WO1997008354A1

WO1997008354A1 - Aluminum alloy sheet excellent in high-speed superplastic formability and process of forming the same

Info

Publication number: WO1997008354A1
Application number: PCT/JP1995/002564
Authority: WO
Inventors: Hideo Yoshida; Hiroki Tanaka; Kouichirou Takiguchi
Original assignee: Sumitomo Light Metal Industries, Ltd.
Priority date: 1995-08-23
Filing date: 1995-12-12
Publication date: 1997-03-06
Also published as: DE69519444T2; JPH0959736A; US20010001969A1; EP0846781B1; JP3145904B2; EP0846781A4; DE69519444D1; EP0846781A1

Abstract

An alloy containing 3.0 to 8.0 wt.% of Mg, 0.001 to 0.1 wt.% of Ti and as small amounts of Fe and Si (as impurities) as 0.06 wt.% or below and the balance consisting of A1 and unavoidable impurities wherein the number per square millimeter of grains of an Al-Fe-Si compound having a diameter of 1 νm or above is 2000 or below, the mean crystal grain diameter is 25 to 200 νm and the elongation is 350 % or above as worked at 350 to 550 °C and a strain rate of 10?-2 to 100¿/s. This alloy may further contain a small amount of Cu, Mn and/or Cr and is formed at a temperature of 350 to 550 °C and a strain rate of 10?-3 to 100¿/s. An aluminum alloy sheet which is excellent in high-speed superplastic formability and therefore can be formed at high temperature and high speed is obtained and the use of this sheet shortens the forming time to improve the productivity.

Description

Description Aluminum alloy sheet excellent in high-speed superplastic forming and forming method

The present invention, high-speed superplastic forming excellent aluminum alloy plate, A 1 one Mg-based alloy sheet, especially strain rate to enable high-speed superplastic forming of 10 one ² ～10Vs, and to a molding how. Background art

A1— A superplastic alloy has been developed that suppresses recrystallization and refines the crystal grains of Mg-based alloys, for example, to produce several hundred percent elongation in the high temperature range of 500 to 550, and is applicable to various applications. have been, conventional a 1 - Mg-based superplastic alloy, in which elongation of the optimum is obtained in the molding at a molding speed (strain rate) is 10- ⁴ ~10_ ³ / s, such molding rate When molding is applied, the molding of general objects and the like takes about 30 to 100 minutes, for example.Therefore, the productivity is low in industrial scale production. There is a need for a superplastic alloy that can be formed.

For example, Mg: 2.0-6.0%, Be: 0.0001-0.01%, Ti: 0.001-0.15%, Fe and Si of impurities are both limited to 0.2% or less, and metals based on impurities are limited. An aluminum alloy plate in which the maximum grain size of the intermetallic compound is limited to 10 / m or less has been proposed (Japanese Unexamined Patent Publication No. 4-72030). This alloy plate has a strain rate of 10% at high temperature deformation at 400 ° C. - while indicating 350% or more elongation at Vs, hand stretch as the molding rate is increased is reduced, 10- not sufficient elongation is obtained in ² / s or more strain rate.

It also contains Mg: 2 to 5%, Cu: 0.04 to 0.10%, further contains a small amount of transition elements, Cr, Zr, and Mn as selective components, the Si of impurities is 0.10% or less, and 6 is 0. A superplastic aluminum alloy sheet with a grain size of 20 m or less and a grain size and volume fraction of transition element-based intermetallic compound of which are limited to 15% or less and which are controlled to specific ranges has also been proposed. No. 4-three hundred eighteen thousand one hundred forty-five JP) is, the alloy plate is also shall that Suitable for molding at 10_ ⁴ / s approximately strain rate, there are problems with high-speed superplastic forming. Disclosure of the invention

In order to solve the above-mentioned conventional problems in the A1-Mg superplastic aluminum alloy, the present invention provides an alloy component and a quantitative combination thereof, an impurity amount, a distribution mode of an intermetallic compound based on the impurity, and a crystal. It was the result of repeated and diversified experiments and studies on the relationship between grain size and superplastic forming.The purpose was to limit Fe and Si as impurities, in particular. the specific crystal grain size and specific distribution of a 1- F e- S i based compound-based, high-speed molding rate, for example 10 - in the molding of a strain rate of ² to 10 ° / s, sufficient elongation An object of the present invention is to provide an aluminum alloy sheet excellent in high-speed superplastic forming and a method for forming the aluminum alloy sheet.

The aluminum alloy sheet excellent in high-speed superplastic forming according to the present invention for achieving the above object contains Mg: 3.0 to 8.0%, Ti: 0.001 to 0.1%, and has Fe as an impurity. 0.01% or less, Si is limited to 0.06% or less, an alloy consisting of the balance of A1 and unavoidable impurities, and an A1-Fe-Si system having a particle size of 1m or more in the matrix of the alloy. compound 2000 / fraction ² below, the elongation when the average crystal grain size was molded at a strain rate of 10- ² ～10Vs in a temperature range of 25~200 jam, 350 ~550 ° C is 350% or more This is a basic feature of the configuration.

In addition, Cu: 0.05 to 0.50% in addition to Mg and Ti; and Mn: 0.10 or less and Cr: 0.10% or less in addition to Mg and Ti Or the second and third features of the present invention are to contain one or two of Mn: 0.10% or less and Cr: 0.10% or less in addition to Mg, Ti, and Cu. . Method of forming an aluminum alloy sheet with excellent high-speed superplastic forming according to the present invention, the above aluminum alloy plate, and characterized in that at a temperature of 350 to 550 ° C, molding pressure E at a strain rate 10- ³ ~10Vs I do. 708354

Explaining the significance of the components contained in the present invention and the reasons for limitation, Mg has an action of recrystallizing the alloy during high-temperature deformation. The preferred content range is 3.0 to 8.0%, and if less than 3.0%, the effect of accelerating recrystallization is small, and if it exceeds 8.0%, hot workability is deteriorated. Ci ^ Al—An element that improves the superplastic elongation of Mg-based alloys. A preferable content range is 0.05 to 0.50%. If the content is less than 0.05%, the effect is not sufficient, and if it exceeds 0.50%, the hot workability is reduced.

Ti refines the crystal grains of the lump and helps to improve the superplastic properties of the alloy. A preferable content range is 0.001 to 0.1%. When the content is less than 0.001%, the effect is small, and when the content exceeds 0.1%, a coarse compound is formed to impair workability and ductility. Mn and Cr have a function of refining recrystallized grains during recrystallization of an alloy during high-temperature deformation. The preferred contents are each in the range of 0.10% or less, and if it exceeds 0.10%, the A1-FeSi-based compound having a particle size of 1 or more tends to increase, and the high-speed superplastic deformability of the alloy tends to decrease. .

In the present invention, it is important to limit each of Fe and Si as impurities to 0.06 or less. The impurities Fe and Si produce insoluble A1-Fe-Si-based compounds, which precipitate at the grain boundaries, increasing the cavity and reducing the superplastic elongation. Preferably, Fe: 0.05% or less and Si: 0.05% or less are limited. In addition, Be can be added in a range of 50 ppm or less to prevent oxidation of the molten metal, as in the case of the ordinary A1-Mg alloy.

Explaining the alloy structure of the present invention, the A1-Fe-Si-based compound present in the matrix of the alloy causes the above-mentioned adverse effects, and the smaller the compound having a particle size of 1 m or more, the better. Its limit is the particle diameter A 1 -Fe- above 1 〃M is S i diameter compounds 2000 /謹² below, when distributed over 2,000 / field ^2, Kiyabiti to the grain boundary is increased more than Reduces plastic elongation.

Regarding the grain size, it is necessary to control the initial average grain size of the aluminum alloy plate to 25 to 200 um. If the initial average crystal grain size is less than 25 m, the original crystal grains will appear when recrystallized during high-temperature deformation, and the insoluble compounds will precipitate. The grain boundaries disappear, and it is difficult to obtain a recrystallized structure composed of clean crystal grains resulting from the recrystallization. If the initial average grain size exceeds 200 jim, as the deformation rate increases, the shear deformation within the grains becomes remarkable and it becomes easy to break, so that the superplastic elongation decreases,

The forming of the aluminum alloy sheet of the present invention is preferably performed at a temperature of 350 to 550. If the temperature is lower than 350 ° C, Al-Mg compounds and A 1 -Mg-(: 11 compounds are likely to precipitate at the crystal grain boundaries and the elongation decreases. If the forming temperature exceeds 550 ° C occur coarsening of crystal grains, the elongation becomes poor. strain rate during molding is preferably in the range of 10 one ³ ~ ^lOVs, the strain rate of less than 10_ ³ / s, elongation crystal grains are coarsened during deformation At a strain rate exceeding 10 ° Λ, shear deformation occurs in the crystal grains and causes cracks, or precipitation occurs at the crystal grain boundaries to reduce elongation.

The method of manufacturing an aluminum alloy sheet according to the present invention will be described. An aluminum alloy having the above composition is melted and manufactured according to a conventional method, and the obtained ingot is homogenized. The homogenization treatment is preferably performed at a temperature of 450 to 550 ° C. If it is less than 450, g Mg and Cu deviated at the crystal grain interface and cell boundary of the lump are not sufficiently re-dissolved to cause hot rolling cracks. At temperatures exceeding 550 ° C, A1-Mg-based or Al-Mg-Cu-based crystallization, which has a low melting point, causes eutectic melting and causes cracking during hot rolling. .

After homogenization, hot rolling is performed, and the rust structure is taken as the wrought material structure. The starting temperature of the hot rolling is from 250 to 500 ° C, and preferably less than 400 ° C. If hot rolling is started below 250 ° C, the hot rolling becomes difficult due to high deformation resistance of the material. When the hot rolling temperature is increased, it may be difficult to obtain a predetermined grain structure and a distribution of the precipitated compound due to a change in the distribution of the precipitate.

After hot rolling, cold rolling is performed. If necessary, intermediate annealing may be performed during cold rolling. The final annealing of cold rolled material is carried out at temperatures between 350 and 550. In the case of annealing at less than 350 ° C, the anisotropy of the structure formed by hot rolling may not be sufficiently eliminated, and if it exceeds 550 ° C, local melting may occur at recrystallized grain boundaries. The final annealing is Preferably, rapid annealing treatment such as continuous annealing is used.

In the present invention, by limiting the impurities Fe and Si in the A1-Mg-based alloy and adjusting the combination of the above-described production conditions according to the combination of the alloy composition, The existing A 1 -Fe-Si compound is controlled to a specific distribution, and the crystal grain size is controlled to a specific range. The formation of cavities as grain boundaries is suppressed, and recrystallized grains of an average of 20 111 or less are formed during high-temperature deformation, and a strain rate of 10—

It is possible to obtain a sufficient ductility of 350% or more, preferably 380% or more, even with high-speed molding. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, examples of the present invention will be described in comparison with comparative examples.

Example 1, Comparative Example 1

An A1-Mg-based aluminum alloy having the composition shown in Table 1 was melted and agglomerated by the DC method. After the obtained lump was homogenized at 530 for 10 hours, the thickness was reduced to 30 and hot rolling was started at a temperature of 390, followed by hot rolling to a thickness of 4 mm. Next, cold rolling was performed to reduce the sheet thickness to 2 mm, and rapid annealing was performed by rapidly heating to a temperature of 480 ° C and holding for 5 minutes. These plate as a test material, Te temperature of 480, a tensile test was performed at a strain rate of 10- ² / s. Elongation measured S to罕, 1 hide ² number per compound, by a tensile test - the average crystal grain size of each test material (average grain size of the plate surface), particle size 1 in more A l - F e The rates are shown in Table 1. The amount of the compound was determined by image processing. Also, in Table 1, those that are outside the conditions of the present invention are underlined. table 1

As shown in Table 1, all of the test materials Nos. 1 to 5 according to the present invention exhibited excellent elongation exceeding 400%. On the other hand, test material No. 6 had too much Cu content, and test material No. 7 had too much Mg content. . Test material No. 8 has a large amount of large-diameter compounds and a low elongation rate because it contains a large amount of impurities Fe and Si. Test material No. 9 has a low Mg content, so the recrystallization is insufficient during bow deformation and the elongation is low.

Example 2, Comparative Example 2

A 1-Mg-based aluminum alloy having the composition shown in Table 2 was melted and manufactured in the same manner as in Example 1, and processed in the same process and under the same conditions as in Example 1 to produce a test material having a thickness of 2 mra. Then, a tensile test was performed on each test material under the same conditions as in Example 1. Average crystal grain size of each test material, amount of A1-Fe-Si-based compound with a grain size of 1 xm or more, measured by tensile test Table 2 shows the calculated elongation. In addition, in Table 2, those which are out of the conditions of the present invention are underlined.

Table 2

As can be seen from Table 2, the test materials Nos. 10 to 12 according to the present invention all exhibited excellent elongation exceeding 380%, whereas the test materials Nos. 13 to 14 had a high Mn content. However, test material No. 15 has a large amount of Cr, so that the distribution of A1-Fe-Si-based compounds with a particle size of 1 zm or more is large, and high-temperature elongation cannot be obtained.

Example 3, Comparative Example 3

An aluminum alloy having the same composition as that of test material No. 5 of Example 1 was melted and produced in the same manner as in Example 1, and the obtained ingot was homogenized at 520 for 8 hours, and then the ingot was removed. Hot rolling was started at a temperature of 390 ° C with a thickness of 30 mm, and hot-rolled to a thickness of 4 mm. Subsequently, a two-thick plate was formed by cold rolling, subjected to rapid annealing at a temperature of 480 and maintained for 5 minutes. As shown in Table 3, a tensile test was performed using the prepared sheet material as a test material while changing the forming temperature and the strain rate. Table 3 shows the elongation percentage of each test material. In Table 3, those out of the conditions of the present invention are underlined. In addition, each The range of both 50-60 m (average crystal grain size of the plate surface) average crystal grain size of the test material, the particle diameter is more than 1 〃M A l - F e - 1 Yuzuru ² per S i based compound The number was less than 2000.

Table 3

As shown in Table 3, the test materials Nos. 16 to 20 according to the present invention all exhibited excellent elongation of 380% or more, but the test material No. 21 had a high tensile test temperature and coarse grains. And the growth rate is decreasing. Test material No. 22 had a low strain rate, so the crystal grains became coarse during deformation and the elongation decreased. In test material No. 23, the elongation was reduced because the strain rate was too high. Industrial applicability

As described above, according to the present invention, at high temperature, strain rate 10 - ² ~10Vs yo Una A 1-M g series aluminum sufficient superplastic elongation can be obtained even in high-speed molding An alloy plate is provided, and the superplastic forming is performed using the aluminum alloy plate, thereby shortening the forming time and improving the productivity.

Claims

The scope of the claims

1. Contain Mg: 3.0-8.0% (wt%, same hereafter), Ti: 0.001-0.1%, limit Fe as impurity to 0.06% or less, and limit Si to 0.06% or less. , The balance consisting of an alloy consisting of A1 and unavoidable impurities, and having a particle size of 1 in the matrix of the alloy.

A 1 -F eS i based compound above 〃M is 2,000 / image ² or less, the average crystal grain size is 25 to 20 0 〃M, strain rate 10- ² to 10 ^Q / s in a temperature range of at 350 to 550 An aluminum alloy sheet excellent in high-speed superplastic forming, characterized by having an elongation of 350 or more when formed by molding.

2. The aluminum alloy sheet excellent in high-speed superplastic forming according to claim 1, characterized by containing Cu: 0.05 to 0.50.

3. The aluminum alloy excellent in high-speed superplastic forming according to claim 1 or 2, wherein one or two of Mn: 0.10% or less and Cr: 0.10% or less are contained.

4. An aluminum alloy sheet according to claim 1 to 3, wherein, at a temperature in the 350 to 550, secondary aluminum with excellent high-speed superplastic forming, characterized in that the molding at a strain rate of 10 one ³ ~ 10 ^e / s A method for forming a pum alloy plate.