RU2558806C1 - Aluminium-based heat-resistant alloy - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: aluminium-based alloy contains copper, magnesium, manganese, zirconium, cobalt, silver, at least one element of group including yttrium, cerium, and at least one element from group including hafnium, titanium, boron, carbon, at the following components ratio, wt %: copper 5.1-6.5, magnesium 0.15-1.0, manganese 0.1-0.9, zirconium 0.005-0.2, cobalt 0.005-0.2, silver 0.25-1.0, at least one element of group including yttrium, cerium 0.005-0.2, at least one element from group including hafnium, titanium 0.001-0.1, boron, carbon 0.0001-0.08, aluminium - rest.

EFFECT: increased ultimate strength and yield strength at room temperature, and long-term strength after strengthening heat treatment upon keeping high level of crack strength.

3 ex, 2 tbl

Description

The invention relates to the field of non-ferrous metallurgy, in particular to deformable thermally hardened aluminum-based alloys intended for use as a structural material for structural elements of aircraft and engineering products subjected to technological and operational heating to temperatures of 175-200 ° C.

Known aluminum alloy grade 1205, having the following composition, wt.%:

copper 5.6-6.8 manganese 0.3-0.8 titanium 0.02-0.1 zirconium 0.08-0.15 cadmium 0.1-0.2 magnesium no more 0.02 aluminum rest

(“Aviation materials. Handbook in 9 volumes”, vol. 4, book 1. Edited by SI Kishkin. Moscow. ONTI, 1982, pp. 453-481).

The disadvantage of this alloy is the low level of long-term strength at temperatures of 175-200 ° C, which allows limited use in heating parts of structures. In addition, it contains cadmium, which significantly impairs the environmental friendliness of alloy production.

Known heat-resistant deformable aluminum alloy containing the following elements, wt.%:

copper 5.5-6.5 manganese 0.4-0.8 magnesium 0.2-0.35 titanium 0.05-0.1 zirconium 0.06-0.2 vanadium 0.05-0.15 molybdenum 0.02-0.08 silicon 0.12-0.25 aluminum rest

(RU 2048577 C1, 11/20/1995).

The disadvantage of this alloy is the low level of mechanical properties at room temperature. The low magnesium content does not provide a yield strength level above 390 MPa. In addition, due to alloying with a large number of elements insoluble in aluminum, in particular silicon, the alloy is characterized by low crack resistance characteristics as a result of the formation of excess coarse intermetallic compounds, which are the centers of nucleation and development of cracks.

The closest analogue is an aluminum alloy having the following chemical composition, wt.%:

Cu 4.1-5.5 Mg 0.30-0.75 Mn 0.15-0.8 Ti 0.05-0.4 Cr 0.05-0.4 Ag 0-0.7 Zr 0-0.2 Fe 0- <0.20, preferably 0- <0.15 Si 0- <0.20, preferably 0- <0.15 Al and other impurities rest

(RU 2418876 C2, 05/05/2011).

The disadvantage of this alloy is the unsatisfactory long-term strength, which significantly limits its use in products subjected to operational and technological heating. The objective of the invention is to develop an aluminum alloy of the Al-Cu-Mg system alloyed with rare (hereinafter - RM) and rare-earth metals (hereinafter - REM) for structural elements of aircraft and engineering products subjected to operational and technological heating, including long-term, up to to temperatures of 175-200 ° C.

The technical result of the claimed invention is to increase the tensile strength and yield strength at room temperature and long-term strength at temperatures of 175-200 ° C after hardening heat treatment while maintaining a high level of crack resistance. The technical result is achieved due to the fact that the proposed alloy based on aluminum, including copper, magnesium, manganese, zirconium, silver, while it additionally contains cobalt, at least one element from the group containing yttrium, cerium, and at least at least one element from the group consisting of hafnium, titanium, boron, carbon, in the following ratio of components, wt.%:

copper 5.1-6.5 magnesium 0.15-1.0 manganese 0.1-0.9 zirconium 0.005-0.2 cobalt 0.005-0.2 silver 0.25-1.0

at least one element from the group containing

yttrium, cerium 0.005-0.2

at least one element from the group containing

hafnium, titanium 0.001-0.1 boron carbon 0.0001-0.08 aluminum rest

Complex alloying of the alloy provides increased strength and long-term strength due to the allocation of hardening phases during aging and the strengthening of grain boundaries by insoluble phases based on aluminum with rare-earth metals.

An increase in the copper content provides hardening of the alloy at room temperature by increasing the density of precipitates of the hardening phases.

The addition of silver ensures the formation of the Ω 'phase as a result of artificial aging, which is released homogeneously and provides an increase in tensile strength and yield strength while maintaining crack resistance.

In order to modify the structure of the ingots and to ensure, after deformation, semi-finished products from this alloy of uniform grain with a regulated size, elements from the group consisting of titanium, hafnium, boron and carbon are introduced, which form compounds with each other and with aluminum that are the crystallization centers during casting, providing fine-grained structure in ingots.

The introduction of rare-earth metals — yttrium and / or cerium into the alloy — strengthens grain boundaries due to the formation of temperature-resistant compounds with aluminum, which impede the movement of dislocations and the development of creep processes, which increases the level of long-term strength, in particular, at temperatures of 175- 200 ° C.

An example implementation.

The method of semi-continuous casting was cast round ingots with a diameter of 110 mm, the chemical composition of which is presented in table 1. After homogenization and turning, the ingots were forged on a flat flat at a temperature of 400-460 ° C. Then, hot rolling of the slider was carried out to a thickness of 6 mm, after which the hot-rolled billets were cold-rolled at a Duo mill to a thickness of 2.5 mm. After rolling, the sheets were tempered in cold water. Then, straightening was carried out by stretching with a degree of residual deformation of 0.5-1.5% to give the necessary flatness and artificial aging in a single-stage mode for maximum strength.

Samples were cut from the sheets for studies of mechanical tensile properties at room temperature, as well as samples for determining long-term strength. The tests were carried out on flat samples according to GOST 1497-84. Long-term strength tests were carried out according to GOST 10145-1. Tensile tests with determination of the critical stress intensity factor under plane stress conditions were carried out according to OST 1 90356-84. The results of the mechanical tests are shown in table 2.

As can be seen from a comparison of the mechanical characteristics of the sheets shown in table 2, the proposed alloy has a 5% increased tensile strength, 10% increased yield strength at room temperature in comparison with the prototype, as well as 20% increased long-term strength while maintaining a high level of crack resistance . This allows the use of this alloy in loaded structural elements under thermal conditions.

Claims (1)

An aluminum-based alloy containing copper, magnesium, manganese, zirconium, silver, characterized in that it further comprises cobalt, at least one element from the group containing yttrium, cerium, and at least one element from the group containing hafnium, titanium, boron, carbon, in the following ratio of components, wt.%:
copper 5.1-6.5 magnesium 0.15-1.0 manganese 0.1-0.9 zirconium 0.005-0.2 cobalt 0.005-0.2 silver 0.25-1.0
at least one element from the group containing
yttrium, cerium 0.005-0.2
at least one element from the group containing
hafnium, titanium 0.001-0.1 boron carbon 0.0001-0.08 aluminum rest