EP1217085B1 - Non hardenable aluminium alloy as semi-product for structures - Google Patents

Abstract

The invention relates to chemical compositions of alloys, particularly naturally hard semi-finished product alloys which should be used in said form as material for semi-finished products. The invention also relates to a naturally hard aluminium alloy for semi-finished product structures which is made of magnesium, titanium, beryllium, zircon, scandium and cerium and additionally manganese, copper, zinc and an element group containing iron and silicon, whereby the ratio of iron to the silicon ranges between 1 and 5. The composition of the aluminium alloy is (in wt. %): magnesium 5.0-5.6; titanium 0.01-0.05; beryllium 0.0001-0.005; zircon 0.05-0.15; scandium 0.18-0.30; cerium 0.001-0.004; manganese 0.05-0.18; iron 0.05-0.18; zinc 0.05-0.15; the element group containing iron and silicon 0.04-0.24 and the rest being aluminium.

Description

The present invention relates to the composition of alloys, in particular of naturally hard semi-finished alloys, which in this form serve as material for structures should be used.

Naturally hard aluminum alloys as semi-finished products for structures (see GOST Standard 4784-74) are used in metallurgy, but especially as an AMg6 alloy, which contains the following (% by weight): magnesium 5.8 - 6.8 manganese 0.5-0.8 titanium 0.02 - 0.1 beryllium 0.0002 - 0.005 aluminum rest

However, such an alloy does not have sufficient strength properties, in particular a low 0.2% proof stress for cold and hot formed semi-finished products.

The document DE-A-198 38 018 discloses a weldable, corrosion-resistant high-magnesium aluminum-magnesium alloy consisting of 5-6% by weight Magnesium (Mg), 0.05-0.15% by weight zirconium (Zr), 0.05-0.12% by weight manganese (Mn), 0.01-0.2% by weight of titanium (Ti), maximum 0.1% by weight of silicon (Si), 0.05-0.5% by weight of one or more elements from the scandium group and / or terbium (Tb), where at least scandium (Sc) is contained, 0.1-0.2% by weight, copper (Cu) and / or 0.1-0.4 % By weight zinc (Zn) as well as aluminum (AI) and unavoidable impurities as the rest.

A naturally hard aluminum alloy that is used as a semi-finished product for structures (see patent RU No. 2085607, IPC class C22 C 21/06) also belongs to the state of the art as a prototype with the following chemical composition (% by weight): magnesium 3.9 - 4.9 titanium 0.01-0.1 beryllium 0.0001 - 0.005 zircon 0.05-0.15 scandium 0.20 - 0.50 cerium 0.001 - 0.004 aluminum rest

This known alloy does not show sufficient static and dynamic strength high processability during the manufacturing process, high corrosion resistance, good weldability and high operability under low temperature conditions.

The invention relates to a new, naturally hard aluminum alloy for semifinished products which, in addition to magnesium, titanium, beryllium, zircon, scandium and cerium, also consists of manganese, copper, zinc and iron and silicon in the following composition of the components (% by weight), the Ratio between iron and silicon is in the range of 1 to 5: magnesium 5.0 - 5.6 titanium 0.01-0.05 beryllium 0.0001 - 0.005 zircon 0.05-0.15 scandium 0.18-0.30 cerium 0.001 - 0.004 manganese 0.05-0.18 copper 0.05-0.15 zinc 0.05-0.15 Iron and silicon 0.04 - 0.24 Aluminum and unavoidable impurities rest

The technical effect is an improvement in the static and dynamic strength properties of the alloy, which increases the service life and operational safety as well as the weight value of the structures exposed to static and dynamic loads, especially the structures of various air and
Spacecraft - including those that burn cryogenic fuel.

Because of the ratio according to the invention between the chemical content and the chemical components, the alloy is more of a ductile matrix that consists of one Mixed crystal consisting of dissolved magnesium, manganese, copper and zinc in aluminum.

The particularly good operability of the alloy under dynamic Alternating stress is due to the high ductility of the matrix. secondary Precipitates from finely divided intermetallic particles, the aluminum, scandium, Contain zirconium, titanium and other transition metals found in the alloy, ensure both the high static strength of the alloy and a good one Resistance to crack propagation under alternating stress. The setpoint of the Relationship between iron and silicon optimizes the morphology from the solidification originating primary intermetallic compounds, which are primarily made of aluminum, Iron and silicon exist and improve the static strength of the Alloy alloy while maintaining its dynamic strength and plasticity become.

example

Using aluminum A85, magnesium MG90, copper MO, zinc TsO, binary Master alloys such as aluminum titanium, aluminum beryllium, aluminum zircon, aluminum scandium, Aluminum cerium, aluminum manganese, aluminum iron and silumin as Additive, the melt was prepared in an electric furnace, followed by 165 x 550 mm large and flat cast blocks of the alloy according to the invention with minimal (Composition 1), optimal (composition 2) and maximum (Composition 3) Ratio of ingredients - including those over the current constraints of the components in excess (Compositions 4 and 5) and the conventional alloy (composition 6) - were cast using semi-continuous casting techniques (Table 1).

If the alloy is prepared under metallurgical production conditions, can Scrap made of aluminum-magnesium alloys can be used as an additive.

The cast blocks were homogenized and machined to a thickness of 140 mm. They were then strengthened to 7 at a temperature of 400 ° C mm hot-rolled and then cold-rolled to a thickness of 4 mm. The cold rolled sheets were heat treated in an electric furnace. The heat-treated sheets served as investigation material.

• Bruchlastspielzahl (N) bei Bestimmung der Kurzzeitfestigkeit (LCF), wofür Proben mit einem Kerbfaktor von K_t = 2,5 und einer maximalen Spannung σ_max 160 MPa verwendet werden;
• Rissausbreitungsgeschwindigkeit da/dN in einem Bereich des Spannungsintensitätsfaktors ΔK = 31,2 MPa√m;
• kritischer Spannungsintensitätsfaktor K_C im ebenen Spannungszustand, wobei die Breite (B) der Probe 160 mm beträgt.

Standard transverse samples worked out from the sheets were used to determine the static tensile strength (R _m , R _p0.2 , A) and the dynamic strength:

• Number of breaking load cycles (N) when determining the short-term strength (LCF), for which samples with a notch factor of K _t = 2.5 and a maximum stress σ _max 160 MPa are used;
• Crack propagation velocity da / dN in a range of the stress intensity factor ΔK = 31.2 MPa√m;
• critical stress intensity factor K _C in the flat stress state, the width (B) of the sample being 160 mm.

All tests were carried out at room temperature.

The test results are listed in Table 2.

Table 2 shows that the alloy according to the invention has a higher static and dynamic strength than the conventional one. This enables one to reduce the weight of the structures made of the alloy according to the invention by 10 to 15% in order to reduce operating costs, which is particularly important for the aircraft industry. The high operability of the alloy according to the invention under static and dynamic conditions and the fact that the alloy according to the invention is a naturally hard, which has a high corrosion resistance and good weldability, enables it for the construction of completely new air and space vehicles, ocean-going vessels, ground-based vehicles and other vehicles, the structural elements of which are connected by welding. The alloy according to the invention can be used as a base material in welded structures and as a filler material for welded joints.

Claims (1)

1. Naturally hard aluminium alloy as a semi-finished product for structures, characterised in that,
   in addition to magnesium, titanium, beryllium, zirconium, scandium and cerium, it additionally consists of manganese, copper and zinc, as well as iron and silicon, in the following composition of the components (% w/w), the ratio between iron and silicon being in the range of 1 to 5: Magnesium 5.0 - 5.6 Titanium 0.01 - 0.05 Beryllium 0.0001 - 0.005 Zirconium 0.05 - 0.15 Scandium 0.18 - 0.30 Cerium 0.001 - 0.004 Manganese 0.05 - 0.18 Copper 0.05 - 0.15 Zinc 0.05 - 0.15 Iron and silicon 0.04 - 0.24 Aluminium and unavoidable impurities remainder