What is Aluminum 7075?
Aluminum 7075 are strong yet light metals that have found uses in almost every market. An alloy is a mixture of metals that, when together, are more useful than their constituents alone. A base metal (in this case aluminum), can be thought to be “improved” by small quantities of different metals, known as alloying elements. Alloys have been invented to provide stronger, more conductive, and/or more resilient materials for designing new ideas, and have revolutionized our engineering capabilities. Aluminum is a very common metal that has many useful alloys; so many in fact that the Aluminum Association has defined classes of these alloys using a numbered-naming scheme based on alloying elements. The topic of this article is from the 7xxx series, or alloys which use zinc as their main alloying element, and its name is type 7075 aluminum alloy. The other three digits in its name specify individual alloys from each other within its series (for a more in-depth explanation of this naming convention, see our article on 6061 aluminum alloy). This article aims to show the properties and uses for 7075 aluminum, and highlight its strengths as an engineering material.
Physical Properties of 7075 Aluminum
7075 aluminum is composed of 90.0% Al, 5.6% Zn, 2.5%Mg, 0.23%Cr, and 1.6% Cu, though 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. 7075 aluminum alloy is one of the strongest aluminum alloys available, making it valuable in high-stress situations. The copper content of 7075 aluminum increases its susceptibility to corrosion, but this sacrifice is necessary to make such a strong-yet-workable material.
7075 aluminum alloy can be further improved by how it is strengthened using a process known as heat-treatment, sometimes referred to as “tempering.” This method uses high heat (300-500 ºC) to reconfigure the metal’s crystal structure to strengthen its overall mechanical properties, and can literally make-or-break a material. There are many methods of tempering 7075 aluminum, but to simplify this article, we will highlight T6 tempered 7075 aluminum alloy (7075-T6). 7075-T6 is a common temper for aluminum plate and bar stock; however, it is important to know that each tempering process gives 7075 aluminum its own distinct values and characteristics.
Mechanical Properties
The measure of a material’s resistance to deformation is given by its modulus of elasticity and shear modulus. The modulus of elasticity for 7075 aluminum is 71.7 GPa (10,400 ksi), and it’s shear modulus is 26.9 GPa (3900 ksi) (see Table 1 for a summary). Generally, this alloy is strong and resists deformation well, which suits it for applications which need a tough-yet-light metal.
When specifying an alloy, one of the most important measures is its yield strength. The yield strength of a material is defined as the maximum amount of stress (or force over some area) that will not permanently deform a material. It is easier to understand in terms of a plastic straw; if you just barely bend the straw, it will naturally return to its original shape. The yield stress indicates the maximum amount of “bending” that can be done before the straw (or the metal) stays permanently bent. 7075 aluminum alloy has a tensile yield strength of 503 MPa (83,000 psi), 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 the huge benefit of alloying aluminum, and why 7075 is a shoo-in for structural materials such as aluminum tubing for frames.
Another useful parameter is the ultimate strength of a material. This parameter is the maximum amount of stress that will not cause the straw as mentioned above to “snap” (in engineering terms, this is known at the “fracture point”). Before this fracture point, the material will undergo plastic (or permanent) deformation, and will not return to its original shape. This value is useful for cases where this kind of deformation is possible, such as in high-risk applications (military, skyscrapers) where 7075 is usually implemented. 7075 aluminum has an ultimate tensile strength of 572 MPa (83000 psi), which is impressively high considering its low density (see Table 1 for a summary).
The shear strength measures the maximum amount of “shearing” stress that a material can experience before it permanently deforms. For a better understanding of what shear stress is, please feel free to check out our article all about 6061 aluminum alloy. The shear strength of 7075 aluminum alloy is 331 MPa (48000 psi, see Table 1 for a summary).
Type 7075 aluminum is often used in the aerospace industry, which has increased concern for fatigue failure. A material can still fail, even though it experiences a force much less than its yield point. If this stress is cyclical, meaning that the material is periodically loaded with this force enough times, micro fractures can occur which weaken the material and will eventually cause it to break. The fatigue strength is a measure of a material’s ability to withstand this cyclical loading, and is useful for applications where a part created using this material is subject to repetitive loading cycles (such as in aircraft or motor vehicles). The fatigue strength of 7075 aluminum alloy is 159 MPa (23,000 psi). This value is calculated using 500,000,000 cycles of continuous, periodic loading below the yield point, which just goes to show how smaller forces can break such a strong alloy, given enough time (see Table 1 for a summary).
XTJ is a leading OEM Manufacturer that is dedicated to providing one-stop manufacturing solutions of Aluminum 7075 Parts from prototype to production. We are proud to be an ISO 9001 certified system quality management company and we are determined to create value in every customer relationship. We do that through collaboration, innovation, process improvements, and exceptional workmanship.
