by the circle of FIG. The figure which shows the element mapping of the cross section of the sample of Example 40. A timepiece to which the Mg-based metal member of the embodiment of the present invention is applied. Eyeglasses to which the Mg-based metal member of the embodiment of the present invention is applied. Tableware to which the Mg-based metal member of the embodiment of the present invention is applied. A smartphone to which the Mg-based metal member of the embodiment of the present invention is applied.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The same elements are given the same numbers, and the description thereof will be omitted.

FIG. 1 is a cross-sectional view schematically showing an Mg-based metal member (for example, a plate material) in an embodiment of the present invention.

The Mg-based metal member 100 of the embodiment of the present invention includes a base 110 made of Mg or an Mg alloy, and an oxide layer 120 that covers the surface of the base 110. Here, the oxide layer 120 contains at least magnesium (Mg) and scandium (Sc) and / or yttrium (Y) and oxygen (O). Since Sc and Y are more easily oxidized than Mg, a dense oxide layer 120 is formed. Therefore, in the embodiment of the present invention, the Mg-based metal member 100 has a metallic luster and is colored by the interference of the oxide layer 120. Further, since the oxide layer 120 is dense, it is excellent in corrosion resistance even when compared with a simple coating layer of Mg oxide. Further, the components of the oxide layer of the Mg-based metal member of the embodiment of the present invention are magnesium (Mg), scandium (Sc) and / or yttrium (Y), oxygen (O), and unavoidable components. It may consist of various impurities. Further, it may be a case where it is substantially composed of only these components. Further, as long as an oxide layer having a predetermined composition is obtained on the surface by a treatment described later, the composition of the Mg alloy substrate may be appropriately selected according to the required mechanical properties and the like. The above-mentioned dense oxide layer 120 may be defined by the covering ratio described later. Further, in the oxidation reaction of Mg + O → MgO, the volume tends to decrease, and in the formation of an oxide layer in which only MgO is formed, a portion where the surface of the substrate is not covered with oxide is likely to be formed, or the oxide layer is formed. There is a risk that voids will easily form inside. On the other hand, it is considered that the volume tends to expand when Y and Sc are oxidized, and it is considered that the effect of improving the coverage of the substrate surface by the oxide layer and reducing the voids in the oxide layer can be obtained. Be done. If the coverage is low, diffused reflection may occur between the region where the oxide film is present and the region where the oxide film is not present, and the gloss is easily lost. It is considered that the metallic luster is exhibited by the metal phase existing directly under the oxide film. Since the oxide layer is transparent to the reflected light from the surface of the metal phase, the Mg alloy having the oxide layer on the surface may exhibit gloss. The above-mentioned interference may mean an interference action with light reflected on the surface of the oxide film based on 2nd = λ (n is the refractive index, d is the film thickness, and λ is the wavelength).

Oxide layer _120, Mg _x M y _{O z} (provided that, x + y + z = 1 , M is Sc and / or Y) is represented by the parameters x, y and z,
0.003 ≤ x ≤ 0.8
0.03 ≤ y ≤ 0.65
0.005 ≤ z ≤ 0.95
Meet. As a result, it becomes a dense oxide layer, has a metallic luster, and develops color.

The parameters x, y and z are preferably
0.2 ≤ x ≤ 0.75
0.2 ≤ y ≤ 0.4
0.005 ≤ z ≤ 0.45
Meet. As a result, it becomes a denser oxide layer, has a metallic luster, and develops color.

In particular, when M is Sc alone, the parameters x, y and z are more preferably.
0.25 ≤ x ≤ 0.75
0.25 ≤ y ≤ 0.35
0.005 ≤ z ≤ 0.4
Meet. As a result, it becomes a denser oxide layer, has a metallic luster, and develops color.

In particular, when M is Y alone, the parameters x, y and z are more preferably.
0.25 ≤ x ≤ 0.4
0.25 ≤ y ≤ 0.35
0.3 ≤ z ≤ 0.4
Meet. As a result, it becomes a denser oxide layer, has a metallic luster, and develops color.

In particular, when M is a combination of Sc and Y, the parameters x, y and z are more preferably.
0.2 ≤ x ≤ 0.4
0.25 ≤ y ≤ 0.4
0.3 ≤ z ≤ 0.4
Meet. As a result, it becomes a denser oxide layer, has a metallic luster, and develops color.

The composition of the oxide layer 120 can be measured by elemental analysis (for example, energy dispersion spectroscopy shown in Examples), and the oxide layer 120 is a composite oxide of Mg and Sc and / or Y. Therefore, its composition does not have a specific chemical spectroscopic composition and varies depending on the alloy composition, thermal oxidation, and anodization conditions. Here, no specific stoichiometric composition, composite oxide represented by a range of parameters such as described above Mg _x M _y O _z are those having the same properties and performance It may mean that the composition is not limited to a specific stoichiometric composition, and the specific stoichiometric composition may also be included in the examples of the present invention as long as it is within the above-mentioned range. Further, even if the oxide layer is formed under the same alloy composition and conditions, the composition has a certain range depending on the measurement location. Therefore, in the present specification, the composition of the oxide layer 120 is an average value of values measured at 10 points in a plurality of fields of view of the obtained oxide layer. For the selection of the visual field, for example, 10 locations may be randomly selected from the region of the oxide layer for which the composition is to be specified, or the entire region is divided into 10 equal parts by the area ratio and one visual field is selected from each compartment. You can also select them one by one. In each field of view, the composition obtained from TEM-EDS can be represented by an average value obtained by arithmetically averaging.

The oxide layer 120 may be polycrystalline. The oxide layer 120 does not need to be composed of single crystals, and fine single crystals may be adjacent to each other. Oxide layer 120 made of an oxide represented by a range of parameters such as described above Mg _x M _y O _z becomes a dense oxide layer has a metallic luster and coloring.

The oxide layer 120 is preferably dense, but simply, if the coverage of the oxide layer 120 on the desired region of the surface of the substrate 110 is at least 70% or more, the oxide layer 120 is dense. Can be determined. As a result, the oxide layer 120 has a metallic luster and is colored. The coverage of the oxide layer 120 on the desired region of the surface of the substrate 110 is more preferably at least 80%, still more preferably 90% or more. As a result, the oxide layer 120 has corrosion resistance and develops color. The coverage can be easily measured by surface observation with a scanning electron microscope or the like, or by energy dispersion spectroscopy or the like in a region where oxygen is present.

The oxide layer 120 preferably has a thickness of 50 nm or more and 1 μm or less. Within this range, the Mg-based alloy 100 develops color in the examples of the present invention. The thickness of the layer can be changed from thin to thicker to purple, blue, patina, blue-green, green, yellow-green, yellow, orange, and red. Here, the thickness of the oxide layer 120 can be obtained by using an element mapping diagram of a cross section including the oxide layer using TEM-EDS. That is, the region where O atoms are detected corresponds to the oxide layer 120, and the region where O atoms are not substantially detected corresponds to the substrate 110. In the vicinity of these boundaries, the concentration distribution of O atoms is linearly approximated, the intermediate value of the concentration is defined as the boundary between the oxide layer 120 and the substrate 110, and the thickness from the surface to the boundary is defined as the thickness of the oxide layer. be able to.

The oxide layer 120 more preferably has a thickness of 100 nm or more and 350 nm or less. Within this range, in the examples of the present invention, the oxide layer 120 of the Mg-based alloy 100 is likely to be formed, and the color is developed. The thickness of the oxide layer 120 may be uniform or may be intentionally changed such as inclination to make it non-uniform. As long as the thickness is constant, in the embodiment of the present invention, the Mg-based alloy 100 can exhibit a specific color according to the thickness. In the embodiment of the present invention, the Mg-based alloy 100 can exhibit a complex color such as a gradation if the thickness is inclined or if the thickness is continuously changed. From this point of view, in the present specification, "the thickness of the oxide layer is non-uniform" means that the thickness of the oxide layer is increased or decreased for the purpose of complex coloration. , Other specific colors that are uniformly colored may be interpreted as "the thickness of the oxide layer is uniform". For example, in a member including the oxide layer 120, the color to be colored changes continuously with respect to the position. Specifically, when the position of the member is continuously changed, the wavelength of the color to be colored is continuous. When it changes, it includes complicated coloration. The color change is, for example, the seven colors of purple, blue, green-blue, blue-green, green, yellow-green, yellow, orange, red, or rainbow (for example, purple, indigo, blue, green, etc.). Yellow, orange, red) may span at least two colors. On the other hand, the uniform specific color is, for example, only one of the seven colors of purple, blue, green-blue, blue-green, green, yellow-green, yellow, orange, red, or rainbow of the above-mentioned coloration types. There may be.

The substrate 110 may be pure Mg or an Mg alloy. In the case of an Mg alloy, preferably Mg is the main component and Sc and / or Y is 0.1 at% or more and less than 50 at% (for example, Sc alone is 0.18% by weight or more and less than 65.0% by weight). In the case of Y alone, it is contained in the range of 0.37% by weight or more and less than 78.5% by weight). Thereby, the oxide layer 120 can be formed only by adopting the manufacturing method (thermal oxidation or anodizing) described later for such an Mg alloy. The amount of magnesium as a main component is intended to contain 50 at% or more. Needless to say, the substrate 110 contains unavoidable impurities.

The Mg alloy more preferably contains Mg as a main component and Sc and / or Y in the range of 0.3 at% or more and 40 at% or less. Within this range, the Mg alloy substrate 110 is more easily available.

Even more preferably, the Mg alloy contains Mg as a main component and Sc in the range of 3 at% or more and 40 at% or less (corresponding to 5.4% by weight or more and 55.2% by weight or less). By containing Sc alone in the above range excluding unavoidable impurities, it is possible to provide an Mg-based alloy having the above-mentioned oxide layer 120.

Even more preferably, the Mg alloy contains Mg as a main component and contains Y in the range of 0.5 at% or more and 3.5 at% or less (corresponding to 1.8% by weight or more and 11.7% by weight or less). By containing Y alone in the above range excluding unavoidable impurities, it is possible to provide an Mg-based alloy having the above-mentioned oxide layer 120.

Even more preferably, the Mg alloy contains Mg as a main component and Sc and Y in a range of 1.5 at% or more and 21.5 at% or less. By containing both Sc and Y in the above range except for unavoidable impurities, it is possible to provide an Mg-based alloy having the above-mentioned oxide layer 120. In this case, preferably, the Mg alloy contains more Sc than Y in the above range.

FIG. 2 is a cross-sectional view schematically showing another Mg-based metal member (for example, a plate material) in the embodiment of the present invention.

In the embodiment of the present invention, another Mg-based metal member 200 includes the above-mentioned Mg or Mg alloy substrate 110 and an oxide layer 220 that covers the surface of the substrate 110. Here, the oxide layer 220 contains at least Mg, Sc and / or Y, and O, like the oxide layer 120, except that the oxide layer 220 has a step on the surface. The step range D is preferably in the range of 5 nm or more and 15 nm or less. Such a step occurs because the growth rate of the oxide layer 220 differs depending on the orientation of the crystal grains of the substrate 110. In such an embodiment of the present invention, another Mg-based alloy 200 exhibits a stained glass tone (for example, a state in which the colors of adjacent regions are different) due to the step difference of the oxide layer 220, and has a design property. Can be further enhanced. Here, for example, a step is a height difference of steps, but in general, a step is a trapezoidal one or each of them that is piled up so as to rise upward, and the trapezoidal shape is (from the surroundings). It is a shape that is slightly taller and has a flat top. That is, it may be said that the difference in height is where the surfaces of the upper part and the lower part are substantially parallel in the place where there is a difference in height including the upper part and the lower part lower than the upper part. When there is a surface that continuously connects the upper part and the lower part, the angle formed by the surface and the surface of the upper part and the lower part may be an angle that can be said to be a step, for example, 30 degrees or more. When the connecting surface is curved, the angle formed by the surfaces can be specified by approximating with a flat surface. Further, here, the step does not only mean the amount of the difference in height, but can also be used as a term indicating such a shape. That is, the step as a shape can have a predetermined width or length, and this width or length may have a distance (or length) in which the above-mentioned height difference continues. In the embodiment of the present invention, the width or length is not particularly limited, but as described above, the step may depend on the direction of the crystal grains of the substrate 110. The Mg-based metal member 200 including such a step can exhibit various colors, and can be said to have a stained glass tone.

In such an embodiment of the present invention, the Mg-based metal members 100 and 200 are lightweight and have excellent corrosion resistance and design. Therefore, a watch, eyeglasses, tableware, or a portable electronic device such as a smartphone or a digital camera. It can be applied to decorative articles such as housings of equipment.

Next, a method for manufacturing the Mg-based metal member will be described in the above-described embodiment of the present invention.
FIG. 3 is a flowchart showing a manufacturing process of the Mg-based metal member in the embodiment of the present invention.

Step S310: The surface-polished Mg alloy is thermally oxidized in a temperature range of more than 50 ° C. and less than 800 ° C. in an atmosphere containing at least oxygen. Here, the Mg alloy contains magnesium (Mg) as a main component and scandium (Sc) and / or yttrium (Y) in a range of 0.1 at% or more and less than 50 at%. By performing thermal oxidation under such conditions, the above-mentioned oxide layer is formed. The inventor of the present application has found that a Mg-based alloy that develops color while maintaining metallic luster can be obtained by simply heat-oxidizing it without using paints and dyes that have been conventionally required. Prior to step S310, a step of preparing a surface-polished Mg alloy may be provided. The oxygen-containing atmosphere described above may include, for example, the atmosphere. If the amount of oxygen contained is small, sufficient oxygen may not be supplied, and a sufficient amount of oxygen may be contained to form an oxide layer. For example, the oxygen partial pressure may be 10 Pa or more, 100 Pa or more, or 1 kPa or more. Further, if too much oxygen is contained, Mg is a relatively active metal, so that the quality of the oxide layer may deteriorate due to an excessive reaction or the like, and the amount of the oxide layer is not hindered from being formed. It may contain oxygen. For example, the oxygen partial pressure may be 100 MPa or less, 10 MPa or less, or 1 MPa or less.

Here, the Mg alloy functions as the above-mentioned substrate 110, and the Mg alloy having the above-mentioned composition is adopted, but it is avoided to explain in duplicate. Further, the Mg alloy is not particularly limited as long as it has the above-mentioned composition, and an available Mg alloy can be used. For example, it may be produced by high-frequency melting and, if necessary, by rolling. The production of such an alloy is carried out, for example, by the methods described in Patent Document 1 and Non-Patent Document 1.

Since the surface of the Mg alloy is surface-polished, a dense oxide layer is formed. For surface polishing, well-known methods such as hand polishing, mechanical polishing, chemical polishing, and electrolytic polishing are adopted. Here, it is preferable to polish the surface so that the surface roughness Ra is 0.0001 μm or more and 2.0 μm or less. As a result, the surface of the Mg alloy becomes a mirror surface or a micro mirror surface, and a dense oxide layer is formed by the subsequent thermal oxidation, and the adhesion between the oxide layer and the substrate is excellent. For hand polishing, for example, abrasive paper to which an abrasive material such as silicon carbide (SiC), zirconium corundum, or boron carbide is applied is used. As the mechanical polishing, wet polishing using polishing fine powder such as diamond, cubic boron nitride, silicon carbide, and alumina can be adopted as an example. For the chemical polishing, for example, a phosphoric acid-nitric acid method using nitric acid, a Kaiser method, an Alupol method using sulfuric acid, or the like can be adopted. As the electrolytic polishing, the Erfwerk method and the Aulflex method can be adopted, for example. The surface roughness Ra is preferably 0.05 μm or more and 2.0 μm or less from the viewpoint of adhesion.

Further, by controlling the surface roughness, the design property based on the obtained oxide layer can be freely changed. The smaller the surface roughness Ra, the higher the metallic luster of the Mg-based metal member, and the larger the surface roughness Ra, the more the Mg-based metal member has a matte surface such as frosted glass. For example, if the surface roughness Ra is controlled to 0.0001 μm or more and 0.2 μm or less, the Mg-based metal member has a metallic luster, and if the surface roughness Ra is controlled to exceed 0.2 μm and 1.6 μm or less, the surface roughness Ra becomes 1.6 μm or less. It is an Mg-based metal member with a matte surface.

Thermal oxidation is performed by installing a surface-polished Mg alloy in an arbitrary furnace such as an electric furnace or an atmosphere furnace and heating it in an atmosphere containing oxygen. The treatment temperature may be appropriately selected according to this atmosphere and other conditions. For example, when the heating and holding temperature is 50 ° C. or lower, the oxide layer may not be sufficiently formed. If the holding temperature exceeds 800 ° C., the Mg alloy may melt. Thermal oxidation is preferably carried out in the range of 300 ° C. or higher and 700 ° C. or lower. In this range, the above-mentioned oxide layer can be formed.

Thermal oxidation is preferably carried out for 5 minutes or more and 100 days or less. The thickness of the obtained oxide layer can be controlled by the temperature and time of thermal oxidation. For example, when thermal oxidation is performed at a low temperature for a short time, a thin oxide layer is formed, and the thickness of the oxide layer becomes thicker as the temperature of thermal oxidation increases or the time increases. In order to obtain an oxide layer having a desired thickness, those skilled in the art can appropriately select the temperature and time of thermal oxidation from the above range.

FIG. 4 is a flowchart showing another manufacturing process of the Mg-based metal member in the embodiment of the present invention.

Step S410: The surface-polished Mg alloy is anodized in an electrolytic solution. Here, the Mg alloy contains magnesium (Mg) as a main component and scandium (Sc) and / or yttrium (Y) in a range of 1 at% or more and less than 50 at%. By anodizing under such conditions, the above-mentioned oxide layer is formed. The inventor of the present application has found that a Mg-based alloy that develops color while maintaining metallic luster can be obtained by simply anodizing, without using paints and dyes that have been conventionally required. Here, since the Mg alloy is as described above, the description thereof will be omitted. Here, too, a step of preparing a surface-polished Mg alloy may be provided prior to step S410.

As the electrolytic solution, an electrolytic aqueous solution containing hydroxides, carbonates, bicarbonates, silicates or silica fluorides of Group 1 and Group 2 elements of the periodic table can be used. Illustratively, hydroxides such as NaOH, KOH, Ba (OH) ₂ , carbonates such as _{Na 2} CO ₃ , K ₂ CO ₃ , CaCO ₃ , MgCO _{3 , NaHCO 3} , KHCO ₃ , Ca (HCO ₃₎ ) _2nd grade bicarbonate etc. can be used. The concentration in the electrolytic solution is preferably in the range of 0.1 or more and 5 or less.

The anodizing is preferably carried out in a voltage range of 2 V or more and 40 V or less, and a current density of 0.5 A / dm ² or more and 20 A / dm ² or less. Within this range, the above-mentioned oxide layer can be formed. The anodizing is more preferably performed in a voltage range of 5 V or more and 15 V or less, and a current density of 1 A / dm ² or more and 10 A / dm ² or less. Also, preferably, anodization is carried out for 5 minutes or more and 20 minutes or less. The thickness of the obtained oxide layer can be controlled by the voltage and time of anodization. For example, anodizing at a low voltage for a short time results in a thin oxide layer, and the thickness of the oxide layer increases as the voltage increases or the time increases. In order to obtain an oxide layer having a desired thickness, those skilled in the art can appropriately select the voltage and time of anodization from the above ranges.

Anodization is preferably carried out with an electrolytic solution in a temperature range of 0 ° C. or higher and 35 ° C. or lower. Thereby, the above-mentioned oxide layer can be formed.

In both the thermal oxidation described with reference to FIG. 3 and the anodizing described with reference to FIG. 4, by using an Mg alloy having random surface crystal grain orientations, as shown in FIG. It is possible to produce an Mg alloy having an oxide layer having a step and having excellent brilliance. The Mg alloy containing Sc having a random surface crystal grain orientation is described in, for example, Y. Manufactured with reference to Ogawa et al., Scripta Materia, 128 (2017) 27-31. The existence of a step in the oxide layer between crystal grains can be easily confirmed by an optical microscope, but can be confirmed in detail by an atomic force microscope, a laser microscope, or a transmission electron microscope.

As described above, the inventor of the present application can form the above-mentioned oxide layer by simply performing thermal oxidation or anodizing using an Mg alloy containing Sc and / or Y, without having a paint or a dye. , It has been found that it is possible to provide an Mg-based metal member having excellent designability, which maintains metallic luster and develops color.

Although not shown, an oxide layer is formed on the surface of pure Mg or the above-mentioned Mg alloy by a physical vapor deposition method or a chemical vapor deposition method using scandium (Sc) and / or yttrium (Y) as a source. It may be formed. Even in this way, the above-mentioned oxide layer can be obtained.

Next, the present invention will be described in detail with reference to specific examples, but it should be noted that the present invention is not limited to these examples.

[Hypokeimenon 1-29]
High-frequency melting (NEV-M5T manufactured by Nissin Giken Co., Ltd.) using commercially available Mg metal (purity 99.9%), Sc metal (purity 99.9%) and Y metal (purity 99.9%) as raw materials, respectively. )did. The Mg metal, Sc metal and Y metal were mixed so as to satisfy the composition ratios shown in Table 1.

Hypokeimenons 1, 2 and 8 to 27 were manufactured as follows. After the raw material was melted, it was not cast and used as a crucible stopper, and high-purity alumina was used for the crucible. The obtained ingot was subjected to a compression ratio of 10%, strained by cold rolling, and heat-treated at 600 ° C. for 16 hours. Then, if necessary, it was heat-treated at 500 to 700 ° C. and cooled with water. This is a treatment for making the characteristics of the substrate desired, and the oxide film on the surface formed during this heat treatment was removed in the subsequent treatment. Next, the obtained plate-shaped Mg-based alloy was mirror-polished using silicon carbide (SiC) polishing paper, diamond paste and a polishing suspension. The Mg-based alloys thus obtained are referred to as substrates 1, 2 and 9 to 27, respectively. Since the substrate 8 did not form an alloy because the Sc content was too high, the subsequent treatment was not performed.

The substrates 3 to 7 were manufactured as follows. After the raw material was melted, it was not cast and used as a crucible stopper, and high-purity alumina was used for the crucible. The obtained ingot was hot-rolled at 600 ° C. After hot rolling, cold rolling was performed while appropriately annealing at 600 ° C. for 10 minutes until a plate having a thickness of about 0.7 mm was formed. Then, if necessary, it was heat-treated at 500 to 700 ° C. and cooled with water. Next, the obtained plate-shaped Mg-based alloy was mirror-polished using silicon carbide (SiC) polishing paper, diamond paste and a polishing suspension. The Mg-based alloys thus obtained are referred to as substrates 3 to 7, respectively.

It was confirmed by composition analysis (energy dispersive X-ray spectroscopy (EDX)) that the compositions of the substrates 1 to 27 corresponded to the charged compositions in Table 1. The surface roughness Ra of the substrates 1 to 7 and 9 to 27 after mirror polishing was in the range of 0.05 μm or more and 0.2 μm or less. The roughness was measured using an atomic force microscope under the conditions conforming to JIS R 1683: 2014.

The substrate 28 was pure Mg. The substrate 29 was AZ31 (Zn: 3 wt%, Al: 1 wt%).

The substrates 1 to 7 and 9 to 29 were formed into a rectangular plate having a size of 10 mm × 10 mm × 0.5 to 5 mm, and subsequent thermal oxidation or anodization was carried out.

[Examples / Comparative Examples 1 to 34]
Thermal oxidation was performed using the substrates 1 to 7 and 9 to 29 under the conditions shown in Table 2. Specifically, each substrate was placed in an electric furnace and thermally oxidized in the air at the temperatures and times shown in Table 2. In the sample of Comparative Example 32, the metal was dissolved by the heat treatment, so no further measurement was performed.

[Example / Comparative Example 35-53]
Anodizing was performed using the substrates 3, 5, 12, 22 and 26 under the conditions shown in Table 3. Specifically, each substrate was immersed in a predetermined sodium hydroxide bath and electrolyzed as a pair of electrodes with a carbon rod. The electrolyte temperature was 25 ° C.

The samples obtained in Examples / Comparative Examples 1 to 53 were subjected to a surface and a transmission electron microscope (TEM, manufactured by JEOL Ltd., JEM-2100F) equipped with energy dispersive X-ray spectroscopy (EDX). The cross section was observed to obtain a diffraction pattern. In addition, the element mapping of the obtained sample was examined by EDX, and the composition was determined by point analysis. The composition was set at 10 locations on the surface of the sample and used as an average value. These results are shown in FIGS. 5 to 8 and Table 4.

Furthermore, the state of the surface of the obtained sample was observed, and the presence or absence of metallic luster and the coloration state were examined. The coverage of the oxide layer was determined by a scanning electron microscope (SEM, manufactured by JEOL Ltd., JSM-7000F). Further, a Scotch tape test (JIS H 8504: 1999 "Plating adhesion test method") was carried out on the obtained sample to examine the adhesion. Moreover, the obtained sample was immersed in water (25 ° C.) for 3 days, and the corrosion resistance was examined. These results are shown in Table 5.

FIG. 5 is a diagram showing a TEM image of a cross section of the sample of Example 40.
FIG. 6 is a diagram showing an enlarged TEM image of the cross section of the sample of Example 40.

According to FIG. 5, it can be seen that the layer (film) is located on the substrate. The thickness of this layer was 180 nm. According to FIG. 6 which was further enlarged, microcrystals were confirmed in the layer. Although not shown, other examples showed similar aspects.

FIG. 7 is a diagram showing an electron diffraction pattern in the region indicated by the circle in FIG.

FIG. 7 showed a spotty ring pattern and the layers were found to be polycrystalline. Although not shown, other examples showed similar aspects. Here, "spotty" means that it is in a sporty state, and specifically, it may mean a state in which there are many spots. Therefore, it can be seen that this oxide layer contains a polycrystal in which fine crystal phases having different crystal orientations are mixed.

FIG. 8 is a diagram showing element mapping of a cross section of the sample of Example 40.

FIG. 8A shows a TEM image of a cross section of the sample of Example 40, and it can be seen that the layer is located on the substrate. 8 (B) to 8 (D) are elemental mappings of oxygen (O), magnesium (Mg) and scandium (Sc) in the layers shown in FIG. 8 (A), respectively. Although the drawings are shown in grayscale, the regions shown brightly at the same positions as the layers shown in FIG. 8 (A) correspond to each element. According to this, it can be seen that oxygen, magnesium and scandium are dispersedly located in the layer. Although not shown, other examples showed similar element mapping.

From these, using an Mg alloy as a substrate, in the examples of the present invention, magnesium, scandium and / or yttrium, and oxygen were added to the Mg alloy by thermal oxidation shown in FIG. 3 and anodizing shown in FIG. It was shown that an oxide layer containing and was formed. According to Table 4, the oxide _layer, Mg _x M y _{O z} (provided that, x + y + z = 1 , M is a is Sc and / or Y) is represented by the parameters x, y and z,
0.003 ≤ x ≤ 0.8
0.03 ≤ y ≤ 0.65
0.005 ≤ z ≤ 0.95
It was found that it was a polycrystal satisfying the above conditions.
The oxide layer is, as long as represented by Mg _x M _y O _z to above may be interpreted as the same oxide is considered to have the same properties and performance. It was experimentally confirmed that this oxide layer contained such a fine crystal phase having the same properties and performance. Therefore, the oxide (or composite oxide) can be specified within the range of such a composition. Here, Sc and Y are both Group 3 elements belonging to the transition metal, their atomic radii are close to 162 pm and 180 pm, and their oxidation numbers may be 3, 2 and 1, and the crystals can be replaced with each other. Can be included in the phase. It was also found that they have the same properties and performance regardless of whether they are formed by thermal oxidation or anodizing. Further, it is considered that when x is larger than y, the oxide layer tends to be coarse as described above, and conversely, when x is smaller, the oxide layer tends to be dense. If the oxide layer becomes too coarse or too dense, its characteristics may deteriorate.
Further, in Table 4, the thickness of the layers of Comparative Examples 34 and 53 cannot be measured due to the large unevenness, but this is because the oxide layer was not continuously formed on the surface of the substrate. This is due to the occurrence of an abnormal value in the (roughness) direction.

According to Table 5, in the examples of the present invention, Examples 1 to 31 and 35 provided with an oxide layer obtained by thermal oxidation shown in FIG. 3 and anodized shown in FIG. 4 and satisfying the above composition. It was confirmed that the samples (Mg-based alloys) of ~ 52 had a metallic luster, exhibited various colors due to the interference of the oxide layer, and were excellent in designability. It was also shown that the coloration can be controlled by changing the thickness of the oxide layer. The samples of all the examples were shown to have high adhesion of the oxide layer without peeling by the tape test. Furthermore, the samples of all the examples had corrosion resistance although some corrosion was observed. In particular, it was shown that the higher the coverage of the oxide layer (for example, 90% or more), the better the corrosion resistance.

According to Table 5, the samples of Examples 46 and 47 having non-uniform layer thickness showed gradation coloration. In addition, the sample of Example 39 had a stained glass tone. When the sample of Example 39 was observed with an optical microscope, it was found that the crystal grains of the substrate were random and that the surface of the oxide layer had a step in the range of 5 nm or more and 15 nm or less.

As described above, in the examples of the present invention, an Mg alloy containing Sc and / or Y is used as a substrate, and simply by performing thermal oxidation or anodizing, metallic luster is provided and color is developed. It was shown that an Mg-based alloy having excellent designability can be provided. Further, such an Mg-based alloy having excellent designability is also excellent in corrosion resistance. The shape of the substrate is not particularly limited, but the shape of the substrate is preferably close to the shape of the final product. For example, it may be a plate-shaped member as shown in FIG.

In the examples of the present invention, the Mg-based metal member having an oxide layer has a metallic luster and coloration, and is therefore excellent in designability. The oxide layer is also excellent in corrosion resistance. Such Mg-based metal members are applied to decorative articles such as watches, eyeglasses, tableware, and housings of portable electronic devices such as smartphones and digital cameras. For example, the Mg-based metal member of the embodiment of the present invention can be applied to the clock frame 310 of the clock 300 shown in FIG. Further, the Mg-based metal member of the embodiment of the present invention can be applied to the spectacle frame 410 of the spectacles 400 shown in FIG. The Mg-based metal member of the embodiment of the present invention can be applied to the tableware (plate) 500 shown in FIG. The Mg-based metal member of the embodiment of the present invention can be applied to the frame 610 of the smartphone 600 shown in FIG. Here, since the oxide layer is easily subjected to surface strain when it is deformed into a predetermined shape, it is preferable to perform thermal oxidation or anodizing treatment to form the surface oxide layer in a state where the shape is almost finished. ..

100, 200 Mg-based metal member 110 Mg or Mg alloy substrate 120, 220 Oxide layer 300 Clock 310 Watch frame with Mg-based metal member 400 Eyeglasses 410 Eyeglass frame with Mg-based metal member 500 Mg-based metal Tableware (plate) to which the material is applied
600 Smartphone 610 Frame to which Mg-based metal member is applied

Claims (20)

With a magnesium or magnesium alloy substrate,
Provided with an oxide layer covering the surface of the substrate,
The oxide layer is a magnesium-based metal member containing at least magnesium (Mg), scandium (Sc) and / or yttrium (Y) and oxygen (O). The oxide _layer, Mg _x M y _{O z} (provided that, x + y + z = 1 , M is Sc and / or Y) is represented by the parameters x, y and z,
0.003 ≤ x ≤ 0.8
0.03 ≤ y ≤ 0.65
0.005 ≤ z ≤ 0.95
The magnesium-based metal member according to claim 1. The parameters x, y and z are
0.2 ≤ x ≤ 0.75
0.2 ≤ y ≤ 0.4
0.005 ≤ z ≤ 0.45
The magnesium-based metal member according to claim 2, which satisfies the above conditions. The magnesium-based metal member according to any one of claims 1 to 3, wherein the oxide layer is polycrystalline. The magnesium-based metal member according to any one of claims 1 to 4, wherein the coverage of the oxide layer on the substrate is 70% or more. The magnesium-based metal member according to any one of claims 1 to 5, wherein the oxide layer has a thickness in the range of 50 nm or more and 1 μm or less. The magnesium-based metal member according to claim 6, wherein the oxide layer has a thickness in the range of 100 nm or more and 350 nm or less. The magnesium-based metal member according to any one of claims 1 to 7, wherein the magnesium alloy contains magnesium as a main component and scandium and / or yttrium in a range of 0.1 at% or more and less than 50 at%. The magnesium-based metal member according to claim 8, wherein the magnesium alloy contains magnesium as a main component and scandium and / or yttrium in a range of 0.3 at% or more and 40 at% or less. The magnesium-based metal member according to any one of claims 1 to 9, wherein the oxide layer has a uniform thickness. The magnesium-based metal member according to any one of claims 1 to 9, wherein the oxide layer has a non-uniform thickness. The magnesium-based metal member according to any one of claims 1 to 11, wherein the oxide layer has a step in the range of 5 nm or more and 15 nm or less on the surface. A surface-polished magnesium alloy containing magnesium as the main component and scandium and / or yttrium in the range of 0.1 at% or more and less than 50 at% in an atmosphere containing at least oxygen, more than 50 ° C and less than 800 ° C. The method for producing a magnesium-based metal member according to any one of claims 1 to 12, which comprises a step of thermally oxidizing in a temperature range. The method according to claim 13, wherein the thermal oxidation step is performed in a temperature range of 300 ° C. or higher and 700 ° C. or lower. The method according to claim 13 or 14, wherein the thermal oxidation step is carried out for 5 minutes or more and 100 days or less. The invention according to any one of claims 1 to 12, further comprising anodizing a magnesium alloy containing magnesium as a main component and scandium and / or yttrium in a range of 0.1 at% or more and less than 50 at% in an electrolytic solution. Method for manufacturing magnesium-based metal members. The method according to claim 16, wherein the step of anodizing applies a voltage of 2 V or more and 40 V or less. The method according to claim 16 or 17, wherein the anodizing step is carried out for 5 minutes or more and 20 minutes or less. It is a decorative article using magnesium-based metal.
The decorative article, wherein the magnesium-based metal is the magnesium-based metal member according to any one of claims 1 to 12. The decorative article according to claim 19, wherein the decorative article is selected from the group consisting of a clock, eyeglasses, tableware, and a housing of a portable electronic device.

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