JPS6263641A - High-strength aluminum-alloy extruded material excellent in low-cycle fatigue characteristics - Google Patents

Abstract

PURPOSE:To obtain a high-strength Al-alloy extruded material excellent in low-cycle fatigue characteristics by incorporating specific percentage of Zn, Fe, Mg and Si to Al. CONSTITUTION:An Al alloy consisting of, by weight, 5.0-10% Zn, 0.25-1.0% Fe, 0.5-3.6% Mg, Si in an amount limited to <=0.20% and the balance Al with inevitable impurities and containing, if necessary, 1 or >=2 kinds among <=0.4% Mn, <=0.3% Cr, <=0.3% Zr, <=0.5% Ti and <=0.05% B is prepared. In this way, the Al-alloy extruded material combining high strength with high toughness, increased in resistance to local brittle fracture which occurs when subjected to light load and also increased in low-cycle fatigue strength can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to high-strength aluminum alloy extrusions with excellent low cycle fatigue properties, particularly aluminum alloys suitable as materials for membrane structures, hard bats, motorcycle rims, etc. Regarding extruded materials.

Conventional Technology and Problems High-strength aluminum alloys are mainly used for the above-mentioned applications, and these high-strength aluminum alloys are generally desired to have high fracture toughness, and for this purpose, conventionally, alloy compositions have been Fe.

Improvements have been made by simultaneously reducing Si (eg, AA7475.7150 alloy).

However, when such an aluminum alloy is molded into Oshiyamamura, the following drawbacks arise. That is, in general, in extruded materials, (111) and [100
], but this tendency is further promoted by the reduction of Fe in the alloy components. For this reason, materials such as those mentioned above are
Although high toughness values were obtained in the 99-based test and it is known to have high strength, when dynamically monitoring fracture using AE (Acoustic Goremission), it was found that the final fracture load was much smaller than the final fracture load. It can be seen that a slight rack is generated due to the load. Therefore, such materials have the problem that even if a load is much smaller than the final breaking load, failure may occur in an extremely short life if repeated stress is applied.

This invention was made to solve these problems, and at the same time maintains high strength and high toughness, (1
11) and (100) as much as possible (by suppressing the textures as much as possible), we aim to provide an aluminum alloy extruded material with particularly improved low cycle fatigue properties by increasing the resistance to local brittle fracture that occurs during low load loading. This was done as a 1j objective.

Means to Solve the Problem - In order to achieve the objective listed in h., the inventors have conducted various experiments and research, and have found that the content of the compound in the alloy composition, whose content had been reduced in the past due to the "toughness" - Regarding Fe and Sl, if only Si is reduced and Fe is actively added, it is possible to not only suppress the texture of the extruded material, but also maintain high strength and toughness. This invention was completed based on this knowledge.

That is, in this invention, Zn: 5.0 to 1 (1 wt%,
Fe: 0.25-1, Owt%, Mg: 0.5-3.6
wt%, or further contains Cu: 3.0 wt% or less, and the content is suppressed to Si: 0°20 wt% or less, and if necessary, Mn + 0.4 wt% or less, Cr
: 0.3wt% or less, Zr: 0.3wt% or less, Ti:
The gist is a high-strength aluminum alloy extruded material with excellent low cycle fatigue properties, containing one or more of B: 0.5 wt% or less, B: 0.05 wt% or less, and the remainder consisting of aluminum and unavoidable impurities. It is.

The meaning of addition of each component in the above aluminum alloy composition and the reason for limiting the composition range will be explained as follows.

Zn is an essential element for increasing the strength of alloys as a hardening element, but if it is less than 5.0 wt%, its effect is small, and if it is contained in a large amount exceeding 10 wt%, stress corrosion cracking resistance deteriorates. This makes it impractical.

Fe is an element necessary to weaken the [111] and (100) textures of the extruded material, in particular, and to prevent the formation of fine racks in the extruded material due to repeated stress under low loads. However, if the content is less than 0°25 wt%, the effect is poor, and on the other hand, if the content exceeds 1°0 wt%, the fracture toughness value decreases. The preferred content range is 0.6 to 0.8wt
%.

Mg contributes to improving the strength of the alloy, but 0.5
If it is less than 3.6 wt%, the effect will be poor, and if it exceeds 3.6 wt%, extrusion processability will deteriorate.

In this invention, in addition to the above essential components, the content of Cu is 3.0w.
It is permissible within a range of t% or less. Cu contributes to improving stress corrosion cracking resistance as well as improving strength, but 3
．． If it exceeds 0 wt%, mechanical properties will deteriorate.

Si originally has the effect of hardening alloys, but as previously thought, Si
Since it forms Si) and lowers the fracture toughness value, it is necessary to keep the content as low as possible, at least 0.2 wt%.

Furthermore, in this invention, in addition to the above components, Mn:
0.4wt% or less, Cr: 0.3wt% or less, Zr: 0
．． 3wt% or less, Ti: 0.5wt% or less, B: 0.0
It is permissible to contain one or more of 5 wt% or less. All of these elements are effective in stabilizing the structure, but when Mn exceeds 0.4 wt% and Cr
exceeds 0.3 wt%, Zr exceeds 0.3 wt%, or Ti exceeds 0.5 wt%, giant crystallized substances are formed and mechanical properties are deteriorated. Also, B is 0.05wt
When it exceeds %, the toughness deteriorates.

Effects of the Invention As is clear from the examples, the aluminum alloy extruded material according to the present invention maintains high material strength by suppressing Si and increasing Fe in the alloy composition. At the same time, it has excellent toughness, and (
111) (100) texture can be suppressed,
Therefore, even when repeated stress with a low load is applied, fine racks do not occur, and low cycle fatigue characteristics can be improved. In addition, this improvement in low cycle fatigue properties can simultaneously reduce stress corrosion cracking susceptibility.

Example Next, examples of this invention will be shown.

A-Zn alloys having various compositions shown in Table 1 were manufactured into extruded materials by a conventional method, and then subjected to a compacting treatment and an aging treatment under the same conditions to prepare samples. For each sample, the tensile strength, 0.2% yield strength, and elongation were measured, and a fatigue test was conducted. The fatigue test was conducted by repeating a load stress of 35 kgf/- 104 times and then examining the presence or absence of breakage of the sample. The results are shown in Table 2.

[Margin below]

Table 2 (Note) ○... No fracture was observed ×... Fracture or observed Although it has the same tensile strength and yield strength, and has the same elongation and excellent toughness, it has excellent low cycle fatigue properties with no breakage observed after fatigue tests. I was able to confirm it.

Patent Applicant Showa Aluminum Co., Ltd. OkiTT: Mrh'77 October 18, 1985 Patent Application No. 203936 2, Title of Invention High strength aluminum alloy extruded material with excellent low cycle fatigue properties 3, Relationship with the case of the person making the amendment Patent applicant address: 6-224 Kaizan-cho, Sakai City Name: Showa Aluminum Co., Ltd. Representative: Ishi
Chika I 4, Agent Address: 72-47 Unagidani Nakano-cho, Minami-ku, Osaka City, Title column of the application subject to amendment, Number of inventions stated in the scope of claims, (2) Title of invention section. Between the inventor's section and the inventor's section, "2
, the number of claimed inventions 2" is added, and subsequent item numbers "2.", "3.", "4.", "5."
．． ” to “3.” and r4., respectively. J, "5.", "6.
” he corrected.

that's all

Claims (2)

[Claims] (1) Zn: 5.0-10wt%, Fe: 0.25-1
．． 0 wt%, Mg: 0.5 to 3.6 wt%, and the content is suppressed to below Si: 0.20 wt%,
And if necessary, Mn: 0.4 wt% or less, Cr: 0.
3wt% or less, Zr: 0.3wt% or less, Ti: 0.5
A high-strength aluminum alloy extruded material having excellent low-cycle fatigue properties, containing one or more of B: 0.05 wt% or less, and the remainder consisting of aluminum and unavoidable impurities. (2) Zn: 5.0-10wt%, Fe: 0.25-1
．． 0 wt%, Mg: 0.5 to 3.6 wt%, Cu: 3.
Contains 0wt% or less, and Si: 0.20wt
% or less, and if necessary, Mn: 0
．． 4wt% or less, Cr: 0.3wt% or less, Zr: 0.
3wt% or less, Ti: 0.5wt% or less, B: 0.05
A high-strength aluminum alloy extruded material with excellent low-cycle fatigue properties, containing one or more of the following by wt% or less, with the balance being aluminum and unavoidable impurities.