RU2473709C1 - High-strength heat-treatable aluminium alloy and article made thereof - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy of light alloys, particularly, to super strong heat-treatable aluminium alloys of Al-Zn-Mg-Cu system intended for making semis, i.e. formed and rolled tubes, stamped covers to be used as has centrifuge parts. Articles are made from alloy containing the following components in wt %: zinc 8.0-9.0, magnesium 2.3-3.0, copper 2.0-2.6, zirconium 0.1-0.2, beryllium 0.0001-0.002, cerium 0.005-0.05, calcium 0.005-0.05, titanium 0.005-0.05, iron up to 0.15, silicon up to 0.1, and at least of element of the group: manganese up to 0.1, aluminium making the rest.

EFFECT: higher strength, ductility, toughness, fatigue strength.

2 cl, 2 tbl, 1 ex

Description

The present invention relates to the field of metallurgy of light alloys and, in particular, aluminum-based alloys, which are intended for the manufacture of deformed semi-finished products in the form of extruded and rolled pipes, stamped covers, used in the form of parts of gas centrifuges operating for a long time under difficult conditions at moderately elevated temperatures.

Known aluminum alloy brand V96tsch of the following chemical composition, wt.%:

Zinc - 8.0-9.0

Magnesium - 2.3-3.0

Copper - 2.0-2.6

Zirconium - 0.1-0.2

Aluminum is the rest.

(Alloys wrought aluminum high purity. Stamps. OST 1 90026-80).

The disadvantage of this alloy is the low structural strength due to brittleness arising from the tendency to grain boundary destruction. The fragility of the alloy also determines its low manufacturability in metallurgical production. The alloy has an increased tendency to hot and cold cracks when casting ingots, is characterized by low flow rates during pressing and allows very limited deformations during forging and rolling.

Known aluminum alloy of the following chemical composition, wt.%:

Zinc - 8.0-9.0

Magnesium - 2.3-3.0

Copper - 2.0-2.6

Zirconium - 0.1-0.2

Iron - 0.05-0.3

Silicon - 0.03-0.15

Beryllium - 0.0001-0.002

Hydrogen - (0.9-3.6) × 10 ^-5

Aluminum is the rest.

(RF patent for the invention No. 2164541, class C22C21 / 10, published March 27, 2001), prototype.

The disadvantage of this alloy is the low structural strength due to brittleness arising from the tendency to grain boundary destruction. This reduces the resource of the product. The alloy is not very technologically advanced in metallurgical production when casting ingots and when processing them by pressure.

An alloy based on aluminum of the following chemical composition, wt.%:

Zinc - 8.0-9.0

Magnesium - 2.3-3.0

Copper - 2.0-2.6

Zirconium - 0.1-0.2

Beryllium - 0.0001-0.002

Cerium - 0.005-0.05

Calcium - 0.005-0.05

Titanium - 0.005-0.05

Iron to 0.15

Silicon up to 0.1.

At least one member from the group:

Manganese to 0.1

Chrome up to 0.05.

The proposed aluminum-based alloy has the following chemical composition and differs from the known one in that it additionally contains cerium, calcium, titanium and at least one of the elements of the group — manganese or chromium, with the following component ratios (mass fraction)%:

Zinc - 8.0-9.0

Magnesium - 2.3-3.0

Copper - 2.0-2.6

Zirconium - 0.1-0.2

Beryllium - 0.0001-0.002

Cerium - 0.005-0.05

Calcium - 0.005-0.05

Titanium - 0.005-0.05

Iron to 0.15

Silicon up to 0.1

At least one member from the group:

Manganese to 0.1

Chrome up to 0.05

Aluminum is the rest.

The proposed alloy is characterized by increased structural strength due to the low tendency to intergranular fracture due to the increased ductility of grain boundaries. As a result, characteristics describing the ductility of the metal increase markedly. Relative elongation increases by 30%, impact strength by 40%, and resistance to repeated loads increases markedly. As a result, the resource of products increases.

Reducing brittleness has a beneficial effect on technological plasticity in metallurgical production. The tendency to hot and cold cracks during casting decreases, their ductility during pressure processing increases.

The reason for the increase in ductility and fracture toughness is a decrease in grain boundary brittleness due to complex microalloying of the alloy with a given composition, which increases the ductility of grain boundaries. The proportion of intergranular fracture in the transition from the known alloy to the proposed decreases several times.

The advantages of the alloy are also manifested in the product made of the above alloy.

Example.

In an electric resistance furnace with a capacity of 170 kg, ingots with a diameter of 65 mm and a diameter of 215 mm were cast from the known and proposed alloys.

The chemical composition is given in table 1.

Table 1 Actual chemical composition of cast ingots from known and proposed alloys,% by weight Alloy Al Zn Mg Cu Zr Be Xie Sa Ti n ₂ Fe Si Mn Cr Famous the basis 8.6 2.6 2,4 0.12 0,0006 - - 2.1 × 10 ^-5 0.12 0,07 - - Proposed the basis 8.5 2.7 2,3 0.13 0.0015 0.01 0.007 0,03 - 0.10 0.06 0,03 0.01

The ingots were homogenized according to the regime of 420 ° C, 6 hours + 460 ° C, 20 hours.

Ingots with a diameter of 65 mm were cut into measuring billets of ⌀65 × 87 mm, turned into ⌀62 mm and stamped into several transitions to billets for parts in the form of covers.

Ingots with a diameter of 215 mm were cut into measuring billets with a length of 600 mm, machined to a diameter of 200 mm and precipitated, followed by laying to a diameter of 290 mm. Billets were extruded from the obtained forgings, from which a ⌀138 × 4 mm pipe was pressed.

Stampings in the form of covers were stacked vertically in a special hardening basket in a checkerboard pattern with a gap of about 40 mm. The temperature in the quenching furnace was maintained at 470 ° C with an accuracy of ± 3 ° C. When the basket with stampings was immersed in a bath with room temperature water, an intensive sparging of water was carried out using compressed air supplied from the bottom of the bath.

The pipes were quenched from a vertical quenching furnace at a temperature of 470 ± 3 ° C in a tank of room temperature water with vertical immersion. After hardening, warped pipes were governed by drawing with a residual plastic deformation of 1.5%.

Hardened stampings and pipes artificially aged 140 ° C, 16 hours.

Table 2 presents the mechanical properties of stampings and pressed pipes from the known and proposed alloys.

table 2 Actual mechanical properties of stampings and pipes from known and proposed alloys. Average values from the results of 10 tests Alloy Semifinished σ _in , MPa σ ₀₂ , MPa δ,% Ψ,% KCU, kgm / cm ² famous Stamping 660 610 4.0 12 0.5 Trumpet 680 630 5,0 fifteen 0.6 proposed Stamping 670 620 7.5 eighteen 0.8 Trumpet 690 650 8.0 21 0.85

Samples with a stress concentrator (Kt = 2.3; f = 3 Hz; R = 0.1) were cut from thermally hardened pipes of the known and proposed alloys for low-cycle endurance tests with pulsating tension at σ _max = 160 MPa. Samples from the known alloy withstood 130-190 thousand cycles to failure, and samples from the proposed alloy - 270-350 thousand cycles.

Thus, the analysis of the test results of pipes from known and proposed alloys shows a clear advantage of the latter.

The proposed alloy has higher relative elongation δ and relative narrowing Ψ, impact strength KCU and in particular a higher fatigue resistance. This makes it possible to increase the resource of the product.

Claims (2)

1. An ultra-strong wrought alloy based on aluminum, containing zinc, magnesium, copper, zirconium, beryllium, iron, silicon, characterized in that it additionally contains cerium, calcium, titanium and at least one element from the group of manganese and chromium in the following ratio components, wt.%:
Zinc 8.0-9.0 Magnesium 2.3-3.0 Copper 2.0-2.6 Zirconium 0.1-0.2 Beryllium 0.0001-0.002 Cerium 0.005-0.05 Calcium 0.005-0.05 Titanium 0.005-0.05 Iron up to 0.15 Silicon up to 0.1
At least one member from the group:
Manganese up to 0.1 Chromium up to 0.05 Aluminum rest 2. The product is made of heavy-duty wrought alloy based on aluminum, characterized in that it is made of an alloy according to claim 1.