Joined member, method for manufacturing the same, and method for manufacturing composite member using the joined member

Abstract

To provide a to-be-bonded member that enables different metal materials to be strongly bonded.SOLUTION: A to-be-bonded member is bonded to a metal member. The to-be-bonded member is an alloy comprising a first metal as a main ingredient and a second metal as an accessory ingredient. The second metal is a metal to have a lowered eutectic point temperature when forming an alloy with the first metal. The abundance of the second metal is higher in a bonding face of the to-be-bonded member to the metal member than the other portions.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The technology disclosed in this specification relates to a member to be joined, a method for manufacturing the member to be joined, and a method for manufacturing a composite member using the member to be joined.

Background Art

[0002] As technologies for joining dissimilar metal materials, technologies such as welding and casting are known. Patent Document 1 discloses a technology in which the surface of a member to be joined is plated, the member to be joined is placed in a cavity of a mold, a raw material for forming a joining member is introduced into the cavity in a molten state, and the joining member and the member to be joined are connected. In Patent Document 1, the plating is melted by a raw material (molten metal) for forming a joining member, and the plating functions as a brazing material.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When joining a joining member and a member to be joined by making plating function as a brazing material as in Patent Document 1, the joining strength between the joining member and the member to be joined depends on the material strength of the plating. Therefore, the effect of improving the joining strength between the joining member and the member to be joined is limited. In addition, since the types of plating materials that can be used are limited with respect to the materials of the joining member and / or the member to be joined, it is not versatile. Furthermore, the manufacturing cost increases due to the addition of a plating process. Therefore, a new technology for firmly joining dissimilar metal materials is required. The purpose of this specification is to provide a new member to be joined that can firmly join dissimilar metal materials.

Means for Solving the Problems

[0005] The joined member disclosed in this specification is joined to a metal member. This joined member is an alloy containing a first metal as a main component and a second metal as a sub-component. And the second metal is a metal whose eutectic point temperature decreases when it forms an alloy with the first metal. Also, the second metal is present in a larger amount on the joint surface of the joined member with the above-mentioned metal member compared to other parts.

[0006] Note that "the second metal is present in a larger amount on the joint surface compared to other parts" means that the second metal is substantially present only on the joint surface and is hardly present in other parts (for example, the central part of the joined member), or the proportion of the second metal present on the joint surface is larger compared to other parts. That is, it means that the degree of segregation of the second metal on the joint surface is larger than that of other parts, and the second metal is unevenly distributed on the joint surface. Also, "main component" means that it has the largest mass ratio among the metals constituting the joined member. "Sub-component" means that it is other than the main component.

[0007] In the above-mentioned joined member, the joint surface is more likely to melt compared to other parts. Therefore, when the raw material of the joining member is supplied to the joined member, a molten layer can be formed on the joint surface. That is, an alloy layer of the raw material metals of both can be formed at the interface between the joining member and the joined member. By using the above-mentioned joined member, the joining strength between the joining member and the joined member can be improved.

[0008] The second metal may be present in a larger amount from the center to the end of the joined member. Compared with the form in which the second metal is substantially present only on the joint surface, the joined member can be easily manufactured.

[0009] This specification also discloses a method for manufacturing a member to be joined that is joined to a metal member. In the manufacturing method, a first metal as a main component and a second metal whose eutectic point temperature decreases when an alloy is formed with the first metal are melted and then solidified. By melting and solidifying the first metal and the second metal, due to the eutectic reaction, the melting point of the obtained alloy becomes lower than the melting point of the first metal. As a result, a member to be joined with improved joining strength to the above-described joining member can be obtained.

[0010] After melting the first metal and the second metal, the molten metal may be slowly cooled while being stirred to form a semi-solid slurry, and the semi-solid slurry may be solidified. An alloy in which the second metal is concentrated in the liquid phase portion can be obtained. Therefore, the melting point of the member to be joined can be further lowered as compared with the manufacturing method of simply melting and solidifying the first metal and the second metal. Note that the semi-solid slurry may be solidified under pressure. By applying pressure, a member to be joined in which more liquid phase portions (that is, more second metal) exist from the center to the end of the member to be joined can be obtained.

[0011] This specification also discloses a method for manufacturing a composite member in which a member to be joined is joined to a metal joining member. In the manufacturing method, the above-described member to be joined is disposed in a cavity of a mold, and a raw material for forming the joining member is introduced into the cavity at a temperature higher than the solution heat treatment line temperature of the surface of the member to be joined at the joining surface of the member to be joined, and the raw material in the cavity is pressurized and solidified. By introducing the raw material for forming the joining member into the cavity at a temperature higher than the solution heat treatment line temperature of the surface of the member to be joined, the surface of the member to be joined melts, and a molten layer is formed on the surface (joining surface) of the member to be joined. As described above, by forming a molten layer on the joining surface, the joining strength between the joining member and the member to be joined can be improved.

[0012] The raw material introduced into the cavity may be a semi-solid slurry. That is, the raw material for forming the composite member is melted, slowly cooled while stirring the molten metal to form a semi-solid slurry raw material, and the semi-solid slurry raw material may be introduced into the cavity at the above-mentioned temperature. This makes it easier to form a molten layer on the joint surface and can further improve the joint strength between the joint member and the member to be joined.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0014] The member to be joined disclosed in this specification is an alloy of a binary system or more. That is, it contains at least a first metal as the main component and a second metal as the sub-component. In this case, the second metal is selected from elements that lower the eutectic temperature. For example, when the first metal is aluminum, examples of the second metal include magnesium, copper, zinc, silicon, etc. The combination of the first metal and the second metal can be selected with reference to the phase diagram of known metals. Also, the first metal can be magnesium and the second metal can be aluminum. The composition ratio of the first metal and the second metal is preferably an alloy composition close to the composition at the eutectic point. This can further lower the liquidus temperature of the member to be joined. When the member to be joined is a ternary alloy, the third metal, like the second metal, is selected from elements that lower the eutectic temperature.

[0015] Figure 1 shows a SEM photograph of the joined member. The joined member in Figure 1 shows an Al-Si-Cu alloy (ternary alloy). As shown in Figure 1, the joined member contains primary crystal 2 and liquid phase 4. When selecting a metal having the above-described characteristics as the first metal, the second metal, and the third metal, the secondary components (Si, Cu) are highly present in the liquid phase 4. The ratio of the primary crystal 2 and the liquid phase 4 in the joined member may be equal overall, or the ratio of the liquid phase 4 to the primary crystal 2 may increase from the center toward the end. In either case, compared with an alloy in which no liquid phase exists, the joining strength with the joined member can be increased. Preferably, in the joined member, the ratio of the liquid phase 4 to the primary crystal 2 increases from the center toward the end.

[0016] A joined member in which the ratio of the primary crystal 2 and the liquid phase 4 is equal overall can be manufactured, for example, using a semi-solidification method. In the semi-solidification method, the molten alloy is gradually cooled while being stirred and solidified. Thereby, an alloy (joined member) in which the ratio of the primary crystal 2 and the liquid phase 4 is equal overall can be manufactured. Note that a joined member in which the ratio of the primary crystal 2 and the liquid phase 4 is equal overall can also be manufactured by a method similar to the casting method. In this case, the molten alloy is introduced into the cavity of the mold, the molten alloy is gradually cooled inside the mold, and primary crystals are generated to obtain a semi-solid state. Thereafter, by rapidly cooling the molten alloy, a joined member in which the ratio of the primary crystal 2 and the liquid phase 4 is equal overall can be manufactured.

[0017] A joined member in which the ratio of the liquid phase 4 to the primary crystal 2 increases from the center toward the end can be manufactured by applying pressure molding to the semi-solidification method described above. When a load is applied to the semi-solid metal, the highly fluid liquid phase flows preferentially over the primary crystal and moves to the outer portion of the joined member. When the semi-solid metal is solidified with the liquid phase having moved to the outer portion of the joined member, a joined member can be manufactured in which the ratio of the liquid phase 4 to the primary crystal 2 increases from the center toward the end. Note that a joined member in which the ratio of the liquid phase 4 to the primary crystal 2 increases from the center toward the end can also be manufactured by other methods. For example, a molten metal containing alloy particles with a high specific gravity and a low melting point is prepared, and the molten metal is introduced into the cavity of a mold and centrifugal casting is performed. Thereby, the alloy particles with a high specific gravity are dispersed in the outer portion of the joined member, and a joined member can be manufactured in which the ratio of the liquid phase 4 to the primary crystal 2 increases from the center toward the end.

[0019] A composite member in which a joined member is joined to a joining member can be manufactured by supplying the raw material of the joining member to the joined member in a state higher than the solvus temperature at the joining interface of the joined member. Specifically, the joined member is disposed in the cavity of a mold, and the raw material (raw material of the joining member) at a temperature higher than the solvus temperature at the joining interface of the joined member is introduced into the cavity of the mold, whereby a composite member can be formed. Further, when pressure is applied with the raw material of the joining member introduced into the cavity, a joined member can be manufactured in which the ratio of the liquid phase 4 to the primary crystal 2 increases from the center toward the end. Note that the composite member can also be manufactured by methods such as die casting, gravity casting, and melt forging.

[0020] (Experimental Example) Composite members were created by joining a joining member of an Al-Si-Cu alloy and a joining member of an Al-Mg-Si alloy, and the joining strength between the two was measured. The joining members used were a sample (Sample 1) in which no liquid phase was confirmed on the surface (joining surface), a sample (Sample 2) in which the ratio of primary crystals to the liquid phase was equal overall, and a sample (Sample 3) in which the ratio of the liquid phase to the primary crystals increased from the center to the end. Sample 1 was produced by extrusion molding the raw material of the joining member. Sample 2 was produced by creating a semi-solid slurry using the raw material of the joining member and solidifying the semi-solid slurry. Sample 3 was produced by creating a semi-solid slurry using the raw material of the joining member and pressure molding the semi-solid slurry. The joining strength was measured by conducting a tensile test, setting the strength of Sample 1 to 100, and calculating the strength ratios of Samples 2 and 3 to Sample 1. The results are shown in Figure 2.

[0021] Also, for the surface (joining surface) of each sample, the ratio of the liquid phase to the primary crystals was measured. The measurement of the liquid phase ratio was performed by counting the Si concentration range (10.2 wt% or more and 14.4 wt% or less) in the temperature-lowering region with respect to the liquidus temperature (594 °C) of Sample 1 from the EDS mapping image. The results are shown in Figure 2.

[0022] As shown in Figure 2, as the ratio of the liquid phase increases, the joining strength (joining strength ratio) improves. This result indicates that the more liquid phase exists on the joining surface of the joining member, the lower the melting point of the joint, and the more melting layer is generated at the interface of the joining surface.

[0023] The specific examples of the technology disclosed in this specification have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. Also, the technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing.

Explanation of Reference Signs

[0024] 2: Primary crystal 4: Liquid phase

Claims

A method for manufacturing a composite member in which a joining member made of metal is joined to a member to be joined, comprising: The member to be joined is an alloy containing a first metal as a main component and a second metal as a sub-component, The second metal is a metal that forms a eutectic when alloyed with the first metal, The member to be joined is manufactured by melting the first metal and the second metal, slowly cooling the molten metal while stirring to form a semi-solid slurry, and pressurizing and solidifying the semi-solid slurry. Placing the member to be joined in a cavity of a mold, Introducing a raw material for forming the joining member into the cavity at a temperature higher than the liquidus temperature of the surface of the member to be joined at the joining surface of the member to be joined to form a molten layer at the interface of the joining surface, A manufacturing method of pressurizing and solidifying the raw material in the cavity. A method for manufacturing according to claim 1, wherein a raw material for forming the composite member is melted, slowly cooled while stirring the molten metal to form a semi-solid slurry raw material, The semi-solid slurry raw material is introduced into the cavity at the temperature.

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