RU2038405C1 - Aluminium-base alloy - Google Patents

Abstract

FIELD: aluminium-base alloys. SUBSTANCE: aluminium-base alloy has, wt. -% magnesium 4-6; lithium 1.3-2.2; copper 0.005-0.2; beryllium 0.0001-0.3; at least one metal taken from the group involving zirconium 0.04-0.12 and scandium 0.03-0.25; at least one metal taken from the group involving calcium and barium 0.002-0.05, and aluminium the rest. EFFECT: enhanced quality of alloy. 2 tbl

Description

 The invention relates to the metallurgy of aluminum-based alloys intended for the manufacture of rolled, pressed and forged semi-finished products used as structural material in critical products, including welded structures.

 Currently, the industry is widely used alloy 1420 of the following composition, wt.

Magnesium 4.5-6.0
Lithium 1.8-2.3
Zirconium 0.08-0.15
Aluminum and impurities Else
(OST 1.90048-77. Deformable aluminum alloys. Grades).

The disadvantages of the alloy are low ductility, especially under shock loads and a low yield strength. Thus a guaranteed level of alloy properties in the longitudinal direction in a state HS1 (heating for quenching 450 ^{° C,} quenching in air, the aging of ¹²⁰ ° C, 12 hours) is as follows: tensile strength of 40 kgf / mm ^2; yield strength 26 kgf / mm ² ; elongation of 7%
Based on the aluminum-lithium-magnesium system, a number of alloys with a higher yield strength have been developed. Closest to the proposed is an alloy [1] based on aluminum, containing, by weight.

Magnesium 4.6-6.0
Lithium 1.3-2.0
Zirconium 0.04-0.12
Scandium 0.03-0.20
At least one
metal selected from
group including
calcium and barium 0.003-0.04
Aluminum Else
The alloy has a high level of mechanical properties (σ _in , σ _0.2 , δ), has good weldability and increased low-cycle fatigue. However, the alloy has a low long-term strength at 20-70 ^about C.

The aim of the invention is to increase long-term strength at 20-70 ^about With maintaining good weldability and a high level of mechanical properties.

 To achieve this goal, beryllium, copper and at least one metal selected from the group consisting of zirconium and scandium are additionally introduced into an aluminum-based alloy in the following ratio of components, wt.

Magnesium 4.0-6.0
Lithium 1.3-2.2
Copper 0.005-0.2
Beryllium 0.0001-0.3
At least one
metal selected from
group including
zirconium 0.04-0.12
Scandium 0.03-0.25
At least one
metal selected from
group including
calcium and barium 0.002-0.05
Aluminum Else In the alloy, the presence of impurities, not more than, wt.

Iron 0.3
Silicon 0.2
Sodium 0.003
The magnesium content in the alloy in the range of 4.0-6.0 wt. provides the necessary level of strength properties and weldability. With a decrease in magnesium content of less than 4.0 wt. the level of properties, especially strength, decreases and the tendency of the alloy to hot cracks increases, both during casting of the alloy and during welding, with an increase in magnesium of more than 6 wt. manufacturability and ductility are falling.

 The lithium content is selected in the range of 1.3-2.2 wt. to ensure weldability, processability during deformation while ensuring the required level of properties. With a decrease in lithium (<1.3 wt.), The elastic modulus decreases, the yield strength, the specific gravity increases, and with a content of more than 2.2 wt. manufacturability, weldability of the alloy is deteriorating.

Copper in an amount of 0.005-0.2 wt. strengthens the solid solution of aluminum, as well as entering the eutectic compounds formed by calcium, barium: α + Al ₄ Ca (Ba, Cu), strengthens the grain boundaries, resulting in higher long-term strength at 20-70 ^{° C,} at a content of more than 0 , 2 wt. weldability deteriorates, and when the content is less than 0.005 wt. long-term strength is reduced.

 Calcium and (or) barium in the indicated amounts neutralize the harmful effect of sodium and exert a modifying effect upon crystallization on the grain structure, as a result of which the weldability is improved and the yield strength is increased. With a decrease in the content of calcium and (or) barium below 0.002 wt. the goal is not achieved, but with an increase in the content of calcium and barium above 0.05 wt. a significant amount of insoluble particles of excess phases are formed, which reduce plasticity, especially in the high-altitude direction. In addition, the indicated contents of calcium, barium and copper make it possible to use a cheaper alloy manufacturing technology and use a secondary charge with waste from a wider range of alloys, including aluminum-lithium-copper system alloys.

Beryllium in an amount of 0.0001-0.3 wt. alter the morphology of the eutectic iron precipitates, thereby increasing creep strength of the alloy at 20-70 ° ^C. In addition, protects the alloy against oxidation in melting processes, casting, welding, and also when process heating under strain and heat treatment. Beryllium in an amount of less than 0.0001 wt. does not significantly affect the properties of the alloy, and the introduction of beryllium more than 0.3 wt. not recommended in terms of occupational health.

Zirconium and / or scandium are usually introduced into the alloy as modifying additives. In addition, these metals (separately and together) provide, as a rule, obtaining a polygonized structure in hot-deformed semi-finished products. When the content of zirconium and scandium, respectively, below 0.04 and 0.03 wt. a positive effect is not manifested, and with contents above 0.12 and 0.24 wt. primary particles of insoluble excess phases of Al ₃ (ScZr), Al ₃ Zr and Al ₃ Sc are released, which leads to a decrease in ductility.

 Thus, in the case of deviations from the indicated limits, both towards lower values and large values of the component content, or the exclusion of any component from the composition, the goal is not achieved.

Introduction of beryllium, copper and at least one metal selected from the group consisting of zirconium and scandium in aluminum-based alloy to increase creep strength at 20-70 ^{° C} for the first time proposed.

Table 1 shows the chemical composition of the tested compositions of the proposed, experimental and known alloys. In preparing the compositions, aluminum, lithium, magnesium, calcium, barium, copper were introduced in pure form, and zirconium, scandium and beryllium in the form of a ligature. Melting was carried out in an electric furnace, cast ingots of D 70 mm were pressed onto a strip of 15 x 60 mm. The mechanical properties and long-term strength were determined on round samples with a working part of D 5.0 mm. Weldability was evaluated using a spot sample. The points were welded by manual argon-arc welding using filler wire svAMg63. Welding mode I _St 220 A, the welding time of one point is 30-50 s. All welded spot samples were subjected to ultrasonic testing. Defectiveness (welding quality) was assessed by the ratio of points rejected by ultrasonic testing to the total number of controlled points. The test results of the samples in the longitudinal direction in the state of TBl (quenching with a regulated cooling rate and artificial aging) are given in table 2.

As apparent from Table 2, the proposed alloy surpasses known for long-term strength at 20-70 ° ^C under similar weldability and the same level of mechanical properties.

 The use of the proposed alloy will improve the reliability and service life of critical products of new technology.

Claims (1)

 ALUMINUM ALLOY, containing magnesium, lithium, at least one metal selected from the group comprising calcium and barium, characterized in that it further comprises beryllium, copper and at least one metal selected from the group including zirconium and scandium , in the following ratio of components, wt. Magnesium 4 6
Lithium 1.3 2.2
Copper 0.005 0.2
Beryllium 0.0001 0.3
At least one metal selected from the group consisting of zirconium 0.04 0.12
Scandium 0.03 0.25
At least one metal selected from the group consisting of calcium and barium 0.002 0.05
Aluminum Else

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