Duralumin
Duralumin (ium) is an aluminum alloy which, especially in comparison with pure aluminum, opened a new era for aluminum due to the high strength and hardness achieved .
development
In 1906, Alfred Wilm developed the first exclusive wrought alloy as part of investigations into increasing the strength of aluminum alloys . His discovery was to increase the hardness of the alloy by transferring the methods used in steel production to increase strength to an aluminum alloy. It was discovered by chance that alloy samples left for a few days after quenching actually showed increased strength. The underlying principle is known as precipitation hardening .
The new material was produced by the Düren metal works from 1909 and the name Duralumin and some similar ones (DURAL) were protected as registered trademarks . Wilm's alloy of aluminum, 3.5 to 5.5 percent copper , 0.5 to 0.8 percent magnesium and 0.6 percent manganese as well as up to 1 percent silicon and 1.2 percent iron has also been registered for a patent. The name was derived from the Latin durus for "hard" (or better: "enduring" in the sense of permanent, resistant), although a connection to the place of work Düren is occasionally described in the literature , as well as the main component of the alloy aluminum . There are now numerous comparable alloys that have inserted the manufacturer name into the alloy designation.
Material properties
Duralumin is one of the aluminum alloys of the AlCuMg group ( material number 2000 to 2999) and is mainly used after being cold-hardened. It is not very corrosion-resistant, can only be anodized and welded to a limited extent. Today the name duralumin is mainly used for a lexical definition. Similar alloys are still used in aviation .
Compared to pure aluminum, duralumin has a slightly higher density. However, the tensile strength is between 180 and 450 N / mm² (according to another source up to 800 N / mm²) and thus up to ten times that of pure aluminum, which has only about 80 N / mm². The technically very important yield point is over 250 N / mm² compared to 30 N / mm² for pure aluminum. The situation is similar with Brinell hardness , where an HB value of around 125 is achieved compared to 22 for pure aluminum. The elongation at break is given as 22 percent, three times higher than 7 percent for pure aluminum. Another important point is that duralumin does not lose any of its strength through aging .
The basis for hardening compared to pure aluminum is that after the alloy has cooled down quickly, after some time a precipitation of a second phase (the intermetallic compound CuAl 2 ) in the basic structure of the alloy, which is initially suppressed during quenching, takes place, a process that results in a significant increase in strength Has. This elimination of the strength-increasing second phase can take place at room temperature as well as at elevated temperatures (“cold aging” - “warm aging”) and reaches its optimum after two days.
The hardening of aluminum alloys has otherwise nothing to do with the processes that take place in steel hardening. There , the strength drops after the quenched steel is reheated, while it increases with the Al alloys.
| material |
Density in kg / dm³ |
E-module in N / mm² |
Tensile strength in N / mm² |
Elongation at break in% |
Brinell hardness HB |
|---|---|---|---|---|---|
| Dural AlCu4Mg1 | 2.75-2.87 | 73,000 | 420- 500 | <22 | 115-135 |
| Pure aluminum Al99.5 | 2.7 | 70,000 | 75- 110 | < 7 | 22- 35 |
| Carbon steel (S355) | 7.9 | 200,000 | 510 | 19th | 120-140 |
| Chrome-nickel steel | 7.9 | 200,000 | 500- 750 | 40 | 130-190 |
| 54SiCr6 ( spring steel ) | 7.46 | 210,000 | 1450-1750 | 6th | 230-280 |
As a result of hardening, duralumin almost reaches the strength of soft steels . The higher susceptibility to corrosion compared to pure aluminum is countered by cladding with pure aluminum, anodizing or painting .
Applications
Due to the improved material properties, the replacement of steel by an aluminum alloy in aviation and weapons technology became useful in the first place. Earlier alloys such as zinc- aluminum alloys were significantly more susceptible to stress corrosion and did not achieve the required strength by far.
As early as 1911, duralumin was used on a large scale for the shoring of the British airship HMA No. 1 Mayfly . From 1914 it was also used for the construction of the German Zeppelin airships (for the first time with the LZ 16 / Z XII) . In 1929 an all-metal airship - the American ZMC-2 - was manufactured. It consisted entirely of duralumin including a sheet metal gas envelope.
In addition to the airship builders, Hugo Junkers was also encouraged to use duralumin in the Junkers J 7 (1917). One of the first passenger aircraft, the Junkers F 13 (1919), was a full metal commercial aircraft in which duralumin was used as the material for the chassis. Duralumin also proved to be well suited for the then new monocoque construction of airframes. In modern aircraft construction, duralumin is known today as a material for 2017, 2117 or 2024.
The use in the automotive industry was initially only possible to a limited extent due to the high price and the difficult processing. However, it has now become common when light weight is important. Examples of use are in particular body parts. Bonnets and trunk lids have now been largely replaced by thin-walled precision die-cast (EVACAL and PORAL processes).
literature
- Paul Krais: Materials . Volume 2, A. Barth, Leipzig 1921, pp. 517-518.
- Entry on duralumin. In: Römpp Online . Georg Thieme Verlag, accessed on January 2, 2015.
- A. von Zeerleder: Technology of light metals . Rascher, Zurich 1947.
- Stephan Hasse. Foundry lexicon . 19th edition. Schiele and Schön, Berlin 2007, ISBN 978-3-7949-0753-3 , see: Duralumin .
Web links
Individual evidence
- ^ J. Gobrecht: Material technology - metals . ISBN 978-3-486-57903-1 .
- ^ A b c Nasser Kanani: Materials science for surface technicians and electroplaters . ISBN 978-3-446-40741-1 .
- ↑ a b c Niels Klußmann, Arnim Malik: Lexicon of aviation . ISBN 978-3-540-49095-1 .
- ↑ 1.7102. 54SiCr6. Cr-Si alloyed spring steel (PDF; 1.4 MB).
- ↑ Wolfgang Bergmann: Material Technology , Part 2. ISBN 978-3-446-41711-3 .
- ↑ Helmut Maier: Armaments research in National Socialism organization, mobilization and delimitation of the technical sciences . Wallstein Verlag, 2002, ISBN 978-3-89244-497-8 , pp. 378 ( limited preview in Google Book search).
- ^ Otto Brandt, H. Dubbel, W. Franz, R. Hänchen, O. Heinrich, Otto Kienzle, R. Kühnel, H. Lux, K. Meller, W. Mitan, W. Quack, E. Sachsenberg: Taschenbuch für den Factory operation . Springer-Verlag, 2013, ISBN 978-3-642-99589-7 , pp. 422 ( limited preview in Google Book search).
- ^ The Naval Airship. (PDF) In: FLIGHT, May 27, 1911. Flightglobal.com , May 27, 1911, pp. 461–462 , accessed on July 28, 2017 (English): “THE NAVY AIRSHIP NO. 1. — The "Mayfly," built by Messrs. Vickers, Ltd., which was successfully launched at Barrow on Monday last. "
- ^ Klaus Hentschel : Duralumin. Use of duralumin. In: 220 tons - lighter than air, material history of the Hindenburg . University of Stuttgart , Historical Institute, Department for the History of Natural Sciences and Technology, 2010, accessed on November 10, 2017 (website for the exhibition in the Zeppelin Museum Friedrichshafen ): "From 1914 (LZ 26), duralumin was used in airship construction."
- ↑ Philipp Hassinger: Between Evolution and Revolution - The Material Change in Aircraft Construction . KIT Scientific Publishing, 2013, ISBN 978-3-86644-998-5 , pp. 145 ( limited preview in Google Book search).
- ↑ Hans Otto Frøland, Mats Ingulstad, Jonas Scherner: Industrial Collaboration in Nazi-Occupied Europe Norway in Context . Springer, 2016, ISBN 978-1-137-53423-1 , pp. 43 ( limited preview in Google Book search).
- ↑ Rambabu, P & Eswara Prasad, N & V. Kutumbarao, V & Wanhill, Russell. (2017). Aluminum Alloys for Aerospace Applications. 29-52. 10.1007 / 978-981-10-2134-3_2.
- ^ Friedrich Ostermann: Application technology aluminum . Springer-Verlag, 2015, ISBN 978-3-662-43807-7 , pp. 24 ( limited preview in Google Book search).