Strengthening Aluminum (casting mix)

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Discussion Overview

The discussion revolves around methods to strengthen aluminum castings, particularly using aluminum scraps. Participants explore alloying elements, heat treatment processes, and the implications of different aluminum compositions on the final properties of the cast part.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • One participant inquires about additives to aluminum melts that could enhance strength, suggesting materials like fine sand or ceramics.
  • Another participant references external articles on aluminum alloys and their effects, indicating a resource for further reading.
  • A participant questions how to cool the aluminum mix after adding iron to avoid forming a two-phase composite, expressing concern about crack formation.
  • Discussion includes the importance of the type of aluminum scraps used, with a suggestion that pure aluminum can be alloyed to create stronger variants like 6061 or 7075.
  • One participant confirms the use of 6061 aluminum scraps and seeks clarification on the optimal heat treatment process for maximizing strength.
  • A later reply provides specific heat treatment temperatures and times for 6061 aluminum, detailing solution heat treatment and precipitation hardening steps.

Areas of Agreement / Disagreement

Participants express varying opinions on the best methods for strengthening aluminum, with no consensus on specific additives or cooling techniques. The discussion remains unresolved regarding the optimal approach to achieve the desired material properties.

Contextual Notes

Participants mention the low solubility of iron in aluminum and its potential to form intermetallic phases, but the implications of this on the casting process are not fully explored. There is also uncertainty about the specific composition of aluminum scraps being used.

Who May Find This Useful

Individuals interested in metal casting, materials science, and those looking to enhance the properties of aluminum alloys through alloying and heat treatment techniques.

Curl
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I want to cast a part out of Aluminum (from scraps). Is there anything I can throw into the melt mix to make it come out stronger (not as gummy and soft) ??

Some sort of ceramic I'm thinking? Very fine sand-like stuff (e.g. CaCO3)?

Any suggestions for heat treatment too? The part will be a shell-type housing, needs to be strong and stiff.
 
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Good stuff.

So if I add some Iron to the mix, how should I cool in order to keep a homogeneous (as close as I can) mixture after hardening. I don't want to form a distinct two phase composite, as I suspect it will lead to crack formation.

What is it talking about here:
"The solubility of iron in the solid state is very low (~0.04%) and therefore, most of the iron present in aluminum over this amount appears as an intermetallic second phase in combination with aluminum and often other elements."
 
What kind of aluminum scraps are you using? If it's pure aluminum, you can add the components necessary to form a higher-strength alloy like 6061 or 7075. Then after casting, you can apply a heat treat like -T6 or -T651 to get the most stength you can out of it.

If its a mix of different aluminum alloys you don't know, well you'll basically be stuck with what you get...
 
It is most likely going to be 6061 heat treated aluminum scraps.

And how should the heat treatment go in order to get highest strength? I remember doing this in a lab at some point but I forgot it completely.
 
Solution heat treat at 990 F for adequate time to allow for thorough heating and then water quench. Precipitation hardening is done at 320 F for 18 hours and air cool, followed by 350 F for 8 hours and air cooling.

Its easy to find by googling 6061 heat treatment.
 

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