HU231418B1 - High-strength aluminium alloy and method for the production thereof - Google Patents

Description

2303748

High-strength aluminum alloy and process for its production

The invention relates to the composition of extremely high strength aluminum alloys belonging to the Al-Zn-Mg-Cu system, suitable for the production of semi-finished and finished products, and their production method.

High-strength aluminum alloys are in great demand in industry. But in addition to strength, such materials must also have plasticity and deformability. It is necessary that the castings of the given alloy are suitable for the production of ready-to-use products, that is, that they can be forged, pressed, stretched, rolled. If applicable, additional requirements are surface hardness, flexibility or corrosion resistance. The results of work carried out and ongoing in this direction are registered in numerous patents, such as: EP-1231290, RU-2556849, RU-2614321, US-6027582, US-7452429, US-4863528, US-7883591, US-10472707. The defining characteristics of the patents, the research of the optimal ratios of the main components of the alloy - Al, Zn, Mg and Cu - and the determination of the type and amount of alloying additives, the use of which enables the parameters set against the finished product to be reached. It is well known that the properties of the finished product are also significantly affected by technological factors, in particular: training, aging, tempering, etc. These questions are usually also the subject of patents.

so e.g. No. US6027582 according to the patent, the composition of the Al-Zn-Mg-Cu high-strength aluminum alloy casting (% by weight): Zn: 5.7-8.7; Mg: 1.7-2.5; Cu: 1.2-2.2; Zr: 0.05-0.15; Fe: 0.07-0.14; Si < 0.11; Mn < 0.02; Cr < 0.02; Mg + Cu < 4.1; the rest: Al and contaminants < 0.05 individually and < 0.10 in total. The finished product, which is produced from a semi-finished product (casting) by forging, rolling and pressing - mainly power elements - is used as airplane wings. During production, a casting is produced from the melt by tapping, followed by its homogenization at 465 °C, hot deformation, solidified heat treatment - quenching from 480 °C in cold water, straightening with 2% subsequent deformation and aging (115 °C, 6 h + 172 ° C, 10 o'clock).

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SZTNH-100371416

Known (patent RU2451097) is the aluminum alloy and its production method with the following composition (% by weight): zinc: 6.35-8.0; magnesium: 0.5-2.5; copper: 0.8-1.3; iron: 0.02-0.25; silicon: 0.01-0.29; zirconium: 0.07-0.2; manganese: 0.001-0.1; chromium: 0.0010.05; titanium: 0.01-0.1; boron: 0.0002-0.008 and at least one element from the group of alkali metals: potassium: 0.0001-0.01; sodium: 0.0001-0.01; calcium: 0.0001-0.01; the rest - aluminum. The alloy also contains 0.0001-0.05% beryllium. The proportions of each alloy are: Zn + Mg + Cu = 8.5-11, and Zr + Mn + Cr = 0.1-0.35 (weight%). According to the description, titanium and boron form finely crystalline titanium diboride inclusion grains. The significant modifying effect of the combined addition of Ti and B is well known, and they are usually added to the liquid alloy in the form of a three-component prealloy or salt mixture. But it is less well known that the size of the formed TiB ₂ particles (which will be the potential centers of crystallization of the alloy) follows the distribution according to the Gaussian curve and about 15% of them are larger, reaching the size of 10 pm, which has a detrimental effect on the plasticity of the alloy. The authors claim that the addition of titanium and boron reduces gas inclusions is wrong, they only achieve that the inclusions are distributed more evenly on the edges of the metal crystal grains. The experience of casting malleable alloys significantly highlighted the negative effect of even a small amount of alkali metal contamination. The achieved strength properties are not high either: G _m = 531 MPa, σ _0;2 = 483 Mpa, δ = 15.9 % (longitudinally), all of this combined with an average grain size of 240 pm.

In other words, the castings made as described above and the products obtained from them are characterized by average strength values, relatively weak corrosion properties and a low plastic flow age, as shown above.

Known (patent RU2614321) is a weldable aluminum-based alloy (mainly for protection against meteorites) which contains: zinc: 2-8.5; magnesium: 1.5-3.5; manganese: 0.1-0.5; chromium: 0.05-0.3; zirconium: 0.05-0.3; hafnium: 0.1-1.5; beryllium: 0.0001-0.01% by weight, and at least one element from the following: copper, titanium, nickel, cobalt (no more than 0.7% by weight of any one), unavoidable impurities (in total no more than 0.7 weight%), the rest aluminum. The alloying of the melt together with titanium, zirconium (or hafnium) inevitably leads to the formation of coarse intermetallic type A13(Zr,Ti) inclusions, the size of which, according to some authors, can reach 60 pm. In other words, the partial bonding of the added titanium into a three-component intermetallic compound leads to the fact that the crystalline structure of the resulting casting is not sufficiently fine-grained. The alloy was intended as shield plates for protection against meteorites, but the obtained mechanical properties (O _m : max. 630 MPa, σ _0.2 : max. 607 MPa, δ = 6.5 - 8.0%) are not high enough.

The result of the process according to US7452429, according to the description, is a material with high strength, improved impact resistance, and high resistance to corrosion and fatigue cracking. This alloy contains (in % by weight): Zn: 6.7-7.5 (ideally 6.9-7.3), Cu: 2.0-2.8 (ideally 2.2-2.6), Mg: 1.6-2.2 (ideally 1.8-2.0), and at least one of the elements listed below, in the following amounts: Zr: 0.08-0.20; Cr: 0.05-0.25; Se: 0.01-0.50; Hf: 0.05-0.20 and V: 0.02-0.20% by weight. Stipulation that: Fe + Si < 0.20, the other elements no more than 0.05 individually and no more than 0.15% by weight in total. They emphasize that individual elements mutually affect the solubility of other elements in the intercrystalline phases that form. thus, the content of copper and magnesium together must be at most 3.8 < Cu + Mg < 4.8 (ideally 4.1 < Cu + Mg < 4.7). However, if the magnesium content is 1.6% or less, there is a risk of micro- and macro-cracks. At the same time, the high magnesium content - more than 2.2% by weight - impairs elasticity. Therefore, its value should be set to 1.7% or rather 1.8%. At the same time, the Cu/Mg ratio should be set between 1.1 and 1.5 (ideally 1.15-1.45). They also point out that the addition of small amounts of zirconium, chromium, vanadium, scandium and hafnium additives has an anti-recrystallization effect, but the total amount of the above is strictly defined and cannot exceed 1% by weight.

The closest analogue, which was accepted as a comparative material as a reference (hereinafter: counterexample), is a high-strength aluminum alloy based on Al-Zn-Mg-Cu according to EP1231290, with the following composition (% by weight): Zn: 7.0-11.0; Mg: 1.8-3.0; Cu: 1.2-2.6; at least one element from the following group: Mn: (0.05-0.4), Cr: (0.05-0.3), Zr: (0.05-0.2), Hf: (0.05- 0.3), V: (0.05-0.3), Ti: (0.01-0.2) and Se: (0.05-0.3), the rest of aluminum and the necessarily associated impurities. An ingot is prepared from the liquid melt of the listed alloy - possibly with subsequent homogenization - which is hot deformed by pressing, rolling or forging, hardened, or subsequently stretched to Pl © m with 1-5% residual deformation. The resulting product is aged at a temperature and with a duration that ensures the maximum value of the yield point that occurs under the longitudinal compressive force. The alloy according to the counterexample and the product produced from it have a relatively low yield strength value, in addition to the high strength values shown at room temperature, the strength certified at higher temperatures is not satisfactory, which limits its applicability in places of high stress.

As an advantage of the process according to our proposal, the broad processability of the alloy can be highlighted, which is the result of the plasticity of the material, which is also associated with the outstanding mechanical strength and heat resistance of the finished products made from it.

The composition of the alloy according to our proposal is as follows (in % by weight): zinc: 10-12; magnesium: 2.5-4.0; copper: 1.0-3.0; manganese: 0.35-0.45; chromium: 0.15-0.25; hafnium: 0.15—0.3; zirconium: 0.1-0.2; beryllium: 0.001-0.005 and at least one element from the yttrium subgroup of the rare earth metals (RFF) group, such as: erbium, dysprosium, terbium or ytterbium, total (in mass %): 0.10-0.20. The rest is aluminum and the inevitable contamination. In determining the composition of the alloy, in addition to the general regularity of the compositional properties of the Al-Zn-Mg-Cu system, we mainly used the conclusions drawn from the results of our experiments as a basis. The selection of magnesium, copper and zinc content in aluminum-based alloys is determined by the general principles of the four-component Al-Zn-Mg-Cu system, since the alloy consists of three phases, i.e. p(MgZn ₂ ), T(Al ₂ Mg ₃ Zn ₃ ) and S(Al ₂ CuMg) areas. As is well known, when cooling to a temperature lower than the temperature of the liquidus curve, primary intermetallic phases crystallize, and when the temperature is lower than the temperature of the solid curve, the secondary phases crystallize. In the case of the Al-Zn-Mg-Cu system, all three intermetallic phases are secondary, and at the same time, during the heat treatment of the alloy, they have a decisive role in the development of strength.

During the development of the high-strength alloy set as the goal, we paid special attention to the interaction of the main components of the alloy on the strength, plasticity, and impact strength of the casting.

2303748

2W3748

It is known that the effect of strength and alloy aging increases with increasing Zn and Mg content. However, the total Zn + Mg content is usually limited due to the formation of coarse-grained intermetallic formations and the associated decrease in plasticity and corrosion resistance. It was determined by us (and this does not contradict the literature data) that by keeping the magnesium in the range of 2.50-4.0% by weight, the plasticity increases in the tempered (re-annealed) state, but it significantly decreases above a magnesium content higher than 4.0% . At the same time, with a magnesium content of less than 2.5%, the strength drops and the yield strength increases. Based on this, the magnesium content in the alloy (mass %) we have chosen is between 2.5% and 4.0% limits, when an optimal correlation between strength and plasticity is formed.

An increase in the strength of the alloy can be achieved with the maximum content of Mg, Cu and Zn in the solid solution. With the appearance of secondary phases outside the solubility limit, the strength (in the freshly hardened state of the casting) begins to decrease. This occurs when the combined copper and magnesium content is 3.0; and 4.0% by weight respectively. In addition, the high copper content reduces the corrosion resistance of the alloy. For this reason, the upper limit of the copper content was limited to 3.0% by weight.

The highest strength value in the hardened and aged state was obtained at an increased Zn content of up to 12%, 4% Mg and 3.0% Cu content (hardening and artificial aging according to TI). By further increasing the zinc content, the strength of the casting practically did not increase, but its flexibility properties suddenly decreased. According to our proposal, we limited the upper limit of zinc to 12% by weight, noting that the strength drops dramatically if the value is lower than 10%. As a final result - the optimal zinc content is fixed at 10-12% by weight.

It is known that heat-resistant and refractory metals, i.e.: Mn, Cr, Hf and Zr, precipitate from the solid solution in the form of fine particles, namely: MnAl ₆ (particle size: 0.21 pm), CrAl ₇ (particle size: tenth of pm), HfAl ₃ and ZrAl ₃ (grain size: hundredths of a pm). Solid solutions of these metals - especially Hf-based ones - are very stable and significantly raise the temperature of the onset of recrystallization. According to our experimental data, the strength increases noticeably, the plasticity decreases slightly

In addition to 2303748, by introducing manganese alloying metal and increasing its amount (% by weight) from 0.25 to 0.45. Therefore, we have defined the interval of Μη content as 0.35-0.45% by weight. It is well known that in Al-Zn-Mg-Cu alloys, the addition of chromium has a greater effect on strength than the addition of manganese, and their combined presence reduces the risk of hot cracks during casting. On the other hand, the presence of manganese reduces the dissolution of chromium in the solid solution, which leads to the separation of primary intermetallic compounds at a chromium content higher than 0.3% by weight. In order to avoid precipitation of coarse-grained primary intermetallic compounds, the total amount of Cr + Mn was determined at 0.7% by weight.

It was established that the introduction of Hf or its combination with Zr as an alloying element forming a solid solution increases the strength of the material by about 20-30 MPa. At the same time, the flexibility of the cast material also increases spectacularly, as a result of the particle size of the cast being smaller. To prevent the formation of primary intermetallic compounds, the upper limit of the content of the alloys is limited: 0.5% by weight Hf, in the case of a combined dosage (% by weight) 0.3 Hf and 0.2 Zr.

It is known from the practice of casting high-strength alloys that it is not advisable to exceed the limit of 0.2% of the zirconium content, due to the formation of primary intermetallic compounds, especially in the presence of hafnium. However, max. By adding 0.3 wt% Hf, it is possible to supplement max. also for the addition of 0.2% by weight of Zr, which overall increases the plasticity of the material and increases its strength - especially at high temperatures.

It is well known that the smaller the grain size of the cast iron, the greater its relative extensibility and the more favorable its technological processability when processed by pressure. But the possibility of modifying the structure by adding hafnium and zirconium is also limited.

However, it is known that the alloying of aluminum with a small amount of rare earth metals (RFF) leads to a reduction in the crystal structure of the castings and, as a consequence, the mechanical properties are improved. In addition, rare-earth additions increase the heat resistance of aluminum due to the formation of high-melting phases in the aluminum alloy, the presence of which limits recrystallization. Our novel finding is that some RFF elements of the yttrium subgroup have a greater effect on increasing the temperature of aluminum recrystallization than readily available metals such as yttrium or gadolinium, and even more so than elements of the cerium subgroup. The experiments we carried out showed that ytterbium, terbium, dysprosium and erbium have a relatively high solubility of 0.3% by weight in the solid solution, while rare earth metals belonging to the non-yttrium subgroup have significantly lower solubility - usually no more than 0.05% by weight more. In aluminum alloys with the quaternary Al-Cu-Mg-Zn system, ytterbium, erbium, dysprosium or terbium additives are found in phases with a complex chemical composition, which are formed during recrystallization. Additions of Er, Yb, Tb or Dy cause the grains to be smaller, increasing the resistance against recrystallization, thanks to which the strength characteristics (especially the cold resistance) are significantly improved. The upper limit of the content of the listed RFF alloys is limited, because by raising their concentration above 0.3% by weight, the strength characteristics decrease spectacularly. This phenomenon is related to the formation of the Al ₈ Cu ₄ RFF phase, which causes a decrease in copper concentration during tempering. However, this last factor reduces the volume ratio of the Al ₂ CuMg phase, which at the same time has a significant role in terms of the strength that develops as a result of subsequent aging. In order to prevent the formation of primary intermetallic compounds, the upper limit of all RFF alloys was limited to 0.2% by weight.

The role of the technologically applied beryllium metal microadditive is to protect the dilute melt from oxidation.

In addition to the composition, the technical result is also ensured by the production method of the alloy, which includes the sequence of addition of additives, the temperature of melting, the use of multi-component prealloy, its alloying with hafnium (and zirconium) salts, and the simultaneous refinement of the alloy.

The casting method we recommend from the given alloy is that the order of adding the elements to the aluminum melt is: A1 + Be + (Cu, Mn, Cr, RFF) + (Zr + Hf) + Zn + Mg. Within this, the total of the selected elements the dilute alloy is added in the form of a multi-component A1 + (Cu, Mn, Cr, RFF) prealloy, and zirconium ® and hafnium are added in the form of their fluoride salts, namely K ₂ ZrF ₆ and K ₂ HfF ₆ ÍN © w, the melt at a temperature of 780 - 850 °C and min. with a 30-minute heat retention time.

It is known that with the intake of a larger amount of alloying material, the mechanical strength generally increases, but at the same time, the plasticity of the resulting alloy decreases, which leads to cracking of the castings. In other words, reducing the grain size is a requirement of utmost importance. In order to ensure this, the alloying elements must be selected, their optimal amount and the purposeful technology of adding them to the melt.

In order to improve the quality and grind the subdendric structure to the greatest possible extent, we use a multi-component prealloy. The rapid precipitation of the solid intermetallic phase dramatically increases the viscosity of the melt, which reduces the size growth of the crystals, increases the amount of subsequent crystallization nuclei, which ultimately leads to the crushing of the grains and, as a consequence, to the increase in the plasticity of the cast. The addition of alloying elements to the base melt in the form of a multi-component prealloy reduces its contamination and segregation, ensures more accurate alloying of the alloy, and optimizes energy costs. During the heat treatment, the solid solution containing hafnium and zirconium breaks up, very slowly coagulating three-component dispersed formations are released, which make the alloy more durable. Finally, during the crystallization of the alloy, the effects of the individual elements are superimposed.

By adding the Zr and Hf components in the form of fluoride salts (K ₂ ZrF ₆ and K ₂ HfF ₆ ), they interact very actively with aluminum, as a result of which very small (max. 20 pm) intermetallic grains are formed on the one hand, and potassium cryolite on the other is formed, which is a perfect refining and degassing melting additive:

K ₂ ZrF ₆ (K ₂ HfF ₆ ) + Al _olv = K ₃ A1F ₆ + ZrAl ₃ + HfAl ₃

By adding fluoride salts containing Hf (and Zr), we avoid the traditional treatment of the melt with melting additives, that is, we associate refining with potassium cryolite and alloying. Since the content of the heat-resistant metals in question in the aforementioned salts is high (48% Hf and 32% Zr), the specific use of the salts for alloying the melt is therefore low. A necessary condition of the technology - mixing of the melt (melting in an induction furnace, mechanical, etc.) during the addition of salt, while the temperature of the melt min. 780 °C and after dosing, heat treat the melt for at least 30 minutes.

No. 1 example

The chemical composition of the material variants according to our application is presented through 5 products (see Table 1). The alloys were made using the traditional method:

• Aluminum was melted in the induction furnace and heated

to 800 °C;

• Beryllium was added to the melt. (Beryllium was added in the amount of 0.0015 to each of the alloys No. 1-5.);

• Within ten minutes, copper, manganese, chromium, terbium (or ytterbium or dysprosium), zirconium and hafnium were added to the melt - in the form of two-component prealloys: (A150Cu, A115Mn, A15Cr, A13Tb, A13Dy, A13Yb , A15Hf, A15Zr);

• Refined with (NaCl + KaCl + Na ₃ AlF ₆ ) addition;

• The melt was heated to 850 °C and heat treated for 30 minutes;

• Zinc and manganese were added, the melt was cooled to 740 °C and slag was removed;

• The castings were cast using a semi-continuous method, in a water-cooled crystallization frame with a diameter of 120 mm, at a stretching speed of 110 mm/min.

We homogenized the autoclave in the following mode: 475 °C - for 6 hours. After cooling, mechanical processing and cutting, it was subjected to heating to 400^420 °C and pressed at a container temperature of 380^100 °C into a 050 mm metal rod with a stretching efficiency of λ = 5.76. The resulting rod was tempered in water at 470 °C, then artificially aged at 120 °C for 24 hours (TI mode), and then the longitudinal mechanical properties of the product were determined (see table no. 2).

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No. 1 spreadsheet

Chemical composition of experimental alloys.

Alloy sign 1 2 3 4 5 Content of components, % Zn 12.0 10.9 11.0 10.0 10.9 Mg 2.5 3.0 3.5 4.0 3.0 Cu 1.0 1.21 2.4 3.0 1.25 Cr 0.15 0.16 0.22 0.25 0.16 Mr 0.35 0.37 0.42 0.45 0.37 HF 0.15 0.21 0.25 0.30 0.21 Zr 0.10 0.17 0.16 0.20 0.16 Dy 0.10 — 0.164 — Etc — 0.152 — 0.20 — Yb — — — — 0.146 Total heat-resistant components, % 0.75 0.88 1.05 1.20 0.90 Hf/Zr ratio 1.5 1.54 1.56 1.5 1.56 The mean diameter of the casting particle size, pm 30.58 24.84 24.80 26.89 25,30

2303741

No. 2 spreadsheet

Mechanical properties of the products.

Alloy sign Tensile strength G _m , MPa Flow limit Oh, 2, MPa Relative elongation δ, % Hardness according to HB, MPa Impact strength KCU, J/cm ² 1 728 719 4.5 2350 there is no death 2 730 711 8.0 2200 H,4 3 740 726 8.0 there is no death there is no death 4 717 701 7,8 2160 12.5 5 734 716 8.2 2180 n.i

23B3748

It can therefore be concluded that the alloy according to our proposal, the optimally chosen chemical composition and the recommended ratio of the elements together ensure very high mechanical properties, high hardness and impact strength, in addition to satisfactory formability/plasticity. The structure of the pressed bars, when heat-treated in the TI mode, is always homogeneous, fine-grained, and free of recrystallization.

No. 2 example

No. 1 example shows the composition of aluminum alloys with the chemical composition according to our proposal and their mechanical properties - with a traditional processing method. No. 2 as an example, we present No. 1 in example 5, the properties of the product produced with the same composition (sample no. 6), but improved - and which is the subject of our application - processing method, compared with the properties of the product (sample no. 7) produced as described in counterexample EP1231290. The chemical composition of the alloys according to our application and according to the counterexample is given in no. 3. table contains:

No. 3 spreadsheet

Chemical composition of alloys.

Chemical symbol of an alloying metal Alloy sign 6 7 (counterexample) Content of alloying elements, mass% Zn 10.93 9.53 Mg 3,013 2.27 Cu 1,249 1.90 Cr 0.158 0.11 Mr 0.374 0.227 Zr 0.155 0.125 HF 0.211 Si: 0.05 Yb 0.146 You: 0.025 Others On: 0.0015 Fe: 0.10 Contamination <0.05 <0.05

23037 <β

The self-shells according to the counterexample (sample no. 7) were produced following the patent description; while self-sealing according to our procedure (sample no. 6) was made according to the following technology:

• Aluminum was melted in the induction furnace, heated to 800 °C;

• Beryllium was added to the melt;

• After ten minutes, copper, manganese, chromium, ytterbium were added to the melt - in the form of a multi-component prealloy: A1 + (2.5Cu; 0.75Mn; 0.32Cr; 0.3Yb);

• Zirconium and hafnium were added in the form of their complex fluoride salts, i.e. K ₂ ZrF ₆ and K ₂ HfF _6; • We heated the melt to 850 °C and heat treated it for 30 minutes;

• Zinc and manganese were added, the melt was cooled back to 740 °C and slag was removed;

• The castings were cast using a semi-continuous method, in a water-cooled crystallization frame with a diameter of 120 mm, at a stretching speed of 110 mm/min.

The novelty of the technology described here is the addition of hard-to-melt alloying elements in the form of a multi-component prealloy, which ensures the early formation of fine-grained intermetallic compounds. These are further distributed in the thinner membranes between the crystal grains. The addition of hafnium and zirconium compounds in the form of their complex fluoride salts (which is also considered a new element of the technology) only stabilizes the given process. No. 2 The microstructure of the self-coatings described in example, made according to our proposed technology, is fine-grained, the size of the thin, dendritic cells is 25-30 pm, and the thickness of the layers located along the border of the intermetallic phases is 1.2-2.5 pm. The microstructure of the self-coatings according to the counterexample is coarse-grained, the size of the dendritic cells is 40-70 pm, and the thickness of the layers between the intermetallic crystals is on average 3-6 pm.

No. 2 castings obtained based on example were homogenized at a temperature of 475 °C for 6 hours. After subsequent mechanical processing and cutting into equal parts, they were subjected to heating to 400-420 °C and pressed at a container temperature of 380^400 °C into a 20x90 mm rectangular shape with a stretching efficiency of λ = 8.0. The 20 mm thick profile obtained in this way was rolled into a 3.0 mm thick plate by longitudinal rolling. The obtained product was hardened in water at 470 °C, artificially aged at 120 °C for 24 hours (TI mode) and its mechanical properties were determined.

No. 4 table presents the most important mechanical properties of the products produced according to our proposal, comparing them with the properties of the products obtained according to the reference patent. The improvement of the properties can also be easily followed by comparing the values of hardness and impact strength.

230374«

No. 4 spreadsheet

Mechanical properties of alloys.

Alloy sign Product Tensile strength _m , MPa Yield strength σ ₀ , ₂ , MPa Relative elongation δ,% Hardness according to HB, MPa Impact strength KCU, J/cm ² 6 profile 748 727 8.2 - - plate 704 689 5.3 2320 12.0 7 (counterexample) profile 682 651 9.0 - - plate 646 630 6.8 1960 8.7

No. 1 Fig. 1 shows the evolution of the mechanical properties of the reference and our proposed alloys as a result of the test temperature. The l.s. Fig. and no. 2 and the 4th no. according to the tables, the proposed alloy is characterized by very high strength values (yield strength: 680-730 MPa, tensile strength: 705-740 MPa), in addition, the hardness of the products made from the alloy (according to HB) reaches 2200-2350 MPa. The impact resistance of the products is also noteworthy: it reaches a value of 12.0-12.5 J/cm ² . The proposed aluminum alloy behaves excellently even at higher temperatures: as no. 1. shows, the tensile strength of the material at a temperature of 200 °C: 480500 MPa; at 250 °C: 350-370 MPa; but even at a temperature of 300 °C it shows values of 180-200 MPa.

In summary, it can be concluded that the composition of the proposed alloy and its production method ensure the formation of a fine-grained - subdendritic cast structure, while preventing the formation of coarse-grained primary intermetallic compounds. As a result of all this, the processability of the casting improves, the quality of the finished products improves by significantly improving the mechanical properties, including hot strength.

2303748

Claims (3)

Demand points 1. The composition of a high-strength aluminum alloy belonging to the Al-Zn-Mg-Cu system, which contains the following components by weight: zinc: 1012; magnesium: 2.5-4.0; copper: 1.0-3.0; manganese: 0.35-0.45; chromium: 0.15-0.25; zirconium: 0.1-0.2; hafnium: 0.15-0.3; beryllium: 0.001-0.005, characterized by the fact that, in addition to the listed elements, it contains at least one of the elements listed here belonging to the yttrium subgroup of rare earth metals (RFF): terbium, ytterbium, dysprosium, erbium in an amount of 0.1-0.2% by weight, where the the total amount of rare earth metals, hafnium and zirconium may not exceed 0.6% by weight, while the total content of the hard-to-melt components hafnium, zirconium, chromium and manganese in the alloy may not exceed 1.25% by weight, while the the ratio of the quantities of hafnium and zirconium min. 1:1 and max. It can be 2:1. 2. The production method of the aluminum alloy with the composition according to claim 1, characterized by the fact that the order of adding the metals to the aluminum melt is: A1 + Be + (Cu, Mn, Cr, RFF) + (Zr, Hí) + Zn + Mg, while the required amount of the named hard-melting metal alloys (Cu, Mn, Cr, RFF) is added to the thin aluminum melt in the form of a multi-component A1 + (Cu, Mn, Cr, RFF) prealloy. 3. The production method of the aluminum alloy according to claim 1 according to claim 2, characterized in that hafnium and zirconium are added in the form of their complex fluoride salts, namely: K ₂ HfF ₆ and K ₂ ZrF ₆ the melt is 780-850 °C temperature, min. 30 minutes with a heat retention time in the melt. 1% Η··ΙΗΙ· SZTNH-100371417