JP6099475B2 - Al-Mg-Si-based alloy member and manufacturing method thereof - Google Patents

Description

  The present invention relates to an Al—Mg—Si alloy member and a method for producing the same, and more particularly to a technique for imparting high strength and elongation.

  Conventionally, lightweight aluminum alloy materials have been provided as materials for structural members for automobiles and the like. When manufacturing a member using an aluminum alloy material as a raw material, first, the aluminum alloy material is forged into a desired shape, and the forged aluminum alloy material is subjected to a solution treatment. There is a manufacturing method in which an aging treatment is performed to precipitate precipitates. In this general manufacturing method, since solution treatment is performed after forging, the effect of work hardening by forging is diminished, and there is a problem that work hardening cannot contribute to material strengthening.

  In the technique described in Patent Document 1, it is said that a desired strength can be obtained by performing forging with an equivalent strain of 2 or more at a temperature of 150 to 250 ° C. after solution treatment of a 6000 series Al alloy material. .

Japanese Patent No. 5082483

  However, although the technique described in Patent Document 1 can obtain a desired strength, there is a problem that the toughness is inferior because the elongation is low.

  Accordingly, an object of the present invention is to provide an Al—Mg—Si alloy member that satisfies the characteristics of a tradeoff between high strength and elongation, and a method for manufacturing the same.

In the method for producing an Al—Mg—Si alloy member of the present invention, the equivalent strain is 0.8 or more at a temperature of 150 to 200 ° C. with respect to the material after solution treatment of the material of the Al—Mg—Si alloy. Further, it is characterized by performing plastic working of less than 2 and then performing aging treatment on the material.

In the present invention, after the material is subjected to solution treatment, plastic processing is performed at a temperature of 150 to 200 ° C. with an equivalent strain of 0.8 or more and less than 2, so the dislocation density does not become excessively high. Elongation can be improved. On the other hand, in the technique described in Patent Document 1, the dislocation density is extremely high because the equivalent strain is strong processing of 2 or more, and the strength by work hardening is greatly increased but the elongation is decreased.

  Further, in the present invention, since warm plastic working is performed between the solution treatment and the aging treatment, dislocations are introduced into the crystal grains, and solute elements are diffused by the heat during the warm plastic working to cause aging precipitation. Happens. Here, when plastic processing is performed at a temperature higher than 200 ° C., the solute element diffuses excessively, so that the precipitates precipitated during the warm plastic processing become coarse, and precipitates largely on the dislocations, so that no precipitation zone is formed around them. This is an undesirable condition for precipitation strengthening.

  In this respect, in the present invention, the plastic working at 200 ° C. or lower suppresses the diffusion distance of the solute element, thereby suppressing the size and pitch of precipitates and further suppressing coarse precipitation to dislocations. Therefore, the formation of a precipitation-free zone is suppressed. As described above, in the present invention, it is possible to keep the size and the existing pitch effective for strengthening the material without coarsely precipitating the solute element dissolved in the aluminum crystal grains by the solution treatment. In the aging treatment, precipitates can be precipitated in the crystal grains without being unevenly distributed in dislocations. Therefore, in the present invention, the strength can be increased by precipitation strengthening with fine precipitates, and the elongation can be improved by suppressing excessive work hardening.

  Here, in the conventional technique in which the hot forging, the solution treatment, and the aging treatment are performed in this order as described above, since the hot forging is performed without uniformly dissolving the solute element, a large precipitate is far away. It will be in a state that exists at the pitch. Further, the dislocation density is lowered by the solution treatment, but the diffusion is fast in the place where the dislocation exists, and a coarse precipitate is deposited, and a non-precipitation zone is formed around it. Therefore, it is not preferable for precipitation strengthening.

  Moreover, in the technique described in Patent Document 1, the dislocation density is very high because the considerable strain due to forging is large. For this reason, the solute element diffuses during forging and deposits on dislocations, resulting in an increase in precipitates, and a precipitate-free zone is formed around the coarse precipitates. Thus, in patent document 1, since the material is strengthened by work hardening with a high dislocation density, elongation is sacrificed.

  In the present invention, an Al-Mg-Si alloy generally called 6000 series is targeted. In addition, the solution treatment referred to in the present invention is a heat treatment in which an aluminum alloy is heated to an appropriate temperature that is equal to or higher than the solid solution limit temperature, and the alloy components are sufficiently solid solution, and then rapidly cooled to a supersaturated solid solution state. It is a process including the process of quenching the heated aluminum alloy. In the invention, the solution treatment is performed at 500 to 600 ° C., for example.

  The plastic working in the present invention includes all processes that give plastic deformation to the material such as rolling, forging, drawing, and extrusion, and is performed at 150 to 200 ° C. The aging treatment is a treatment in which a solid solution element in a solution-treated aluminum alloy is heated to precipitate as a precipitate. In the present invention, for example, the treatment is performed at 180 ° C. or lower.

  According to the present invention, an Al-Mg-Si alloy member excellent in strength and elongation is provided because the material is strengthened by precipitating fine precipitates uniformly in crystal grains while suppressing work hardening. can do.

Hereinafter, the present invention will be described in more detail with reference to specific examples.
First, a 6061 series alloy round bar made of Mg: 0.95%, Si: 0.66%, Cu: 0.25%, Cr: 0.08%, the balance Al and inevitable impurities was prepared. Next, a solution treatment was performed on the aluminum alloy material. In the solution treatment, the aluminum alloy material was solution-treated at 570 ° C. and then immersed in water and quenched. Next, the aluminum alloy material was heated to 150 to 200 ° C. and forged so as to have a predetermined shape. The equivalent strain in forging was 0.8. Next, an aging treatment was performed on the forged product, and samples of Examples 1 to 3 were obtained. Table 1 shows the conditions of the above processing.

  For comparison, the same aluminum alloy material as in Examples 1 to 3 was used, and forging was first performed under the temperature conditions shown in Table 1. The equivalent strain at that time was 0.8. Next, solution treatment was performed, and an aging treatment was performed under the conditions shown in Table 1 to obtain samples of Comparative Examples 1 to 3. The 0.2% yield strength, tensile strength, and elongation were measured for the above samples. The results are also shown in Table 1. Table 1 also shows the JIS standard values for tensile properties.

  As shown in Table 1, in Examples 1 to 3, the 0.2% yield strength and the tensile strength are excellent, and the elongation is sufficient to maintain 10% or more of the JIS standard. On the other hand, the 0.2% yield strength and tensile strength in Comparative Examples 1 to 3 are lower than those in Examples 1 to 3. This is because the precipitates of Comparative Examples 1 to 3 are coarse, and are largely precipitated in dislocations, and a precipitate-free zone is generated in the periphery. Moreover, in Comparative Examples 1-3, since the solution treatment was performed after forging, the effect of work hardening by forging was diminished.

  Since this invention has high intensity | strength and elongation, it can be utilized for the structural member for motor vehicles, for example.

Claims (2)

After solution treatment of the Al—Mg—Si alloy material, the material is subjected to plastic working at a temperature of 150 to 200 ° C. with an equivalent strain of 0.8 or more and less than 2, and then the material is subjected to plastic working. The manufacturing method of the Al-Mg-Si type alloy member characterized by performing an aging treatment.   The method for producing an Al-Mg-Si based alloy member according to claim 1, wherein the Al-Mg-Si based alloy member is a structural member for an automobile and the plastic working is forging.