Alumentary: Is aluminum soft?

“Aluminum is soft?” – Why that’s not true in fastening technology

Yes, pure aluminum is considered relatively soft and highly malleable. In practice, however, it can be used to manufacture high-strength fasteners—but how does that work?

In manufacturing, we generally do not work with pure aluminum (typically approx. 99.0–99.9% Al), but rather with aluminum alloys, such as the AlMgSiCu alloy AA 6056.

By adding elements such as magnesium (Mg) and silicon (Si)—as well as copper (Cu), depending on the alloy—significantly higher strengths can be achieved. Many of these alloys are also heat-treatable: A suitable heat treatment (solution annealing, quenching, aging) creates a fine precipitation structure that further increases strength.

In addition, cold forming (work hardening) can increase strength and hardness—though usually at the expense of ductility.

Conclusion: While pure aluminum is soft, aluminum alloys such as AA 6056 can be transformed into high-strength materials through alloying, heat treatment, and/or work hardening, making them ideal for our ESKA fasteners.