Aluminium comes in various alloys with varying features and properties depending on the application in question. When choosing an alloy, you have to consider the attributes required by the final applications.Essential considerations include conductivity, corrosion resistance and strength. Aluminium alloys 7075 and 6061 are among the most common types of alloy in the industry with vast applications and, as you would expect, numerous differences.
1.Chemical Composition
The 7075 aluminium alloy comes from the 7XXX series and comprises copper and zinc as the main alloying elements.
6061 is from the 6XXX series, where silicon and magnesium are the primary alloying elements. Below is the full chemical composition of both alloys;
| 7075 Aluminium | 6061 Aluminium | |
| Aluminium (%) | 97.9% | |
| Zinc (%) | 5.6% | ___ |
| Magnesium (%) | 2.5% | 0.1% |
| Chromium (%) | 0.23% | 0.2% |
| Copper (%) | 1.6% | 0.28 |
| Silicon (%) | ___ | 0.6% |
2.Differences in Characteristics
Because the two alloys have different alloying elements in various concentrations, they differ in more than just the chemical composition. They also differ in the properties they exhibit;
Strength
In the "T6 condition" (both metals heat-treated with a solution and aged), aluminium 7075 T6 has a tensile strength nearly double that of 6061 T6 aluminium. 7075 alloy also has a higher shear strength which is about 1.5 times that of 6061 alloys in the same T6 condition. Overall, 7075 T6 is also harder than 6061 T6 alloys.
Machinability
Machinability is a property that shows the measure of how a material reacts to machining processes like cutting, drilling, milling and die-casting, among others. Both 7075 and 6061 aluminium alloys have good machinability. But 6061 is the more preferred choice for applications where machining is necessary. However, 7075 aluminium alloy is also rated to have fair machinability.
Formability and welding
6061 aluminium alloy has good formability and welding because it has silicon and magnesium as its principal alloying elements. 7075 is a harder material because of the higher zinc content. It is not conducive to forming or welding unless it is in the annealed condition where it can be formed and heat-treated if necessary and welded.
Corrosion resistance
Both alloys have excellent corrosion resistance properties because aluminium forms a layer of oxide when exposed to air or water. This oxide layer renders the alloy non-reactive to the elements that are corrosive to the metal underneath. However, 6061 alloy has copper as an alloying element, making it slightly less corrosion resistant than other alloys, including 7075 alloys. However, corrosion resistance can be enhanced by coating 6061 aluminium alloy with a protective layer.
3.Applications of 7075 Vs 6061 Aluminium Alloys
The difference in the properties and characteristics of the alloys determines which applications each is best suited for.
7075
7075 alloy doesn't have the best formability and weldability. But, it excels in high-stress applications that require strength. 7075 is also referred to as an "aircraft grade" alloy because it has one of the highest strength aluminium alloys in the market.
It's used for spacecraft, aircraft missiles and other defence applications. It is also not uncommon to see 7075 grade in parts subjected to high wear and tear, military applications and structural materials.
6061
6061 aluminium alloy is more versatile because of its workability, corrosion resistance, strength and joinability. It has a vast range of applications that include welded assemblies, electronics, structural materials, piping, and fasteners, among others. It is used across various industries in various applications, including:
· Furniture
· Aircraft fittings and structure
· Yachts, sailboats, marine fittings and other shipbuilding hardware
· Trucks, brakes, bus bodies, hydraulic pistons and other automotive applications
· Mouldings
· Awnings
· Food and beverage cans
· Appliance fittings
6061 aluminium comes in various forms, including aluminium plate, aluminium bar and aluminium tube.
