Quick Answer
In absolute terms, steel is generally stronger and stiffer than aluminum – most structural steels exceed common aluminum alloys in tensile strength. But aluminum is roughly one-third the weight (2.7 vs 7.85 g/cm³), so on a strength-to-weight basis, high-strength aluminum alloys like 7075-T6 (about 500 MPa yield) can outperform mild steels like A36 (about 250 MPa yield). The right choice depends on load, weight, corrosion exposure, and cost – not strength alone.
Summary
When engineers and contractors need a metal for their ongoing project, they want to choose the best metal. They often compare aluminum to steel. The question is how strong is aluminum? Is it stronger than steel? Steel is known for its strength and durability, while aluminum is known for its lightweight and corrosion resistance.
So, which one is stronger- aluminum or steel?
This blog answers this question.
The key highlights of the blog are:
- How aluminum vs steel strength differs across common grades
- Why steel is stronger than aluminum depends on the alloy and application
- How the aluminum vs steel weight ratio affects structural design
- Differences in the yield strength of aluminum vs steel
- How structural aluminum vs steel performs in real-world applications
“Is steel stronger than aluminum?”
When the two metals are compared, the answer seems evident. At first glance, steel is stronger than aluminum. However, both metals have their strengths and shortcomings. When choosing between the two for a certain project, strength isn’t the only deciding factor.
The choice depends on what you are trying to accomplish and how you want the metal to perform. For example, if you need excellent load-bearing capacity, steel is the right choice, but for a lightweight transportation system, aluminum’s low density is an advantage.
Read on further to learn more about the two metals.
Comparing Strength: Yield and Tensile Performance
Two important measurements are yield strength and tensile strength. Yield strength indicates the stress at which a material begins to deform permanently, while tensile strength represents the maximum stress it can withstand before breaking.
The yield strength of aluminum vs steel varies significantly by grade. The common 6061-T6 aluminum alloy has a yield strength of about 276 MPa, while 7075-T6 aluminum alloy can reach approximately 500 MPa. By comparison, ASTM A36 structural steel has a minimum yield strength of about 250 MPa, although many structural and high-strength steels have considerably higher values.
Steel also generally offers higher tensile strength. For example, A36 steel has a specified minimum tensile strength of around 400 MPa, while higher-strength steels can exceed 600 MPa.
So, steel can’t be declared the winner without considering the full engineering picture.
| Material & Grade | Yield Strength | Tensile Strength | Density | Standout Property |
|---|---|---|---|---|
| 6061-T6 aluminum | ~276 MPa | ~310 MPa | 2.7 g/cm³ | Balance: weldable, corrosion-resistant |
| 7075-T6 aluminum | ~500 MPa | ~570 MPa | 2.8 g/cm³ | Aerospace-grade strength |
| A36 structural steel | ~250 MPa (min) | ~400 MPa (min) | 7.85 g/cm³ | Low cost, easy fabrication |
| High-strength steels | 350-700+ MPa | 600+ MPa | 7.85 g/cm³ | Maximum absolute strength & stiffness |
The Aluminum vs Steel Weight Ratio
One of aluminum’s greatest advantages is its low density. Aluminum has a density of approximately 2.7 g/cm³, compared with roughly 7.85 g/cm³ for carbon steel. This means steel is nearly three times as dense as aluminum.
The aluminum-to-steel weight ratio therefore becomes particularly important in transportation, aerospace, mobile equipment, and applications where reducing structural weight improves efficiency.
An aluminum component requires greater thickness to achieve comparable strength and stiffness. Since weight plays a crucial role in transportation structures, aluminum remains the preferred choice. Despite steel’s strength, aluminum offers other advantages.
Real Customer Experience
A FedEx Ground contractor came to AZ Metals needing shelving for a new delivery truck – a textbook weight-ratio decision. Steel shelves would have carried the load, but every extra pound cuts payload and fuel efficiency across years of routes. Our team reviewed his design and built the shelving in aluminum: strong enough for daily parcel loads, light enough to protect the truck’s capacity. The right answer wasn’t the stronger metal – it was the stronger metal per pound.
Does Choosing the Strongest Aluminum Alloy Work?
When discussing strength, aluminum grade 7075-T6 is often cited for its high strength. It is a popular choice in aerospace and other demanding applications. However, choosing the strongest alloy doesn’t answer the question because 7075 has lower corrosion resistance and weldability than some other aluminum alloys.
In contrast, 6061-T6 provides a useful balance of strength, corrosion resistance, machinability, and weldability, making it highly versatile for fabrication – our aluminum grades guide breaks down which grade fits which job.
So, choosing the strongest alloy isn’t the answer if it’s not a viable option for the project.
Structural Aluminum vs Steel
Is structural aluminum better than steel?
This is another question you might ask.
The answer is that steel is often used for heavy-duty projects, such as buildings, bridges, heavy machinery, industrial frames, and other applications. Its load-bearing capacity makes it the first choice.
However, when it comes to strength-to-weight ratio, structural aluminum often comes out on top because, despite its lightweight nature, it has high strength, making it ideal for architectural systems and heavy-duty vehicles.
Its lower density produces substantial weight savings when the design is optimized around aluminum’s properties.
Expert Insight – Doug Cone, Co-Owner, AZ Metals
“In 40 years around metal, the question I hear most is ‘which is stronger’ – and the question that actually matters is ‘stronger for what.’ A trailer builder and a bridge contractor both need strength, but one is fighting weight and the other is fighting deflection. Tell us the load, the span, and the environment, and the steel-versus-aluminum answer usually settles itself in one conversation.”
Choosing the Right Material for Fabrication
When choosing between steel and aluminum grades, it’s important to consider their fabrication capabilities for the underlying project.
Aluminum can be cut, machined, formed, and welded, but its thermal characteristics differ significantly from steel. Steel is easier to select for heavy structural applications because of its established fabrication methods and extensive range of grades.
Consider expected loads, required dimensions, operating environment, joining methods, corrosion exposure, and target weight before choosing between the two – our guide on choosing the right alloy for heavy-duty projects walks through this decision. Cost is also an important factor. Aluminum might be more expensive than carbon or mild steel and required for a particular lightweight design, but steel offers strength and stiffness.
Confused Between The Two Metals?
So, is steel stronger than aluminum? Should you choose it for your project?
The answer depends on the application and project needs. If you need a lightweight metal, aluminum is the better choice, but consider corrosion resistance, fabrication requirements, operating conditions, and more.
If you find it confusing to choose the right metal grade, consult us at AZ Metals, where we stock various aluminum and steel grades and will help you choose the right metal.
Our trained staff and years of experience back us. We can fulfill both retail and wholesale needs and pride ourselves on being the best fabrication experts in Phoenix and Mesa.
Give us a call for more information!
Frequently Asked Questions
Q: Is steel stronger than aluminum?
A: Generally, steel has higher absolute strength and stiffness than common aluminum alloys. However, some high-strength aluminum alloys can approach or exceed the yield strength of certain structural steels.
Q: What is the strongest aluminum alloy?
A: 7075-T6 is among the strongest commonly used aluminum alloys, with a yield strength around 500 MPa. Its suitability depends on corrosion, welding, and application requirements.
Q: Why is aluminum lighter than steel?
A: Aluminum has a density of approximately 2.7 g/cm³, compared with about 7.85 g/cm³ for steel, making it roughly one-third the weight by volume.
Q: Which is better for structural applications: aluminum or steel?
A: Steel is preferred for heavily loaded structures requiring high stiffness, while aluminum is advantageous where low weight, corrosion resistance, and easier handling are priorities.
Q: How does yield strength differ between aluminum and steel?
A: Yield strength depends on the specific grade and temper. For example, 6061-T6 aluminum is around 276 MPa, while 7075-T6 is approximately 500 MPa; structural steels vary widely by grade.
Doug Cone is the Co-Owner of AZ Metals and brings more than 40 years of experience in the metals industry. Throughout his career, he has developed extensive expertise in operations, manufacturing, and customer service. Doug previously served as Plant Manager for a large-scale metal processing facility, where he led production, quality, and operational performance. He also owned and operated a successful metal franchise for 10 years, gaining valuable experience in business development, sales, and customer relationships.
At AZ Metals, Doug combines his technical knowledge with hands-on leadership to deliver high-quality products, dependable service, and practical solutions for customers across a wide range of industries. His commitment to integrity, operational excellence, and long-term partnerships has earned him the trust of clients and colleagues alike, making him an integral part of AZ Metals' continued growth and reputation for reliability.
