7000 Series Aluminum Alloys
The 7000(*) series aluminum alloys have zinc as main alloy element (aka zinc grades) and they are the hardest and strongest commercial grades of aluminium, a preferred choice for applications of aerospace, vehicle and high-demanding industries. These alloys feature a higher strength than low-carbon steel and a good wear resistance and weldability, besides, they can also be strengthened by heat treatment. Two widely used alloys in this series are 7050 and 7075 discussed below.
(*) Aluminum alloys are named in accordance with a four-digit naming system developed by the US Aluminum Association to characterize a wide range of alloys on the basis of their main alloying elements.
Common 7000 Series Aluminum Alloys
7050 (known as a commercial aerospace alloy) is a heat-treatable aluminium alloy with zinc as the main alloying element, combining high mechanical strength (slightly lower strength than 7075), great wear resistance and stress-corrosion cracking resistance, an excellent resistance to exfoliation corrosion and toughness at subzero temperatures. The 7050 aluminum alloy has a higher corrosion resistance than 7075 but a relatively poor weldability. Particularly suited to heavy plate aerospace and other commercial and military applications, such as fuselage frames, bulkheads, wing skins and aircraft structures. Aluminum 7050 alloy can be hardened by precipitation heat treatment. It can be heat treated at 477°C (890°F) and cold worked using conventional methods. Welding should be avoided with Aluminum 7050, as the process weakens the alloy. It comes in different shapes (bars, plates and sheets) and different tempers such as H112, T7651 & T7451. Μeet strict industry standards like those from AMS, ASTM, QQ, and UNS.
7075 is another "aircraft grade" high-strength aluminum alloy with high stress-corrosion cracking resistance, high fatigue strength and great machinability. It has zinc and copper as its major alloying elements (typically composed of 90.0% Al, 5.6% Zn, 2.5%Mg, 0.23%Cr, and 1.6% Cu, although these numbers nominally fluctuate depending upon manufacturing factors). Its density is 2.81 g/cm3 (0.102 lb/in³), which is relatively light for a metal. The copper content of 7075 aluminum increases its susceptibility to corrosion, but this sacrifice is necessary to make such a strong-yet-workable material.
This alloy features a high strength, low density (high strength-to-weight ratio), but also thermal properties and ability to be polished which makes AL7075 a preferred choice for the mold making industry. Furthermore, it can be further improved by how it is strengthened using a process known as heat-treatment, sometimes referred to as “tempering”, where high heat (300-500 ºC) is used to reconfigure the metal’s crystal structure to strengthen its overall mechanical properties. There are many methods of tempering 7075 aluminum with each tempering process providing the 7075 aluminum with its own distinct values and characteristics. The 7075-T6 is a common temper for aluminum plate and bar stock but 7075 aluminum is also available as annealed (O Temper) or other or tempered grades such as 7075-T651. Like aluminum alloy 2024, the 7075 is typically used in aerospace and defense, automotive, manufacturing and other applications including highly stressed structural parts, aircraft parts and fittings, gears and shafts requiring lighter weight, very high strength and durable material without a high demand for corrosion resistance.
In terms of its mechanical properties as indicated by the respective measures, the 7075 aluminum alloy has a tensile yield strength of 503 MPa (83,000 psi) compared to 455 MPa (65992 psi) of 7050, which means it takes 503 MPa of stress on a piece of 7075 alloy before it cannot return to its original shape. This value shows why 7075 is a chosen metal for structural materials such as aluminum tubing for frames. Its ultimate tensile strength (i.e. the maximum amount of stress the material can undertake till its fracture point) of 572 MPa (83000 psi) compared to 515 MPa (74695 psi) of 7050 alloy, is impressively high considering its low density. The shear strength (maximum amount of “shearing” stress before its permanent deformation) is 331 MPa (48000 psi). The 7075 measures of a material’s resistance to deformation (modulus of elasticity and shear modulus) also feature high values. The modulus of elasticity is 71.7 GPa (10,400 ksi) compared to 70-80 GPa (10153-11603 ksi) of 7050, and the shear modulus is 26.9 GPa (3900 ksi) indicating that this alloy is strong and resists deformation. Finally, the 7075 fatigue strength is 159 MPa (23,000 psi), although lower than that of 7050 alloy (240 MPa (34809 psi)), reflecting the ability of this alloy to withstand cyclical stress loading and thus its suitability for applications with increased concern for fatigue failure.
Aluminum alloy metals from different series are offered as part of our own labelled (AVIATIONEU NEW ERA) product lines in various forms (tubes/pipes, sheets/plates, bars/rods). Sourced from quality producers, they are offered in different cross-sections (for tubes or bars) such as round, hexagonal, square and others, tempers, specifications (depending on the selected product) dimensions/thicknesses, pre-cut or cut-to-order lengths to meet order quantity and application requirements. They can be supplied in pieces or tons depending on the wanted order quantity. For additional information, please refer to our Brief Guide on Aluminum Grades & Temper Designations, the individual product presentations or contact us.
