7075 aluminium alloy (AA7075) is an aluminium alloy with zinc as the primary alloying element. It has excellent mechanical properties and exhibits good ductility, high strength, toughness, and good resistance to fatigue. It is more susceptible to

embrittlement Embrittlement is a significant decrease of ductility of a material, which makes the material brittle. Embrittlement is used to describe any phenomena where the environment compromises a stressed material's mechanical performance, such as temperatu ...

than many other aluminium alloys because of microsegregation, but has significantly better corrosion resistance than the alloys from the 2000 series. It is one of the most commonly used aluminium alloys for highly stressed structural applications and has been extensively used in aircraft structural parts. 7075 aluminium alloy's composition roughly includes 5.6–6.1%

zinc Zinc is a chemical element; it has symbol Zn and atomic number 30. It is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodic tabl ...

, 2.1–2.5%

magnesium Magnesium is a chemical element; it has Symbol (chemistry), symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 ...

, 1.2–1.6%

copper Copper is a chemical element; it has symbol Cu (from Latin ) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkish-orang ...

, 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 1935, and eventually used for airframe production in the

Imperial Japanese Navy The Imperial Japanese Navy (IJN; Kyūjitai: Shinjitai: ' 'Navy of the Greater Japanese Empire', or ''Nippon Kaigun'', 'Japanese Navy') was the navy of the Empire of Japan from 1868 to 1945, Potsdam Declaration, when it was dissolved followin ...

. 7075 was reverse engineered by

Alcoa Alcoa Corporation (an acronym for "Aluminum Company of America") is an American industrial corporation. It is the world's eighth-largest producer of aluminum. Alcoa conducts operations in 10 countries. Alcoa is a major producer of primary alu ...

in 1943, after examining a captured Japanese aircraft. 7075 was standardized for aerospace use in 1945.

Basic properties

Aluminium 7075A has a density of 2.810 g/cm³.

Mechanical properties

The mechanical properties of 7075 depend greatly on the tempering of the material.Alcoa 7075 data sheet
(PDF), accessed October 13, 2006 Aluminum 7075 has a low

formability Formability is the ability of a given metal workpiece to undergo plastic deformation without being damaged. The plastic deformation capacity of metallic materials, however, is limited to a certain extent, at which point, the material could experien ...

at low room temperature and is vulnerable to

stress corrosion cracking Stress corrosion cracking (SCC) is the growth of crack formation in a corrosive environment. It can lead to unexpected and sudden failure of normally ductile metal alloys subjected to a tensile stress, especially at elevated temperature. SC ...

. Using different elevated temperature forming techniques has been shown to reduce springback and fracture. Examples of those elevated temperature forming techniques are retrogression forming and warm forming.

7075-O

Un-heat-treated 7075 (7075-0 temper) has a maximum

tensile strength Ultimate tensile strength (also called UTS, tensile strength, TS, ultimate strength or F_\text in notation) is the maximum stress that a material can withstand while being stretched or pulled before breaking. In brittle materials, the ultimate ...

of no more than , and maximum

yield strength In materials science and engineering, the yield point is the point on a stress–strain curve that indicates the limit of elastic behavior and the beginning of plastic behavior. Below the yield point, a material will deform elastically and w ...

of no more than . The material has an elongation (stretch before ultimate failure) of 9–10%. As is the case for all 7075 aluminum alloys, 7075-0 is highly corrosion-resistant combined with generally acceptable strength profile.

7075-T6

T6 temper 7075 has an ultimate tensile strength of and yield strength of at least . It has a failure elongation of 5–11%. The T6 temper is usually achieved by homogenizing the cast 7075 at 450 °C for several hours, quenching, and then ageing at 120 °C for 24 hours. This yields the peak strength of the 7075 alloys. The strength is derived mainly from finely dispersed eta and eta' precipitates both within grains and along grain boundaries.Park, J. K., and A. J. Ardell. "Microstructures of the Commercial 7075 AI Alloy in the T651 and T7 Tempers". ''Metall. Trans. A.'' 14A (1983): 1957. Print.

7075-T651

T651 temper 7075 has an ultimate tensile strength of and yield strength of . It has a failure elongation of 3–9%. These properties can change depending on the form of material used. The thicker plates may exhibit lower strengths and elongation than the numbers listed above.

7075-T7

T7 temper has an ultimate tensile strength of and a yield strength of . It has a failure elongation of 13%. T7 temper is achieved by overaging (meaning aging past the peak hardness) the material. This is often accomplished by aging at 100–120 °C for several hours and then at 160–180 °C for 24 hours or more. The T7 temper produces a microstructure of mostly eta precipitates. In contrast to the T6 temper, these eta particles are much larger and prefer growth along the grain boundaries. This reduces the susceptibility to

. T7 temper is equivalent to T73 temper.

7075-RRA

The retrogression and reage (RRA) temper is a multistage heat treatment temper. Starting with a sheet in the T6 temper, it involves overaging past peak hardness (T6 temper) to near the T7 temper. A subsequent reaging at 120 °C for 24 hours returns the hardness and strength to or very nearly to T6 temper levels. RRA treatments can be accomplished with many different procedures. The general guidelines are retrogressing between 180 and 240 °C for 15 min 10 s.

Equivalent materials

Uses

The world's first mass-production usage of the 7075 aluminum alloy was for the

Mitsubishi A6M Zero The Mitsubishi A6M "Zero" is a long-range carrier-capable fighter aircraft formerly manufactured by Mitsubishi Aircraft Company, a part of Mitsubishi Heavy Industries. It was operated by the Imperial Japanese Navy (IJN) from 1940 to 1945. The ...

fighter. The aircraft was known for its excellent maneuverability which was facilitated by the higher strength of 7075 compared to previous aluminum alloys. 7000 series alloys such as 7075 are often used in transport applications due to their high

specific strength The specific strength is a material's (or muscle's) strength (force per unit area at failure) divided by its density. It is also known as the strength-to-weight ratio or strength/weight ratio or strength-to-mass ratio. In fiber or textile applic ...

, including marine, automotive and aviation.T Hashimoto, S Jyogan (Showa Aluminium), K Nakata, Y G Kin and M Ushio (Osaka University): FSW joining of high strength Al alloy These same properties lead to its use in rock climbing equipment, bicycle components, inline-skating-frames and hang glider airframes are commonly made from 7075 aluminium alloy. Hobby-grade RC models commonly use 7075 and 6061 for chassis plates. 7075 is used in the manufacturing of

M16 rifle The M16 (officially Rifle, Caliber 5.56 mm, M16) is a family of assault rifles adapted from the ArmaLite AR-15 rifle for the United States Armed Forces, United States military. The original M16 was a 5.56×45mm NATO, 5.56×45mm automatic ...

s for the U.S. military as well as AR-15 style rifles for the civilian market. In particular high-quality M16 rifle lower and upper receivers, as well as extension tubes, are typically made from 7075-T6 alloy. Desert Tactical Arms,

SIG Sauer SIG Sauer is since the 1970s a combined brand name of several Firearms manufacturing companies, with SIG referring to ''Swiss Industry Group'' originally founded 1853, while the latter part comes from Sauer & Sohn, founded in 1751 in Germany a ...

, and French armament company PGM use it for their precision rifles. It is also commonly used in shafts for

lacrosse Lacrosse is a contact team sport played with a lacrosse stick and a lacrosse ball. It is the oldest organized sport in North America, with its origins with the indigenous people of North America as early as the 12th century. The game w ...

sticks, such as the STX sabre, and camping knife and fork sets. It is a common material used in competition yo-yos as well. Another application for the 7075-series alloy has been in

connecting rod A connecting rod, also called a 'con rod', is the part of a reciprocating engine, piston engine which connects the piston to the crankshaft. Together with the crank (mechanism), crank, the connecting rod converts the reciprocating motion of the p ...

s used in

drag racing Drag racing is a type of motor racing in which automobiles or motorcycles compete, usually two at a time, to be first to cross a set finish line. The race follows a short, straight course from a standing start over a measured distance, mos ...

engines. Aluminum rods do not have the

fatigue life In materials science, fatigue is the initiation and propagation of cracks in a material due to cyclic loading. Once a fatigue crack has initiated, it grows a small amount with each loading cycle, typically producing striations on some parts of ...

of forged steel rods, but have less mass than their steel counterparts, resulting in lower mechanical stress during periods in which an engine is operated under full-throttle, high-RPM conditions. It has also been the standard material for crankcase guards on off-road motorcycles. Due to its high strength, low density, thermal properties, and its ability to be highly polished, 7075 is widely used in mold tool manufacturing. This alloy has been further refined into other 7000 series alloys for this application, namely 7050 and 7020.

Aerospace applications

7075 was used in the Space Shuttle SRB nozzles, and the

external tank The Space Shuttle external tank (ET) was the component of the Space Shuttle launch vehicle that contained the liquid hydrogen Rocket propellant, fuel and liquid oxygen oxidizer. During lift-off and ascent it supplied the fuel and oxidizer und ...

SRB beam in the Inter-tank section. The forward- and aft skirt as well as the Interstage of the

S-II The S-II (pronounced "S-two") was the second stage of the Saturn V rocket. It was built by North American Aviation. Using liquid hydrogen (LH2) and liquid oxygen (LOX) it had five J-2 engines in a quincunx pattern. The second stage accelerated ...

, the second stage of the

Saturn V The Saturn V is a retired American super heavy-lift launch vehicle developed by NASA under the Apollo program for human exploration of the Moon. The rocket was human-rated, had multistage rocket, three stages, and was powered by liquid-propel ...

was made from 7075.

Applications

# Aircraft fittings # Gears and shafts # Missile parts # Regulating valve parts # Worm gears # Aerospace/defense applications # Automotive # Bicycle Chainrings # Bicycle Gearboxes # Archery equipment

Trade names

7075 has been sold under various trade names including Zicral, Ergal, and Fortal Constructal. Some 7000 series alloys sold under brand names for making molds include Alumec 79, Alumec 89, Contal, Certal, Alumould, and Hokotol.

References

External links

Aluminum 7075 Properties
{{Aluminium alloys Aluminium–zinc alloys