Duralumin

Duralumin (also called duraluminum, duraluminium, duralum, dural(l)ium, or dural) is a trade name for one of the earliest types of age-hardenable aluminium alloys. Its use as a trade name is obsolete, and today the term mainly refers to aluminium–copper alloys, designated as the 2000 series by the International Alloy Designation System (IADS), as with 2014 and 2024 alloys used in airframe fabrication.

DLZ129 spar
Fire-damaged Duralumin cross brace from the Zeppelin airship Hindenburg (DLZ129) salvaged from its crash site at Lakehurst Naval Air Station, NJ on May 6, 1937
Corrosion of Duralumin
Corrosion of duralumin

Alloying elements

In addition to aluminium, the main materials in duralumin are copper, manganese and magnesium. For instance, Duraluminium 2024 consists of 91-95% aluminium, 3.8-4.9% copper, 0.3-0.9% manganese, 1.2-1.8% magnesium, <0.5% iron, <0.5% silicon, <.0.25% zinc, <0.15% titanium, <0.10% chromium and no more than 0.15% of other elements together.[1]

History

Duralumin was developed by the German metallurgist Alfred Wilm at Dürener Metallwerke AG. In 1903, Wilm discovered that after quenching, an aluminium alloy containing 4% copper would slowly harden when left at room temperature for several days. Further improvements led to the introduction of duralumin in 1909.[2] The name is obsolete today, and mainly used in popular science to describe the Al-Cu alloy system, or '2000' series, as designated by the International Alloy Designation System (IADS) originally created in 1970 by the Aluminum Association.

Aviation applications

ZRS-4 USS Akron duralumin sample
Duralumin sample from the USS Akron (ZRS-4)
Junkers J.I - Ray Wagner Collection Image (20821101334)
The first mass-production aircraft to make extensive use of duralumin, the armored Junkers J.I sesquiplane of WW I.

Duralumin, its composition and heat treatment, was openly published in the German scientific literature before World War I. Despite this, it was not adopted beyond Germany until after World War I. Reports of German use during World War I, even in technical journals such as Flight, could still mis-identify its key alloying component as magnesium rather than copper.[3] In the UK there was little interest in its use until after the War.[4]

The earliest known attempt to use duralumin for a heavier-than-air aircraft structure occurred in 1916, when Hugo Junkers first introduced its use in the creation of the Junkers J 3's airframe, a single-engined monoplane "technology demonstrator" that marked the first use of the Junkers trademark duralumin corrugated skinning. Only the covered wings and tubular fuselage framework of the J 3 were ever completed, before the project was abandoned. The slightly later, solely IdFlieg-designated Junkers J.I armoured sesquiplane, known to the factory as the Junkers J 4, had its all-metal wings and horizontal stabilizer made in the same manner as the J 3's wings had been, along with the experimental and airworthy all-duralumin Junkers J 7 single-seat fighter design, which led to the Junkers D.I low-wing monoplane fighter, introducing all-duralumin aircraft structural technology to German military aviation in 1918.

Its first use in aerostatic airframes was in rigid airship frames eventually including all those of the "Great Airship" era of the 1920s and 1930s: the British built R-100, the German passenger Zeppelins LZ 127 Graf Zeppelin, LZ 129 Hindenburg, LZ 130 Graf Zeppelin II, and U.S. Navy airships USS Los Angeles (ZR-3, ex-LZ 126), USS Akron (ZRS-4) and USS Macon (ZRS-5).[5][6]

Corrosion protection

Although the addition of copper improves strength, it also makes these alloys susceptible to corrosion. For sheet products, corrosion resistance can be greatly enhanced by metallurgical bonding of a high-purity aluminium surface layer. These sheets are referred to as alclad, and are commonly used by the aircraft industry.[7][8]

Applications

Aluminium alloyed with copper (Al-Cu alloys), which can be precipitation hardened, are designated by the International Alloy Designation System as the 2000 series. Typical uses for wrought Al-Cu alloys include:[9]

  • 2011: Wire, rod, and bar for screw machine products. Applications where good machinability and good strength are required.
  • 2014: Heavy-duty forgings, plate, and extrusions for aircraft fittings, wheels, and major structural components, space booster tankage and structure, truck frame and suspension components. Applications requiring high strength and hardness including service at elevated temperatures.
  • 2017 or Avional (France): Around 1% Si.[10] Good machinability. Acceptable resistance to corrosion in air and mechanical properties. Also called AU4G in France. Used for aircraft applications between the wars in France and Italy.[11] Also saw some use in motor-racing applications from the 1960s,[12] as it is a tolerant alloy that could be press-formed with relatively unsophisticated equipment.
  • 2024: Aircraft structures, rivets, hardware, truck wheels, screw machine products, and other structural applications.
  • 2036: Sheet for auto body panels
  • 2048: Sheet and plate in structural components for aerospace application and military equipment

Popular culture

In the Mistborn series by Brandon Sanderson, duralumin is one of the allomantic metals. It is discovered by Vin, early in The Well of Ascension, and plays an important plot role.

In the manga series Yotsubato! by Azuma Kiyohiko, the titular character Yotsuba Koiwai names her teddy bear Duralumin.[13]

In the Anime series Fullmetal Alchemist: Brotherhood the artificial limbs, or automail, designed for cold weather are made from an alloy including duralumin.[14]

References

  1. ^ "United Aluminum - ALLOY 2024". Retrieved 8 October 2018.
  2. ^ J. Dwight. Aluminium Design and Construction. Routledge, 1999.
  3. ^ "Zeppelin or Schütte-Lanz?". Flight: 758. 7 September 1916.
  4. ^ Thurston, A.P. (22 May 1919). "Metal Construction of Aircraft". Flight: 680–684.
  5. ^ Burton, Walter E. (October 1929). "The Zeppelin Grows Up". Popular Science Monthly: 26.
  6. ^ "The Great Airships" Century of Flight
  7. ^ J. Snodgrass and J. Moran. Corrosion Resistance of Aluminum Alloys. In Corrosion: Fundamentals, Testing and Protection, volume 13a of ASM Handbook. ASM, 2003.
  8. ^ Parker, Dana T. Building Victory: Aircraft Manufacturing in the Los Angeles Area in World War II, p. 39, 87, 118, Cypress, CA, 2013. ISBN 978-0-9897906-0-4.
  9. ^ ASM Handbook. Volume 2, In Properties and Selection: Nonferrous alloys and special purpose materials. ASM, 2002.
  10. ^ John P. Frick, ed. (2000). Woldman's Engineering Alloys. ASM International. p. 150. ISBN 9780871706911.
  11. ^ "Italian Aircraft: Macchi C.200". Flight: 563. 27 June 1940.
  12. ^ Sackey, Joe (2008). The Lamborghini Miura Bible. Veloce Publishing. p. 54. ISBN 9781845841966.
  13. ^ Kiyohiko., Azuma,; あずまきよひこ. (2003-). Yotsuba to! (Shohan ed.). Tōkyō: Media Wākusu. ISBN 4840224668. OCLC 71833438. Check date values in: |date= (help)
  14. ^ "FullMetal Alchemist: Brotherhood Episode 34 - Ice Queen at 0:50".
7075 aluminium alloy

7075 aluminium alloy is an aluminium alloy, with zinc as the primary alloying element. It is strong, with a strength comparable to many steels, and has good fatigue strength and average machinability. It has lower resistance to corrosion than many other aluminium alloys, but has significantly better corrosion resistance than the 2000 alloys. Its relatively high cost limits its use.

7075 aluminium alloy's composition roughly includes 5.6–6.1% zinc, 2.1–2.5% magnesium, 1.2–1.6% copper, and less than a half percent of silicon, iron, manganese, titanium, chromium, and other metals. It is produced in many tempers, some of which are 7075-0, 7075-T6, 7075-T651.

The first 7075 was developed in secret by a Japanese company, Sumitomo Metal, in 1943. 7075 was eventually used for airframe production in the Imperial Japanese Navy.

Alfred Wilm

Alfred Wilm (25 June 1869 – 6 August 1937) was a German metallurgist who invented the alloy Al-3.5–5.5%Cu-Mg-Mn, now known as Duralumin which is used extensively in aircraft.Whilst working in military research NUTZ in Neubabelsberg in 1901, Wilm discovered age hardening, in particular age hardening of aluminium alloys. This discovery was made after hardness measurements on Al-Cu alloy specimens were serendipitously found to increase in hardness at room temperature. This increase in hardness was identified after his measurements were interrupted by a weekend, and when they were resumed on the Monday the hardness had increased.By 1906, Wilm had developed an alloy – Al-3.5–5.5%Cu-Mg-Mn, Mg and Mn were < 1%, for which a patent was filed. Later this patent was purchased and the alloy marketed as Duralumin. Somewhat unusually, Wilm did not write his first article on age hardening until 1911.

At the time Wilm was developing an aluminium alloy to replace brass in ammunition. The patent on Duralumin was ignored and breached by many firms, and he struggled without success to protect his rights under it.

In 1919 Wilm retired from research and became a farmer. He died at his farm in Saalberg on 6 August 1937.

Birmabright

Birmabright is a trade name of the former Birmetals Co. (Birmabright works in Clapgate Lane, Quinton, Birmingham, UK) for various types of lightweight sheet metal in an alloy of aluminium and magnesium. The alloy was introduced by the Birmid Group in 1929 and was particularly noted for its corrosion resistance. Birmal Boats was created in 1930 for the building of light-alloy boats. Birmetals Ltd was formed in 1936 and during the war produced both copper bearing aluminium alloys and the Birmabright magnesium bearing alloys, mainly for aircraft production.The constituents were from 1% to 7% magnesium, with <1% manganese, and the remainder aluminium. The alloys were provided in different temper conditions. e.g. soft, 1/4 hard, 1/2 hard and were designed to be work hardened e.g. by cold pressing into shape. They do not exhibit age hardening, or have a precipitation heat treatment to promote hardening (unlike other contemporary aluminium alloys such as Duralumin). Weldability is good but machinability is only fair to poor. The alloy has good seawater corrosion resistance (unlike Duralumin).

Birmetals Ltd Birmabright grades included the following :

The Birmabright designations are obsolete, but equivalent grades exist, for example BB2 equivalent specifications are British standard NS4, American 5251 and ISO designation AlMg2.

Gas welding of Birmabright is easier than that of pure aluminium and may be carried out autogenously using scraps of the same material as a filler rod.

Birmabright is best known as the material used in the body of the Land Rover from its launch in April 1948, and in a few other classic British vehicles. The doors, boot lid and bonnet of most Rover P4 models were also Birmabright, however towards the end of production this was changed to steel to reduce costs. An early use in the 1930s was for the bodywork of the land speed record car, Thunderbolt. Also used for the bodywork of Bluebird K7 used for the Coniston speed record attempt by Donald Campbell.

The well known Laurent Giles designed 46ft sailboat Beyond was built of riveted sheets of Birmabright and circumnavigated in the early 1950s by Tom and Ann Worth. The hull proved corrosion resistant but required re-riveting later due to crystallisation of the rivet heads, and lasted well until being sunk in the Caribbean as an artificial diving reef in the 1980s.

Birmetals (part of the Birmid Qualcast Group) closed its factory in 1980 after losing money in 1977-1979, followed by a protracted strike over wages by key staff which prevented production.

Caudron C.140

The Caudron C.140 was a French tandem cockpit sesquiplane designed in 1928 as a combination of liaison aircraft and observer and gunnery trainer.

Honda XR600

The Honda XR600R was a very popular offroad motorcycle with an air-cooled single cylinder, four-stroke engine. The bike was manufactured by Honda from 1985 to 2000 and was part of the Honda XR series. The currently available road oriented XR650L model is similar to the XR600R with an engine of more displacement but lower compression and less horsepower. The XR600R was superseded by the XR650R with a 649cc liquid-cooled engine and an aluminum frame.

The engine displacement is 591 cc with four valves placed in a RFVC (Radial Four Valve Combustion) radial disposition with a single camshaft. It has a dry sump lubrication system. The engine has a compression of 9.0:1 with a bore/stroke of 97 × 80 mm.

The engine is fed by a 39 mm piston-valve carburetor.

The front suspension is managed by two conventional cartridge valve 43 mm forks with compression and rebound adjustability, and in the rear is a Prolink single shock with preload, compression and rebound adjustability.

The bike has a five-speed transmission and a kickstarter.

1985 models weighed 121 kg with later models gaining 20 kg plus as materials cheapened with swing arms and wheel base growing. Catch phrase of Duralumin kick starter to highlight Hondas commitment to the first of the XR600 range featured heavily in initial advertising

IAR 14

The IAR 14 is a Romanian low-wing monoplane fighter-trainer aircraft designed before World War II.

Junkers

Junkers Flugzeug- und Motorenwerke AG (JFM, earlier JCO or JKO in World War I, English: Junkers Plane and Motor Works) more commonly Junkers, was a major German aircraft and aircraft engine manufacturer. It produced some of the world's most innovative and best-known airplanes over the course of its fifty-plus year history in Dessau, Germany. It was founded there in 1895 by Hugo Junkers, initially manufacturing boilers and radiators. During World War I, and following the war, the company became famous for its pioneering all-metal aircraft. During World War II the company produced some of the most successful Luftwaffe planes, as well as piston and jet aircraft engines, albeit in the absence of its founder, who had been removed by the Nazis in 1934.

Junkers A 32

The Junkers A 32 was a mail plane built in prototype form in Germany in the late 1920s, and later developed as a prototype reconnaissance-bomber under the designation K 39. The design was a conventional low-wing cantilever monoplane with fixed tailskid undercarriage. Construction was metal throughout, with corrugated duralumin skin. Three open cockpits were provided in tandem; the third seat intended from the outset to accommodate a tail gunner for a military version of the aircraft. In fact, the militarised version developed in Sweden by AB Flygindustri featured a fourth crew position as well, for a bombardier. This version featured twin machine guns built into the engine cowling, and a trainable machine gun for the tail gunner.

Only two A 32s were built, and the first prototype was destroyed in a crash on 2 November 1927 that killed Junkers engineer Karl Plauth. The sole K 39 constructed may have been modified from the second prototype. No sales of either the civil or military version ensued.

Junkers CL.I

The Junkers CL.I was a ground-attack aircraft developed in Germany during World War I. Its construction was undertaken by Junkers under the designation J 8 as proof of Hugo Junkers' belief in the monoplane, after his firm had been required by the Idflieg to submit a biplane (the J 4) as its entry in a competition to select a ground-attack aircraft. The J 8 design took the J 7 fighter as its starting point, but had a longer fuselage to accommodate a tail gunner, and larger wings. The prototype flew in late 1917 and was followed over the next few months by three more development aircraft. The Idflieg was sufficiently impressed to want to order the type, but had misgivings about Junkers' ability to manufacture the aircraft in quantity and considered asking Linke-Hoffmann to produce the type under licence. Finally, however, Junkers was allowed to undertake the manufacture as part of a joint venture with Fokker, producing a slightly modified version of the J 8 design as the J 10. Like the other Junkers designs of the period, the aircraft featured a metal framework that was skinned with corrugated duralumin sheets. 47 examples were delivered before the Armistice, including three built as floatplanes under the designation CLS.I (factory designation J 11). After the war, one or two CL.Is were converted for commercial service by enclosing the rear cockpit under a canopy.

Junkers Ju 60

The Junkers Ju 60 was a single engine airliner built in prototype form in Germany in the early 1930s. It was designed to meet a requirement issued by the Reichsverkehrsministerium (Reich Transport Ministry) for a German-built equivalent to the Lockheed Vega with which to equip Deutsche Luft Hansa. The result was a sleek, cantilever monoplane of conventional configuration, with wings skinned in the corrugated duralumin that had been a hallmark of Junkers designs up to this time, although this would be the last Junkers aircraft to have this feature. The main units of the tailwheel undercarriage were retractable.

The Ju 60 was evaluated by Deutsche Luft Hansa against the Heinkel He 70. With the latter able to demonstrate a top speed 75 km/h (47 mph) better than the Ju 60, development of the Junkers design was halted before the third prototype had been completed. The two examples that had already been constructed eventually saw service with the Luftwaffe as liaison aircraft until 1942. The work done on the design would later form the basis of the Ju 160.

Mallite

Mallite is a type of laminate composite material, formerly manufactured by the William Mallinson & Sons company. The material is formed of a core sheet of end grain balsa wood, faced by duralumin sheets. This construction endows the finished material with greater strength and rigidity than a light alloy sheet of equal mass. The material was originally developed in the late 1950s for use in the aerospace industry, primarily for use in flooring and internal partitioning in jet airliner construction. However, it found fame as one of the first engineered composite materials to be employed in the motorsport industry. Robin Herd, formerly a designer on the Concorde project, used his aerospace knowledge to design the first McLaren single-seater racing cars. The M2A prototype used Mallite extensively, throughout its construction. The final production model, the Formula One McLaren M2B of 1966, only used Mallite for its internal skins and lower bodywork; a lack of understanding of the material's properties had led the team to design the car with conventional curved bodywork, creating problems during the fabrication process as the inherently inflexible material would not readily conform to complex, compound curvatures. With greater understanding of Mallite's properties Herd later used the material to construct the unraced Cosworth four-wheel drive Formula One car of 1969, noted for its slab-sided, angular looks.

PZL Ł.2

The PZL Ł.2 was the Polish Army cooperation and liaison aircraft, built in 1929 in the Polskie Zakłady Lotnicze (PZL) in Warsaw. Only a small series of 31 aircraft, including prototype, were made, and used by the Polish Air Force in the 1930s. The aircraft was known in Poland for accomplishing of a long-distance tour around Africa in 1931.

Polikarpov I-5

The Polikarpov I-5 was a single-seat biplane which became the primary Soviet fighter between its introduction in 1931 through 1936, after which it became the standard advanced trainer. Following Operation Barbarossa, which destroyed much of the Soviet Air Forces (VVS), surviving I-5s were equipped with four machine guns and bomb racks and pressed into service as light ground-attack aircraft and night bombers in 1941. They were retired in early 1942 as Soviet aircraft production began to recover and modern ground-attack aircraft like the Ilyushin Il-2 became available. A total of 803 built (including 3 prototypes).

Polikarpov NB

The Polikarpov NB (Nochnoi Bombardirovshchik—Night Bomber) was a Soviet twin-engined bomber designed during World War II. Only a single prototype had been built before the program was terminated upon the death of Nikolai Nikolaevich Polikarpov, the head of the aircraft's design bureau, in 1944.

Short Cockle

The Short S.1 Cockle was a single-seat sport monoplane flying boat, with a novel monocoque duralumin hull. It was underpowered and so did not leave the water easily, but it proved that watertight and corrosion-resistant hulls could be built from metal.

Short Mussel

The Short S.7 Mussel was a single-engined two-seat monoplane built by Short Brothers to test the performance of their duralumin monocoque floats. Two were built.

Short S.6 Sturgeon

The Short S.6 Sturgeon was a prototype single-engined biplane naval reconnaissance aircraft, built to an Air Ministry specification but mostly intended as a demonstrator of the corrosion resistance of duralumin aircraft structures. Two were made.

Vallot Hut

The Vallot Hut (French: Refuge Vallot) is a refuge in the Mont Blanc massif on the upper slopes of Mont Blanc in the Alps. It is located below the Bosses Ridge between the Dome du Gouter and Mont Blanc summit, at an altitude of 4,362 metres. Intended only as an emergency shelter, and not as a base for ascending Mont Blanc, this unheated duralumin box was designed to accommodate up to 12 people, but often contains considerably more.

Y alloy

Y alloy is a nickel-containing aluminium alloy. It was developed by the British National Physical Laboratory during World War I, in an attempt to find an aluminium alloy that would retain its strength at high temperatures.Duralumin, an aluminium alloy containing 4% copper was already known at this time. Its strength, and its previously unknown age hardening behaviour had made it a popular choice for zeppelins. Aircraft of the period were largely constructed of wood, but there was a need for an aluminium alloy suitable for making engines, particularly pistons, that would have the strength of duralumin but could retain this when in service at high temperatures for long periods.

The National Physical Laboratory began a series of experiments to study new aluminium alloys. Experimental series "Y" was successful, and gave its name to the new alloy. Like duralumin, this was a 4% copper alloy, but with the addition of 2% nickel and 1.5% magnesium. This addition of nickel was an innovation for aluminium alloys. These alloys are one of the three main groups of high-strength aluminium alloys, the nickel-aluminium alloys having the advantage of retaining strength at high temperatures.

The alloy was first used in the cast form, but was soon used for forging as well. One of the most pressing needs was to develop reliable pistons for aircraft engines. The first experts at forging this alloy were Peter Hooker Limited of Walthamstow, who were better known as The British Gnôme and Le Rhône Engine Co. They license-built the Gnôme engine and fitted it with pistons of Y alloy, rather than their previous cast iron. These pistons were highly successful, although impressions of the alloy as a panacea suitable for all applications were less successful; a Gnôme cylinder in Y alloy failed on its first revolution. Frank Halford used connecting rods of this alloy for his de Havilland Gipsy engine, but these other uses failed to impress Rod Banks.Air Ministry Specification D.T.D 58A of April 1927 specified the composition and heat treatment of wrought Y alloy. The alloy became extremely important for pistons, and for engine components in general, but was little used for structural members of airframes.In the late 1920s, further research on nickel-aluminium alloys gave rise to the successful Hiduminium or "R.R. alloys", developed by Rolls-Royce.

1000 Series (pure)
2000 Series (+Cu)
3000 Series (+Mn)
4000 Series (+Si)
5000 Series (+Mg)
6000 Series (+Si+Mg)
7000 Series (+Zn)
8000 Series (misc)
Others

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