Aluminum stress relief vs. artificially age 1

[dwillms]

We're doing some machining to a beefy 6061-T6 extrusion and are VERY concerned about residual stresses in the material afterwards(as a result of extruding and machining). Two questions:

1. Any idea if dimensional creep is likely as a result of machined in stresses over the life of the part? For this application 5 micron is too much!

2. What heat treatment would remove residual stresses but preserve the T6 temper?

Thanks!

 

[TVP]

You need to consider two different approaches:

1. Extrusion then heat treatment then machining then ???

or

2. Extrusion then machining then heat treatment


You may be able to obtain the extrusion in a stress-relieved treatment, say -T6510 or T6511, which may eliminate the necessity for any post-machining thermal treatment/stress relief. This would provide the higher strength conferred by the precipitation hardening process, and may minimize any distortion during/after machining.

The other option to consider is machining prior to the precipitation heat treatment. Have you considered this processing route? Perhaps this would allow for the desired final product, with minimal residual stresses from machining.

 

[AUME]

I might suggest that you post your thread in the aerospace section. I worked with a bunch of engineers at a major airline, that did structural design. These guys are the masters of aluminum structures.