Aluminum alloys 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.
Physical Properties of 7075 Aluminum
7075 aluminum mainly composed are Aluminum, Zinc, Magnesium and Copper. Its density is 2.81 g/cm3, 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. Like T6, T651 it’s typical temper.
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, and it’s shear modulus is 26.9 GPa. 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, 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.
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.
Applications of 7075 Aluminum
Type 7075 aluminum is one the strongest aluminum alloys. Its high yield strength (>500 MPa) and its low density make the material a fit for applications such as aircraft parts or parts subject to heavy wear. While it is less corrosion resistant than other alloys (such as 5083 aluminum alloy, which is exceptionally resistant to corrosion), its strength more than justifies the downsides. Some major applications of 7075 aluminum alloy include:
- Aircraft fittings
- Gears and shafts
- Missile parts
- Regulating valve parts
- Worm gears
- Aerospace/defense applications
Post time: Dec-24-2020