Q to Metal Masters

[XOverZero]

A question for the metallurgical yodas: Regarding 2024T3 Alclad, are its mechanical properties affected in any adverse way by bead blasting and anodizing? Thanks in advance.

[krw5927]

Yes and yes.

In general, bead blasting or shot peening will create residual compressive stresses on the surface which usually tend to increase fatigue life. Without a known almen height, intensity, and coverage, the exact increase is unknown. If the surface is not REALLY clean prior to blasting, however, you can force whatever foreign materials that reside on the surface of the metal further into the grain structure which would potentially reduce fatigue and tensile properties. Blasting/peening clad aluminum sheet may be another matter entirely. I wonder (don't know, but will ask around to the metal gurus at work) whether forcing pure (weak) aluminum into the alloyed (strong) substrate would degrade yield and ultimate tensiles for the sheet. Interesting question.

Anodizing has an effect to decrease fatigue properties. Yes, Vans anodizes wing spars. This can safely be done as long as the structure is designed with this slightly reduced fatigue property in mind.

[krw5927]

An expert metallurgist colleague confirms that there would be no negative effect to ultimate tensile strength from peening alclad sheet. With enough intensity the clad layer might be removed, but this wouldn't appreciably affect tensiles.