RU2394113C1 - High-tensile deformed alloy on base of aluminium and item out of this alloy - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention refers to deformed thermally hardened high-tensile aluminium alloys Al-Zn-Mg-Cu designed for fabrication of all kinds of deformed semi-finished products, including thin sheets used in aircraft and machine engineering and other branches of industry. Deformed alloy on base of aluminium and an item out of it contain the following components, wt %: zinc 2.5-4.0, magnesium 4.1-6.5, copper 0.2-1.0, iron to 0.25, silicon to 0.15, scandium 0.005-0.3, zirconium 0.005-0.25, nickel and/or cobalt to 0.1, titanium to 0.15, boron and/or carbon to 0.05, at least one element out of group: hafnium to 0.15, molybdenum to 0.15, cerium to 0.15, manganese to 0.5, chromium to 0.28, yttrium to 0.15, vanadium to 0.15, niobium to 0.15, aluminium and unavoidable impurities - the rest, also ratio of Mg contents to Zn contents is more or equal to 1.1.

EFFECT: production of alloy and items out of it possessing raised strength properties at simultaneous increased wear-resistance, reduced rate of crack growth, increased durability of welded connections and reduced density, which results in increased resource and reliability of items operation and in reduced weight of structures.

3 cl, 2 tbl, 1 ex

Description

The invention relates to the field of metallurgy, in particular to deformable heat-hardenable high-temperature aluminum alloys of the Al-Zn-Mg-Cu system, intended for the manufacture of all types of deformable semi-finished products (including thin sheets) used in aircraft manufacturing, mechanical engineering and other industries, including for welded structures.

Known high-strength alloy system Al-Zn-Mg-Cu (RF Patent 2165996, published 04/27/2001, C22C 21/10) of the following chemical composition (mass fraction,%):

Magnesium 1.8-2.8 Zinc 5.0-7.0 Copper 1.4-2.0 Manganese 0.2-0.6 Chromium 0.1-0.25 Iron 0.05-0.25 Silicon 0.02-0.1 Titanium 0.005-0.07 Aluminum rest

The ratio of Mn to Cr is more than or equal to 1.5.

The disadvantage of this alloy is its high density (d = 2.85 g / cm ³ ), insufficiently high strength and resource characteristics, which reduces the reliability and service life of the products, as well as their weight efficiency. In addition, this alloy is not welded.

Closest to the proposed invention is a weldable alloy based on aluminum of the Al-Zn-Mg-Cu system, having the following chemical composition (mass fraction,%):

Zinc 4.4-9.0 Magnesium 0.5-3.5 Copper 0.01-1.2 Iron up to 0.35 Silicon up to 0.25 Nickel and / or cobalt up to 0.1 Chromium up to 0.35 Vanadium up to 0.15 Titanium up to 0.15 Boron up to 0.03 Calcium up to 0.05

At least one member from the group:

Manganese up to 0.8 Zirconium up to 0.25 Scandium up to 0.25 Hafnium up to 0.25 Aluminum rest

With a ratio of Mg / Cu≥1.8 (application RU No. 2006132906/02, class C22C / 21/10).

A disadvantage of the known alloy is its high density (d = 2.85 g / cm ³ ), insufficiently high strength properties and resource characteristics, such as fracture toughness, crack growth rate, and fatigue life.

The objective of the invention is to create a structural alloy based on aluminum, which has a reduced density, high strength, high resource characteristics with high strength welded joints.

The technical result is to increase the strength properties of the alloy while increasing fatigue resistance, reducing the crack growth rate, increasing the strength of welded joints and reducing the density (specific gravity), which leads to an increase in the resource and reliability of the products, reduces the weight of the structures.

The technical result is achieved in that the aluminum-based alloy has the following chemical composition (mass fraction,%):

Zinc 2.5-4.0 Magnesium 4.1-6.5 Copper 0.2-1.0 Iron up to 0.25 Silicon up to 0.15 Scandium 0.005-0.3 Zirconium 0.005-0.25 Nickel and / or cobalt up to 0.1 Titanium up to 0.15 Boron and / or carbon up to 0.05

At least one member from the group:

Hafnium up to 0.15 Molybdenum up to 0.15 Cerium up to 0.15 Manganese up to 0.5 Chromium up to 0.28 Yttrium up to 0.15 Vanadium up to 0.15 Niobium up to 0.15 Aluminum rest

The ratio of the Mg content to the Zn content is greater than or equal to 1.1.

The alloy may also contain elements such as calcium, bismuth, sodium, potassium, hydrogen, beryllium, lead, tin and lithium in amounts of not more than 0.01% each and not more than 0.1% in total.

The problem is also solved by the product made of the above alloy.

The fundamental difference between the proposed alloy and the known one is that due to the selected range of contents of such elements as magnesium, zinc, copper and the ratio between Mg and Zn≥1.1, it is in a different phase region than the known alloy. If in the known alloy the phase hardener is particles of the η phase (MgZn ₂ ), then in the proposed alloy there are particles of the triple phase T (Al ₂ Mg ₃ Zn ₃ ), which provide a higher complex of resource and strength properties and their increased stability. The selected range of the content of the main elements (magic, zinc, and copper) provides a lower density (specific gravity) of the proposed alloy compared to the known one.

The combined presence in the alloy of such elements as scandium, zirconium, nickel and / or cobalt leads to the formation of a complex Al ₃ phase (Sc, Zr, Ni / Co), which leads to additional hardening of the alloy, obtaining by superfine an unrecrystallized structure in cold-rolled sheets, improving the properties of welded joints.

In addition, the excess magnesium content (as compared to the zinc content), large atoms of which, entering the solid aluminum solution, increase the crystal lattice parameter of the aluminum matrix, practically eliminate the difference in the lattice parameters of the aluminum matrix and the Al ₃ phase released from the solid solution ( Sc, Zr, Ni / Co), thereby increasing their dispersion and thermal stability. As a result, the positive effect of the Al ₃ phase (Sc, Zr, Ni / Co) in the proposed alloy is noticeably higher than in the known one.

Copper is included both in the solid solution and in the composition of the T phase (Al ₂ Mg ₃ Zn ₃ ), which provides a greater hardening effect. The introduction of at least one element from the group of hafnium, molybdenum, chromium, yttrium, manganese, cerium, vanadium, niobium increases the thermal stability of the Al ₃ (Sc, Zr, Ni / Co) phase due to the dissolution of these elements in this phase. This leads to the preservation of a stable non-crystallized structure of products, increasing their mechanical properties. The presence of complex intermetallic compounds formed by these elements also allows to obtain high properties of the welded joint.

Examples

The method of semi-continuous casting received flat ingots with a cross section of 165 × 550 mm, the composition of which is shown in table 1.

The ingots were homogenized, machined and rolled first hot to a thickness of 5.0 mm, and then cold to 2.5 mm thick sheets, which were hardened and artificially aged. Similar sheets were obtained from a prototype alloy. The test results of artificially aged sheets are presented in table 2.

As can be seen from table 2, the sheets of the proposed alloy surpass the known alloy in terms of static strength: tensile strength σ _in 5-7% and yield strength (σ ₀₂ ) by 10-15%. The proposed alloy has a 4-5% lower density than the known one. Moreover, the proposed alloy has significantly higher resource characteristics: almost two times lower fatigue crack growth rate (SRTU), 10-20% higher fracture toughness (K _C ^U ) and twice as many cycles until fracture when tested on fatigue. In addition, the strength of the welded joint (automatic argon-arc welding) is also higher for the proposed alloy by 8-14%.

Using the proposed alloy will reduce the weight of products made from them due to the lower density of the alloy and higher strength of both the base material and welded joints, as well as to increase the reliability of the products due to the large values of the fracture toughness characteristics and lower fatigue crack speed and higher fatigue resistance .

Table 1. Chemical composition (mass fraction,%) Chemical
element Alloy composition, mass fraction,% Famous Proposed one 2 Zn 6.3 2,8 3,5 Mg 2.6 6.2 5,0 Cu 0.35 0.65 0.45 Fe 0.26 0.16 0.14 Si 0.12 0.1 0.08 Ni 0.01 0.001 - Co - - 0.01 Cr 0.21 - 0.01 V 0.08 0.005 - Ti 0.06 0.04 0,03 B 0.001 0,0008 0,0005 C - 0,0003 Ca 0,0008 - - Mn 0.25 - 0.01 Mo - 0.01 - Sc - 0.24 0.15 Zr 0.06 0.06 0.12 Ce - - 0,03 Y - 0.005 - Hf - - 0.005 Nb - - 0.001 Al rest rest rest

table 2 Comparison of typical properties of sheets with a thickness of 2.5 mm from the proposed alloy and from a known alloy. Alloy Density, g / cm ³ σ _in , MPa σ ₀₂ , MPa δ,% SRTU, mm / ktsikl for ΔК = 30MPa√m K _C ^U , MPa√m for samples 160 mm wide Fatigue resistance, cycle, at σ _max = 160 MPa, f = 30 Hz σ _in ^St. MPa Suggested 1 2.70 560 500 14.5 2.0 80 400 350 Suggested 2 2.71 580 520 12.5 2.6 85 480 370 Famous 2.85 530 440 10.5 5,6 65 250 320

Claims (3)

1. A deformable aluminum-based alloy containing zinc, magnesium, copper, iron, silicon, scandium, zirconium, nickel and / or cobalt, titanium, aluminum and inevitable impurities, characterized in that it additionally contains boron and / or carbon and at least one element from the group: hafnium, molybdenum, cerium, manganese, chromium, yttrium, vanadium, niobium in the following ratio of elements, wt.%:
Zinc 2.5-4.0 Magnesium 4.1-6.5 Copper 0.2-1.0 Iron up to 0.25 Silicon up to 0.15 Scandium 0.005-0.3 Zirconium 0.005-0.25 Nickel and / or cobalt up to 0.1 Titanium up to 0.15 Boron and / or carbon up to 0.05 at least one element from the group: Hafnium up to 0.15 Molybdenum up to 0.15 Cerium up to 0.15 Manganese up to 0.5 Chromium up to 0.28 Yttrium up to 0.15 Vanadium up to 0.15 Niobium up to 0.15 Aluminum and inevitable impurities rest
moreover, the ratio of Mg to Zn is greater than or equal to 1.1. 2. The alloy according to claim 1, characterized in that it contains calcium, bismuth, sodium, potassium, hydrogen, beryllium, lead, tin and lithium as inevitable impurities in an amount of not more than 0.01 wt.% Each and not more than 0 , 1 wt.% In total. 3. A product from a deformable alloy based on aluminum, characterized in that it is made of an alloy according to claim 1.