Are Welds and Fasteners Undermining Your 7075-T6 Designs?

You build complex, mission-critical parts from high-strength 7075-T6 sheets¹. But you rely on welds and fasteners, accepting that every single joint is a potential point of failure.

An assembly from sheets bets its integrity on its weakest joint. We eliminate that bet. Our forging process creates a single, monolithic part, replacing failure points with an unbroken grain flow of pure, integrated strength.

I remember a project with a new client in the defense sector. They were building a critical mounting bracket by welding several precision-cut 7075-T6 plates together. The design was failing vibration tests, with cracks forming right next to the welds. The problem was clear: the intense heat of welding destroyed the T6 temper in the surrounding area, creating a soft, weak zone. They were building a high-strength assembly with built-in weak points. We redesigned the bracket as a single-piece forging. Our process not only eliminated the welds but also oriented the grain flow to reinforce the high-stress areas. The new forged part passed the tests with flying colors and was even lighter. They didn't just buy a stronger part; they bought reliability.

What is the ultimate strength of 7075-T6 aluminum?

You need the highest strength for your component and the spec sheet for 7075-T6 looks impressive. But does that number reflect the actual strength of your finished, assembled part?

The typical ultimate tensile strength of 7075-T6 aluminum is about 572 MPa (83,000 psi). However, a component's true strength is defined by its weakest point, which is almost always a joint or fastener, not the material itself.

Ultimate tensile strength (UTS) is the maximum stress a material can withstand while being stretched or pulled before it breaks. For 7075-T6, this number is among the highest of all aluminum alloys, making it a star performer for aerospace and defense applications. But this is the strength of the material in an ideal state. The moment you cut it and join it to another piece, the system's strength changes. A welded joint will have a much lower strength than the parent metal. A hole for a fastener creates a stress concentration point, making that area more likely to fail under load. So, while you start with an 83 ksi material, your assembly might realistically only be as strong as the 30 ksi fastener or the 40 ksi weld holding it together. Forging, on the other hand, creates a monolithic part with no joints. The strength is continuous and integrated, allowing you to actually achieve the full potential of the alloy.

What are the disadvantages of 7075 aluminum?

You've chosen 7075 for its incredible strength. But you can't ignore its downsides, like poor weldability, which complicates your assembly process and introduces risk.

The main disadvantages of 7075 aluminum are its poor weldability, lower corrosion resistance² compared to 6xxx alloys, and higher cost. These factors make it challenging to use in assembled structures, especially in certain environments.

While 7075 is a champion of strength, it comes with significant trade-offs that are critical to understand. First, it is generally considered unweldable for structural applications. The high heat required for fusion welding ruins the carefully achieved T6 temper and can cause cracking, severely compromising the part. This forces designers to rely on mechanical fasteners like bolts and rivets, which add weight, complexity, and points of failure. Second, its corrosion resistance is only fair. It is much more susceptible to environmental degradation than an alloy like 6061, often requiring a protective coating like anodizing or cladding. When you cut or drill a sheet, you expose a raw, unprotected edge that becomes a prime spot for corrosion to start. A single-piece forged part can be treated uniformly, ensuring complete protection. Finally, the higher price means that using it inefficiently—like machining away large amounts of a plate or bar—is extremely wasteful.

What is the price of 7075 aluminium?

You need the performance of 7075 but must justify the cost. The raw material price is high, making every ounce you machine into scrap a direct hit to your bottom line.

7075 aluminum is a premium alloy, typically costing two to three times more than general-purpose 6061. Its price reflects the expensive alloying elements like zinc and a more complex manufacturing and heat treatment process.

The price of 7075 aluminum is a major consideration for any project. You are paying a premium for its top-tier strength. This high cost makes wasteful manufacturing processes, like subtractive machining from a large block or plate, very expensive. If you start with a 10kg block of 7075 to machine a 2kg part, you have just turned 8kg of premium, expensive material into low-value scrap chips. This is where the economics of near-net shape forging become so powerful. We start with a billet of material that is much closer to the final part's mass. By shaping the metal instead of cutting it away, we drastically reduce material waste. While the initial tooling cost for forging needs to be considered, for production runs, the savings in raw material and reduced machine time often make forging a more cost-effective solution than machining from plate, especially with a high-value alloy like 7075.

What is the difference between 7075-T651 and 7075-T6?

You see different temper designations like T6 and T651 and need to know the difference. Choosing the wrong one can lead to parts warping after machining, wasting time and expensive material.

The main difference is stress relief. The "51" in T651 indicates the material has been stretched after heat treatment to relieve internal stresses. This makes T651 much more dimensionally stable during machining than standard T6.

Both T6 and T651 tempers have virtually identical mechanical properties like strength and hardness. The difference is all about internal stress. The process of heat treating and rapidly quenching aluminum to achieve the T6 temper creates significant internal stresses within the material. If you take a standard T6 plate and machine away a large amount of material from one side, you unbalance these internal stresses, and the part can warp, bow, or twist. To solve this, the T651 temper was created. After quenching, but before aging, the material (usually plate or bar) is put into a machine and stretched by a controlled amount (1.5% to 3%). This stretching process mechanically relieves the vast majority of the internal stresses. For our machining customers, this is critical. Using 7075-T651 plate means they can perform heavy machining operations and trust that the part will remain straight and true to the print, minimizing scrap and ensuring precision.

Conclusion

Stop building weak points into your strong designs. Choose monolithic, forged components from SWA Forging to harness the full, uninterrupted strength of 7075 aluminum for ultimate reliability.