BHN of Al7075-T6 6

[WTP60]

Can someone confirm that The Brinell Hardness of 7075 with T6 heat treat should be at a minimum of 150? I've been told that this isn't achievable (repeatable) by a supplier. It is my suspicion that that since they are getting around 140 on a consistent basis that they are not correctly heat treating the parts. If they aren't getting to 900-925 or keeping the temperature there for a long enough period, would that result in a lower BHN? What about aging at 250 for an insufficient amount of time?

Based on other threads on this forum, I believe that the correct procedure would be:

Solution Heat Treat to 900-925 for a minimum of an hour
Water quench
Age for 24 hours at 250
Cool to room temperature

If the raw material is truly 7075, with the heat treatment performed as described above, this should result in BHN150. Correct?

Thank you for your help to anyone who can provide insight or confirmation.

Tim60

 

[SSfix]

To solution heat treat the aluminum might remove the residual stress but I am not sure it will become harder through the process but rather just cycle back around to the properties within the T6 temper designation.

you should also be careful depending on what type of material it is being sheet, plate, bar, forging etc because you solution HT temperature might be lower than 900 degrees.

 

[WTP60]

Thanks SSfix

They are forged components and About .375" thick. Is the BHN150 an average or a minimum when you look at the specifications? Whether I'm looking at properties on Kaiser's data base or Alcoa or any other specification I can find on line, it is consistently showing BHN150 for 7075-T6.

 

[tbuelna]

MMPDS-01 lists a min Ftu of 75ksi for forged 7075-T6 (AMS 4126) having a section thickness at/below 1". This is a value that would be used for analysis purposes.

 

[WTP60]

So, based on this data, one should assume that a HB of approximately 172 is possible? 75ksi-~517Mpa. 517mpa / 3 = 172. Or, is there some other K factor than 3 that should be used for Al?

 

[CoryPad]

The ASM Handbook and the Aluminum Association Standards and Data Book both show 7075-T6 to have a typical hardness of 150 HB. MIL-H-6088G shows 7075-T6 to have a typical minimum hardness of 135 HB.

 

[WKTaylor]

WTP60, all...

AMS2658 Rev C Hardness and Conductivity Inspection of Wrought Aluminum Alloy Parts...
7075 [bare]
Temper: T6x
BH min: 135
RHB min: 84
RH-15T: 87
Conductivity IACS: 30.5 - 36.0
NOTE that the hardness requirements are specified as MINIMUM.

From a USAF T.O. [temper assessment]
7075 [bare]
Temper: T6x
RHB: 83.5--94
Conductivity IACS: 30.0 - 34.0

Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true.
o For those who believe, no proof is required; for those who cannot believe, no proof is possible.
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion"]
o Learn the rules like a pro, so you can break them like an artist. [Picasso]

 

[WTP60]

Thank you to all for your input and posts!