RU2247168C1 - Aluminum-based alloy - Google Patents

Abstract

FIELD: metallurgy, in particular aluminum-based alloys.

SUBSTANCE: claimed alloy contains (mass %) magnesium 4.0-5.6; lithium 1.3-1.8; zirconium 0.08-0.15; titanium 0.05-0.1; boron 0.0001-0.0005; beryllium 0.001-0.01; bismuth 0.01-0.1; and balance: aluminum. Alloy of present invention is useful in manufacturing of rolled, pressed and forged semimanufactured articles for construction materials, as well as in welded constructions.

EFFECT: alloy with improved ductility of main metal and welded constructions, reasonable weldability and strength of welded constructions.

3 tbl, 1 ex

Description

The present 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 welded structures of critical products.

Known alloy grade 1420 (OST 1.90048-77) of the following composition, wt. %:

Magnesium 4.5-6.0

Lithium 1.8-2.3

Zirconium 0.08-0.15

Iron no more than 0.2

Silicon no more than 0.15

Copper no more than 0.05

Titanium not more than 0.1

Sodium no more than 0,0006

Aluminum rest

Currently, parts made of alloy grade 1420 are used in aviation and aerospace engineering, where low density is required in combination with high rigidity and strength. The disadvantage of this alloy is the low ductility of semi-finished products (rolled - in the longitudinal direction, forged - in the direction transverse in thickness) and a low yield strength (not more than 28 kgf / mm ² ).

Known aluminum alloys with lithium, which are characterized by a low density and high yield strength, but have a low fracture toughness and low ductility.

One of these alloys, the closest in technical essence and the achieved positive effect, taken as a prototype, is an alloy according to US patent No. 4584173 from 04/22/86, class. 420-533, which has the following chemical composition, wt.%:

Magnesium 3.0-5.5

Lithium 2.1-2.9

Copper 0.2-0.7,

and one or more elements from the group consisting of zirconium, hafnium, niobium and boron:

Zirconium 0.05-0.25

Hafnium 0.10-0.50

Niobium 0.05-0.30

Boron 0.0001-0.0005

and one or more elements from the group

Zinc 0-2.0

Titanium 0-0.5

Manganese 0-0.5

Nickel 0-0.5

Chrome 0-0.5

Germanium 0-0.2

The rest is aluminum.

This alloy does not have sufficient ductility of the base metal and welded joints to obtain complex welded structures such as trusses and frames.

The problem of the present invention is the creation of an alloy with increased ductility characteristics of the base metal and welded joints, as well as weldability and strength of welded joints at a sufficiently high level, which will allow to obtain thin-walled pressed and forged semi-finished products of various shapes and complex welded structures.

To solve this problem, beryllium and bismuth are additionally introduced into the well-known aluminum-based alloy in the following ratio of components, wt.%:

Magnesium 4.0-5.6

Lithium 1.3-1.8

Zirconium 0.08-0.15

Titanium 0.05-0.1

Boron 0.0001-0.0005

Beryllium 0.001-0.01

Bismuth 0.01-0.1

Aluminum rest

The magnesium content in the range of 4.0-5.6 wt.% Provides the necessary level of strength characteristics and weldability of the alloy. With a decrease in magnesium content of less than 4.0%, the values of temporary resistance and yield strength decrease, the tendency of the alloy to hot cracks increases both during casting of the alloy and during welding. With an increase in the magnesium content of more than 5.6 wt.%, The manufacturability and ductility of the alloy semi-finished products decrease.

The lithium content is selected in the range of 1.3-1.8 wt.% To ensure manufacturability during deformation and to obtain the required complex of mechanical properties. With a decrease in the lithium content in the alloy (below 1.3 wt.%), The elastic modulus decreases and the density of the alloy increases. The increase in lithium content above 1.8 wt.% Affects the manufacturability and weldability of the alloy.

Zirconium is introduced into aluminum alloys as a modifying additive. Being a transition element, it provides a polygonized structure in hot-deformed semi-finished products. When the zirconium content is below 0.08 wt.%, No positive effects are manifested, when its content is above 0.15 wt.%, Coarse primary particles are released that are insoluble in the aluminum solid solution of the Al ₃ Zr phase, which leads to a sharp decrease in the plasticity of semi-finished products.

Titanium and boron together improve the structure of the alloy and increase its strength. The introduction of titanium more than 0.1% and boron more than 0.0005%, i.e. in amounts exceeding the permissible limits, leads to a decrease in the ductility of the alloy.

Beryllium in an amount of 0.001-0.01 wt.% Protects the alloy from oxidation in the processes of melting, casting, welding, as well as during technological heating under deformation and heat treatment. Beryllium in an amount of less than 0.001 wt.% Does not significantly affect the properties of the alloy, and the introduction of beryllium of more than 0.01 wt.% Is not recommended from the point of view of occupational health.

Bismuth improves the ductility of aluminum alloys of both the base metal and welded joints by binding sodium, which is a harmful impurity in aluminum, to Na ₃ Bi compounds. When the content of this element below the specified (0.01 wt.%) Positive effects were not detected. With the introduction of bismuth in larger than suggested amounts (0.1 wt.%), It forms a complex fusible phase, which are released in the form of globules along grain boundaries, which reduces the values of the elongation of the material.

Thus, in the case of deviations from the specified limits in the direction of both smaller and larger values of the content of the components or the exclusion of any component from the composition, the problem is not solved.

The invention is illustrated by an example.

Table 1 shows the chemical compositions of the tested compositions of the proposed and known alloys. The compositions of alloys 1-3 correspond to the proposed. Alloy 1 is alloyed at the lower limit, alloy 2 is alloyed at the average limit, alloy 3 is at the upper limit.

Table 1 The chemical composition of the alloys Alloy Magnesium Lithium Copper Zirconium Titanium Boron Beryllium Bismuth Zinc Aluminum one 4.0 1.3 - 0.08 0.05 0.0001 0.001 0.01 - The basis 2 4.8 1,5 - 0.1 0.08 0,0003 0.005 0.05 - The basis 3 5,6 1.8 - 0.15 0.1 0,0005 0.01 0.1 - The basis four 3,5 0.8 - 0.05 0.02 0.00001 0,0008 0.007 - The basis 5 6.3 2,3 - 0.22 0.15 0,0006 0,03 0.15 - The basis 6 4.2 2,4 0.3 0.12 0.2 0.5 The basis

Alloy 4 is alloyed below the lower limit, alloy 5 is above the upper limit. Alloy 6 is a known alloy (prototype).

Melting was prepared in an electric furnace, ingots with a diameter of 70 mm were cast in a semi-continuous way. The charge was melted, the melt was refined, and ingots were cast at a temperature of 700–730 ° С. Cast ingots were homogenized according to a regime of 380-400 ° C. Homogenized ingots were pressed onto a strip of 15 × 60 mm. After heat treatment of the strips, samples were cut to determine the mechanical properties. The determination of the mechanical properties of the base metal at a temperature of 20ΔС was carried out according to GOST 1497-84. Welded joints were performed by argon-arc welding using filler wire. Weldability was evaluated using a fish skeleton sample, the mechanical properties of welded joints at a temperature of 20 ° C were determined on samples according to GOST 1497-84. Determination of the impact strength of welded joints at low and room temperature was carried out according to GOST 9454-78. Tests for bending angle (α) were performed according to GOST 6996-66.

The mechanical properties of the base metal and welded joints are shown in tables 2 and 3.

The alloys of the proposed composition (1-3) have strength characteristics at the level of the prototype, but large values of elongation compared to it.

The proposed alloys have good weldability, which allows them to be used in the manufacture of welded structures. The strength of welded joints of alloys is at the level of 32.0-33.5 kgf / mm ² . The values of the plasticity characteristics (bending angle and impact strength) of the proposed alloy at room temperature and at minus 196 ° C are higher than that of the prototype.

A decrease in the content of alloying components (alloy 4) below the proposed composition leads to a decrease in the properties, especially ductility, of welded joints.

The increase in the content of alloying components: magnesium above 5.6 wt.% And lithium above 1.8 wt.% (Alloy 5) leads to a decrease in the ductility of the alloy, especially at a temperature of minus 196 ° C. The introduction of more zirconium, bismuth, and boron into the alloy leads to the formation of coarse inclusions that reduce the quality of the material.

Thus, the proposed alloy composition is optimal. Alloys having transcendental component contents do not possess the necessary set of properties.

table 2 The mechanical properties of pressed strips Alloy σ _V , kgf / mm δ _0.2 , kgf / mm δ,% one 44.0 33.0 11.5 2 44.5 33.5 11.8 3 45.0 34.5 11.3 four 40,0 28.5 12.0 5 43.5 32,0 6.0 6 44.0 32,5 8.0 Table 3 Properties of welded joints. Alloy σ _V , kgf / mm ² α, degree KCU, kgf m / cm ² 20 ° C -196 ° C one 32,0 80 0.90 0.89 2 33.0 78 0.92 0.90 3 32,5 80 0.88 0.79 four 29.0 80 0.88 0.87 5 33.0 55 0.65 0.50 6 32,0 56 0.74 0.50

Claims (1)

An aluminum-based alloy containing magnesium, lithium, zirconium, titanium, boron, characterized in that it additionally contains beryllium and bismuth in the following elements, wt.%: Magnesium 4.0-5.6 Lithium 1.3-1.8 Zirconium 0.08-0.15 Titanium 0.05-0.1 Boron 0.0001-0.0005 Beryllium 0.001-0.01 Bismuth 0.01-0.1 Aluminum Else