×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Mysterious blue particles in A356 aluminum castings

Mysterious blue particles in A356 aluminum castings

Mysterious blue particles in A356 aluminum castings

(OP)
On the metallograph, there are some blue colored particles. The only thing I can guess is that it might be from light diffraction hitting oil or some residue polishing compound, however I have my doubts about this because it is restricted to the particle itself?

Do you have any explanations for the appearance of these blue particles after viewing at 100, 200X, 400X, etc?

RE: Mysterious blue particles in A356 aluminum castings

A picture's worth a thousand words. If you can post a micrograph, we might be able to offer some suggestions.


                                       Maui

RE: Mysterious blue particles in A356 aluminum castings

okay what etchant and what addition do you make to the metal,

i would narrow it down to one of three things


silicon based either primary crystals
titanuim or Ti-B
Mg particles - unliklel

I used to have a boo that told you what elements showed up l;ike under etchant, did you use kellers reagent?

RE: Mysterious blue particles in A356 aluminum castings

(OP)
Believe it or not,this was unetched. I will get a picture. I haven't uploaded any to this before. Is there a special trick to uploading pictures?

RE: Mysterious blue particles in A356 aluminum castings

EngineerDave,

Mg2Si particles are blue.

Regarding pictures - you can't upload them to an Eng-Tips server.  Rather, you have to store them on another server, then link to them using the TGML code shown in the Process TGML link (this link is included within Step 2 Options at the bottom of the Your Reply window.

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

RE: Mysterious blue particles in A356 aluminum castings

(OP)
Thanks guys. For now I'll hold off on uploading a picture, because quite honestly the blue isn't as evident in the digital photomicrograph as it is when you look through the scope.

RE: Mysterious blue particles in A356 aluminum castings

As CoryPad mentioned, Mg2Si particles are blue.  Proper solution treatment should dissolve these, so this may be an indication of incomplete homogenization during the solution treatment.

RE: Mysterious blue particles in A356 aluminum castings

(OP)
Is it correct to predict that the Mg2Si particles will behave in a brittle fashion?

Also a general forums based question. How long does a thread stay on here after being inactive. My interest is basically what happens after no responses have been made for 6 months or a year. Does it get deleted? I know some forums that go back 2-3 years, just curious about this one, because it'd be great to refer back to these. I think to be safe, I'll just save them from time to time.

RE: Mysterious blue particles in A356 aluminum castings

I thought that Mg2Si was soft?

nick

RE: Mysterious blue particles in A356 aluminum castings

Mg2Si particles are brittle.

Currently, all posts are kept.  This policy may change, although I think this is highly unlikely.



Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources