Aluminum nitride precipitation hardening
Aluminum nitride precipitation hardening prevents grain growth at high annealing temperatures and stabilizes mechanical properties through fine AlN particles.
Physical-Chemical Mechanism of Action
In aluminum nitride precipitation hardening, the aluminum in the melt reacts with nitrogen from the environment or the welding process gases. This leads to the formation of fine AlN particles that anchor in the grain growth and restrict the growth of new crystal grains.
Metallurgical Relevance & Welding Risks
This hardening method increases the strength and toughness of the aluminum alloy, prevents grain coarsening, and reduces the risk of hot cracking. However, insufficient nitrogen content can lead to incomplete hardening, while too much nitrogen can result in excessive strength and possible destruction of material properties.
Workshop Practice & Action Instructions
To successfully implement aluminum nitride precipitation hardening, a controlled nitrogen flow must be ensured during the welding process. This can be achieved by using shielding gas systems. The nitrogen content should be set to provide sufficient hardening without destroying material properties. Recommended nitrogen contents are typically between 10 and 25 vol-%, depending on the specific aluminum alloy.