November 2025 Volume 7

MATERIALS

Aluminum has many useful properties such as a high strength to weight ratio, high corrosion resistance, high conductivity, and high malleability, making aluminum useful for many different industries 4 . Aluminum forgings are most used in industries such as aerospace and aviation (structural and propulsion), automotive (body and engine), and semiconductor (etch chambers) 6 . Aluminum is used for semiconductor etching chambers because its high strength, corrosion resistance, low electrical resistance, and compatibility with silicon dioxide make it ideal for manufacturing microchips.

Non-heat treatable alloys are strengthened through cold working. Cold working occurs during rolling methods and is the action of “working” the metal to make it stronger. For this reason, the non-heat treated grades are not commonly forged (hot worked). The non-heat treated alloys include the 1xxx series (pure Al), 3xxx series (manganese), 4xxx series (Silicon), and 5xxx series (Mg). Typically forging alloys are strengthened by solution heat-treating and then quenching, or rapid cooling. The heat treatable alloys include: • 2xxx series - copper is used as the principle alloying element and can be strengthened significantly through solution heat treating. Alloys like 2618 and 2219 are commonly forged. • 6xxx series - versatile, heat treatable, highly formable, weldable and have moderately high strength coupled with excellent corrosion resistance. Alloys in this series contain silicon and magnesium to form magnesium silicide within the alloy. 6061 is the most common forging alloy in this series. • 7xxx Series - Zinc is the primary alloying agent for this series, and when magnesium is added in a smaller amount, the result is a heat-treatable, very high strength alloy. The most known alloys are 7050 and 7075.

Figure 5: Temperature vs. Specific Strength for Various Metals Aluminum makes up about 75% to 85% of a modern aircraft's weight, with specific percentages varying by model and manufacturer. It is used for the fuselage, wings, and other structural components due to its high strength-to-weight ratio and corrosion resistance. Newer planes may incorporate more composite materials, which changes the overall weight percentage, as seen with the Boeing 787, which is 50% composite and 20% aluminum by weight. Aluminum’s wide use in various industries comes not only from the unique properties that aluminum has but also from the many different alloys and production methods that are used to make aluminum useful to many industries. Casting is commonly used to produce components made from aluminum and aluminum alloys which involves melting the aluminum and pouring the molten metal into a mold of the desired shape 7 . Aluminum Forging Alloys The aluminum alloys are differentiated by the main alloying element(s) and whether they can be strengthened by heat treatment or not. Figure 6 shows the main series and their alloying elements and whether heat treatable or not.

Figure 6: Aluminum Forming Processes 11 Aluminum alloys are formed using various techniques, most of which are shown in Figure 6. The featured forming method for producing components from aluminum is forging (NAICS 332112). Forging aluminum alloys can produce highly refined final parts with a wide range of different forging techniques 8 . Aluminum alloys can be forged using many different techniques including open-die forging, closed-die forging, upset forging, roll forging (see Figure 7), orbital/rotary forging, spin forging, ring rolling, mandrel forging, and reverse or forward extrusion 8 .

Figure 7: Example Ring Rolling Process and Aluminum Rings

Figure 6: Aluminum Alloy Series 13

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