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7075 Aluminium vs 6061 Aluminium
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. Here's a look at how these two aluminium alloys compare.
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% |
Differences in Characteristics
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.
Differences in Characteristics
Differences in Characteristics
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.
Differences in Characteristics
Differences in Characteristics
Anodising
Anodising is converting the metal surface into a decorative and durable anodic oxide finish using an electrochemical process. 6061 and other alloys in the 6XXX series have excellent anodising qualities. The oxide layer that forms after the anodising process is transparent and offers protection to the surface.
7075 alloy is also a good candidate for anodising and forms the same transparent and protective oxide layer on the surface of the alloy after anodising. However, if there’s too much zinc in the alloy, the oxide layer created by anodisation can turn brown.
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.
Density
Aluminium has the same density. But because these are alloys made by adding other metals with different densities, the density of the alloy will change. Density is one of the most essential characteristics to consider when comparing the physical properties of metals.
7075 aluminium has a density of 2.81g/cm3, which is higher than that of pure aluminium. The alloy can also be strengthened using heat treatment processes, with the most common temper being 7075-T6.
6061 aluminium has a density of 2.7 g/cm3. It is about the same as pure aluminium metal, largely because of the high amount of aluminium the alloy contains.
Mechanical Properties
The alloys also have different mechanical properties with varying compositions in types and concentrations of alloying elements.
| Type 6061 Aluminium | Type 7075 Aluminium | |||
| Metric | English | Metric | English | |
| Yield strength | 276 MPa | 40,000 psi | 503 MPa | 73,000 psi |
| Modulus elasticity | 68.9 GPa | 10,000ksi | 71.7GPa | 10,400ksi |
| Thermal conductivity | 167 W/m-K | 1160 BTU-in/hr-ft2_0F | 130 W/m-K | 900 BTU-in/hr-ft2_0F |
| Melting point | 1080-12050F | 582 - 6520C | 890-11750F | 477-6350C |
| Electrical resistivity | 3.99 x 10-6 ohm-cm | 5.15 x 10-6 ohm-cm | ||
| Hardness (Brinell) | 95 | 150 | ||
| Machinability | Good | Fair | ||
Thermal Conductivity
Thermal conductivity measures how well a material transfers heat. Although 6061 and 7075 are heat treatable, 7075 is much stronger than 6061 and melts at a slightly lower temperature.
6061 aluminium, on the other hand, has a higher thermal conductivity than 7075 and is better suited for certain applications. Among the heat-treated options, the aluminium plate is more versatile and best known for its corrosion resistance and high toughness.
Closing Remarks
Understanding the differences between two alloys, even those with the same base metal, better informs which of the two is better suited for the intended applications. The addition of alloying elements greatly alters the metal’s properties, hence the need to consider the differences between 6061 and 7075 aluminium.
Partnering for Excellence:
Our experts are committed to guiding you through this crucial decision-making process. We have both alloys in stock and ready to be dispatched to your site.
