RU2268319C1 - Wrought not thermally hardened aluminum-based alloy - Google Patents

Abstract

FIELD: wrought not thermally hardened alloys used as structural materials in shipbuilding; aerospace engineering; oil-and-gas extraction industry.

SUBSTANCE: proposed alloy contains the following components, mass-%: magnesium, 5.5-6.5; scandium, 0.10-0.20; manganese, 0.5-1.0; chromium, 0.10-0.25; zirconium, 0.05-0.20; titanium, 0.02-0.15; zinc, 0.1-1.0; boron, 0.003-0.015; beryllium, 0.0002-0.005; the remainder being aluminum.

EFFECT: high ductility of alloy with strength characteristics at prototype level.

2 tbl, 1 ex

Description

The proposed invention relates to the field of metallurgy of alloys, in particular deformable thermally unstrengthened aluminum alloys intended for use as structural material in the form of deformed semi-finished products in various branches of technology: shipbuilding, aerospace and oil and gas industry, transport engineering, etc.

There are a number of deformable thermally unstrengthened aluminum alloys of medium strength alloyed with magnesium, manganese, zirconium and other transition metals in an amount that provides the optimal combination of strength and plastic properties. The most common of this group of alloys is an alloy of grade 1561, the chemical composition of which is regulated by OST 1.92014-90.

At present, more durable thermally unstrengthened alloys of the aluminum-magnesium-scandium system have been developed.

The closest in technical essence and accepted by us for the prototype is a thermally unstrengthened Al-Mg-Sc alloy, the composition of which is disclosed in RF patent No. 2081934. This alloy contains the following components in wt.%:

magnesium 5.3-6.5 manganese 0.2-0.7 zirconium 0.02-0.15 beryllium 0.0001-0.005 scandium 0.17-0.35 at least one metal from the group containing titanium and chromium 0.01-0.25 aluminum rest

The disadvantage of this alloy is its low technological ductility, which prevents the use of complex schemes of stress-strain state during plastic processing (for example, forging, stamping, etc.).

The technical result of the proposed invention is the creation of an alloy having high technological plasticity with strength characteristics at the level of the prototype alloy, which is achieved by the fact that zinc and zinc are additionally introduced into the aluminum-based alloy containing magnesium, scandium, manganese, chromium, zirconium, titanium, beryllium boron, the content of scandium is lowered, the minimum total content of scandium, manganese and chromium is limited to 0.85% and the components are taken in the following proportions, wt.%:

magnesium 5.5-6.5 scandium 0.10-0.20 manganese 0.5-1.0 chromium 0.10-0.25 zirconium 0.05-0.20 titanium 0.02-0.15 zinc 0.1-1.0 boron 0.003-0.015 beryllium 0.0002-0.005 aluminum rest

Magnesium and manganese in the alloy are the most effective hardeners. Manganese also reduces the tendency to intergranular and stress corrosion.

Scandium is the most effective modifier and alloying element, contributes to the preservation of non-crystallized structure, increases the mechanical properties of aluminum alloys. However, with its increased content in multicomponent alloys, their technological ductility decreases.

When the content of scandium is less than 0.10%, the strength properties of the proposed alloy become lower than the properties of the prototype alloy.

Alloying an alloy with chromium promotes a more homogeneous precipitation of dispersed intermetallic compounds, increases the strength properties of the alloy, and increases resistance to corrosion cracking.

Due to the fact that manganese and chromium crystallize in aluminum alloys by eutectic and peritectic reactions, respectively, manganese strengthens the peripheral volumes of grain, and chromium - internal.

The introduction of zirconium into the alloy enhances the effect of scandium, has a modifying effect on the structure of the ingots, crushes the precipitation of the β phase, provides an unrecrystallized structure of deformed semi-finished products, reduces the tendency to crack during welding, and increases the mechanical properties of welded joints.

Beryllium protects the metal during oxidation.

Titanium is one of the most active modifiers of aluminum alloys, increases their strength and plastic properties.

Alloying the alloy with zinc increases its technological plasticity and strength characteristics. The combined introduction of zinc and chromium improves the corrosion resistance of the alloy under stress.

When the zinc content is less than 0.1%, its effect is ineffective.

When the zinc content is more than 1.0%, the technological plasticity of the alloy is reduced due to the formation of intermetallic Al-Zn-Mg phase T.

Boron modifies the structure of the alloy, increases its manufacturability. The introduction of boron into the alloy increases the ability of the alloy to deform, which makes it possible to manufacture forgings and stampings. With the joint introduction of boron and titanium into the alloy, the modification effect is significantly enhanced and the mechanical properties of the alloy increase.

When the boron content is less than 0.003%, the strength of the proposed alloy does not reach the strength of the prototype alloy.

When the boron content is more than 0.015%, it does not significantly affect the structure and strength properties of the alloy.

When the total content of scandium, manganese and chromium is less than 0-85%, the strength properties of the alloy become lower than the properties of the prototype alloy.

Ensuring the strength of the proposed alloy at the level of the alloy properties of the prototype is achieved with a total content of scandium, manganese and chromium of at least 0.85%.

The decrease in the content of scandium in the proposed alloy significantly - in 1.5-2.0 times - reduces its cost compared to the prototype.

Example

Samples for research were made from an alloy of the proposed composition with alloying at the lower (taking into account the total content of scandium, manganese and chromium of at least 0.85%), the middle, upper levels and beyond compositions, as well as from the prototype alloy (see Table 1) .

Smelting was carried out in a reflective electric furnace. As the mixture used aluminum grade A85, magnesium grade MG, zinc grade C0, aluminum alloys with all alloying elements that make up the alloy.

The method of semi-continuous casting was cast ingots with a cross section of 60 × 240 mm. The ingots were homogenized at a temperature of 400 ^{± 5} ° C for 24 hours. From ingots, billets for rolling 55 × 230 × 350 mm in size were made by machining. The billets were heated to a temperature of 400-420 ° C and rolled onto sheets with a thickness of 10 mm. The resulting sheets were examined.

The strength properties of the sheets were determined at room temperature when testing standard round samples in tension.

The strength characteristics were taken as the tensile strength (σ _in ) and yield strength (σ _0.2 ).

The deformability of the metal during hot processing (technological ductility) was evaluated at a temperature of 420 ° C according to the results of rolling wedge samples and precipitation of cylindrical samples cut from an ingot. To assess the deformability during rolling of wedge samples, we used the criterion K = l ₁ / l ₀ × 100%, where l ₀ is the total length of the deformed sample, l ₁ is the length of the deformed part of the samples to the first crack. To assess the deformability during the sedimentation of the specimen, we took the relative deformation ε = (h ₀ -h ₁ ) / h ₀ × 100%, where h ₀ is the initial height of the specimen, h ₁ is the height of the specimen when the first crack appeared on the side surface.

The results of mechanical tests and data on the deformability of the alloy at a temperature of hot plastic processing (technological ductility) are shown in table 2.

As can be seen from table 2, the proposed alloy has a higher than the prototype, technological ductility - the ability to deform during hot processing by pressure.

The results of mechanical tests show that the proposed alloy in terms of strength characteristics (σ _in = 411-428 MPa; σ _0.2 = 288-304 MPa) is not inferior to the prototype alloy.

When the content of alloying elements is extremely low, the strength properties of the alloy decrease, and when their content is extremely high, the technological ductility of the alloy decreases.

The technical and economic effect of the use of the invention compared to the prototype is to increase the yield of hot strength semi-finished products during hot deformation, the possibility of manufacturing high-strength semi-finished products using complex stress-strain state schemes (for example, forging and stamping) and to increase the productivity of the process of manufacturing semi-finished products by increasing manufacturability of the alloy with a significant reduction in its cost.

Table 1
The content of the main components in the proposed alloy and prototype Alloy Composition number Chemical composition, wt.% Magnesium Mg Scandium sc Manganese Mn Chrome Cr Zirconium Zr Titanium Ti Zinc Zn Bor B Beryllium Be Sc + Mn + Cr Aluminum Al Proposed one 5.5 0.10 0.65 0.10 0.05 0.02 0.1 0.003 0,0002 0.85 Rest 2 6.0 0.15 0.50 0.22 0.11 0.10 0.6 0.008 0.0026 0.87 Rest 3 6.5 0.20 1,0 0.25 0.20 0.15 1,0 0.015 0.005 1.45 Rest Outrageous component content four 5,4 0.09 0.40 0.13 0.04 0.01 0.09 0.002 0.0001 0.62 Rest 5 6.6 0.21 1.10 0.26 0.21 0.16 1,1 0.017 0.0052 1,57 Rest Prototype 6 6.3 0.23 0.50 0.23 0.08 0.04 - - 0.001 Rest

table 2
The mechanical properties of the proposed alloy and prototype Alloy The mechanical properties of the sheets Composition number Strength properties * Technological plasticity,% ** Tensile Strength (σ _in ), MPa Yield Strength (σ _0.2 ), MPa When rolling, K In draft, ε Proposed one 411 288 92 76 2 420 295 87 72 3 428 304 84 60 Outrageous component content four 398 274 94 74 5 432 306 82 62 Prototype 6 416 292 81 62 Note:
* average results on the basis of testing 5 samples;
** average results based on tests of 3 samples.

Claims (1)

Wrought thermally non-hardening aluminum-based alloy containing magnesium, scandium, manganese, chromium, zirconium, titanium, beryllium, characterized in that zinc and boron are additionally introduced into it in the following ratio of components, wt.%: Magnesium 5.5-6.5 Scandium 0.10-0.20 Manganese 0.5-1.0 Chromium 0.10-0.25 Zirconium 0.05-0.20 Titanium 0.02-0.15 Zinc 0.1-1.0 Boron 0.003-0.015 Beryllium 0.0002-0.005 Aluminum Rest with a total content of scandium, manganese and chromium not less than 0.85%.