RU2419663C2 - High-strength alloy on base of aluminium - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: alloy on base of aluminium contains following components wt %: zinc 5-8, magnesium 2-3.1, nickel 1-4.2, iron 0.02-1, zirconium 0.02-0.25 %, copper 0.05-0.3 %. Also, temperature of equilibrium solidus of material is as high as 550°C and hardness is as high as 180 HV. Alloy has a structure corresponding to matrix formed with solid solution of aluminium with uniformly distributed disperse particles of secondary discharges in it and particles of aluminides containing nickel and iron of eutectic origin uniformly distributed in matrix. Also, alloy contains matrix and aluminides at the following ratio, vol % aluminides containing nickel and iron 5.0-6.3, matrix - the rest.

EFFECT: production of new high-strength alloy thermally hardenable and designed both for fabrication of shaped casting and of deformed semi-products.

4 cl, 5 tbl, 4 ex

Description

The invention relates to the field of metallurgy of aluminum-based materials and can be used to obtain products operating under high loads at temperatures up to 150-200 ° C: details of aircraft (aircraft, helicopters, rockets), cars and other vehicles (bicycles, scooters, trolleys), parts of sports equipment (the body of golf clubs, tennis rackets), etc.

The strongest wrought aluminum alloys of type B95 (σ _in = 500-600 MPa) refer to the system Al-Zn-Mg-Cu (Industrial aluminum alloys / Ref. Ed. / Alieva SG, MB Altman et al. M., Metallurgy, 1984, 528 p.). They have low casting properties, so these alloys are practically not used to produce shaped castings.

Known alloy based on aluminum-Nickel eutectic, disclosed in patent RU 2158780 from 10.11.2000,

This alloy contains a matrix formed by a solid solution of zinc, magnesium and copper in aluminum with uniformly distributed dispersed particles of phases formed by aluminum, zinc, magnesium and copper, particles of crystallization-derived nickel aluminides uniformly distributed in the matrix and particles evenly distributed in the matrix, at least , one of the aluminides selected from the group consisting of chromium aluminides and zirconium aluminides, with a total content of from 0.1 to 0.5 vol.% material.

From this alloy, castings with improved casting properties can be obtained by adding nickel, which forms aluminides of eutectic origin.

However, to achieve high strength properties, it is necessary to provide these aluminides with a globular shape, which requires a spheroidizing annealing operation. Since copper, which is part of the known material, greatly reduces the equilibrium solidus (for the average composition it is below 530 ° C), a relatively high dispersion of the initial structure is required, which limits the use of the proposed alloy to relatively small castings of a simple form. In addition, the presence of copper in the latter complicates the phase composition, which can lead to instability of mechanical and technological properties.

Closest to the proposed is an alloy based on aluminum, disclosed in patent RU 2245388 (publ. 27.01.2005, bull. No. 3). This alloy contains zinc, magnesium and nickel and is characterized by a structure that is a matrix formed by a solid aluminum solution with dispersed secondary precipitates of the hardener phase uniformly distributed in it and uniformly distributed in the matrix by particles of nickel aluminides of crystallization origin. The amount of nickel aluminides is 5.3-7 vol.%, The matrix as dispersed particles contains 5-10 vol.% Particles of the T 'phase, which are metastable modifications of the T phase (Al ₂ Mg ₃ Zn ₃ ), and the temperature of the equilibrium solidus material is at least 540 ° C.

From this alloy castings can be obtained with an improved combination of mechanical properties and manufacturability (for shaped casting and pressure treatment). However, the preparation of this alloy requires high-purity aluminum, which complicates its industrial use. The second disadvantage is the strong tendency of deformed semi-finished products to recrystallize when heated for hardening, which limits their strength.

The objective of the invention is the creation of a new high-strength aluminum alloy, smelted on the basis of technical aluminum and designed to produce both shaped castings and deformed semi-finished products.

The problem is solved in that the aluminum-based alloy containing zinc, magnesium and nickel additionally contains iron, zirconium and copper at the following component concentrations, wt.%:

Zinc 5-8 Magnesium 2.0-3.1 Nickel 1-4,2 Iron 0.02-1 Zirconium 0.02-0.25 Copper 0.05-0.3 Aluminum Rest

and the temperature of the equilibrium solidus is at least 550 ° C, and the hardness is at least 180 HV.

The achievement of high mechanical properties is achieved by the implementation of a structure that is a matrix formed by a solid solution of aluminum with uniformly distributed dispersed particles of secondary precipitates and particles of aluminides containing nickel and iron uniformly distributed in the matrix of eutectic origin. The amount of these aluminides is 5.0-6.3 vol.%.

The temperature of the equilibrium solidus, as well as the volume fraction of aluminides containing iron and nickel, is determined using the Thermo-Calc program (TTAL5 database or later).

The material can be made in the form of castings having the following tensile properties: temporary resistance (σ _in ) - not less than 610 MPa, yield strength (σ _0.2 ) - not less than 550 MPa, elongation (δ) - not less than 4% .

In addition, the material can be made in the form of deformed semi-finished products (in particular, sheets and rods) with the following tensile properties: tensile strength (σ _in ) of at least 640 MPa, yield strength (σ of _0.2 ) of at least 550 MPa, elongation (δ) of at least 5%.

The invention consists in the following.

The presence of alloying elements within the stated limits, taking into account the requirements for hardness, allows for the best combination of mechanical properties. The claimed limitation on the temperature of equilibrium solidus allows spheroidizing annealing at sufficiently high temperatures, ensuring the formation of relatively globular particles of aluminides, in particular, Al ₃ Ni and Al ₉ FeNi phases. The number of the latter within the stated limits allows you to provide the best combination of mechanical and technological properties and at the same time to allow the possibility of using technical aluminum for alloy preparation.

EXAMPLE 1

Ingots of 5 alloys were prepared, the compositions of which are indicated in Table 1. Alloys were prepared in an electric resistance furnace in graphite chamotte crucibles from aluminum of the grades A99 (99.99%) and A7 (99.7%), zinc grade Ts0 (99.9%), magnesium grade Mg90 (99.9%), copper grade M1 ( 99.9%) and Al-Ni, Al-Fe and Al-Zr alloys.

The temperature of the equilibrium solidus, as well as the volume fraction of aluminides containing iron and nickel, was determined using the Thermo-Calc program (TTAL5 database). The calculated values are given in table.2.

Castings were heat treated according to T6 mode (two-stage quenching heating, quenching in cold water and aging). Vickers hardness was determined according to GOST 2999-75. The experimental values are given in table.2.

Table 1 The compositions of the experimental alloys No. Zn,% Mg,% Ni,% Fe,% Zr,% Cu,% Al one four 1,5 0.5 0.01 0.01 0.02 rest 2 5 3,1 4.2 0.02 0.02 0.3 rest 3 6.7 2,8 2 0.4 0.15 0.2 rest four 8 2.0 one one 0.25 0.05 rest 5 8.5 3,5 4,5 1,2 0.3 0.5 rest

table 2 Characteristics of experimental bullion alloys No. Q ¹ , vol.% Ts, ° C Hv Al ₃ Ni Al ₉ FeNi Amount one 0.72 0.14 0.86 607 90 2 6.09 0.20 6.29 553 185 3 0.24 5.60 5.84 554 192 four 0 5.01 5.01 569 187 5 0 15.27 15.27 485 210 6 ³ 5.3-7 - 5.3-7 ≥540 ≥160 HB ¹ volume fraction of inclusions of aluminides (Al ₃ Ni and / or Al ₉ FeNi); ² temperature of equilibrium solidus; ³ prototype (according to patent RU 2245388)

From table 2 it is seen that only the inventive alloy (compositions 2-4) provides the required values of Q, T _s and HV. In alloy 1, the number of phases and hardness are below the required level. In alloy 5, the value of T _{s is} lower than the required level, and the value of Q, on the contrary, is higher.

In the prototype alloy, the guaranteed value of T _s is at an unacceptably low level (540 ° C), which makes it difficult to obtain globular inclusions during spheroidizing annealing. Moreover, the complete binding of nickel to the Al ₃ Ni phase requires very strict restrictions on the concentration of iron in the alloy: less than 0.01%. This necessitates the use of high-purity aluminum for smelting the alloy (in the examples given in patent RU 2245388, aluminum with a purity of 99.99% was used). In the proposed alloy, the iron concentration can reach 1% (composition No. 4).

EXAMPLE 2

Alloys No. 1, No. 3 and No. 5 (Table 1) were obtained in the form of shaped castings by liquid stamping. Castings from alloy No. 3 did not contain casting defects, and castings from alloys No. 1 and No. 5 had cracks; therefore, their mechanical properties were not determined. After heat treatment, providing the hardness indicated in Table 2, the mechanical properties of cylindrical samples cut from alloy castings No. 3 were determined according to GOST 1497-84.

From table 3 it is seen that the alloy of the claimed composition is significantly superior to the prototype alloy in terms of strength properties.

Table 3 Mechanical properties of experimental alloys in castings Alloy σ _in , MPa σ _0.2 , MPa δ,% No. 3 ¹ 620 550 4,5 Prototype ² > 510 > 420 > 4 ¹ according to table 1, ² according to patent RU 2245388

EXAMPLE 3

Alloy No. 3 (Table 1) was obtained in the form of 2 mm sheets by technology, which included the following operations:

- obtaining a flat ingot;

- homogenization annealing at a maximum heating temperature of 10 ° C below T _s ,

- hot rolling with a compression ratio of about 90%,

- heating for hardening,

- quenching in cold water,

- aging.

After heat treatment, providing the hardness indicated in Table 2, the mechanical properties of flat samples cut from sheets were determined according to GOST 1497-84.

From table 4 it is seen that the alloy of the claimed composition (No. 3) significantly exceeds the prototype alloy in terms of strength properties.

Table 4 Mechanical properties of experimental alloys in sheets Alloy σ _in , MPa σ _0.2 , MPa δ,% No. 3 ¹ 650 560 5.5 Prototype ² > 570 > 480 > 5 ¹ according to table 1, ² according to patent RU 2245388

EXAMPLE 4

Alloy No. 3 (Table 1) was obtained in the form of 12 mm rods by technology, which included the following operations:

- receiving a round ingot,

- homogenization annealing at a maximum heating temperature of 10 ° C below T _s ,

- hot pressing with a compression ratio of about 90%,

- heating for hardening,

- quenching in cold water,

- aging.

After heat treatment, providing the hardness indicated in Table 2, the mechanical properties of cylindrical specimens machined from rods were determined according to GOST 1497-84.

From table 5 it is seen that the alloy of the claimed composition (No. 3) significantly exceeds the prototype alloy in terms of strength properties.

Table 5 Mechanical properties of experimental alloys in bars Alloy σ _in , MPa σ _0.2 , MPa δ,% 3 ¹ 670 580 6 Prototype ² > 570 > 480 > 5 ¹ according to table 1, ² according to patent RU 2245388

Claims (4)

1. An aluminum-based alloy containing zinc, magnesium and nickel, characterized in that it additionally contains iron, zirconium and copper at the following component concentrations, wt.%:
zinc 5-8 magnesium 2-3,1 nickel 1-4,2 iron 0.02-1 zirconium 0.02-0.25 copper 0.05-0.3 aluminum rest,
the temperature of equilibrium solidus is at least 550 ° C, and the hardness is at least 180 HV. 2. The alloy according to claim 1, characterized in that it is characterized by a structure in the form of a matrix formed by a solid solution of aluminum with dispersed particles of secondary precipitates uniformly distributed in it and particles of aluminides uniformly distributed in it containing nickel and iron of eutectic origin, with this alloy contains a matrix and aluminides in the following ratio, vol.%:
Nickel and Iron Aluminides 5.0-6.3 Matrix rest. 3. The alloy according to claim 1 or 2, characterized in that it is obtained in the form of castings having the following tensile properties: tensile strength σ _in - at least 610 MPa, yield strength σ _0.2 - at least 550 MPa, elongation δ - not less than 4%. 4. The alloy according to claim 1 or 2, characterized in that it is obtained in the form of deformed semi-finished products with the following tensile properties: tensile strength σ _in - at least 640 MPa, yield strength σ _0.2 - at least 550 MPa, relative elongation δ - not less than 5%.