In mechanical design, we often use aluminum alloys. These metals have good strength, corrosive resistance, and machinability. Aluminum 6061 and 7075 are the two most popular aluminum alloys. Their high strength-to-weight ratios make them good options for non-intensive and general purposes, especially for weight-sensitive places like high-speed sports platforms, aircraft structures, bicycle racks, etc.
While 6061 and 7075 aluminum grades are similar in some respects, there are notable distinctions between the two. So here comes the question, what is the difference between 6061 and 7075? This article briefly introduces aluminum alloys 6061 and 7075 and compares their composition, mechanical properties, and applications. Hopefully, it will assist you in choosing which alloy is best for your project.
What is 6061 Aluminum Grade?
Type 6061 aluminum belongs to the 6xxx class of aluminum, and its main alloying elements are magnesium and silicon. The elemental composition of 6061 aluminum alloy includes 0.6% Si, 1.0% Mg, 0.2% Cr, 0.28% Cu, and 97.9% Al.
This alloy is one of the most common aluminum grades due to its excellent mechanical properties and fair corrosion resistance. Besides, the 6061 aluminum grade can be manufactured easily, has excellent formability, and is weldable using any method, including furnace brazing. It is perfect for producing diverse and accurate components in various shapes.
As a great general-purpose alloy, the applications of 6061 aluminum can be found in structural materials, welded assemblies, pipelines, fasteners, electronic parts, and many more. Here should be mentioned that the aluminum 6063 is also a popular choice in the aluminum series 6xxx. However, it has nearly half the strength of aluminum 6061 owing to its lower alloy elements proportion of magnesium and silicon. As a result, aluminum 6063 is appropriate for situations where strength is unimportant.
What is 7075 Aluminum Grade?
The 7075 aluminum alloy comes from the 7xxx series, in which zinc is the major alloying element. However, auxiliary elements are frequently employed. It has a nominal elemental composition of 90.0% Al, 5.6% Zn, 2.5% Mg, 0.23% Cr, and 1.6% Cu.
The zinc content in 7075 aluminum is higher than in 6061 aluminum. This results in greater strength and a higher strength-to-weight ratio for 7075. However, zinc makes this alloy less weldable and has poor formability. The impressive strength makes 7075 aluminum excel in high-stress situations such as the aerospace sector, high-wear parts, structural materials, and military applications.
Alloy 7075 offers only average corrosion resistance, an outcome of the small amount of copper in its chemical composition. However, thanks to its high fatigue resistance and good ductility, 7075 aluminum grade is often employed in highly stressed applications and aircraft structural parts. When 7075 aluminum is compared to 6061 aluminum, the 7075 alloy has a comparatively higher cost.
6061 vs. 7075 Aluminum: What are Their Differences?
6061 and 7075 are two of the most prevalent aluminum alloys for high-strength, low-weight applications. Both share superb properties, while some properties distinguish the two.
The key differences between 6061 and 7075 aluminum are the following parameters:
- Alloy Series and Chemical Composition
- Material Properties
- Applications
- Fabrication Considerations
Each parameter is discussed separately below to compare 6061 and 7075 aluminum.
6061 vs. 7075 Aluminum: Alloy Series and Chemical Composition
The first distinction between 6061 and 7075 is immediately apparent by comparing their number designations. 6061 is from the 6XXX series of aluminum alloy grade, while 7075 is from the 7XXX series. Given this information, it can be deduced that 6061 will have a higher silicon content, and 7075 will have a much higher zinc concentration. The precise ranges of the two alloys reveal that both contain significant amounts of magnesium. However, compared to 6061, 7075 has slightly more magnesium and copper in chemical composition.
The table below summarises the alloy composition of 6061 aluminum and 7075 aluminum.
| Chemical Elements | 7075 Aluminum | 6061 Aluminum |
|---|---|---|
| % Aluminum (Al) | 90.0% Al | 97.9% Al |
| % Magnesium (Mg) | 2.5% Mg | 1.0% Mg |
| % Zinc (Zn) | 5.6% Zn | — |
| % Chromium (Cr) | 0.23% Cr | 0.2% Cr |
| % Copper (Cu) | 1.6% Cu | 0.28% Cu |
| % Silicon (Si) | — | 0.6% Si |
6061 vs. 7075 Aluminum: Material Properties
To illustrate the differences between 6061 and 7075 aluminum alloys, a comparison of their material properties will be described. The following table covers some properties of alloys 6061 and 7075, but note that the values listed below change depending on how the alloy is strengthened.
| Material properties | Type 6061 Aluminum Alloy | Type 7075 Aluminum Alloy | ||
|---|---|---|---|---|
| Units | Metric | English | Metric | English |
| Yield Strength | 276 MPa | 40000 psi | 503 MPa | 73000 psi |
| Modulus of Elasticity | 68.9 GPa | 10000 ksi | 71.7 GPa | 10400 ksi |
| Thermal Conductivity | 167 W/m-K | 1160 BTU-in/hr-ft²-℉ | 130 W/m-K | 900 BTU-in/hr-ft²-℉ |
| Melting Point | 582 – 652℃ | 1080 – 1205℉ | 477 – 635℃ | 890 – 1175℉ |
| Electrical Resistivity | 0.00000399 ohm-cm | 0.00000515 ohm-cm | ||
| Hardness (Brinell) | 95 | 150 | ||
| Machinability | Good | Fair | ||
Yield Strength
The yield strength refers to the maximum stress that the alloy will not permanently deform. When the yield strengths of 6061 and 7075 aluminum are compared, it is clear that 7075 aluminum is significantly greater by a factor of approximately 2. In essence, 7075 aluminum can sustain more impact and pressure without deformation for some time. This is due to the chemical composition of 7075 and heat treatment. However, 6061 alloys are not considered weak since their yield strength of 276 MPa is just slightly lower than that of some low-carbon steels.
Thermal Conductivity
Thermal conductivity measures how well a material transfers and conducts heat. Suppose the material possesses a high thermal conductivity, meaning it rapidly conducts heat and is not insulating. It should be noted that these values fluctuate depending on heat treatment, alloy composition, and other considerations.
Since the thermal conductivity of 6061 aluminum is commonly higher than that of 7075 aluminum, 6061 aluminum is better adapted for heat-dissipative applications (such as heat sinks and heat exchangers). However, the thermal conductivity of 7075 aluminum is nevertheless fairly excellent.
Modulus of Elasticity
The modulus of elasticity of a material refers to a measure of its resistance to permanent deformation. It may be used to define the “stiffness” of a material. When the elasticity modulus of these 6061 and 7075 alloys are compared, there is a minor difference, indicating that these materials behave similarly when elastically deformed. Regarding metric, 6061 aluminum has 68.9 GPa, whereas 7075 aluminum has 71.7 GPa.
Electrical Resistivity
A material’s electrical resistivity is the ability to resist the transfer of electricity. It is the inverse of electrical conductivity and works similarly to thermal conductivity but with an electrical charge rather than heat.
6061 and 7075 alloys have low electrical resistivity, implying high conductivity. Therefore, they are conductive materials suitable for electrical applications. In general, 6061 aluminum is ideal for these applications because it is more commonly available, can be shaped and welded more easily, and is more conductive than 7075 aluminum.
Hardness
A material’s hardness is defined as its response to local indentation from a standardized force. In general, a harder material fails more easily through a brittle fracture. Hence a balance between hardness and ductility must be established.
6061 and 7075 alloys are hard enough to resist deformity and ductile enough not to shatter or crack readily, making them good construction materials. However, 7075 aluminum should be specified if hardness is required since it is typically harder than type 6061 alloy.
Machinability
The machinability of a material is a measurement of how it responds to machining processes such as milling, cutting, die-casting, etc. When machining a particular alloy, the machinability is calculated using tooling speed, surface finish, and tool life. Aluminum 6061 is easier to machine than aluminum 7075. Therefore, aluminum 6061 is the material of choice if machinability is of some concern.
Temperature Resistance
Comparing the melting points of 7075 and 6061 can determine their temperature resistance. The melting point of 7075 aluminum is 477 – 635°C, somewhat lower than 6061 aluminum, which has a 582 – 652°C melting point. As a result, 6061 alloys can endure higher temperatures than 7075 alloys. However, 7075 aluminum reacts well to heat treatment. It also provides for a significantly better distribution of alloying elements.
Corrosion Resistance
6061 aluminum alloy is more corrosion-resistant than 7075 aluminum alloy. This is because the copper content of the 7075 alloys is much higher than that of the 6061 alloys. Since copper is more reactive to the environment, corrosion is inevitable.
Density
When comparing the physical properties of 7075 aluminum to 6061 aluminum, density is one factor to consider.
7075 aluminum has a slightly larger density than pure aluminum, with 2.81 g/cm³ (0.102 lb/in³), and it may additionally be strengthened via heat treatment (the most common temper being 7075-T6).
The density of 6061 aluminum alloy is 2.7 g/cm³ (0.0975 lb/in³), similar to that of pure aluminum metal.
6061 vs. 7075 Aluminum: Applications
Although 6061 and 7075 alloys can be used for automobile parts, aerospace components, building construction, and consumer goods, they differ in their use.
For example, in the aerospace sector, 7075 is more likely to be utilized as a gear or rod, whereas 6061 is more likely to be employed in an area that demands higher ductility. Regarding bike parts, some riders would prefer the increased strength of the 7075 aluminum alloy. Molds and industrial tooling are more likely to be made with 7075 than 6061. Because it is more formable than 7075, 6061 is more commonly utilized for tanks and other shapes with rounded contouring.
Typical applications of 6061 aluminum:
- Building products
- Electrical products
- Bicycle frames
- Piping
- Furniture
- Automotive parts
- Food and beverage packaging
- Industrial and manufacturing equipment
- Marine applications
Typical applications of 7075 aluminum:
- Gears and shafts
- Fuse parts
- Regulating valves
- Aircraft wings and fuselages
- Missile parts
- Worm gears
- Sporting equipment
- Rock climbing gear
- Fishing gear
6061 vs. 7075 Aluminum: Fabrication Considerations
Regarding fabrication, 6061 aluminum alloy has an advantage over 7075 aluminum alloy. This is frequently owing to the 6061 alloy’s lower hardness and tensile strength. Its lower hardness makes machining easier, and its lower tensile strength assures greater formability. Therefore, the 6061 aluminum boasts better fabrication compared with the 7075 aluminum.
Both materials can be joined via soldering, brazing, or adhesives. 6061 aluminum, on the other hand, is weldable, but 7075 aluminum is not. Even though 6061 is deemed weldable, correct weld filler metal selection is critical. Post-weld heat treatment and aging may be necessary to restore the weld area to its original “-T” designation. Following welding, 7075 is particularly prone to cracking.
6061 vs. 7075 Aluminum: Which is the Right One for You?
Choosing between titanium and stainless steel might be straightforward. However, answering the question “Which aluminum alloy is better for my project” will be difficult. Both 6061 and 7075 alloys are frequently applied and have outstanding mechanical properties. Then we must examine priorities, such as the part’s final usage. Of course, production conditions and cost are also important considerations.
Aluminium 6061’s main selling points are its low cost and versatility. Additionally, it has great machinability and corrosion resistance and may be extruded and welded. Because of its low weight and medium to high strength, it is a preferred choice for medical, electronics, automotive, and other applications.
Aluminum 7075 costs more than aluminum 6061 because of its higher strength and superior surface polish; nevertheless, machinability is slightly lower. The main drawback of utilizing aluminum 7075 is that it has a poorer corrosion resistance than aluminum 6061.
Summary
Aluminum alloys are widely employed in the building, aerospace, sports equipment, electrical, and automotive sectors. When the product is welded or shaped and requires moderate to high tensile strength, or critical corrosion resistance, aluminum 6061 is preferable. It’s also a superior choice for extruding intricate forms or when the funds are limited.
The primary feature of aluminum 7075 is its extremely high strength. As a result, it is ideal when extremely high tensile strength is required, together with a high strength-to-weight ratio and good fatigue resistance.
Do you have a challenge deciding between aluminum 6061 and aluminum 7075? Then you can contact LEADRP for support. LEADRP understands the importance of selecting appropriate materials in product development. As a result, we use our knowledge to select the right material for your project. Moreover, LEADRP has over a decade of CNC machining and prototyping experience and is always ready for your projects. Contact us today!
References
What are the Differences Between 6061 and 7075 Aluminum? – From Metal Supermarkets
6061 Aluminum vs. 7075 Aluminum – Differences in Properties, Strength, and Uses – From Thomas
FAQ
Alloys in the 6xxx series have an outstanding anodizing response. 6061 aluminum is a structural alloy with high strength and exceptional machinability. When parts are to be hard anodized in various colors, 6061 aluminum is the material of choice for many businesses.
7075 aluminum is an ultra-high-strength alloy widely used in the aviation and aerospace sectors. Depending on the alloy and the anodizing process, they anodize grey, blue-gray, and brown-black (mottled).
Because 7075 contains over 1% Cu, it is more susceptible to caustic environments and lacks the high corrosion resistance of other aluminum alloys.
The yield strength of 7075 aluminum alloy is higher than that of 6061 aluminum. This is because of its chemical composition. Therefore, it is more resistant to impact and deformation than 6061.
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