Aluminum ASTM B211 vs B221

[Dinosaur]

I have been asked to consider a substitution of ASTM B221 Aluminum 6061-T6 for ASTM B211 Aluminum 6061-T6. The B221 is a spec for extruded bars, etc, and the B211 is a spec for cold-finished or cold rolled. The application is for aluminum nuts on a threaded stainless steel rod so the nut is expected to strip before the rod. Can anyone tell me if there is any reason to be concerned with this substitution? According to the ASTMs, the alloy 6061-T6 has the same yield strength under each spec. but the ultimate strength is 38 ksi vs 42 ksi. A physical test of the specimen shows the specimen failed well above the 42 ksi. Thanks in advance.

 

[TVP]

Extruded bar is cheaper than cold-drawn bar. The surface roughness and straightness will be better with cold-drawn bar. If your application is not sensitive to these items, then it likely will not be a problem. I would be more concerned about galvanic corrosion due to an Al nut being used on a stainless steel rod.