JP2006009066A - Member made of aluminum alloy having excellent ductility - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a member made of an aluminum alloy having excellent ductility which can be subjected to aging treatment in a shaped material form such as a flat sheet form or a straight pipe form, and thereafter can be subjected to working or forming under the condition wherein working inferior in loading efficiency or aging treatment after forming is abolished. <P>SOLUTION: A prescribed shaped material is produced using an aging treatable aluminum alloy. The shaped material is subjected to solution treatment, thereafter, working strain in a prescribed amount is applied thereto, and subsequently, aging treatment is performed. The amount of the working strain preferably lies in the range of 10 to 60%. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a technology for improving ductility in, for example, a 6000 series rolled aluminum alloy material, an extruded aluminum alloy material, and the like, which is used after aging treatment to ensure necessary mechanical properties such as strength.

Aluminum alloys are lightweight and have relatively high strength, and are therefore widely used as structural materials.
However, aging treatment aluminum alloy that secures the necessary strength as a structural material by applying aging treatment, ductility decreases by aging treatment, and plastic processing such as bending becomes difficult, so aging treatment is usually used. Plastic processing and molding before, and then aging treatment.
However, the product shape three-dimensionalized by bending or the like has a technical problem that the loading efficiency with respect to the aging furnace is poor and the heat treatment cost increases.

  Therefore, in order to reduce the price of aluminum alloy parts, instead of aging treatment with a shape after processing and forming with poor loading efficiency, a flat plate such as a rolled plate or an extruded shape, a straight tube shape, etc. A step of aging treatment with a shape material (coarse shape material) and then processing / molding into a product shape such as a structural material shape is preferable.

The inventors of the present application have so far mainly studied the relationship with age hardening and published the results regarding the influence of processing on the age precipitation of an Al—Mg ₂ Si-based alloy.
This time, the effect of preliminary strain (preliminary plastic working) on ductility has been clarified, and the present invention has been achieved.

Kenji Matsuda, Jun Terasaki, Shizuo Tada, Susumu Ikeno, “Light Metal, Vol 43, No3”, 1993, P127-P133 Kenji Matsuda, Jun Terasaki, Shizuo Tada, Susumu Ikeno, “Light Metal, Vol 45, No 2”, 1995, P95-P100 Kenji Matsuda, Tsunaki Iwashita, Masakazu Ishido, Seiichi Renkakuji, Yasuhiro Uedani, Susumu Ikeno, "Light Metal, Vol47, No7", 1997, P385-P390

  The present invention provides an aluminum alloy member having excellent ductility that can be aged and processed after forming and aging with a shaped material shape such as flat plate and straight pipe shape after eliminating aging treatment after processing and forming with poor loading efficiency. It is a technical subject to do.

In order to solve the above problems, an aluminum alloy member excellent in ductility according to the present invention is manufactured by manufacturing a predetermined shape material using an aging-processable aluminum alloy and subjecting the shape material to a solution treatment. The amount of processing distortion is given, and then an aging treatment is performed.
Here, the amount of processing strain is preferably in the range of 10 to 60%.

The aluminum alloy composition contains 0.6 to 1.6% by mass of Mg ₂ Si in the stoichiometric composition and contains excess Si in an amount of 0.4% by mass or less than the Mg ₂ Si balance composition. Good.
Furthermore, it is more desirable to contain Cu in the above component composition in a range of 0.5% by mass or less.

Aged 6000 series aluminum alloys have increased strength due to the formation of Mg ₂ Si precipitates in the crystal grains.
Therefore, in the present invention contains 0.6 to 1.6 wt% in the _Mg 2 Si stoichiometric composition represented by pseudo binary system mass%, the excess amount of Si than _Mg 2 Si balanced composition 0. It is contained in the range of 4% by mass or less.
The reason why the strength is increased by the precipitation of the Mg ₂ Si precipitate is that when the dislocations existing in the aluminum alloy move with respect to the processing and forming, a so-called shearing or bypass mechanism causes deformation resistance.
In this mechanism, Mg ₂ Si precipitates sheared by the shearing mechanism can easily provide a slip surface after that, and aging-treated 6000 series aluminum alloy concentrates stress at grain boundaries during processing and forming. To do.
Further, PFZ (no precipitation zone) in which no Mg ₂ Si precipitates are present exists at the grain boundaries.
This PFZ is weak because there is no Mg ₂ Si precipitate, so that the difference in strength between the crystal grain and the crystal grain boundary becomes significant, and fracture occurs at the crystal grain boundary.
In order to process and shape after the aging treatment, it is preferable to narrow the PFZ interval by strengthening the PFZ by forming Mg ₂ Si precipitates inside the PFZ.
In addition, it is preferable that the crystal grain boundary is greatly curved and the propagation of cracks along the crystal grain boundary is suppressed.
Therefore, according to the present invention, by introducing cold strain after the solution treatment, it is possible to introduce the grains into the PFZ existing at the grain boundaries, and the Mg ₂ Si precipitates are formed on the dislocations. The PFZ interval is narrowed and the PFZ can be strengthened.
Further, since the crystal grain boundary is greatly curved due to strain, propagation of cracks can be suppressed.

Hereinafter, the influence of the components will be described.
Mg and Si components form a supersaturated solid solution by solution treatment, generate Mg ₂ Si precipitates in the subsequent aging treatment, and improve the strength by a shearing or bypass mechanism.
However, if it is contained in a large amount, it is contained in the supersaturated solid solution after the solution treatment, so that the strength immediately after the solution treatment is increased and the processing / molding becomes difficult. Therefore, the stoichiometric composition Mg ₂ Si is 1.6% by mass. The following is preferable.
Here, the reason why the amount of the component as the stoichiometric composition Mg ₂ Si is 0.6% by mass or more is that if it is less than this value, it is presumed that preferential precipitation on dislocations is achieved without introducing strain.
Further, when the excessive Si amount is contained in a large amount, Si precipitates during the aging treatment, which may be the starting point of fracture.
Considering this, the excess Si amount is preferably suppressed to 0.4 mass% or less than the Mg ₂ Si balance composition.

Cu is preferably contained in order to ensure strength and ductility, but if it is excessive, corrosion resistance is lowered.
In addition, the strength immediately after the solution treatment increases, and it tends to be difficult to process and mold.
Considering this, it is preferable to set it to 0.5 (mass)% or less.

In the present invention, a strain of 10% or more is introduced immediately after the solution treatment of the base material.
Thereby, dislocations can be introduced into PFZ, and PFZ can be strengthened by the formation of Mg ₂ Si precipitates on the dislocations.
In addition, the crystal grain boundary is greatly curved, and the propagation of cracks can be suppressed.
The reason why the processing strain after the solution treatment of the base material is set to 10% or more is that dislocations can be introduced on the PFZ side by introducing strain.
In addition, the effect by the curvature of the crystal grain boundary is better when the amount of processing strain is large.
Therefore, the amount of processing strain is preferably in the range of 20 to 60%, ideally 30% or more.

  According to the aluminum alloy member of the present invention, the ductility capable of being processed and formed after the aging treatment can be improved by introducing a strain of 10% or more immediately after the solution treatment.

In the present invention, the molten metal is adjusted to a predetermined component composition and cast into a predetermined shape such as a bus bar or billet, and then a raw material manufactured into a plate or an extruded shape by hot rolling or extrusion is obtained.
Such a shaped material is subjected to a solution treatment, and processing strain is applied by cold rolling, pulling, drawing, or the like. Further, the amount of processing distortion refers to a dimensional change ratio with respect to before processing, such as thickness.

Dissolving raw materials ingredients adjusted to the composition of the _{Al-1% Mg 2 Si-} 0.5% Cu, it was melted prismatic I隗.
Thereafter, it was hot-rolled at 400 ° C. for 50%, subjected to solution treatment at 575 ° C. for 1 hr, and quenched in ice water. Thereafter, it was 30% cold-rolled so as to decrease in thickness by 30%, and subjected to aging treatment at 150 ° C. (423K) and 200 ° C. (473K) to produce a sample.
For comparison, the same aging treatment without cold rolling was also produced.
A tensile test piece having a distance between scores of 17.5 mm, a width of 5.8 mm, and a thickness of 0.8 mm was cut out from the manufactured sample and subjected to a tensile test.
FIG. 1 shows the results of a tensile test of a sample aged at 150 ° C. (423 K), and similarly FIG. 2 shows the results of a tensile test when aged at 200 ° C. (473 K).
As the nominal strain increased, the nominal stress increased and after reaching TS (tensile strength) (indicated by the arrows in the figure), the stress decreased rapidly and broke.
In the case of 30% cold rolling immediately after solution treatment, the elongation from the beginning of tension to TS (hereinafter referred to as uniform elongation) increases, and the elongation at break (hereinafter referred to as elongation at break) also increases. became.

For samples that were cold-rolled 30% immediately after solution treatment of the samples aged at 150 ° C. in FIG. 3 and at 200 ° C. in FIG. 4 (shown as 0% in FIGS. 3 and 4), An observation result is shown.
In the case of 30% cold rolling after the solution treatment, no grain boundary is seen on the fracture surface, and the grain boundary is not broken.
However, in the case of not cold rolling, crystal grain boundaries are observed on the tensile fracture surface, and grain boundary fracture occurs.
For this reason, it has been clarified that those subjected to cold working immediately after the solution treatment have improved uniform elongation and breaking elongation.
FIG. 5 and FIG. 6 show the structure observation results near the grain boundaries. In the case of 30% cold rolling immediately after the solution treatment, dislocations exist up to the vicinity of the grain boundary, and it can be confirmed that PFZ is narrowed.
More specifically, as shown in FIGS. 5 and 6, the aging treatment 423K has an average PFZ width reduced from 70 nm to 50 nm, and the aging treatment 473K has a 160 nm reduction to 120 nm. .
FIG. 7 shows an enlarged photograph thereof. It can be confirmed that Mg ₂ Si precipitates are generated along the dislocations.
Thereby, PFZ can be strengthened and it can be considered that the grain boundary destruction was suppressed.

FIG. 8 to FIG. 10 show curing curves at respective aging treatment temperatures.
As a result, it has been clarified that when the amount of processing strain is 10% or more, the maximum hardness is rapidly increased.

FIG. 11 shows the results of investigating the effects of excess Si amount and Cu component on elongation.
The effect of processing strain could be confirmed even when 0.4% excess Si was added.
Further, not only the strength of the Cu component but also the effect of improving the elongation is recognized.

The tension test result of what was age-treated at 423K is shown. The tension test result of what was age-treated at 473K is shown. The fracture surface of what was age-treated at 423K is shown. The fracture surface of what was age-treated at 473K is shown. The PFZ after aging treatment at 423K is shown. The PFZ after aging treatment at 473K is shown. An enlarged view of the organization is shown. The hardening curve of aging treatment temperature 423K is shown. The hardening curve of aging treatment temperature 448K is shown. The hardening curve of aging treatment temperature 473K is shown. Elongation measurement results are shown. In the table, 0% indicates that no processing strain is introduced, and 30% indicates that the strain amount is 30%.

Claims (4)

  It is excellent in ductility by producing a predetermined shape material using an aging treatment aluminum alloy, applying a predetermined amount of processing strain after solution treatment of this shape material, and then performing an aging treatment after that. An aluminum alloy member characterized by the above.   2. The aluminum alloy member according to claim 1, wherein the amount of processing strain is in the range of 10 to 60%. The stoichiometric composition contains Mg ₂ Si in an amount of 0.6 to 1.6% by mass, and contains Si in excess of 0.4% by mass in excess of the Mg ₂ Si balance composition. 3. An aluminum alloy member according to 1 or 2. In the stoichiometric composition, Mg ₂ Si is contained in an amount of 0.6 to 1.6% by mass, excess Si is contained in an amount of 0.4% by mass or less than the Mg ₂ Si balance composition, and copper is contained in an amount of 0.5% by mass. The aluminum alloy member according to claim 1, wherein the aluminum alloy member is contained in a range of not more than%.