JPH02258958A - Production of high tensile al-li alloy for superplastic forming - Google Patents

Abstract

PURPOSE:To produce a high tensile Al-Li alloy for superplastic forming having high strength and high elongation by subjecting an ingot of an alloy in which specific percentages of Li, Cu, Mg, and Zr are incorporated to Al to precipitation treatment under specific conditions. CONSTITUTION:An ingot of an alloy having a composition consisting of, by weight, 2.80-4.00% (not including 2.80%) Li, 0.80-2.50% Cu, 0.50-1.80% Mg, 0.08-0.20% Zr, and the balance Al with inevitable impurities is subjected to precipitation treatment at 220-400 deg.C for 1-100hr. By this method, the high tensile Al-Li alloy in which structure is homogenized and workability and elongation are improved and which shows strength and elongation superior to those of seven thousand series Al alloy by means of proper ageing treatment after superplastic forming is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing an Al-Li alloy for superplastic forming, which is lightweight and has excellent high-strength characteristics, and is suitable for example as an aircraft material.

[Conventional technology]

A/, -Li-based alloys are attracting attention as materials for transportation equipment, especially aircraft, because of their light weight and high strength.

In addition, Mutr, +i series alloys exhibit excellent superplastic properties,
Large elongation occurs at high strain rates. Integral molding that utilizes this superplasticity reduces the number of parts, eliminates the need for rivets and other joints, and enables further weight reduction, which is useful for increasing aircraft operating efficiency and reducing operating costs. .

It is particularly useful as a replacement for parts such as door panels that have many parts. This alloy has a matrix of Al, which is often used as an aircraft material, so one of its advantages was that it could be applied without major design changes.

[Problem to be solved by the invention]

Conventionally, as an AL-Li alloy (209 with 3u added)
0 alloy, 8090 alloy with added Cu and Mg, etc. have been developed, and some have been put into practical use as materials for aircraft.
Ru. Although it has been actively researched as a superplastic molding material, it has not yet been put into practical use.

These 2090 alloys and 8090 alloys exhibit sufficient superplastic properties, but the 70 alloys conventionally used in aircraft
Slightly inferior in strength and elongation at room temperature compared to 00 series Al alloys (tensile strength of approximately 45
kgf/am”, elongation 5 壬).For practical use as an aircraft material, the tensile strength must be 60 kgf/wsx.
``It requires an elongation of 10 minutes or more.

An object of the present invention is to improve the above-mentioned points and provide a method for producing a high-strength Al-Li alloy that has higher strength and elongation than conventional materials.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides alloy components such as Li,
After specifying Cu, Mg, and Zr, sufficient precipitation treatment is performed to homogenize the structure to improve workability and elongation, and by appropriate aging treatment after superplastic forming, the strength exceeds that of 7000 series Al alloy. and was able to exhibit elongation.

[Effect]

The reason why the alloy component composition range and heating temperature range are limited in the present invention will be explained.

Li: Below 2.80Wt, the strength is insufficient and 4.00Wt is insufficient.
If wt exceeds 1, casting becomes difficult, the obtained ingot has many defects, and even with this manufacturing method, the workability becomes poor.

Ou:0. If it is less than 80 wt'j, the strength will be insufficient and 2
．． When it exceeds 50wt1, workability decreases.

Similar to Mg: Ou, strength is insufficient when α50 is less than 4, and workability is reduced when it exceeds 1.80 wtl.

Zr: 0. If it is less than O8Wt1, the grains will not be refined and the superplastic properties will deteriorate, and if it exceeds α20wt'l, it will be difficult to cast.

If the precipitation treatment temperature of the ingot is less than 220°C, one brittle phase will precipitate, and subsequent workability will deteriorate. Moreover, if the temperature exceeds 440° C., the precipitates are solid-dissolved again and the material is hardened, resulting in a decrease in subsequent workability, so that the structure after processing is not homogenized.

If the precipitation treatment time is less than 1 hour, the precipitation treatment will not be effective.
If it exceeds 100 hours, the effect will be saturated and it will be uneconomical.

If the forging temperature is less than 220°C, a brittle δ phase will precipitate, which tends to cause processing cracks, and if it exceeds 440°C, the processed structure will not be homogenized.

If the precipitation treatment temperature during processing is less than 220°C, brittle δ phase will precipitate and subsequent workability will deteriorate; if it exceeds 440°C, the precipitates will re-dissolve into solid solution, hardening the material and reducing subsequent workability. descend. If the precipitation treatment time is less than 1 hour, the precipitation treatment has no effect, and if it exceeds 100 hours, the effect is saturated and it is uneconomical.

〔Example〕

Example 1 Li: A OWt'l, Ou: 1.2 wtl, M
A 100 t (200 W) ingot with alloy components of g: Q, 9 wtl and zr: α12 wtl was used. 530℃
After soaking for 24 hours, a precipitation treatment was performed at 400° C. for 12 hours. It was forged from 200t to 40t at 400°C. After precipitation treatment at 300℃ x 72 hours, 50t on the surface side
And so. It was rolled to 1.5t at 300°C and its performance was investigated.

The evaluation method was to quench the rolled material at 500°C, which is the superplastic forming temperature, and then perform an aging treatment at 160°C for 72 hours, and then investigate the tensile properties. A commercially available 7475 alloy was used. The superplastic elongation was 1.5, which was defined as the elongation when stretched at 500° C. and an initial strain rate of 5.6×10-”/8 in the plate direction.

Example 2 Li: K 2 wtl, Ou: t 5 vt%, M
g: 0. 9 wtl, Zr: +112 wtl,
The remaining Al alloy ingot (100mm thickness, 200W width) was
After soaking at 530°C for 24 hours, precipitation treatment was performed at 420°C for 12 hours. It was then rolled at 500°C to a thickness of 2cm. This rolled material was quenched at 500°C, which is the superplastic forming temperature, and then subjected to aging treatment at 160°C for 72 hours, and its performance was investigated.The tensile strength was 5.53, and the specific strength was 9/-2. It had 09 x 10' fins and a length of 411 α6.

These results are summarized in Table 1.

〔Effect of the invention〕

Since the present invention is configured as described above, the T6 treatment after superplastic forming according to the present invention can achieve a strength of 50
kg/war" or more, and the specific strength is also 7475.
It has now become possible to produce an AA-Li alloy for superplastic forming, which has an elongation of 10 times or more, exceeding that of the alloy.

Claims (3)

[Claims] (1) Li: 2.80 to 4.00wt% (however, 2.80wt%
(excluding wt%), Cu: 0.80 to 2.50wt%,
Mg: 0.50-1.80wt%, Zr: 0.08-0
．． A lightweight, high-strength superplastic forming Al-
A method for producing a Li-based alloy. (2) The lightweight high-strength superplastic forming Al-
A method for producing a Li-based alloy. (3) The method for producing a lightweight, high-strength Al-Li alloy for superplastic forming according to claim 1 or 2, wherein a precipitation treatment is performed at 220° C. to 440° C. for 1 to 100 hours during or after processing.