3 ms·

I would guess not at all, from the composition.

by kergonath 2y ago

throwup238 2y ago
Why? The vast majority of alloys can be recycled by just melting them down and separating the elements.
- kergonath 2y ago
  The difficulty is separating the components. At least nickel and aluminium, and also iron and aluminium forms lots of intermetallics, they really don’t want to separate. Aluminium is notorious for this.
  - throwup238 2y ago
    But wouldn’t those intermetallics be extractable via pyro/hydrometallurgical processes or molten metal extraction, leaving mostly aluminum? The ratio of Al to the other components is over 10:1 so as long as the intermetallics can be separated, they don’t even need to be recycled, just slagged off (then sent to a more specialized recycler)
    - kergonath 2y ago
      That’s not possible for all of them (for reasons slightly different for each element so I am not going to write a wall of text; happy to provide more information if you want). If we assume that it is possible, then for Al92Ti2Fe2Co2Ni2 the waste would be Fe2Al6 + Ti2Al6 + Co2Al9 + Ni2Al6, so 27 of your 92 Al would be tied up in the waste. It’s a rough estimate and there are some caveats (I did not bother looking at ternary or quaternary intermetallics, or the miscibility of the binary ones, for example). A more realistic scenario would be to dilute that with pure Al to get some lower-grade Al alloy, rather than recycling it directly into pure Al or very specific, very complex alloy.
      - throwup238 2y ago
        > (for reasons slightly different for each element so I am not going to write a wall of text; happy to provide more information if you want) Yes, please :-)
        kergonath 2y ago
        Here’s an attempt :) # caveats This is just my feeling. I looked only at the binary phase diagrams, in reality there could be ternary or quaternary compounds. The article mentions that the alloy is an Al-rich matrix with the other elements in small crystals within it, with different structures and compositions. So the picture is quite complicated. To get a definitive answer, someone would need to do a proper study. I am not saying that it is impossible, just that it sounds very hard. That said, there could very well be other ways that escape me at the moment. I am happy to investigate further for a fee :) # Fe-Al, looking at the phase diagram here [1] There is a tiny temperature range (between around 650 and 660 °C) in which solid Al coexists with liquid Fe-Al. So in theory the mixture could be heated until it is all molten, then cooled slightly to precipitate Al, which could then be taken out, leaving Fe-enriched liquid. It seems feasible but impractical (temperature control would need to be absolutely spot on, and other elements would probably change the picture a bit). # Ti-Al, phase diagram here [2] There is a temperature range in which Al-rich liquid coexists with solid TiAl3. That solid could be removed, leaving a liquid that is mostly Al but still has significant Ti impurities. # Co-Al, phase diagram here [3] This one is similar to Ti-Al, except that Co is more soluble in liquid Al than Ti is, so there would be more Co impurities after taking out the Co2Al9 solid. The temperature range is also much narrower (650°C-700°C, eyeballing the diagram). # Ni-Al, phase diagram here [4] It’s worse than the others, because Ni is soluble even in solid Al. Also, melting is almost congruent, meaning that all the solid would melt at the same time, there is no coexistence of a liquid and a solid phase. This prevents from trapping the impurities in a solid to purify the liquid or the other way around. I don’t really see a way with this one. # magnetism Using magnetism was mentioned in the thread. I don’t think it would help. At high temperature, all these elements are paramagnetic. Some of them (Fe, Ni and Co) have a larger magnetic moment and would be more strongly attracted in a magnetic field than Al and Ti, but I don’t think it would be sufficient to really separate them (all of them are in minority compared to Al). And Al and Ti are not that different from a magnetic point of view and i don’t see them being separated by a magnetic field. # oxidation It is not inconceivable to inject oxygen to try to trap some elements in oxides that have typically much higher melting points than the metals, which would help with the narrow temperature ranges. These metals can form spinel compounds, at least TiFe2O4, NiFe2O4, and many more. One problem is that Al2O3 is also very stable (which is why it is very costly to get aluminium metal from aluminium ore. There are also aluminate compounds such as FeAl2O4. Figuring out which one is more stable and whether it could be feasible is quite a bit of work in itself. [1] https://www.researchgate.net/profile/Qingyou-Han/publication/225778007/figure/fig2/AS:393820391919622@1470905506653/The-iron-aluminum-phase-diagram.png https://www.researchgate.net/profile/Qingyou-Han/publication... [2] https://www.researchgate.net/publication/325471220/figure/fig1/AS:1086464163086390@1636044650678/a-Al-Ti-phase-diagram-3-b-Aluminum-rich-corner-of-the-Al-B-phase-diagram-6-c.jpg https://www.researchgate.net/publication/325471220/figure/fi... [3] https://www.mdpi.com/materials/materials-13-03152/article_deploy/html/images/materials-13-03152-g001.png https://www.mdpi.com/materials/materials-13-03152/article_de... [4] https://www.researchgate.net/profile/Matthew-Weeks-3/publication/258543820/figure/fig5/AS:347572364431362@1459879117526/The-Al-Ni-phase-diagram-showing-the-composition-range-of-aluminum-in-nickel-in-which.png https://www.researchgate.net/profile/Matthew-Weeks-3/publica...
  - SoftTalker 2y ago
    Naively I would think iron could be separated magnetically. Or is molten iron not attracted to a magnet?
    - pfdietz 2y ago
      Molten iron is not ferromagnetic. Even solid iron ceases to be ferromagnetic above the Curie temperature of 770 C.
- s0rce 2y ago
  Probably can't directly separate the elements in the melt here but I'm not an expert on melt processing/purification of aluminum. Certainly possible with other methods but might not be economical.
  - kergonath 2y ago
    We can have a look at phase diagrams for this. For example, for Fe-Al here: https://www.researchgate.net/profile/Qingyou-Han/publication/225778007/figure/fig2/AS:393820391919622@1470905506653/The-iron-aluminum-phase-diagram.png https://www.researchgate.net/profile/Qingyou-Han/publication... . This shows that Al with some Fe is in 2 phases when it is solid (pure Al on one side and FeAl3 on the other). However, above 660.452°C, there is only one liquid and Al and Fe cannot be separated. There is a tiny temperature range where there is a combination of liquid Al and solid FeAl3, between 655°C and 660.452°C, so completely impractical from an industrial point of view. That’s an example; it’s even worse with Al and Ni because even the solid is a mixture. I am less familiar with the Al-Co and Al-Ti phase diagrams, but looking at them Al-Co seems similar to Al-Ni and Al-Ti to Al-Fe. Multi-elements alloys would be a bit different but not too much: if everything is soluble in Al separately, then all of them at once are also soluble to some extent. In short, it might be possible to extract pure Al for recycling, but it does not seem to be easy and there would still be a lot of Al bound to the other metals in the waste.
    - HPsquared 2y ago
      Ah, so that's why "irony aluminium" scrap (that is aluminium with iron in it, like an aluminium casting with steel bolts) has such a drastically lower value than pure aluminium scrap.
  - pfdietz 2y ago
    They could probably be separated by distillation, but the temperature would be quite high. Alternately, maybe some element could be found that would preferentially dissolve aluminum (magnesium?) and that then could be separated, again perhaps by distillation. Al/Mg mixtures can melt as much as ~200 C cooler than pure Al.
creato 2y ago
This particular alloy is specifically designed to be melted and cooled as part of its manufacturing process. It seems like it would be the easiest to recycle: just melt it back down in a different 3d printer. Maybe grind it up first?
- detritus 2y ago
  If you somehow accumulate for re-processing solely this alloy, then sure. It's where it gets mixed up with other 'waste', that complicates things.
  - HPsquared 2y ago
    It's the same issue as plastics. But if the material becomes ubiquitous enough that it's worth building a special recycling stream, products would probably be built to facilitate recycling. Markings etc.

I would guess not at all, from the composition.

throwup238 2y ago

Why? The vast majority of alloys can be recycled by just melting them down and separating the elements.

kergonath 2y ago
The difficulty is separating the components. At least nickel and aluminium, and also iron and aluminium forms lots of intermetallics, they really don’t want to separate. Aluminium is notorious for this.
- throwup238 2y ago
  But wouldn’t those intermetallics be extractable via pyro/hydrometallurgical processes or molten metal extraction, leaving mostly aluminum? The ratio of Al to the other components is over 10:1 so as long as the intermetallics can be separated, they don’t even need to be recycled, just slagged off (then sent to a more specialized recycler)
  - kergonath 2y ago
    That’s not possible for all of them (for reasons slightly different for each element so I am not going to write a wall of text; happy to provide more information if you want). If we assume that it is possible, then for Al92Ti2Fe2Co2Ni2 the waste would be Fe2Al6 + Ti2Al6 + Co2Al9 + Ni2Al6, so 27 of your 92 Al would be tied up in the waste. It’s a rough estimate and there are some caveats (I did not bother looking at ternary or quaternary intermetallics, or the miscibility of the binary ones, for example). A more realistic scenario would be to dilute that with pure Al to get some lower-grade Al alloy, rather than recycling it directly into pure Al or very specific, very complex alloy.
    - throwup238 2y ago
      > (for reasons slightly different for each element so I am not going to write a wall of text; happy to provide more information if you want) Yes, please :-)
      - kergonath 2y ago
        Here’s an attempt :) # caveats This is just my feeling. I looked only at the binary phase diagrams, in reality there could be ternary or quaternary compounds. The article mentions that the alloy is an Al-rich matrix with the other elements in small crystals within it, with different structures and compositions. So the picture is quite complicated. To get a definitive answer, someone would need to do a proper study. I am not saying that it is impossible, just that it sounds very hard. That said, there could very well be other ways that escape me at the moment. I am happy to investigate further for a fee :) # Fe-Al, looking at the phase diagram here [1] There is a tiny temperature range (between around 650 and 660 °C) in which solid Al coexists with liquid Fe-Al. So in theory the mixture could be heated until it is all molten, then cooled slightly to precipitate Al, which could then be taken out, leaving Fe-enriched liquid. It seems feasible but impractical (temperature control would need to be absolutely spot on, and other elements would probably change the picture a bit). # Ti-Al, phase diagram here [2] There is a temperature range in which Al-rich liquid coexists with solid TiAl3. That solid could be removed, leaving a liquid that is mostly Al but still has significant Ti impurities. # Co-Al, phase diagram here [3] This one is similar to Ti-Al, except that Co is more soluble in liquid Al than Ti is, so there would be more Co impurities after taking out the Co2Al9 solid. The temperature range is also much narrower (650°C-700°C, eyeballing the diagram). # Ni-Al, phase diagram here [4] It’s worse than the others, because Ni is soluble even in solid Al. Also, melting is almost congruent, meaning that all the solid would melt at the same time, there is no coexistence of a liquid and a solid phase. This prevents from trapping the impurities in a solid to purify the liquid or the other way around. I don’t really see a way with this one. # magnetism Using magnetism was mentioned in the thread. I don’t think it would help. At high temperature, all these elements are paramagnetic. Some of them (Fe, Ni and Co) have a larger magnetic moment and would be more strongly attracted in a magnetic field than Al and Ti, but I don’t think it would be sufficient to really separate them (all of them are in minority compared to Al). And Al and Ti are not that different from a magnetic point of view and i don’t see them being separated by a magnetic field. # oxidation It is not inconceivable to inject oxygen to try to trap some elements in oxides that have typically much higher melting points than the metals, which would help with the narrow temperature ranges. These metals can form spinel compounds, at least TiFe2O4, NiFe2O4, and many more. One problem is that Al2O3 is also very stable (which is why it is very costly to get aluminium metal from aluminium ore. There are also aluminate compounds such as FeAl2O4. Figuring out which one is more stable and whether it could be feasible is quite a bit of work in itself. [1] https://www.researchgate.net/profile/Qingyou-Han/publication/225778007/figure/fig2/AS:393820391919622@1470905506653/The-iron-aluminum-phase-diagram.png https://www.researchgate.net/profile/Qingyou-Han/publication... [2] https://www.researchgate.net/publication/325471220/figure/fig1/AS:1086464163086390@1636044650678/a-Al-Ti-phase-diagram-3-b-Aluminum-rich-corner-of-the-Al-B-phase-diagram-6-c.jpg https://www.researchgate.net/publication/325471220/figure/fi... [3] https://www.mdpi.com/materials/materials-13-03152/article_deploy/html/images/materials-13-03152-g001.png https://www.mdpi.com/materials/materials-13-03152/article_de... [4] https://www.researchgate.net/profile/Matthew-Weeks-3/publication/258543820/figure/fig5/AS:347572364431362@1459879117526/The-Al-Ni-phase-diagram-showing-the-composition-range-of-aluminum-in-nickel-in-which.png https://www.researchgate.net/profile/Matthew-Weeks-3/publica...
- SoftTalker 2y ago
  Naively I would think iron could be separated magnetically. Or is molten iron not attracted to a magnet?
  - pfdietz 2y ago
    Molten iron is not ferromagnetic. Even solid iron ceases to be ferromagnetic above the Curie temperature of 770 C.
s0rce 2y ago
Probably can't directly separate the elements in the melt here but I'm not an expert on melt processing/purification of aluminum. Certainly possible with other methods but might not be economical.
- kergonath 2y ago
  We can have a look at phase diagrams for this. For example, for Fe-Al here: https://www.researchgate.net/profile/Qingyou-Han/publication/225778007/figure/fig2/AS:393820391919622@1470905506653/The-iron-aluminum-phase-diagram.png https://www.researchgate.net/profile/Qingyou-Han/publication... . This shows that Al with some Fe is in 2 phases when it is solid (pure Al on one side and FeAl3 on the other). However, above 660.452°C, there is only one liquid and Al and Fe cannot be separated. There is a tiny temperature range where there is a combination of liquid Al and solid FeAl3, between 655°C and 660.452°C, so completely impractical from an industrial point of view. That’s an example; it’s even worse with Al and Ni because even the solid is a mixture. I am less familiar with the Al-Co and Al-Ti phase diagrams, but looking at them Al-Co seems similar to Al-Ni and Al-Ti to Al-Fe. Multi-elements alloys would be a bit different but not too much: if everything is soluble in Al separately, then all of them at once are also soluble to some extent. In short, it might be possible to extract pure Al for recycling, but it does not seem to be easy and there would still be a lot of Al bound to the other metals in the waste.
  - HPsquared 2y ago
    Ah, so that's why "irony aluminium" scrap (that is aluminium with iron in it, like an aluminium casting with steel bolts) has such a drastically lower value than pure aluminium scrap.
- pfdietz 2y ago
  They could probably be separated by distillation, but the temperature would be quite high. Alternately, maybe some element could be found that would preferentially dissolve aluminum (magnesium?) and that then could be separated, again perhaps by distillation. Al/Mg mixtures can melt as much as ~200 C cooler than pure Al.

creato 2y ago

This particular alloy is specifically designed to be melted and cooled as part of its manufacturing process. It seems like it would be the easiest to recycle: just melt it back down in a different 3d printer. Maybe grind it up first?

detritus 2y ago
If you somehow accumulate for re-processing solely this alloy, then sure. It's where it gets mixed up with other 'waste', that complicates things.
- HPsquared 2y ago
  It's the same issue as plastics. But if the material becomes ubiquitous enough that it's worth building a special recycling stream, products would probably be built to facilitate recycling. Markings etc.