When it comes to structural metal fabrication, perhaps only one metal gets anywhere near the attention given to steel, and that is aluminium. It’s roughly a third of the weight of steel while still having exceptional mechanical properties. However, not all aluminium grades are created equal, so it is critical to understand the differences among aluminium alloy grades during the material selection process. Two of the most popular aluminium alloy grades for structural applications are 6082 and 7075. While similar in some ways, there are also large differences worth noting.
What are the Differences Between 6082 and 7075 Aluminium?
The main differences between 6082 and 7075 aluminium are the following attributes:
- Alloy Series & Chemical Composition
- Mechanical Properties
- Fabrication Considerations
Alloy Series and Chemical Composition
Perhaps the most apparent difference between 6082 and 7075 is found just by looking at their number designations. 6082 is in the 6XXX series of aluminium alloy grades and 7075 is in the 7XXX series. Knowing the general properties of the aluminium alloys in the 6XXX and 7XXX series, without even digging into their individual material data sheets, one can understand that there is several important differences in terms of chemical composition. The 6XXX series are aluminium grades alloyed with magnesium and silicon. The 7XXX series are aluminium grades that have been alloyed with zinc and magnesium. Therefore, it can be determined that 6082 will have a higher amount of silicon, and that 7075 will have a much higher amount of zinc. When looking at the exact ranges of chemical compositions between the two alloys, 7075 also has greater additions of copper in its chemical makeup.
Both 6082 and 7075 are heat-treatable, therefore, in order to make a direct comparison of the two, they must be evaluated under the same type of heat treatment. When looking at both alloys in the -T6 condition (meaning solution heat-treated then artificially aged), several noticeable differences are observed. First off is that the tensile strength of 7075-T6 is nearly double that of 6082-T6. The shear strength of 7075-T6 is roughly 1.5 times that of 6082-T6. 6082-T6 is quite soft when compared with 7075-T6 as well.
6082 is, in general, more easily fabricated than 7075. Its lower strength, lower hardness, and somewhat higher ductility are the reasons for this. The lower hardness of 6082 allows it to be turned, milled, drilled, and machined in other ways more easily than 7075. The lower tensile strength means that 6082 is easier to form than 7075. While both materials can be joined by soldering, brazing or adhesives, 6082 is weldable and 7075 is generally considered not weldable. Even though 6082 is considered weldable, care must be taken to select the proper weld filler metal. Post-weld heat treatment and aging may be required to get the weld area back to the original “-T” designation. 7075 is extremely prone to cracking following welding.
There is much application overlap between the 6082 and 7075 aluminium alloys. As previously mentioned, both are structural grades of aluminium. Both are used for bike parts, aerospace components, and building construction. They differ in these areas on how they are used though. For instance, in the aerospace industry, 7075 may be more likely to be used as a gear or rod, and 6082 may be more likely to be implemented in an area that requires more ductility. With bike parts, some riders prefer the increased strength that comes with the 7075 aluminium alloy. 7075 is more likely to be used for molds and industrial tooling than 6082. Since it is more formable than 7075, 6082 is used more often for tanks as well as other shapes with rounded contouring.
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