JP2007302952A - ALUMINUM BASED ALLOY OF Al-Mg-Ge SYSTEM AND ALUMINUM ALLOY MATERIAL USING THE SAME - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aluminum based alloy whose high temperature hardness and high temperature strength are high, and in which the temperature stability of the highest hardness and age hardening speed properties are excellent. <P>SOLUTION: The aluminum based alloy comprises, by atom, 0.2 to 1.0% Mg and 0.1 to 0.5% Ge, and has excellent age hardening speed properties and high temperature strength. Preferably, the Mg content is 0.4 to 0.8%, and the Ge content is 0.2 to 0.4%. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a novel aluminum-based alloy, and particularly to an Al—Mg—Ge-based aluminum-based alloy and aluminum alloy material having high high-temperature hardness and high-temperature strength and excellent age hardening rate.

  Aluminum alloy materials using Al-Mg-Si alloys known as JIS 6000 series aluminum alloys are excellent in extensibility, are easy to press work, and are weak in natural aging. Predetermined strength can be obtained by performing plastic working and then artificial aging treatment.

Al-Mg-Si-based alloys have been widely adopted as aluminum sashes by obtaining extruded shapes by extrusion since they are excellent in extensibility.
In recent years, there has been a method of performing artificial aging treatment using the baking temperature of the paint in the painting process, such as press molding at the stage of soft material properties before aging treatment, taking advantage of the characteristics weak to natural aging. It is being considered.
However, the baking temperature in the coating process is generally 175 to 250 ° C. × 10 to 30 minutes in the mounting industry in consideration of the physical property value and productivity of the paint, and the conventional Al—Mg— In the case of a Si-based alloy, there has been a technical problem that the baking condition of the paint is not a condition that makes full use of the physical properties of the aluminum alloy material.
That is, in order to secure strength by artificial aging treatment in an Al—Mg—Si alloy, stable β ″ phase precipitation is indispensable, and low temperature and long term aging at 200 ° C. or lower is necessary. In order to grow into a β′-Mg ₂ Si phase, there is a problem that the consistency with the parent phase is interrupted and sufficient hardness and strength cannot be obtained.

  (Non-Patent Document 1) discloses the aging phenomenon of Al—Mg—Ge-based alloys, but only describes the precipitation behavior in the aging treatment. Knowledge about the temperature stability of the highest hardness and the age hardening rate is not available. It is not done.

“Aging phenomenon of Al—Mg—Ge alloys” Hisashi Suzuki, Mikihiro Kanno, Goro Ito: Light Metal, Vol. 31, no. 4,1981

  An object of the present invention is to provide an aluminum-based alloy and an alloy material having high high-temperature hardness and high-temperature strength, and excellent temperature stability and age-hardening rate at the highest hardness.

The inventors of the present application focused on the crystal structure of a product (intermediate phase) that contributes to strength, and developed an alloy that can exhibit strength at high temperatures by manipulating the lattice constant.
In the case of a conventional Al—Mg—Si alloy, the precipitate that is supposed to contribute to the strength is the β ″ phase.
If it is β ”phase, it is consistent with the crystal lattice of the aluminum matrix and strain hardening for the matrix is obtained. However, when the β” phase grows into a β′-Mg ₂ Si phase, the crystal lattice of the aluminum matrix is obtained. It is considered that the strength cannot be obtained because the effect of strain hardening on the matrix is extremely reduced due to the interruption of the consistency with the matrix.
The present invention forms an ternary solid solution with an Al-Mg alloy and can be handled industrially in the same manner as a conventional Al-Mg-Si alloy, and further maintains consistency between the precipitated intermediate phase and the matrix phase. Therefore, we focused on Ge, which is the same family as Si atoms, has an atomic number different by one period, and has an atomic radius larger than Si.
FIG. 1 shows an estimation diagram of a crystal lattice in the case where Ge is completely substituted with Si constituting β ′ to form a β′-Mg ₂ Ge phase.
The values shown in parentheses are for Si, and the values shown in bold are the expected values when Ge is substituted.
If the c-axis (0.405 nm) does not change, the a-axis extends about 0.002 nm and the crystal lattice extends about 0.023 nm ³ .
As a result, the lattice misfit between the aluminum matrix {100} plane and the β ′ phase {1120} plane is improved from −13.33% to −12.59%.
The lattice misfit between the aluminum matrix {200} plane and the β3 phase {3300} plane does not change at 0.5%.
Since consistency with the aluminum matrix is improved, coarse precipitates that do not contribute to hardening in the past contribute to sufficient hardening, and are expected to contribute to improvement in hardness on the high temperature side.
In addition, maintaining consistency between the aluminum matrix and the precipitation intermediate phase is presumed that the phase transformation of the precipitate proceeds smoothly, and the age hardening rate is expected to be improved. It can be expected to be obtained.

As a result of designing and test-evaluating an Al—Mg—Ge alloy from the above viewpoint, the aluminum-based alloy according to the present invention has Mg: 0.2 to 1.0 at%, Ge: 0.1 to 0.5 at%. It is characterized by being excellent in age hardening rate and high temperature strength.
Moreover, as a preferable aluminum base alloy composition, it is good to contain Mg: 0.4-0.8at%, Ge: 0.2-0.4at%.
Furthermore, you may contain Mn: 0.01-0.1at%.
Here, at% means atomic weight%.
Mg: 0.2-1.0 at%, preferably Mg: 0.4-0.8 at%, Ge: 0.1-0.5 at%, preferably Ge: 0.2-0.4 at% No. expects the strain effect due to the precipitation of the Mg ₂ Ge phase.
Therefore, if the Mg component is less than 0.2 at%, the increase in hardness (strength) is small, and if the Mg component exceeds 1.0 at%, Mg becomes excessive with respect to the balance with Ge, and addition of Mg When the amount is large, the ductility of the aluminum alloy is remarkably lowered.
Further, when the Ge component is less than 0.1 at%, the precipitation effect of Mg ₂ Ge is weak, and when it exceeds 0.5 at%, solid solution becomes difficult.
Therefore, as will be described later, it can be handled in the same way as a conventional Al-Mg-Si alloy, high strength can be obtained even at high temperature heat treatment, and heat treatment temperature stability with the highest hardness can be obtained. And in order to be excellent in high temperature strength, Mg: 0.4-0.8 at% and Ge: 0.2-0.4 at% are preferable.
Further, if the purpose of replacing Si with Ge is obtained, it is not always necessary to completely replace the Si component with Ge.
An aluminum alloy material using such an aluminum-based alloy is characterized in that an aging treatment is performed so that a 1.0 to 1.4 mass% Mg ₂ Ge precipitated phase appears in the aluminum alloy material.
Here, the excellent age-hardening rate property means that even if the precipitate β ″ phase becomes a β′-Mg ₂ Ge phase, the phase transformation of the precipitate proceeds promptly because it is excellent in consistency with the aluminum matrix phase. It means that the artificial aging speed is faster than the conventional Al-Mg-Si alloy.
More specifically, the maximum hardness is reached within 20 minutes at a heat treatment temperature of 523K.
In addition, the fact that the high temperature strength is excellent means that in a conventional Al—Mg—Si based alloy, when the artificial aging treatment is performed at 523 K, the maximum hardness is HV (micro Vickers hardness) 60 or less. The -Ge-based alloy means that HV80 or more can be secured and a tensile strength of 200 MPa or more can be obtained.
In particular, in the Al—Mg—Ge alloy according to the present invention, even when the heat treatment temperature is changed to 423 to 523 K, the maximum hardness value can be suppressed to a difference of about 10 or less in HV hardness.
Therefore, the aluminum alloy material using the aluminum base alloy according to the present invention can obtain stable hardness and high strength at a mounting temperature of 448 to 523 K (175 to 250 ° C.) in the baking coating process.
Further, the Al—Mg—Ge alloy according to the present invention may contain impurities equivalent to those of the conventional Al—Mg—Si alloy, and a crystal grain refining element such as Mn, Cr, or Zr is added. In that case, 0.01 at% or more and 0.1 at% or less is preferable as each component.

Even if the artificial aging temperature or baking coating temperature is high, sufficient strength can be obtained in a shorter time than conventional.
Accordingly, even if a difference occurs in the heat treatment conditions, variations in material reliability such as hardness, strength, and elongation can be reduced.

Fig. 2 shows the hardness change curve when Mg and Ge are dissolved in pure aluminum ingot and Mg: 0.4at%, Ge: 0.2at% aluminum-based alloy is prototyped and aged at 423, 473, 523K. Shown in
When the component composition of the prototype alloy was analyzed, Mg: 0.49 at%, Ge: 0.19 at%, Fe: 0.02 mass% or less, Cr: 0.01 mass% or less, Mn: 0.01 mass %: Ti: 0.01% by mass or less, Cu: 0.01% by mass or less.
Compared to the Al—Mg (0.4 at%)-Si (0.2 at%) alloy in FIG. 3, the Al—Mg—Ge alloy has a maximum hardness of approximately 90 ± 5 HV at any aging temperature, This is very different from the Al—Mg—Si alloy whose hardness decreases as it rises.
Moreover, it is clear that the rise of hardness in the early aging period is faster with the Al—Mg—Ge alloy, and the time to reach the maximum hardness is shorter.
4A is a TEM bright field image of a sample obtained by aging an Al—Mg—Si alloy for 12 ks at 523 K. FIG. 4B shows that the latter has a larger number of precipitates. it is obvious.
FIG. 5 shows the result of confirming the consistency with the aluminum matrix by observing the β ′ phase in the Al—Mg—Ge alloy with a high-resolution transmission electron microscope.
When the crystal lattice fringes of the central β ′ phase and the surrounding aluminum matrix are connected, it is found that the connection is good and the matching is good.
Furthermore, FIG. 6 is an electron diffraction pattern obtained from the β ′ phase in the Al—Mg—Si alloy (a) (c) and the Al—Mg—Ge (b) (d) alloy.
The circles (c) and (d) in the figures are the aluminum matrix, and the circles are the electron diffraction patterns from the β ′ phase. In particular, the diffraction spots of the β ′ phase indicated by the large arrows are Al. The -Mg-Ge alloy overlaps with the aluminum matrix, whereas the Al-Mg-Si alloy is displaced.
This is the same result as the matching in the high-resolution transmission electron microscope shown in FIG. 5, and the β-phase of the Al—Mg—Si alloy has poor matching, whereas the Al—Mg—Ge alloy is good. It was confirmed that.
FIG. 7 shows the results of actual measurement of the lattice constant of the Al—Mg—Ge alloy according to the present invention.
In actual measurement, the lattice constants were calculated as a = 0.72 nm and c = 0.405 nm.
Based on this, the lattice misfit of the {100} face of the aluminum matrix and the {1120} face of the β ′ phase was significantly improved from the expected 12.59%, which is estimated to be 11.11%.
On the other hand, the lattice misfit between the aluminum parent phase {200} plane and the β3 phase {3300} plane increased to 2.46%, but it is less than 10% and there is no problem.
Such a large change in lattice constant suggests that the Mg / Ge ratio, which is the chemical composition expected by the β ′ phase, is not 2: 1, and that the ratio of Mg or Ge may be high.
The result of the elemental analysis experiment shows that the chemical composition of the β ′ phase is Mg: Ge = 3: 1, which is considered to be the reason that the crystal lattice expands and the consistency with the parent phase is improved.
FIG. 8 shows a tensile test result of a sample that has been subjected to aging treatment up to the maximum hardness at 523K.
Compared to the reference Al-Mg-Si pseudo binary alloy (base) (a) and excess Si type alloy (exSi) (b) that have been aged to 423K for reference, the maximum strength is inferior There is no.
Moreover, above all, the characteristic is that the growth of several percent is usually improved by over 10%.
From the above results, the intermediate phase precipitated by aging treatment has a different lattice constant from that of the Al-Mg-Si alloy, and can maintain resistance to the parent phase even at high temperatures, which can be a resistance to deformation. We obtained direct evidence that even coarse, it contributes to hardness.

Next, as an excess Mg alloy, an aluminum-based alloy of pure aluminum with Mg: 0.8 at% and Ge: 0.2 at% was prototyped.
The composition analysis results after the trial production were Mg: 0.95 at%, Ge: 0.22 at%, Fe: 0.02 mass% or less, and Cr, Mn, Ti, and Cu were each 0.01 mass% or less.
FIG. 9 shows an age hardening curve of the previous balance composition alloy (Mg: 0.4 at%, Ge: 0.2 at%) and the current excess Mg alloy (Mg: 0.8 at%, Ge: 0.2 at%). Indicates.
FIG. 10 shows a TEM image (transmission electron microscope) of the precipitated structure, and FIG. 11 shows an HRTEM image (high resolution transmission electron microscope) of the intermediate phase.
As a result, it is presumed from the TEM image of FIG. 10 that the excess Mg alloy has a larger number of precipitates per unit area than the balanced composition alloy, and the maximum hardness value is higher as shown in FIG.
Further, from the HRTEM image shown in FIG. 11, even in the case of an excess Mg alloy, an intermediate phase showing a 0.72 nm lattice spacing in which the crystal lattice is expanded is observed as in the case of the balance composition alloy.

  Since the Al-Mg-Ge-based alloy and the alloy material using the same according to the present invention can provide high strength even at a relatively high temperature, it is excellent in baking hardness that can be artificially aged simultaneously with baking coating. Therefore, it has a high utility value as a material used in a relatively high temperature environment such as an automobile material, an industrial machine material, or an engine surrounding material.

The change in crystal lattice expected when Si in the β ′ intermediate phase is replaced by Ge is shown. The hardness change curve when an Al-Mg-Ge alloy is aged at 423, 473, 523K is shown. The hardness change curve when an Al-Mg-Si alloy is aged at 423, 473, 523K is shown. The TEM bright field image of the sample which aged Al-Mg-Si alloy (a) and Al-Mg-Ge alloy (b) for 12 ks at 523K is shown. The high resolution transmission electron microscope observation result of the β ′ phase in the Al—Mg—Ge alloy is shown. The electron diffraction pattern obtained from the β 'phase in the Al-Mg-Si alloy (a) (c) and the Al-Mg-Ge alloy (b) (d) is shown. The lattice constant measurement result of the β ′ intermediate phase in the Al—Mg—Ge alloy is shown. The tension test result of an Al-Mg-Ge alloy and an Al-Mg-Si alloy is shown. (Al-Mg-Ge alloy was 523K, Al-Mg-Si alloy was 423K, and a sample that had been aged to the maximum hardness was used.) The 523K age hardening curve of a balance composition alloy and Mg excess alloy is shown. The TEM image of the precipitation structure | tissue of a balance composition alloy and Mg excess alloy is shown. The HRTEM image of the intermediate phase of a balance composition alloy and Mg excess alloy is shown.

Claims (4)

  An aluminum-based alloy containing Mg: 0.2 to 1.0 at%, Ge: 0.1 to 0.5 at%, and excellent in age hardening rate and high temperature strength.   An aluminum-based alloy characterized by containing Mg: 0.4 to 0.8 at%, Ge: 0.2 to 0.4 at%, and being excellent in age hardening rate and high temperature strength.   Furthermore, Mn: 0.01-0.1at% is contained, The aluminum base alloy of Claim 1 or 2 characterized by the above-mentioned. The aluminum alloy using the aluminum-based alloy according to any one of claims 1 to 3, wherein the aluminum alloy is aging-treated so that 1.0 to 1.4 mass% of Mg ₂ Ge precipitation phase appears in the aluminum alloy material. Wood.