Aluminum Alloys: Does Your Manufacturing Process Create Strength or Just a Shape?

You bought a block of high-grade aluminum and machined it into a perfect part. But it failed in service, cracking under stress. You're left holding a useless part, facing project delays and costly rework.

Your manufacturing choice is critical. Machining simply carves a shape from a block, exposing its existing grain structure. Forging, however, is a dynamic process that refines the grain and aligns it with the part's shape, creating engineered reliability.

A few years ago, we had a new customer in the automotive performance sector. They were machining beautiful suspension arms from large, expensive blocks of 7075-T651 plate. The parts looked incredible, but they kept seeing fatigue cracks develop near the mounting points after track testing. They blamed the material. We showed them it wasn't the material, but the method. The straight grain of the rolled plate was being cut across by the part's geometry, creating weak points. We proposed a switch to a near-net shape forged blank. By forging the arms, we directed the grain flow to follow the contours of the part, reinforcing the high-stress areas. The forged parts were lighter, stronger, and completely eliminated the cracking issue. They learned that you don't just machine a strong part; you start with a part that's been forged for strength.

How are basic aluminum alloys made?

You handle aluminum alloys¹ every day, but do you know where they come from? Understanding the fundamental process helps you appreciate the quality of the starting material, or billet, that we use for forging.

Aluminum alloys are made by melting pure aluminum and precisely mixing in other elements (like zinc, copper, or silicon). This molten mixture is then cast into large forms like billets or ingots, which become the raw material for all subsequent manufacturing.

The creation of an aluminum alloy is a precise metallurgical recipe. It is not a simple mechanical mixture; it is a true solution where the atoms of different metals combine to form a new material with superior properties.

1. Melting: It starts with high-purity aluminum ingots, which are melted in a large furnace.
2. Alloying: Based on the desired alloy (e.g., 6061 or 7075), carefully measured amounts of other elements are added to the molten bath. The chemistry is checked constantly to ensure it meets exact specifications.
3. Degassing: Impurities and dissolved gases, especially hydrogen, are removed from the molten metal. This is a critical step to prevent porosity (tiny gas bubbles) in the final product, which can lead to weakness.
4. Casting: The refined, molten alloy is then cast into large cylindrical logs called billets or rectangular slabs called ingots.

At SWA Forging, we only source our billets from top-tier mills that certify the chemistry and internal cleanliness of every single billet. The quality of a forged part begins with the quality of the raw material.

How are most aluminum parts made?

You get a request for a custom aluminum part. You need to decide: should it be cast, extruded, machined from plate, or forged? Choosing the wrong process can lead to a part that is too weak, too heavy, or too expensive.

Most aluminum parts are made through casting (pouring liquid metal into a mold), extrusion (pushing metal through a die), or machining (cutting from a solid block). Forging is reserved for parts requiring the highest strength and reliability.

Each manufacturing method offers a different balance of cost, complexity, and performance. As a supplier, we help our clients choose the method that best fits their application and budget.

Our expertise lies in forging. When a client comes to us with a part that keeps failing, it's often because it was made using one of the other methods when the application truly demanded the structural integrity that only forging can provide.

Why is forging a superior metallurgical event?

You hear that forging is "stronger," but what does that really mean? You need to understand the science behind it to confidently explain the value to your customers and justify the investment.

Forging is not just shaping metal; it's a metallurgical process that refines and directs the grain structure. The immense pressure breaks down the coarse, random grains of a cast billet and realigns them to follow the part's geometry, eliminating internal defects.

When we receive a cast billet, its internal grain structure is large and random, like a pile of loose rocks. This structure can contain microscopic voids or weak spots. The forging process fundamentally changes this.

1. Grain Refinement: Under the massive pressure of the forging press, the large, brittle cast grains are crushed and broken down into much smaller, tougher grains. A fine-grain structure is a strong-grain structure.
2. Defect Elimination: The compressive force physically squeezes shut any internal voids or pores that may have existed in the original billet, creating a perfectly solid and dense material. This is why forged parts are essential for pressure vessels and other applications where leaks are not an option.
3. Grain Flow Alignment: As the metal is forced to flow into the shape of the die, these newly refined grains are aligned to follow the contours of the part. This creates a continuous, uninterrupted grain flow that directs strength exactly where it is needed most.

You aren't just buying a shape. You are buying a component where the internal structure has been re-engineered for maximum performance and reliability.

Conclusion

Choose your manufacturing process wisely. Machining gives you a shape, but forging delivers engineered reliability by refining the metal's grain and aligning it for superior, directional strength.Deconstructing the Request

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