DE1130187B - Annealed, heat-resistant and creep-resistant aluminum alloy - Google Patents

Description

Heat-treated, heat-resistant and creep-resistant aluminum alloy The invention relates to heat-treatable, heat-resistant and creep-resistant aluminum alloys, which are particularly suitable for use at elevated temperatures.

Certain aluminum alloys have long been used in certain parts of internal combustion engines, such as. B. pistons, cylinder heads, etc. used. For building stronger machines for work at higher temperatures and at larger ones Experience has shown that these known products are not sufficient to withstand stresses than before more.

It is an alloy of 5 to 7% copper, 0.01 to 0.6% titanium, 0.01 to 1% manganese and the remainder of aluminum including the impurities became known, which also has many other additions, including u. a. Vanadium and zirconium, in an amount up to a total of 0.75 0io for the purpose of modification, Degassing or grain refinement can be incorporated. Here is magnesium not included as a component.

According to the invention, a combination is obtained by adding to aluminum of elements, especially by replacing titanium with vanadium and zirconium, and Added magnesium an aluminum alloy with superior strength and improved Creep resistance and fatigue resistance at elevated temperatures.

The invention is based on the discovery that the introduction of 0.05 up to 0.70% magnesium to a non-state-of-the-art aluminum alloy from 5 to 130% copper, 0.2 to 1.7% manganese, 0.05 to 0.20% vanadium, 0.05 to 0.30% zirconium and aluminum as the remainder, if necessary with the addition of certain grain refinement elements, the strength (heat resistance) and resistance to creep and fatigue The base alloy improves at elevated temperatures if the alloy is also improved is subjected to correct solution heat treatment and age hardening (precipitation hardening). A temperature range of 205 to 260 ° C. is particularly favorable and hardened alloys within the specified composition range have a tensile strength of the order of magnitude at 2051 C after 100 hours of 32 kg / mm2, a lowest creep strain of about 0.00025 mm / mm / hour. under one Stress of 175 kg / mm2 and a fatigue strength of 16 kg / mm2 at 1000 000 load changes.

In order to achieve such properties, those in the alloy should existing impurities of iron 0.75% and of silicon 0.40 0% do not exceed. It is best to set the iron content to at most 0.50% and that of silicon to 0.30% % limited.

The best combination of properties at elevated temperatures when using 5 to 9% copper, 0.2 to 1.2% manganese, 0.05 to 0.15% vanadium, 0.05 to 0.25% zirconium and 0.25 to 0.50% magnesium. Here the iron and silicon impurities are preferably within the aforementioned limits the manganese content is best between 3 and 13% of the copper content matters.

Besides these emptying elements to form the base alloy it may be expedient to add 0.01 to 0.25% of one or more high-melting points Metals of the group cobalt, nickel, molybdenum, tungsten, chromium, titanium, boron, tantalum and add niobium, the total amount of which should not exceed 0.25%. These elements serve to refine the grain size or to improve lower-quality properties of the alloys without changing their basic properties.

To achieve the desired properties at elevated temperatures The required heat treatment consists of a 1 to 24 hour solution heat treatment at 515 to 550 ° C, a quench and a 1 to 50 hour precipitation hardening at about 175 to 320 ° C. The duration of the solution heat treatment depends on the condition the alloy, d. H. that is, whether it is cast or forged, and according to its size of the object to be treated. Precipitation hardening temperature and treatment time are determined by similar considerations, with shorter treatment times being known at temperatures in the upper range to approximately the same results as longer treatment times at a correspondingly lower temperature.

The alloys can be immersed in any liquid for quenching purposes are immersed, which exerts a strong effect and so the dissolved constituents in solution holds. Quenching in water at room temperature is usually sufficient; but where inner If tensions need to be kept to a minimum, water is the best way to use it of about 65 ° C or more or another medium to reduce the strength of the quenching process.

The alloy of the invention can be either cast or are mostly preferably used in forged form. Forgings have turned out Proven to be particularly useful. The minimum creep rate here mentioned type was obtained as follows: test rods with a diameter of about 1.25 cm are made in small electrically heated air ovens with automatic temperature control during the entire test period with the help of a dead weight under constant load held. The expansion or creep measurements are made during the entire test period carried out with an accuracy of 0.000125 mm in certain gaps. The measured Creep values are plotted against time on Cartesian coordinates; thereafter the smallest slope of the curve obtained is determined. The minimum creeping speed found in this way is also known as the secondary creep speed.

The stresses at certain creep speeds become more common Way in a graphical way by plotting this logarithmically against the voltage certainly. Tension values leading to breakage are similarly determined in such a way that one the time required to break at a given stress for a variety determined by specimens under different stresses.

In Table I are the compositions of the alloys tested, in which in each case the balance is aluminum; reproduced: Table I - Percentage composition of the alloys Alloy Cu Fe si Mn V Zr Mg A 5.98 0; 11 0.07 0.21 0.10 0.23 - B 6.09 0.15 0.11 0.32 0.18 0.20 0.25 C 12.12 0.14 0.10 0.41 0.10 0.26 - D 12.12 0.16-0.10 0.40 0.10 0.25 0.24 These alloys were cast into blocks and forged in the usual way into test bars with a cross-section of about 6 cm2. These were solution heat treated for 2 hours at about 530 to 540 ° C, then quenched in cold water and then precipitation hardened by heating to about 190 ° C for 12 hours. Table II shows the average values for the tensile properties of the various test bars at room temperature and at 205 ° C. after the alloys had been held at this temperature for 100 hours. Table 1I Tensile properties at room temperature and at 205 ° C At room temperature at 205 ° C Alloy Tensile Strength Yield Strength Elongation Tensile Strength Yield Strength Elongation kg / mm2 kg / mm2 ° / o kg / mm2 kg / mm2 ° / o A 43.1 30.1 17 24.5 18.3 24 B 49.8 39.0 13 32.1 26.9 21 C 44.4 33.5 10 27.5 21.1 14 D 46.5 36.5 8 32.2 25.4 13 According to this, the addition of magnesium increases the strength of both the low and high copper alloys.

The creep and fatigue properties of the alloys were determined at 205 ° C (Tables III and IV). Table III Creep elongation values at 205 ° C Tension (in kg / mm2) tension (in kg / mm2) for the minimum creep speed Alloy in mm / mm / hour to break with different test duration 0.00025 0.0025 0.025 10 hours 1 100 hours 1 1000 hours A 13.6 16.4 19.2 20.3 17.8 - B 20.3 23.8 - - 23.8 18.9 C - 16.1 18.9 20.3 18.2 - D 16.1 21.0 - - 23.1 17.5 Table IV Fatigue strength at 205 ° C Alloy tension (in kg / mm2) up to breakage of the after 10s load changes 1 after 107 load changes A 14.0 10.1. B 16.1 12.2 C 14.0 10.8 D 18.5 12.9 This clearly shows the value of the magnesium addition. It is interesting that both the creep strain and the fatigue values are obtained which are considerably superior to those of the magnesium-containing alloys previously used in internal combustion engines.

Claims (3)

PATE NTANS PR 1fC'.TH F 1. Heat-treated, heat-resistant and creep-resistant Aluminum alloy, characterized in that it consists of 5 to 13% copper, 0.2 to 1.7% manganese, 0.05 to 0.2% vanadium, 0.05 to 0.3% zirconium, 0.05 to 0.7 % Magnesium, the remainder aluminum, with iron impurities 0.75% and silicon does not exceed 0.4% and that it is obtained by solution heat treatment for 1 to 24 hours at 515 to 550 ° C, quenching and subsequent precipitation hardening from 1 to 50 hours at 175 to 230 ° C is heat treated. 2. Alloy according to claim 1, characterized in that it contains 5 to 9% copper, 0.2 to 1.20% manganese (the Manganese content is limited to 3 to 13% of the copper content), 0.05 to 0.15% Contains vanadium, 0.05 to 0.25% zirconium and 0.25 to 0.50% magnesium and the Impurity of the alloy in iron not more than 0.50% and the impurity of silicon makes up at most 0.30%. 3. Alloy according to claim 1 or 2, characterized characterized in that it contains 0.01 to 0.25% of at least one metal from the group cobalt, Nickel, tungsten, chromium, titanium, boron, tantalum, molybdenum and niobium, the The total amount of these elements does not exceed 0.25%. Considered publications: U.S. Patent No. 2,459,492.