JP2013091856A - Method for manufacturing hardened aluminum material using cross coupling reaction - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a hardened aluminum material having a thick hardened layer whose surface is very hard and which becomes gradually soft from the surface to the inside.SOLUTION: The method for manufacturing a hardened aluminum material is a method to harden the surface of an aluminum alloy material containing the element Mg, and includes a first step and a second step. In the first step, a nickel layer 20 of 15 μm in thickness is formed on the surface of an aluminum alloy material 10. In the second step, the aluminum alloy material 10 formed of the nickel layer 20 is heated up to 550° and held for 60 to 90 minutes. Thus, the element Mg in a base material (aluminum alloy material 10) can become a catalyst and an Mg ion and an Al ion are diffused toward the surface of the nickel layer 20 to form a hardened layer of high hardness intermetallic compound of Al and Ni.

Description

  In the present invention, when a nickel layer having an appropriate thickness is formed on the surface of an aluminum alloy material containing Mg element and heated to 500 to 600 degrees, the surface layer part is formed by a cross-coupling reaction using Mg ions as a catalyst. Is a processing method showing that a film of an intermetallic compound such as high hardness AlNi, Al3Ni, Al3Ni2, AlNi3, Al3Ni5 (hereinafter referred to as AlmNin as appropriate) can be formed.

  Until now, most of the components of automobiles have been composed of steel parts having a relatively large specific gravity. However, in order to improve fuel efficiency, a low-specific gravity and light base material has been demanded instead of steel parts. Therefore, an aluminum alloy material that is about one third of the specific gravity of iron has attracted attention as an alternative material. However, although the aluminum alloy material is a light specific gravity material, the strength and the like are greatly inferior to those of the steel material even when subjected to a normal heat treatment. Furthermore, since an aluminum alloy material forms an inactive oxide film on the outermost surface in the air, surface hardening treatment such as nitriding treatment is difficult. Therefore, a surface hardening method for improving the surface hardness of the aluminum alloy material has also been proposed. One of them is the following example.

  The following Patent Document 1 describes a surface hardening method for performing ion (plasma) nitriding treatment. In this surface hardening method, first, an iron-chromium alloy plating layer is formed on the surface of an aluminum alloy material by a plating method, and then ion nitriding treatment is performed on the plated aluminum alloy material. In this ion nitriding treatment, nitrogen ions collide with the surface of the treated product with high energy by glow discharge. Nitrogen ions react with iron-chromium during collision and enter and diffuse from the surface of the treated product to form a hardened (nitrided) layer of 5 to 20 μm made of chromium nitride. Thereby, the Vickers hardness of the surface of an aluminum hardening material can be enlarged to 700-1200HV.

Japanese Patent Laid-Open No. 06-235096

However, the ion nitriding process of Patent Document 1 has the following problems.
First, it is difficult to form the above-mentioned very hard cured layer of 20 μm or more, and the cured layer becomes very thin. The reason is that the formation of chromium nitride on the surface makes it difficult for the glow discharge to activate the nitrogen ions to be sustained, making it difficult for the nitrogen ions to penetrate and diffuse into the treated product.
A portion where nitrogen ions do not enter and diffuse, that is, a portion where the hardened layer is not formed is softer than the hardened layer. For this reason, the aluminum hardening material of the said patent document 1 does not become soft gradually from the surface toward the inside, but has a very hard and thin hardened layer only near the surface. Therefore, when using the aluminum hardening | curing material of the said patent document 1 in the place where sliding friction is very large, a thin hardened layer is consumed quickly and is unpreferable on product safety. Moreover, when twist etc. acted on the aluminum hardening material of the said patent document 1, there existed a possibility that a crack or peeling might arise in the boundary part of a hardening layer.

  The present invention has been made to solve the above-described problems, and provides a method for producing an aluminum hardened material having a thick hardened layer whose surface is very hard and gradually softens from the surface toward the inside. With the goal.

  A method for producing an aluminum hardened material according to the present invention is a method for surface hardening an aluminum alloy material containing magnesium element, wherein a nickel layer is formed to a thickness of 10 μm or more after removing an oxide film on the surface of the aluminum alloy material. And a second step of heating the aluminum alloy material on which the nickel layer is formed at a temperature of 500 ° C. or more and 600 ° C. or less for a predetermined time. In the second step, based on the thickness of the nickel layer and the heating temperature, magnesium ions and aluminum ions in the base material diffuse toward the surface of the nickel layer, and metal is formed by a cross-coupling reaction. It is necessary to hold for a predetermined time until the intermetallic compound is formed on the surface layer.

  According to the present invention, since the heating temperature of the heat treatment is a high temperature atmosphere of 500 ° C. or more and 600 ° C. or less, the Mg (magnesium) element having a low vapor pressure is ionized and actively diffuses toward the surface layer portion. At that time, the ionized Mg element induces the surrounding ionized Al (aluminum) element and moves toward the surface layer portion of the aluminum alloy material. And the Al ion induced to the surface layer part combines with Ni (nickel) element ionized in the surface layer part, and intermetallic compounds (AlmNin) such as AlNi, Al3Ni, Al3Ni2, AlNi3, Al3Ni5 with high hardness Generate. That is, in a high temperature atmosphere, Mg element acts as a catalyst to react ionized Al element and Ni element to produce a high hardness intermetallic compound. As a result, the depth of the hardened layer becomes 1.5 or more times the thickness of the hardened layer obtained by plating or the like, and an aluminum hardened material having a thick hardened layer that gradually softens toward the inside can be manufactured.

  Moreover, in the manufacturing method of the aluminum hardening | curing material which concerns on this invention, you may heat in the decompression room | chamber interior of the low vacuum state of 100 Pa or less at the said 2nd process. In this case, since the heat treatment is performed in a low oxygen concentration state, a hardened aluminum material with a clean surface can be produced, and the function of the ionized Mg element as a catalyst becomes active, and the reaction treatment time Can be shortened. Further, in the second step, heating may be performed by glow discharge using an external heating type ion vacuum furnace.

  According to the present invention, it is possible to manufacture an aluminum hardened material having a thick hardened layer whose surface is very hard and gradually softens from the surface toward the inside. The manufactured aluminum hardened material is preferable in terms of product safety because the hardened layer does not wear out quickly even if it is used in parts where the sliding friction is extremely large in parts constituting an automobile, etc. Even so, cracking or peeling is unlikely to occur at the boundary portion of the hardened layer. Moreover, if it is used for a wristwatch band or a wristwatch display case, an ideal product that is light and hardly scratched can be expected.

It is the schematic which showed the aluminum alloy material which is a base material. It is the schematic which showed the aluminum alloy material in which the nickel layer and the chromium layer were formed by the 1st process. It is the schematic which showed the aluminum hardening material in which the hardened layer was formed by the 2nd process. It is a phase diagram of a binary alloy of aluminum and magnesium. It is a hardness transition curve of the aluminum hardening material of this embodiment. It is a component table | surface which showed weight% of each metal element in each spectrum of the aluminum hardening | curing material of this embodiment. It is an electron microscopic image of a surface part, when carrying out the surface hardening process of the aluminum alloy material containing a magnesium element. It is a binary phase diagram of aluminum and nickel. It is a hardness transition curve of the aluminum hardening material of a comparative example. It is a component table | surface which showed weight% of each metal element in each spectrum of the aluminum hardening | curing material of a comparative example. It is an electron microscopic image of a surface part, when carrying out surface hardening processing of the aluminum alloy material which does not contain magnesium.

  Embodiments of a method for producing a cured aluminum material according to the present invention will be described below with reference to the drawings. FIG. 1 is a schematic view showing an aluminum alloy material 10 which is a base material for producing a hardened aluminum material. The aluminum alloy material 10 is No. 6061 in JIS standard, and Mg by weight is 0.8 to 1.2%, Si is 0.4 to 0.8%, Fe is 0.7%, Cu 0.15 to 0.40%, Mn 0.15%, Cr 0.04 to 0.35%, Ti 0.15%, and the remaining Al. Here, the aluminum alloy material 10 only needs to contain Mg element. For example, the aluminum alloy material 10 may be those in the 5000s and 6000s according to JIS standards. The aluminum alloy material 10 is subjected to surface hardening treatment by the following first and second steps.

<First step>
FIG. 2 is a schematic view showing the aluminum alloy material 10 on which the nickel layer 20 and the chromium layer 30 are formed in the first step. Here, since the aluminum alloy material 10 shown in FIG. 1 has a very high affinity with oxygen, it has a thin oxide film (alumina layer) of about 100 angstroms on the surface. With this oxide film, a plating layer having good adhesion cannot be directly formed on the surface of the aluminum alloy material 10. Therefore, in the first step, first, the aluminum alloy material 10 is immersed in a zinc acid solution to remove the oxide film. Since the aluminum alloy material 10 from which the oxide film has been removed is transferred to the next step in the plating solution, no new oxide film is formed on the surface. Then, a 15 μm nickel layer 20 is formed on the surface of the aluminum alloy material 10 by electroless plating. Thereafter, a 0.2 μm chromium layer 30 is formed on the surface of the nickel layer 20 by electroplating. Thus, the aluminum alloy material 10 (hereinafter referred to as “plating layer-attached alloy material 10A”) on which the nickel layer 20 and the chromium layer 30 are formed is formed. In the present embodiment, the chromium layer 30 is formed for the purpose of preventing oxidation of the outermost surface, but there is no problem even if the chromium layer 30 is not actually provided. The method of forming the nickel layer 20 is not limited to the electroless plating method, and can be changed as appropriate. The nickel layer 20 may be formed by an electroplating method or a nickel powder bonding method.

<Second step>
FIG. 3 is a schematic view showing the aluminum hardened material 10B on which the hardened layer T1 is formed in the second step. In the second step, first, in order to lower the oxygen partial pressure in the decompression chamber (vacuum furnace), it is evacuated to about 0.1 Torr (about 13.3 Pa) or less by a vacuum pump. Then, the pressure in the vacuum chamber is restored to about 500 Torr (about 66500 Pa) with nitrogen as an inert gas. In this state, the temperature is raised to 450 to 500 degrees. This is because heat conduction by gas convection is much faster than vacuum radiant heating. After raising the temperature by heating to 450 to 500 degrees, the pressure in the decompression chamber is reduced to a low vacuum state of about 20 Pa (about 2.0 × 10 ⁻⁴ atm). This is a preparation for a cross-coupling reaction. In this reduced-pressure atmosphere, the vacuum chamber is heated to 550 degrees (can be used up to 600 degrees for mass production) and kept soaked for 60 to 90 minutes. During this time, the Mg element of the aluminum alloy material 10A is ionized and moves and diffuses to the nickel layer 20 in the surface layer portion of the aluminum alloy material 10A together with surrounding ionized Al ions. In the surface layer portion of the aluminum alloy material 10A, Al ions and Ni ions induced by Mg ions are continuously generated by a cross coupling reaction. After holding 550 degrees x soaking time 60 minutes to 90 minutes, the furnace is cooled to 500 degrees to 450 degrees in this vacuum atmosphere. The reason for gradually cooling in this way is to prevent peeling of the produced intermetallic compound. That is, between the hard intermetallic compound layer produced by the cross-coupling reaction and the core material of the core that is thermally expanded, a considerable tensile stress should be exerted between the two due to cooling. In order to reduce the stress between the two, it is necessary to reduce the cooling rate of the workpiece. When the furnace temperature reaches around 500 to 450 degrees, the pressure is restored to 500 Torr, the fan is cooled to near room temperature, and the pressure is changed to atmospheric pressure, and the finished aluminum hardened material 10B is taken out.
When heat treatment is performed by glow discharge using an ion vacuum furnace, it is preferable to use an externally heated ion vacuum furnace that heats the inside of the decompression chamber from the outside. In a normal ion vacuum furnace, it is difficult to continuously maintain a set temperature at a set temperature only during a period of ion sputtering in which a workpiece having a small mass is heated to a set temperature during discharge of the workpiece at the time of glow discharge. Therefore, an ion vacuum furnace having a heating element on the outside of the vacuum vessel is necessary for heat treatment of mass production of parts having a small mass. In this case, the workpiece (alloy material with plating layer 10A) to be heated can be heat-treated without being cooled, and the heat treatment can be stably performed.
Note that the heat treatment can be performed using an atmospheric furnace in addition to a normal vacuum furnace or an ion vacuum furnace, regardless of the length of surface oxidation or heat treatment time.

Here, the reason why the heating temperature is set to 550 degrees will be described with reference to FIG. FIG. 4 is a phase diagram of a binary alloy of aluminum and magnesium. First, the heating temperature needs to be a temperature above the solidus line SL shown in FIG. 4 and a temperature below the liquidus line LL shown in FIG. That is, the temperature is 450 degrees or more and 660 degrees or less. This is because the solid phase of Mg and Al is melted to make Mg and Al ionized in the base material (aluminum alloy material 10) easy to move.
By the way, the melting point of Al is 660 degrees. For this reason, when the alloy material 10A with a plating layer is heated to around 660 degrees, Al changes from a solid to a liquid and the base material is plastically deformed. On the other hand, the inventor has experimentally confirmed that cracking tends to occur when the plated layer-attached alloy material 10A is heated to 480 degrees under the above-described conditions. Therefore, it has been found that in this embodiment, it is preferable to heat the plated layer-attached alloy material 10A at a temperature of 500 degrees or more and 600 degrees or less.

  The reason why the pressure in the decompression chamber is reduced to about 20 Pa is that the heat treatment is performed in a low oxygen concentration state, so that the hardened aluminum material 10B having a clean surface can be manufactured. Furthermore, it is because it becomes easy to move actively so that the Mg ion ionized within the base material evaporates, and the reaction processing time can be shortened. However, the heat treatment is not necessarily performed in a low vacuum state such as 100 Pa or less, and even in an atmospheric pressure state, the treatment time is required and some oxidation of the surface cannot be avoided, but the heat treatment can be performed.

  Next, the component of the metal element in the manufactured aluminum hardening material 10B is demonstrated using FIG.6 and FIG.7. This aluminum hardened material 10B is analyzed using a scanning electron microscope and an energy dispersive X-ray analyzer (SEM-EDX). FIG. 7 is an electron microscope image of the surface portion of the aluminum hardened material 10B, and FIG. 6 is a component table showing the weight percentage of each metal element in each spectrum of the aluminum hardened material 10B of the present embodiment. As SEM-EDX, Hitachi-Hitec S-4800 & Horiba EX350-act is used. As an analysis condition, the acceleration voltage is set to 20 kV.

  In FIG. 7, in the first layer S1 on the surface side of the hardened aluminum material 10B, that is, in the range of spectra 1 to 3, the color is darker than the lower second layer S2. This first layer S1 is an extremely hard portion. The color is lighter in the second layer S2 below the first layer S1, that is, in the range of spectra 4-8. The second layer S2 is a portion where the properties of the nickel layer 20 remain largely. Further, the color is darker in the third layer S3 below the second layer S2, that is, in the range of the spectrum 9-11. The third layer S3 is a portion where the properties of the base material (aluminum alloy material 10) and the properties of the nickel layer 20 are mixed.

  In FIG. 6, the depth (μm) from the surface and the weight% of each metal element are shown for each spectrum. Here, first, the weight% of Mg, Al, Ni in the first layer S1 will be described. The first layer S1 has a spectrum in the range of 1 to 3, and is a portion having a depth from the surface of 0.00 to about 3.73 μm. The first layer S1 is a portion in which a 0.2 μm chromium layer 30 is formed on the surface and a 15 μm nickel layer 20 is formed under the chromium layer 30 before the second step. Since the chromium layer 30 is a very thin layer, the weight percentage of Cr is ignored. In the first layer S1 before passing through the second step, the nickel layer 20 contains an extremely large amount of Ni (for example, 80% or more). However, as a result of passing through the second step, as shown in FIG. 6, in the first layer S1, Ni is reduced to 20% or less, while Al is 70% or more. This is considered to be due to evaporation and transfer from the inside of the base material to the surface layer portion while acting as a catalyst (Mg ions) and remaining in the surface layer portion by 5% or more. That is, the following can be considered.

  In the first layer S1, if there is 5% or more of Mg that hardly exists unless the second step is performed, it is considered that the second layer has moved in an ionized state from the inside of the base material to the surface layer portion. In addition, Al that hardly exists without passing through the second step is 70% or more. The Mg itself that has moved from the inside of the base material to the surface in the second step simultaneously acts as a catalyst, and the inside of the material. This is because Al was ionized and diffused into the surface layer. On the other hand, Ni, which should be present in large quantities unless the second step is performed, is 20% or less after the second step. This is because, in the second step, Ni diffuses toward the inside of the base material as Mg and Al move, and bonds with Al of the base material, and intermetallic compounds such as AlNi, Al3Ni, Al3Ni2, AlNi3, Al3Ni5, etc. This is because (AlmNin) was generated. Here, FIG. 8 is a binary phase diagram of aluminum and nickel, where the horizontal axis indicates the percentage by weight of each of Al and Ni, the vertical axis indicates the temperature, both Al and Ni. Shows what relationship is. From the binary phase diagram shown in FIG. 8, it can be seen that the five intermetallic compounds (AlNi, Al3Ni, Al3Ni2, AlNi3, Al3Ni5) described above were generated.

  Next, the weight percentage of Mg, Al, Ni in the second layer S2 will be described. The second layer S2 has a spectrum in the range of 4 to 8, and has a depth from the surface of 5.53 to 26.9 μm. This second layer S2 is a portion where the nickel layer 20 was formed in the upper portion S2a (range of spectra 4 and 5) before passing through the second step, and the lower portion S2b (range of spectra 6 to 8). ) Is the base material. For this reason, in the upper part S2a of the second layer S2 before passing through the second step, the nickel layer 20 contains an extremely large amount of Ni. Further, in the lower portion S2b of the second layer S2 before passing through the second step, an extremely large amount of Al is contained by the base material. However, as a result of the second step, as shown in FIG. 6, in the second layer S2, the Ni element is 30% or more and 50% or less, and the Al element is 70% or less and 50% or more. Thus, the Mg element is 5% or less. From this result, the following can be considered.

  The reason why the amount of Mg in the second layer S2 is less than that in the first layer S1 is that a large amount of Mg has moved from the base material to the first layer in the second step. In addition, in the upper portion S2a of the second layer S2, Al element which hardly exists unless the second step is performed is 70% or less and 50% or more because Al is the base material and the second layer in the second step. This is because it has moved from the lower part S2b of S2. In addition, in the lower portion S2b of the second layer S2, Ni that hardly exists unless the second step is performed is not less than 30% and not more than 50%. This is because they have moved from the upper portion S2a of the first layer S1 and the second layer S2.

  Subsequently, in the third layer S3, the weight% of Mg, Al, Ni in particular will be described. The third layer S3 has a spectrum in the range of 9 to 11, and has a depth from the surface of 30.44 to 38.9 μm. The third layer S3 is a portion that was a base material before the second step. For this reason, the third layer S3 before passing through the second step contains an extremely large amount of Al. However, as a result of passing through the second step, as shown in FIG. 6, in the third layer S3, the weight percentage of Al increases toward the inner side (from spectrum 9 to spectrum 11). Is 90% or more. Further, as shown in FIG. 7, in the third layer S3, the weight percentage of Ni decreases toward the inner side, and in the spectrum 11, Ni is 1% or less. From this, as it goes to the inner side in the third layer S3, it approaches the properties of the base material, and the influence of the surface hardening treatment in the second step is reduced.

  Next, the relationship between the Vickers hardness (HV) of the aluminum hardened material 10B and the depth (μm) from the surface will be described with reference to FIG. In addition, the hardness transition curve of the aluminum hardening material 10B shown in FIG. 5 is created by the following method. First, the hardened aluminum material 10B is cut perpendicularly to the surface, and the cut surface is polished to obtain a test surface. And about the position which is going to measure the to-be-tested surface, it measures sequentially by a Vickers hardness test, sending aluminum hardening material 10B. In this way, a hardness transition curve is created.

  As shown in FIG. 5, in this aluminum hardened material 10B, the Vickers hardness as a base material is 84 HV, the depth is 75 μm, and the Vickers hardness is 95 HV. The hardened layer T1 of the hardened aluminum material 10B is a layer in which an intermetallic compound (AlNi, Al3Ni, Al3Ni2, AlNi3, Al3Ni5) is generated. And since the Vickers hardness is 780 HV on the surface and the Vickers hardness is 742 HV at a depth of 20 μm from the surface, the surface portion is very hard. This can be inferred from the distribution of Al and Ni in the region of the first layer S1 (Spectrum 1 to Spectrum 3) shown in FIG. Further, since the Vickers hardness is 237 HV at a depth of 50 μm from the surface, the hardened layer T1 is thick and gradually softens from the surface toward the inside. That is, the weight percentage of Ni ions for generating an intermetallic compound (AlmNin) from a region exceeding 20 μm from the outermost surface becomes 30% or less, and the hardness decreases.

  By the way, the inventor thought that the reason why the hardened layer T1 as described above is formed is caused by the Mg element contained in the aluminum alloy material 10. Therefore, the inventor uses the aluminum alloy material 40 not containing Mg element instead of the aluminum alloy material 10 containing Mg element, and the same surface hardening as in the first step and the second step described above. As a comparative example, an aluminum hardened material (hereinafter referred to as an aluminum hardened material 40B) was manufactured. The aluminum alloy material 40 used as a base material is No. 2011 in JIS standard, and Si is 0.40%, Fe is 0.7%, and Cu is 5.0 to 6.0 by weight%. %, Zn is 0.3%, Pb is 0.2 to 0.6% or Bi is 0.2 to 0.6%, and all the remaining Al is included. The component of the metal element in the manufactured aluminum hardening material 40B is demonstrated using FIG.10 and FIG.11.

  In FIG. 11, the color is light in the first layer U1 on the surface side of the hardened aluminum material 40B, that is, in the range of spectra 1 to 3. When looking at the spectra 1 to 3 in FIG. 10, Ni is contained in an extremely large amount, whereas Al is not contained at all. In FIG. 11, the color is darker than the first layer U1 in the second layer U2 below the first layer U1, that is, the spectrum 4. When the spectrum 4 is seen in FIG. 10, Ni is less than the first layer U1, while Al is more than the first layer U1. When looking at the spectra 5 to 6 in FIG. 10, Ni is hardly contained, whereas Al is contained very much. From this, the hardened aluminum material 40B is not a material in which Al diffuses from the base material toward the surface as in the hardened aluminum material 10B, but a large amount of Ni constituting the nickel layer remains on the surface side. is there.

  Next, the relationship between the Vickers hardness (HV) and the depth (μm) from the surface of the aluminum cured material 40B will be described with reference to FIG. In the aluminum hardened material 40B, as shown in FIG. 9, the Vickers hardness as a base material is 73 to 79 HV, the depth is 20 μm, and the Vickers hardness is 64 HV. For this reason, the aluminum hardened material 40B has a hardened layer harder than the base material up to a depth of about 15 μm from the surface. However, the aluminum hardened material 40B is originally formed with a 15 μm nickel layer, and the hardness of the hardened layer is the same as the hardness of the nickel layer. Therefore, the hardened layer is not newly formed in the second step, but the nickel layer remains as it is.

The effect of this embodiment is demonstrated.
According to this embodiment, by heating in a high temperature atmosphere, the Mg element having a low vapor pressure is ionized and actively diffuses toward the surface layer. At that time, the ionized Mg element induces the surrounding ionized Al element and moves toward the surface layer portion. And the Al ion induced | guided | derived to the surface layer part couple | bonds with the Ni element ionized by the surface layer part, and produces | generates a high hardness intermetallic compound (AlmNin). That is, the Mg element acts as a catalyst in a high temperature atmosphere to cause a cross coupling reaction between the ionized Al element and Ni element to form a high hardness intermetallic compound. As a result, the depth of the hardened layer T1 is 1.5 times or more the thickness of the hardened layer obtained by, for example, plating, and the aluminum hardened material 10B having the thick hardened layer T1 that gradually softens toward the inside is obtained. Can be manufactured.

The hardened aluminum material 10B manufactured according to the present embodiment can be used for parts constituting automobiles, for example, cylinders and valves that are subjected to friction such as sliding, and has a Vickers hardness of 750 HV or more on the surface. In addition, since the Vickers hardness is 700 HV or more at a depth of at least 20 μm from the surface, the surface portion is very hard. In particular, since the Vickers hardness is 200 HV or more at a depth of at least 50 μm from the surface, the hardened layer T1 is thick and gradually softens from the surface toward the inside. Therefore, this aluminum hardened material 10B is preferable in terms of product safety because the hardened layer T1 is not consumed quickly even if it is used in a part where the sliding friction is extremely large. Cracks or delamination is unlikely to occur at the boundary.
On the other hand, stainless steel wristbands that have been resistant to rusting have been used in the past, but because they are relatively heavy and made of austenitic stainless steel, the surface of the parts is soft and easily damaged. On the other hand, if the manufactured aluminum cured material 10B is used for a wristwatch band, the surface is made of an intermetallic compound (AlmNin) and has a Vickers hardness of 750 HV or more.

  In addition, the inventor replaces the aluminum alloy material 10 in which the 15 μm nickel layer 20 and the 0.2 μm chromium layer 30 are formed with respect to the aluminum alloy material 10 in which only the 15 μm chromium layer 30 is formed. The surface hardening process of the process was performed. In this case, the Vickers hardness of the outermost surface of the chromium layer 30 was 1048 HV, but the hardened layer of the manufactured aluminum hardened material was peeled off in a crushed state. Therefore, the inventor confirmed the effectiveness of performing the surface hardening treatment in the second step on the aluminum alloy material 10 on which the nickel layer 20 is formed.

  Note that, as the thickness of the nickel layer 20 increases and the heating temperature decreases, the time required for Mg ions and Al ions in the base material to diffuse toward the surface of the nickel layer 20 increases. For this reason, the predetermined time for heating and holding the plating layer-attached alloy material 10A is that Mg ions and Al ions in the base material diffuse toward the surface of the nickel layer 20 based on the thickness and heating temperature of the nickel layer 20. In addition, the time until the Ni ions in the nickel layer 20 diffuse toward the inside of the base material is set.

As mentioned above, although the manufacturing method of the aluminum hardening material which concerns on this invention was demonstrated, this invention is not limited to this, A various change is possible in the range which does not deviate from the meaning.
For example, the method of removing the oxide film of the aluminum alloy material 10 is not limited to the method of immersing in the zinc acid solution, and the oxide film may be removed by sputtering, for example.

In addition, the thickness of the chromium layer 30 (0.2 μm), the heating temperature (550 degrees), the pressure in the decompression chamber (about 20 Pa), and the processing time of the second step (60 minutes to 90 minutes) are limited to the above values. It can be changed as appropriate.
In this embodiment, the nickel layer 20 having a thickness of 15 μm is formed. However, if the thickness is 10 μm or more, a cured layer of 15 μm intermetallic compound that is at least 1.5 times or more can be formed. . Accordingly, the thickness of the nickel layer 20 can be appropriately changed as long as it is 10 μm or more.

  The time and thickness at which the hardened intermetallic compound hardened layer is formed are determined by the heat treatment time to be set (temperature of 500 ° C. or more and 600 ° C. or less) and the holding time. And although the aluminum alloy material which is a base material has a large thermal expansion / shrinkage rate, the generated hardened layer has a very small thermal expansion / shrinkage rate. Therefore, between the surface layer portion (cured layer) cured at the stage where the heat treatment is completed and the sample is cooled to room temperature and the non-cured portion of the base material, the surface layer portion has a drag strength A1 and the non-cured portion shrinks. Tensile stress B1 works. When the tensile stress B1 is larger than the drag strength A1, the hardened layer may be peeled off. Therefore, the tensile stress B1 is calculated from a portion that is a half of the thickness of the aluminum alloy material, and this tensile stress B1. It is only necessary to calculate the tensile strength A1 exceeding the value and determine the thickness of the nickel layer formed on the surface of the aluminum alloy material.

DESCRIPTION OF SYMBOLS 10 Aluminum alloy material 10A Alloy material 10B with a plating layer Aluminum hardening material T1 Hardening layer S1 1st layer S2 2nd layer S3 3rd layer 20 Nickel layer 30 Chromium layer 40 Aluminum alloy material

Claims (4)

In the method of manufacturing an aluminum hardened material that hardens the surface of an aluminum alloy material containing magnesium element,
A first step of forming a nickel layer of 10 μm or more after removing the oxide film on the surface of the aluminum alloy material;
A second step of heating the aluminum alloy material on which the nickel layer is formed at a temperature of 500 degrees to 600 degrees and holding for a predetermined time;
The manufacturing method of the aluminum hardening | curing material characterized by having. In the manufacturing method of the aluminum hardening material of Claim 1,
In the second step, based on the thickness of the nickel layer and the temperature to be heated, magnesium ions and aluminum ions in the base material are held for a predetermined time until they diffuse toward the surface of the nickel layer. A method for producing a cured aluminum material. In the manufacturing method of the aluminum hardening | curing material of Claim 1 or Claim 2,
In the second step, the method for producing a hardened aluminum material is characterized in that heating is performed in a reduced-pressure chamber in a low vacuum state of 100 Pa or less. In the manufacturing method of the aluminum hardening material in any one of Claims 1 thru | or 3,
In the second step, the method for producing a hardened aluminum material is characterized in that heating is performed by glow discharge using an externally heated ion vacuum furnace.