KR100469929B1 - Aluminium Alloy Product - Google Patents

Abstract

The present invention relates to an aluminum alloy product for use as an article of good damage tolerance for aircraft, such as a faceplate of a fuselage. The aluminum alloy composition is formed of dispersed particles selected from the group consisting of 3-7% by weight of magnesium, 0.03-0.2% by weight of zirconium, 0.2-1.2% by weight of manganese, 0.15% by weight of silicon and scandium, erbium, yttrium, gadolinium, holmium and hafnium 0.05-0.5% by weight of element, the remainder of aluminum and inevitable impurities.

Description

Aluminum alloy and aircraft parts made therefrom {Aluminium Alloy Product}

Almost all aircraft have a fuselage plate made of Alclad 2024-T3. The base metal, 2024-T3 sheet, has the necessary strength and damage tolerances for applications in the aircraft industry, but has weak problems with point corrosion and / or grain boundary corrosion. To compensate for this problem, the base metal is effectively isolated from the external environment by a paint or coating system or a coating layer combining the two.

The coating process involves bonding a thin layer of aluminum alloy, the cathode of 2024-T3, to both sides of the 2024-T3 sheet. These layers act as protective layers and provide galvanic protection against 2024-T3 if the coating is damaged. If these layers are intentionally removed by mechanical or chemical milling for weight reduction, the 2024-T3 sheet may be protected by coating and / or cathodication.

The protection system is generally effective, but has some disadvantages. Alclad layers contribute little to strength, increase the weight of the sheet and can cause fatigue cracking. Other coating systems also add weight and cannot protect the 2024-T3 base metal if damaged. Cathodic surfaces are fragile and can cause cracks. Another disadvantage of the 2024-T3 sheet is its relatively high density (0.101 lb / in ³ ).

The present invention relates to aluminum alloy products, and more particularly, to aluminum alloy products applicable to the aerospace industry.

It is a primary object of the present invention to provide an aluminum alloy article having good damage tolerances, useful for aircraft including fuselage plates, wings, stringers and / or pressure bulkheads. The alloy of the invention has a bulkhead with low density, good corrosion resistance and strength and toughness, eliminating the need for coating, painting and or other basic metal protection systems.

Another object of the present invention is to provide excellent damage, such as fuselage plates, with sufficient strength usually produced through work hardening of a uniform matrix composition, without precipitating particles that are electrochemically different from the matrix, such as 2024-T3 aluminum. It is to provide an aluminum alloy product having a tolerance.

It is another object of the present invention to provide an alloy of lower density than 2024-T3 in order to reduce weight in commercial aircraft. Low density alloys can increase fuel efficiency and improve payload. Another object of the present invention is to provide an aluminum alloy system that maintains good performance over the long life of a commercial aircraft (typically 20 to 40 years). It is also an object of the present invention to provide a material with improved fatigue strength.

One example of the present invention is dispersed particles selected from the group consisting of 3-7% by weight of magnesium, 0.03-0.2% by weight of zirconium, 0.2-1.2% by weight of manganese, 0.15% by weight of silicon and scandium, erbium, yttrium, gadolinium, holmium and hafnium An aluminum alloy product composed of an aluminum alloy composition containing 0.05 to 0.5% by weight of a forming element and the remaining aluminum and inevitable impurities.

In the following, unless otherwise stated, all aluminum compositions are expressed in weight percent. Marked with a numeric range includes each corresponding number and all fractions in between. For example, 0.05-5 wt% scandium includes 0.48,0.49 and 0.4995 wt% scandium in the same manner as 0.06, 0.07, 0.08 and 0.1 wt%.

By "substantially free" is meant that it is not intentionally added to the alloy composition, which means that it contains no content other than the amount of inevitable impurities in the final product.

The alloy of the present invention is dispersed particles selected from the group consisting of 3-7% by weight of magnesium, 0.03-0.2% by weight of zirconium, 0.2-1.2% by weight of manganese, 0.15% by weight of silicon and scandium, erbium, yttrium, gadolinium, holmium and hafnium It consists of an aluminum alloy composition containing 0.05-0.5 weight% of forming elements and remainder aluminum and an unavoidable impurity. More preferably, the alloy of the present invention is composed of an aluminum alloy composition comprising 3.5-6% by weight of magnesium, 0.06-0.12% by weight of zirconium, 0.4-1% by weight of manganese, 0.08% or less by weight of silicon and 0.16-0.34% by weight of scandium. . Preferred examples of this aluminum alloy are substantially free of zinc and lithium.

Although not limited to a specific theory, it is believed that the formation of rare earth-rich precipitates through the addition of rare earths such as scandium imparts excellent strength and corrosion resistance. These precipitations prevent the loss of strength resulting from plastic deformation. Because of the relatively small size and fine distribution of these particles, the recovery and recrystallization of the resulting alloy is also inhibited.

The alloy of the present invention is an adduct with temperature resistance compared to the same alloy without scandium or similar adducts. "Temperature resistance" means that most of the strength and structure imparted by this alloy remains in the final fuselage's plate article even after exposure to high temperatures of 450 ° F. or higher in subsequent rolling and other operations.

Of the main alloy components of the present invention, the remaining aluminum and impurities not intentionally added do not affect the properties of the alloy of the present invention. Among the main alloy components of the present invention, magnesium is believed to contribute to work hardening and strength. The addition of zirconium is believed to retard the rapid growth of scandium precipitation. Scandium and zirconium also serve other purposes. When added to the alloy to the aluminum-magnesium of the genus, scandium forms finely dispersed intermetallic particles, Al ₃ X, where X is Sc, Zr or both Sc and Zr, a precipitate. Al ₃ (Sc, Zr) dispersed particles impart strength as precipitation-reinforced compounds and in particular delay the recovery and recrystallization process caused by a phenomenon called the Zener drag effect. [CSSmith, TMS-AIMF, 175, 15 (1948) Reference]

This is believed to be the result of the following: Scandium dispersed particles are large in number but very small in size. They act as "fixed" points for the particle migration boundary and points that must pass for metal softening. Recrystallization and recovery are important metalworking processes that soften AIMF metals. In order to soften metals with a large number of Al ₃ (Sc, Zr) particles, it is necessary to heat the material to a higher temperature than metals without such particles. In other words, when subjected to work hardening and quenching under the same conditions, sheet products containing Al ₃ (Sc, Zr) dispersed particles have excellent Sc, Zr strength in alloys without such particles.

The products of the present invention for application to fuselage faceplates and other aircraft components do not soften even during the high temperature heat exposures required for roll sheet products. Thus, the alloy of the present invention maintains the strength obtained through rolling. Other alloys that do not include scandium tend to weaken through rolling, thus weakening the strength of the final product. The advantage of adding zirconium is to maintain the small, AIMF space of the Al ₃ X particles, resulting in the Zener drag effect.

Although it is desirable to limit the silicon in aluminum alloys, the silicon in the refractory should necessarily be included. Since at least 80% of the alloy in commercial is obtained from scrap, silicon is added. The alloy of the present invention contains 0.15% by weight or less, preferably 0.08% by weight or less, most preferably 0.05% by weight or less.

The aluminum alloy products of the present invention are particularly suitable for products requiring damage tolerance. In particular, it is suitable for aluminum products used in various aircraft body plates, wings, stringers, or pressure bulkheads.

The following examples are provided to illustrate the present invention and do not limit the present invention thereto.

Example

This example adds the following main components to the aluminum base alloy of the present invention.

Mg Mn Sc Zr

Alloy A 4.0-0.23 0.10

Alloy B 4.1 0.62 0.23 0.09

Alloy C 6.5-0.23 0.09

The remainder of each alloy is made of aluminum and indispensable impurities.

The alloy was cold cast into 2-1 / 2 × 12 inch ingots and the rolled surface was scraped. Alloy A was not ingot and Alloy B was homogenized 5 hours at 550 ° F. and 5 hours at 800 ° F. Alloy C was homogenized at 500 ° F. for 5 hours and at 750 ° F. for 6 hours. The scraped ingot was heated at 550 ° F. for 30 minutes and cross-rolled about 50% to an official thickness of 1 inch. Alloys A and B were reheated to 550 ° F. and rolled to a final formula thickness of 0.1 inch. After stabilizing at 550 ° F. for 5 hours, the mechanical properties of each alloy were evaluated. Ingot of alloy C was heated to 700 ° F. and cross-rolled to about 1 inch. The slab was reheated to 530 ° F. and rolled to 0.5 inch thick. Plates made of Alloy C were aged for 15 hours at 500 ° F. until they reached 28% of the International Annealing Copper Standard (IACS) electrical conductivity. The alloy C plate was reheated back to 500 ° F., rolled to a final thickness of 0.1 inch, and then final heat treated at 500 ° F. for 2 hours.

Table 1 shows the mechanical properties and corrosion data of alloys A, B, and C, together with fuselage plate materials known as 2024-T3 aluminum, 6013-T6 aluminum and Alcoa's C-188 products manufactured by US Pat. No. 5,213,639. Compared.

The material of the present invention has a moderate tensile strength. Toughness FCG can be seen from the toughness and fatigue crack growth (FCG) per center notch, the toughness index of alloys A and B. The resistance to intergranular attack of the present invention is also excellent. The standard for measuring such attack for Al-Mg based alloys is the ASSET (or ASTM G-66) test after sensitization at 212 ° F. Alloy B only showed delamination of the EA level but good resistance to delamination attack. Other materials of the comparative example showed point corrosion and some blisters. The material of the present invention showed excellent SCC resistance even in immersion tests using sodium chloride solution.

Table 1

Property Alcad2043-T3 AlcadC-188 6013-T6 Alloy A Alloy B Alloy C Strength (ksi) UTS L 66 66 57 56 61.4 63.7 LT 65 57 57 55 60.4 64.6 45 > 68.5 --- --- 51 55.6 60.0 TYS L 55 55 53 48 48.2 51.8 LT 45 45 51 49 48.9 53.0 45 > 50.4 --- --- 45 45 49.5 Elongation L 14 14 11 11.0 12.0 LT 18 18 11 16 16.2 12.0 45 > 21 --- --- 22 18.8 12.0 Density (lb / in ³ ) 0.101 0.100 0.098 0.0958 0.0963 0.0943 Toughness (ksi√in) 6 "panel / 16" 6 "panel 6 "panel Kc T-L --- --- 108/147 91.4 97.2 Kapp T-L --- --- 62/94 60.5 62.8 fatigue Life at 25 ksi (Kt = 3; R = 0.1) --- --- 3 X 10 ⁴ 3 X 10 ⁴ 2 X 10 ⁴ DKT-L at 10 (-4) 20 24 --- 23/24 21 15 Elongation (Msi) 10.6 10.6 9.9 10.1 10.4 10 Corrosion (after 1 week at 212 ° F) ASSET (24 hours) ASTM G-66 EC EC PA EA P Exco (96 hours) ASTM G-34 ED ED N --- N MASTMASSIS (4 weeks) ASTM G-85 ED ED N --- EA SWAAT (2 weeks) ASTM G-85 --- --- --- EC --- SCC ¹ ASTM G-47 (180 day exposure) --- --- 0/3 0/3 0/3

1.SCC: (Failure Recovery / Samples) Reverse, 75% Y.S (after 1 week at 212 ° F)

The aluminum alloy of the present invention is useful for aircraft parts, particularly fuselage plates, vanes, stringers, pressure bulkheads, and the like.

Claims (104)

Consisting of 3.5-6% magnesium, 0.03-0.2% zirconium, 0.2-1.2% manganese, 0.15% or less silicon, 0.16-0.34% scandium, 0.25% copper and erbium, yttrium, gadolinium, holmium and hafnium An aluminum alloy composed of a composition comprising 0.05-0.5% by weight of a dispersed particle forming element selected from the group and the remaining aluminum and unavoidable impurities. delete delete delete delete delete delete delete delete delete delete delete delete The aluminum alloy according to claim 1, wherein the alloy does not contain zinc and lithium. delete delete Magnesium 3.5-6%, Zirconium 0.03-0.2%, Manganese 0.2-1.2%, Silicon 0.15% or less, Scandium 0.16-0.34%, Copper 0.25% or less and Erbium, Yttrium, Gadolinium, Holmium and Hafnium An aircraft component of low density, good corrosion resistance and good strength and toughness, made of an aluminum alloy comprising 0.05-0.5% by weight of a dispersed particle forming element selected from the group consisting of the remaining aluminum and unavoidable impurities. 18. The aircraft component of claim 17, wherein the aircraft component is selected from the group consisting of fuselage faceplates, vanes, stringers, and pressure bulkheads. delete delete delete delete delete delete delete delete delete delete delete 18. The aircraft component of claim 17, wherein the alloy does not contain zinc. 18. The aircraft component of claim 17, wherein the alloy does not contain lithium. delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete