RU2284367C1 - Method of manufacture of articles from wrought aluminum alloys - Google Patents

Abstract

FIELD: non-ferrous metallurgy; methods of production of parts and semi-finished products from aluminum alloys containing additives of transition metals; aerospace engineering; shipbuilding; transport engineering as load-bearing structures and skins.

SUBSTANCE: proposed method of manufacture of parts from alloys containing at least one transition metal includes homogenization of ingot, cooling, heating to temperature of plastic deformation, plastic deformation and heat treatment. Homogenization of ingot is carried out in two stages: at first stage, heating is performed at range of temperatures of minimum stability of solid solution of main alloying components in aluminum at rate of heating of 2-5°C/h; at second stage, heating is continued to temperature of 450-470°C at rate of 30-50°C/h followed by holding at temperature of heating during period of time sufficient for dissolving of particles of excessive eutectic phases.

EFFECT: improved strength characteristics; enhanced ductility, enhanced resistance to cracks, fatigue, corrosion; increased service life of structure; enhanced weight efficiency.

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Description

The invention relates to the field of non-ferrous metallurgy, in particular to a method for producing parts and semi-finished products from aluminum alloys containing transition metal additives, such as Zr, Sc, Mn, Cr and others, for use in aerospace engineering, shipbuilding and transport engineering as parts power set, skins, etc.

A known method of manufacturing products from high-strength deformable aluminum alloys of the 7XXX series, including the following operations: homogenization of ingots ⌀300 mm at a temperature of 450 ° C for 24 hours, preliminary deformation at a temperature of 450 ° C to a thickness of 30-60 mm, quenching from a temperature of 400 ° C after holding for 8 hours, rolling to a thickness of 20 mm, re-hardening from a temperature of 475 ° C, 1 h, dressing with a degree of deformation of 0.5% and three-stage aging (US Patent No. 5,858,133).

A known method of manufacturing parts from wrought aluminum alloys of the Al-Zn-Mg-Cu system containing small additives of transition metals, consisting of the following operations: the ingot undergoes two-stage homogenization, the first stage being heating in a temperature range from 399 ° C to 476 ° C for 2-20 hours, the second stage - heating at a temperature of 488 ° C, after homogenization, the metal is rolled at a temperature of 399 ° C, followed by quenching from a temperature of 471 ° C into water with a temperature of no more than 38 ° C, straightening by stretching with a degree residual deformations> 1% and artificial two-stage aging according to the regime: the first stage is heating at a temperature of 77-143 ° C for 2-100 hours, the second stage is heating at a temperature of 149-177 ° C for 2-48 hours (US Patent No. 5,865,911).

The disadvantage of the above known methods is the significant anisotropy of the mechanical properties and fracture toughness in the product. Especially strong reductions in ductility and viscosity are observed in the direction perpendicular to the plane of deformation (in the direction high-relative to the fiber), which significantly reduces the structural strength and weight efficiency of the parts.

The closest analogue taken as a prototype is a method of manufacturing products from aluminum alloys containing at least one transition metal, which includes the following operations: homogenization of the ingot at a temperature of 300-448 ° C, cooling to a temperature of 18-35 ° C at a speed of at least 100 ° C / h, heating to a temperature of preliminary plastic deformation corresponding to the temperature of precipitation of the strengthening phases, subsequent plastic deformation at this temperature, heating to a temperature of final plastic deformation ns and with a degree of deformation of 75% at a heating and heat treatment (Patent RF №2087582).

The disadvantage of this method is the presence in the product structure of a significant amount of insoluble particles of excess phases of crystallization origin, which are associated with a deterioration in crack resistance (K _1C , SRTU), a decrease in corrosion resistance under stress and fatigue characteristics of the material, which significantly reduces the service life of parts and reduces weight efficiency designs.

An object of the present invention is to develop a method for manufacturing products from aluminum wrought alloys having an improved set of strength characteristics, ductility (including technological ductility of ingots), crack resistance, fatigue characteristics, and corrosion properties, which will provide an increase in the life and weight efficiency of the structure.

To solve the technical problem, we propose a method of manufacturing products from aluminum wrought alloys containing at least one transition metal, including ingot homogenization, cooling, heating to plastic deformation temperature, plastic deformation, heat treatment, characterized in that the ingot is homogenized in two stages :

- the first stage is carried out in the temperature range of minimum stability of a solid solution of the main alloying components in aluminum with a heating rate of 2-5 ° C / hour;

- at the second stage, heating is carried out to a temperature of 450-470 ° C at a rate of 30-50 ° C / hour, followed by exposure at a heating temperature for a time sufficient to dissolve the particles of excess phases and equalize the chemical composition in the volume of the product.

The first is the low-temperature stage of homogenization, which is carried out in order to form fine particles of excess phases due to the intense decomposition of a supersaturated solid solution of the main alloying components in aluminum. This leads to an increase in the interphase contact surface, an increase in the concentration gradient over the volume of the cast grain and helps to increase the homogenization efficiency at the second high-temperature stage (more intensive dissolution of nonequilibrium eutectic phases due to an increase in the diffusion rate).

In addition, the first low-temperature stage provides a higher density of precipitates of fine particles of transition metal aluminides Zr, Sc, Mn, Cr, etc., as compared with single-stage homogenization at elevated temperature.

The proposed method allows, thanks to the homogenization mode, to create the optimal structure in ingots, inherited in deformed parts. A characteristic feature of such a structure is a more uniform distribution of alloying components, including transition metals in the volume of the dendritic cell, a higher distribution density of “dispersoids” - transition metal aluminides (Zr, Sc, Mn, Cr, etc.), a small volume fraction of excess particles phases of crystallization origin. The presence of such a structure provides the necessary set of properties in detail: - high strength and fatigue resistance combined with increased ductility, fracture toughness, corrosion resistance and low fatigue crack growth rate.

Examples of implementation.

In industrial conditions, ingots with a diameter of 300 mm were cast from semi-continuous casting from alloys of the following chemical composition, wt.%:

- No. 1 and No. 2 - 6.2% Zn; 2.5% Mg; 1.8% Cu; 0.12% Zr; 0.10% Fe; 0.07% Si; the rest is Al; the temperature range of the minimum stability of a solid solution of Zr in Al is 280-340 ° C;

- No. 3 - 6.9% Zn; 2.2% Mg; 1.1% Cu; 0.09% Zr; 0.15% Sc; 0.10% Fe; 0.06% Si; the rest is Al; the temperature range of the minimum stability of the Zr + Sc solid solution in Al is 270-320 ° C;

- No. 4 - 6.2% Zn; 2.2% Mg; 1.8% Cu; 0.13% Zr; 0.11% Fe; 0.09% Si; the rest is Al.

Semi-finished products were made from the obtained ingots: from alloys No. 1, 4 — 50 mm thick plates, from alloys No. 2, 3 — forgings 80 × 400 × 800 mm in size. Modes of obtaining semi-finished products are presented in table 1, where examples 1-3 are the proposed method, example 4 is the prototype method.

Tables 2 and 3 show the structural parameters and a set of operational properties of products manufactured by the proposed method (examples 1-3) and the prototype method (example 4).

As can be seen from the tables, the proposed method allows to obtain a more favorable product structure, characterized by a low volume fraction of excess eutectic phases of crystallization origin and a high density and uniformity of the distribution of particles of "dispersoids" - transition metal aluminides in the volume of the material compared to the prototype method. This allows to obtain in the products an improved complex of strength properties, ductility, fracture toughness (fracture toughness - K _1C and fatigue crack growth rate - SRTU), fatigue properties and corrosion resistance.

Thus, the proposed method allows to obtain products for the construction of aerospace engineering, shipbuilding and transport engineering, such as power packs, cladding, etc., from aluminum deformable alloys containing transition metal additives with an increased set of operational properties, which ensures an increase in service life , reliability and weight efficiency of structures in 1.5-2 times.

Table 1 The technology for producing products from aluminum deformable alloys No. Product Type Homogenization Plastic deformation Heat treatment 1st stage 2nd stage Quenching Aging The heating rate (V ₁ ), ° C / h Temperature range, ° С Heating rate (V ₂ ) ° C / h Holding temperature, ° С Holding time, h Cooling Temperature ° С Holding time, h Type, degree (ε),% The temperature of exposure, ° C Holding time, h Cooling Holding temperature, ° С Holding time, h one Plate, thickness. 50 mm 3 280-340 thirty 450 12 In air up to 30 ° С 390 four rolling 465 four In water Т-ра = 38 ° С 1st stage ε = 65% 115 8 2nd stage 170 10 2 Forging 80 × 400 × 800 mm 5 280-340 40 470 5 On air
up to 30 ° С 390 5 forging 470 5 In water Т-ра = 35 ° С 1st stage ε = 75% 115 8 2nd stage 170 8 3 Forging 2 270-320 fifty 465 6 On air 410 3,5 forging 465 6 In water Т-ра = 32 ° С 1st stage ε = 75% 110 8 2nd stage 170 8 four Plate thickness. 50 mm 300 ° C - 3 hours In air Up to 35 ° С. h Preliminary Forging ε = 50% 470 5 In water Т-ра = 45 ° С 1st stage 250 10 110 8 Final Rolling, ε = 64% 2nd stage Cooling Speed = 120 ° C / h 365 8 170 10

table 2 Properties of ingots and parameters of product structure No. Properties of ingots at a t-re deformation of 400 ° C Structure parameters Tensile deformation resistance, MPa Elongation at Tension,% The maximum degree of deformation during upset,% Volume fraction of particles of excess phases,% The particle size of the "dispersoids", nm Bulk density of particles - "dispersoids", cm ^-3 one 3,5 82 65 1.8 10-12 2.5-3.5 × 10 ¹⁵ 2 3.2 80 65 2.0 9-12 2.1-2.6 × 10 ¹⁵ 3 3,1 85 70 1.9 10-13 2.2-2.6 × 10 ¹⁵ four 4.3 42 fifty 2.9 13-15 1.1-3.1 × 10 ¹⁵

Table 3 Properties of products obtained by the proposed method and method prototype No. p / p Product Sample direction Tensile properties Crack resistance Fatigue Corrosion resistance σ _B , MPa σ _0.2 MPa δ,% K _1C , MPa √m SRTU, mm / ktsikl MCU, bikes Day to failure at σ = 240 MPa one Plate thickness. Longitudinal 550 510 12 42 4.1 210 - 50 mm High altitude 535 490 8 31 - - > 30 2 Forging 80 × 400 × 800 Longitudinal 548 500 fourteen 41 3.8 200 - mm High altitude 540 490 8 33 - ^- > 30 3 Forging 80 × 400 × 800 Longitudinal 560 510 13 42 3.4 250 - mm High altitude 550 487 7 32 - - > 30 four Plate thickness. Longitudinal 515 480 9 39 5.7 150 - Prototype 50 mm High altitude 490 460 6.5 thirty - - fourteen where σ _In - tensile strength, σ _0.2 - yield strength, δ is the elongation, To _1C - fracture toughness, SRTU - fatigue crack growth rate at ΔК = 31 MPa √ m, MCU - low-cycle fatigue at σ _max = 157 MPa; frequency (f) = 3-5 Hz; Kt = 2.6.

Claims (1)

A method of manufacturing products from aluminum wrought alloys containing at least one transition metal, including the homogenization of the ingot, cooling, heating to the temperature of plastic deformation, plastic deformation, heat treatment, characterized in that the homogenization of the ingot is carried out in two stages: the first stage is carried out in the range temperatures of minimum stability of a solid solution of the main alloying components in aluminum with a heating rate of 2-5 ° C / h; at the second stage, heating is carried out to a temperature of 450-470 ° C at a rate of 30-50 ° C / h, followed by exposure at a heating temperature for a time sufficient to dissolve the particles of excess eutectic phases.