RU2560481C1 - Al-Cu-Li-INTERMETALLIDE-BASED ALLOY AND ARTICLES MADE THEREOF - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: proposed composition contains the following substances, in wt %: copper 2.5-3.3; lithium 0.6-1.6; magnesium 0.25-1.2; silver 0.2-0.6; zirconium 0.05-0.13; zinc 0.01-0.8; cerium 0.005-0.1; beryllium 0.00001-0.001; at least one element of the group including: calcium 0.001-0.05; titanium 0.005-0.15; manganese 0.005-0.5; chromium 0.01-0.2; vanadium 0.01-0.2; iron 0.01-0.05; silicon 0.01-0.12 and at least one element of the group including: scandium 0.01-0.11; nickel 0.005-0.1; tin 0.0001-0.05; aluminium making the rest.

EFFECT: higher fracture toughness, ultimate stress, σ_"в", ductility σ0,2, better plasticity at cold rolling for production of 0,5 mm deep sheets and weldability.

2 cl, 1 ex, 2 tbl

Description

The invention relates to the field of metallurgy, in particular to high-resource deformable thermally hardenable weldable alloys of reduced density of the Al — Cu — Li system with increased fracture toughness intended for use as structural materials in aerospace engineering. Such alloys are made from this alloy as: fuselage and wing cladding, both in the compressed and in the stretched zone of aircraft structures and various elements of the power set, operating at temperatures from + 175 ° C to -70 ° C, welded fuel tanks for operation at temperatures from + 20 ° C to -253 ° C.

МПа√м на образце шириной 100 мм) и значительной анизотропией свойств, обусловленные грубыми выделениями упрочняющих фаз Al₂CuLi на границах зерен и субзерн. Этот сплав преимущественно находит применение в виде горячекатаных плит толщиной 40-80 мм в термоупрочненном состоянии.Known alloy system Al - Cu - Li (see RF patent No. 2164940. Publ. 10.03.2001) of the following composition (wt.%): Copper 2.5-3.5; lithium 1.5-1.95; zirconium 0.05-0.15; scandium 0.01-0.15; calcium 0.001-0.05; chromium 0.01-0.3; hydrogen 1.5 · 10 ^-5 -5.0 · 10 ^-5 ; at least one element from the group consisting of: magnesium 0.01-0.6; titanium 0.005-0.009; boron 0.0002-0.007; manganese 0.005-0.6; vanadium 0.01-0.15; cerium 0.005-0.2; iron 0.01-0.5 and at least one element from the group consisting of: zinc 0.01-0.8; tin 0.005-0.1; nickel 0.005-0.15; beryllium 0.0001-0.2; sodium 0.0003-0.001; the rest is aluminum. However, sheets of this alloy are characterized by a lower fracture toughness ( $${\mathrm{TO}}_{\mathrm{FROM}}^{\mathrm{At}}=47-51$$

MPa √ m on a sample 100 mm wide) and significant anisotropy of properties due to coarse precipitation of hardening phases Al ₂ CuLi at grain and subgrain boundaries. This alloy is mainly used in the form of hot-rolled plates with a thickness of 40-80 mm in a heat-strengthened state.

Also known alloy system Al - Cu - Li (see patent FR 2894985. publ. 22.06.2007) of the following composition (wt.%): Copper 2,1-2,8; lithium 1.1-1.7; silver 0.1-0.8; magnesium 0.2-0.6; manganese 0.2-0.6; iron and silicon not more than 0.1; the rest is aluminum. This alloy is characterized by a fairly high fracture toughness of up to 68-73 MPa√m (on samples 100 mm wide). However, this alloy has reduced strength characteristics (σ _in not more than 440 MPa) and technological plasticity during rolling of sheets, which ensures the manufacture of sheets with a thickness of at least 3-5 mm. Therefore, the alloy may have limited application in the fuselage skin of an aircraft.

The closest in technical essence and the achieved effect is an alloy of the Al - Cu - Li system (see patent FR 2889542. publ. 09.02.2007) with high fracture toughness for the fuselage panels of an aircraft of the following chemical composition when the ratio Cu + 5 / 3Li <5 , 2 (% by weight): copper 2.7-3.4; lithium 0.8-1.4; magnesium 0.2-0.6; silver 0.1-0.8, at least one element from the group containing zirconium 0.05-0.13; titanium 0.05-0.15; manganese 0.05-0.8; hafnium 0.05-0.5; chrome or scandium 0.05-0.3; aluminum rest. The alloy has increased strength properties and fracture toughness characteristics. However, sheets of this alloy are made with a thickness of only more than 3.2 mm, which limits the scope of application in the casing of aircraft and helicopters. In addition, the high temperature and duration of heating before hot rolling (520 ° C, 20 h) leads to a strong oxidation of the surface of the workpieces and a decrease in the surface quality of the sheets. Protection against oxidation will require the use of plating, which will reduce fatigue performance.

), предела прочности (σ_в), предела текучести (σ_0,2), повышенной технологической пластичностью при холодной прокатке, обеспечивающей получение тонких листов (толщиной до 0,5 мм) и хорошей свариваемостью ( $${\sigma }_{В}^{СВ}/{\sigma }_{В}^{ОСН.МЕ}$$

где $${\sigma }_{В}^{ОСН.МЕ}$$

- предел прочности основного металла, $${\sigma }_{В}^{СВ}$$

- предел прочности сварного шва), а также изделие, выполненное из разработанного сплава.The technical result of the invention is the creation of an alloy with high fracture toughness characteristics ( $${\mathrm{TO}}_{\mathrm{FROM}}^{\mathrm{At}}$$

), tensile strength (σ _in ), yield strength (σ _0.2 ), increased technological ductility during cold rolling, providing thin sheets (up to 0.5 mm thick) and good weldability ( $${\sigma }_{\mathrm{AT}}^{\mathrm{FROM}\mathrm{AT}}/{\sigma }_{\mathrm{AT}}^{\mathrm{ABOUT}\mathrm{FROM}N.ME}$$

Where $${\sigma }_{\mathrm{AT}}^{\mathrm{ABOUT}\mathrm{FROM}N.ME}$$

- ultimate strength of the base metal, $${\sigma }_{\mathrm{AT}}^{\mathrm{FROM}\mathrm{AT}}$$

- the tensile strength of the weld), as well as the product made of the developed alloy.

To achieve the technical result, an alloy based on the Al - Cu - Li system containing copper, lithium, magnesium, silver additionally contains zinc, zirconium, at least one element from the group consisting of calcium, titanium, manganese, chromium, vanadium, cerium , iron, silicon, and at least one element from the group consisting of scandium, nickel, beryllium tin, in the following ratio of components in wt.%: copper 2.5-3.3; lithium 0.6-1.6; magnesium 0.25-1.2; silver 0.2-0.6; zirconium 0.05-0.13; zinc 0.01-0.8; at least one element from the group consisting of: calcium 0.001-0.05; titanium 0.005-0.15; manganese 0.005-0.5; chromium 0.01-0.2; vanadium 0.01-0.2; cerium 0.005-0.1; iron 0.01-0.05; silicon 0.01-0.11 and at least one element from the group consisting of: scandium 0.01-0.11; nickel 0.005-0.1; beryllium 0.00001-0.001; tin 0.0001-0.05; aluminum rest.

The invention also claims an alloy product based on the Al-Cu-Li system, made of an alloy with the above chemical composition.

In the alloy with the specified composition, such a concentration ratio of copper, lithium and magnesium is created that provides its relatively low density and the creation of effective hardening phases. The total content of these elements in the alloy remains below the solubility limit, which avoids a decrease in the level of fracture toughness.

A positive effect on the strength properties is also achieved by introducing additional alloying elements Zr, Sc, Mn, Cr into the alloy, which affect the degree of recrystallization, grain size and technological properties in the production of semi-finished products. The introduction of these elements contributes to the formation of a homogeneous fine-grained structure in semi-finished products, increasing the fracture toughness characteristics and improving weldability by all types of welding.

The introduction of silver contributes to the creation of additional hardening phases with copper and intensifies the hardening decomposition of a supersaturated solid solution during artificial aging, providing an increase in strength characteristics.

The addition of tin to alloys containing copper significantly affects the effect of hardening during aging by suppressing the formation of GP zones (Guinier-Preston) and accelerating the formation of metastable phases.

The introduction of calcium into the alloy reduces surface tension, contributing to the formation of a more rounded shape of the released excess intermetallic compounds, which increases the process ductility during cold rolling.

Beryllium during melting, casting of ingots, during welding and heat treatment protects the alloy from undesirable oxidation.

Titanium, vanadium, iron, nickel and cerium contribute to an increase in the temperature of recrystallization and the formation of a subgrain structure and additional hardening of the alloy.

Examples of implementation:

Alloys, the chemical composition of which is given in Table 1, (alloy composition No. 1 corresponds to the prototype, the remaining alloys No. 2-10 are proposed) are prepared in electric resistance furnaces using chamotte-graphite crucible. After complete dissolution of the aluminum, Al-Zr alloy, pure Cu was introduced, then aluminum alloys were added alternately with selected elements: Sc, Mn, Be, Ni, Ti, V, Fe, Si, Cr, Ce, then pure low-melting elements Zn, Mg were introduced , Ca, Sn, Li, Ag. Ingots with a diameter of 70 mm were cast from the obtained alloys. After the homogenization of the ingots, a pressed strip with a cross section of 12 × 60 mm was made. Then, 4.0 mm thick sheets were obtained from the pressed blanks by hot rolling, then, after preliminary annealing, sheets were cold rolled to a thickness of 1.5 mm. The sheets were quenched with cooling in water, straightening by stretching and artificial aging.

). Технологическая пластичность оценивалась по уровню степени холодной деформации при холодной прокатке, при которой появлялись боковые трещины величиной более 10 мм (ε_КР).Samples from the obtained sheets were tested under static tension with determination of tensile strength, yield strength, elongation, and fracture toughness characteristics were determined ( $${\mathrm{TO}}_{\mathrm{FROM}}^{\mathrm{At}}$$

) Technological ductility was assessed by the degree of cold deformation during cold rolling, in which side cracks of more than 10 mm in size appeared (ε _КР ).

) в 1,2-1,3 раз, по пластичности в 1,1-1,2 раз. Значения предела прочности и предела текучести нового сплава выше на 35-60 МПа и на 20-40 МПа, соответственно, значений известного сплава.From Tab. 2 shows that the proposed composition of the new alloy exceeds the known alloy (prototype) in terms of fracture toughness characteristics ( $${\mathrm{TO}}_{\mathrm{FROM}}^{\mathrm{At}}$$

) 1.2-1.3 times, plasticity 1.1-1.2 times. The values of the tensile strength and yield strength of the new alloy are higher by 35-60 MPa and 20-40 MPa, respectively, of the values of the known alloy.

нового сплава в 1,2-1,25 раза выше, чем у прототипа.The properties of the welded joints of the proposed alloy after automatic argon-arc welding are close to the properties of the base metal, while the weldability $${\sigma }_{\mathrm{AT}}^{\mathrm{FROM}\mathrm{AT}}/{\sigma }_{\mathrm{AT}}^{\mathrm{ABOUT}\mathrm{FROM}N.ME}$$

the new alloy is 1.2-1.25 times higher than that of the prototype.

Thus, the proposed alloy ensures the achievement of the goal - increasing the characteristics of ductility and fracture toughness, and improving technological ductility during cold deformation, in comparison with the known alloys.

The new alloy, combining increased performance and lower density, allows you to produce the necessary product range on existing industrial equipment. Products from the new alloy (welded fuel tanks, various elements of the power set and cladding of the fuselage and wing, both in the compressed and in the stretched zone of aircraft structures) will have a reduced weight of 15-35%, increased reliability and service life, and an extended range operating temperatures.

Claims (2)

1. An alloy based on the Al - Cu - Li system containing copper, lithium, magnesium, silver, characterized in that it additionally contains zinc, zirconium, cerium, beryllium, at least one element from the group comprising calcium, titanium, manganese , chromium, vanadium, iron and silicon, and at least one element from the group consisting of scandium and nickel, tin, in the following ratio, wt. %:
copper 2.5-3.3 lithium 0.6-1.6 magnesium 0.25-1.2 silver 0.2-0.6 zirconium 0.05-0.13 zinc 0.01-0.8 cerium 0.005-0.1 beryllium 0.00001-0.001,
at least one element from the group consisting of:
calcium 0.001-0.05 titanium 0.005-0.15 manganese 0.005-0.5 chromium 0.01-0.2 vanadium 0.01-0.2 iron 0.01-0.05 silicon 0.01-0.12
and at least one element from the group consisting of:
scandium 0.01-0.11 nickel 0.005-0.1 tin 0.0001-0.05 aluminum rest 2. An alloy product based on the Al - Cu - Li system, characterized in that it is made of an alloy according to claim 1.