Continue to Site

Eng-Tips is the largest engineering community on the Internet

Intelligent Work Forums for Engineering Professionals

Register Log in
  • Congratulations waross on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!

Aluminum 7075 - T6

Status
Not open for further replies.
M. BR

M. BR

Student
Mar 1, 2024
15
Hello guys,

I'm doing a failure analisys on an aluminum 7075 T6. I think the failure mode is brittle. Attached the SEM image.

The supplier send the "recipe" for the T6. What do you think about this recipe?

Solution Heat treatment: 470°C(880F) - 2h - water cooling
Precipitation: 120°C(250F)2h + 180°C(360F)
Recristalization: 260°C(500F) - 3h - air cooling

Some times they do the T6 twice. Do you think this is a problem?


 
 https://files.engineering.com/getfile.aspx?folder=129956fe-4a20-4308-ab53-c9f666b09d6c&file=7075-_1.JPG
Replies continue below

Recommended for you

Sort by date Sort by votes
I'd be surprised if 7075T6 is "brittle" ... sure it may be an overload failure but Aluminium has some ductility.

You can find out about 7075T6 for online sources, like Mil Handbook 5J or AR-MMPDS-01 (or -0x, there are several versions, some behind pay walls).

"T6" should be thin sheet can be thick plate (but more often T651). some specs ... AMS 4044, AMS 4045, AMS QQ-A-250/12

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.
 
Upvote 0 Downvote
I was also suprised analysing it..... but on SEM images/analysis there was no signs of deformation, voids... nothing...
 
Upvote 0 Downvote
is it thin sheet ? plate ?? machining ??

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.
 
Upvote 0 Downvote
OP
As RB said not enough info.
What it is and what are the stress loads. Shear or tensile
 
Upvote 0 Downvote
In the latest pictures it looks like beach marks, possibly low cycle fatigue from stress exceeding the material properties.
 
Upvote 0 Downvote
Its not fatigue, the part was just machined and assembled.
 
Upvote 0 Downvote
It spontaneously snapped sitting by itself?
 
Upvote 0 Downvote
no, after assembly, obnline testing
 
Upvote 0 Downvote
What testing was done? Is there a photo of the item in the test fixture?
 
Upvote 0 Downvote
Was there any straightening involved.
It may be from forging. And how it was heat treated.
Take the whole part and have it zyglo penetrant inspected. Now that is scrap. And not repairable. Cut it up and do met lab samples.
Spectral analysis
Sem
Pull a couple of tensile
Do a charpy test. If it's brittle that will tell you. So will the tensile.
Your on a mission to what it is not.
 
Upvote 0 Downvote
not that it's a big deal but heat treating to T6 after the original melt makes T62, which has all the properties of T6.

There look to be some awful stress concentrations in those sharp corners ?

yes, cut coupons from the scrap and verify properties (just to be sure).



"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.
 
Upvote 0 Downvote
rb1957 said:
I'd be surprised if 7075T6 is "brittle"...
Click to expand...

I tried to move a tent that had poles made from Aluminium 7005-T6. There was no discernable ductility. The first sign of trouble was when they snapped. Now that is not 7075 alloy, but the yield and ultimate stresses are awfully close together.

--
JHG
 
Upvote 0 Downvote
One other thought - check to see if that really is 7075. I've had suppliers substitute other alloys before.
 
Upvote 0 Downvote
M.BR said:
Its not fatigue, the part was just machined and assembled.
Click to expand...

Did you watch the assembly or do it yourself? Perhaps something was off and a lot of stress induced during the assembly.
 
Upvote 0 Downvote
Status
Not open for further replies.

Similar threads

wardstone
  • Locked
  • Question
calculation of the energy needed to heat an aluminum block
Replies
8
Views
166
3DDave
3DDave
mamirzaei
  • Locked
  • Question
ALUMINUM TIG WELDING
Replies
3
Views
73
mfgenggear
mfgenggear

Part and Inventory Search

Sponsor

Back
Top Bottom