[HN Gopher] Additive manufacturing of an ultrastrong, deformable...
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Additive manufacturing of an ultrastrong, deformable Aluminum alloy
Author : PaulHoule
Score : 65 points
Date : 2024-08-02 17:09 UTC (1 days ago)
(HTM) web link (www.nature.com)
(TXT) w3m dump (www.nature.com)
| bloopernova wrote:
| In materials science, are alloys as seemingly complex as
| "Al92Ti2Fe2Co2Ni2" commonplace?
|
| How do we arrive at that kind of alloy? (If it was explained in
| the paper, I didn't understand it)
| marcosdumay wrote:
| What features exactly are you asking about on that "like"?
|
| The paper has links for other work with all kinds of
| similarity.
| bloopernova wrote:
| I rephrased it a little, I was wondering if other materials
| were as complex as that alloy appears to be, or if an alloy
| with that number of elements was used widely.
|
| Apologies for the poorly phrased comment.
| cwillu wrote:
| I'm not familiar with that format, but it's not rare for alloys
| to have half a dozen or more alloying elements.
| kergonath wrote:
| That notation is used sometimes in the literature on model
| alloys. This does not survive contact with engineering, where
| they tweak the formula to a hundredth of a percent.
| throwup238 wrote:
| Even with a precise formula that's only 20% of the work.
| With these superalloys the hard part is getting them to
| crystalize correctly so that all of the elements fit in the
| right spots in the matrix and stay there while it cools. A
| lot of them require seed crystals to form, which
| complicates the problem.
|
| That's why this laser sinterable superalloy is really
| interesting.
| kergonath wrote:
| Oh yes, of course. I only referred to the notation.
| Additive manufacturing adds tons of issues on top of the
| basic problem of getting the alloy to crystallise in the
| right form (which we've had to deal with for millennia).
|
| But the field is developing rapidly and we are already
| talking about complex concentrated superalloys. There are
| spectacular advances happening right now at every level
| of alloy development. The fact that additive
| manufacturing is far out of equilibrium is a problem for
| now, but this could become an advantage instead with the
| right alloys.
| tcpekin wrote:
| This is not a superalloy (i.e. turbine blade material),
| just a strong normal aluminum alloy that can be
| additively manufactured.
| kergonath wrote:
| It is not uncommon to have an alloy with 10 elements. Usually
| it is 1 to 3 main elements and some minor additives, and that's
| the case here.
|
| Steels can be very complex as well.
| quickthrowman wrote:
| If you just look at stainless steels, there are many alloys
| with 6+ elements, example below (904L is also know as Rolesor,
| used for steel Rolex watches)
|
| SS 904L: Nickel, Chromium, Carbon, Copper, Molybdenum,
| Manganese, Silicon, Iron
|
| Tool steel alloys (used for machine tools, hand tools, knives,
| etc) have iron, carbon, tungsten, chromium, vanadium and
| molybdenum.
|
| Carbon steel is the most basic alloy steel, it consists of iron
| and carbon (and impurities).
| ok123456 wrote:
| They're telling you the mole fraction of each element of the
| powder. It sums to 100.
| adrian_b wrote:
| As mentioned in the paper, this is a typical "medium-entropy"
| alloy.
|
| Pure metals are soft, because all their atoms have the same
| size, so the atom layers can slide over the others.
|
| Mixing metals with different sizes increases the strength,
| because now the atom layers are no longer smooth, but they have
| bumps, which prevent sliding.
|
| It can be shown that mixing many different kinds of atoms,
| taking from each about the same quantity, can provide very good
| mechanical properties, because the bumps in the atom layer will
| be frequent and they will have varied sizes and a random
| distribution, which will prevent any alignment between bumps,
| which could facilitate the sliding of the layers. Think about
| how to design an anti-sliding shoe sole. Random bumps of random
| size would give the best result.
|
| The so-called "high entropy" alloys contain at least 5
| different metals, with about the same quantity from each.
|
| However the alloys that contain almost equal quantities of each
| component are very expensive. In order to make a cheap alloy,
| one must have one or at most two components in a much larger
| quantity than the others, so that the abundant components can
| be chosen from the few cheap metals, e.g. iron, manganese or
| aluminum, while the other components, which are added in small
| quantities, can be chosen from expensive metals, like nickel
| and cobalt.
|
| For this reason, the better "high-entropy" alloys are normally
| replaced by the cheaper "medium-entropy" alloys, which use 5
| metals, like the "high-entropy", but which are used in quite
| different quantities, with larger quantities from the cheaper
| metals, if possible.
|
| The use of "high-entropy" alloys and "medium-entropy" alloys
| has begun only relatively recently. They are used to replace
| the cheaper classic alloys only when they offer a decisive
| advantage that can justify their higher cost.
|
| This case is one such example. From the classic aluminum
| alloys, some of the weaker alloys, like AlSi or AlMgSi can be
| easily 3D printed, but they have low strength. The classic
| high-strength aluminum alloys cannot be 3D printed. Therefore
| this was a clear case when a newer kind of alloy must be tried,
| if high strength is desired. They have experimented with
| certain kinds of medium-entropy aluminum alloys, to keep the
| cost acceptable (and also in this case the high content of
| aluminum keeps the density low and the conductivity high, which
| are frequently the reasons for choosing an aluminum alloy), and
| the results were good.
|
| Nevertheless, this alloy is likely to be several times more
| expensive than AlSi or AlMgSi, so it will be used only when its
| high strength is necessary.
| HPsquared wrote:
| I get the sense that stronger alloys are more "brittle" and
| harder to do things like welding, as they'll crack instead of
| yielding from all the thermal stresses. This is probably the
| same sort of thing with laser melting and 3D printing:
| solidification under high thermal gradients. It seems this
| material is not only high-strength but also ductile enough to
| gracefully handle the thermal stresses.
| benhoff wrote:
| It's more complex than that. A lot of the material
| properties depend on both the cooling and the tempering in
| aluminum alloys.
|
| The phase diagrams for these types of alloys look wild (you
| often want to achieve a certain material phase during
| cooling to "lock" in to get certain characteristics), and
| it can be difficult to ensure that the smaller metals
| participate during cooling. Also difficult to dissipate
| these slightly during tempering, typically to increase
| ductility.
|
| This is probably why 3d printing hasn't been done in
| earnest, you can't design something within tight tolerances
| with unknown material properties.
| HPsquared wrote:
| So you need to control the solidification process to plot
| a course through the phase diagram, spending the right
| amount of time in each region, and ending up in a good
| place. And this alloy has a phase diagram that is
| compatible with a method of 3d printing.
| jdietrich wrote:
| 3D printing of metals is being done in earnest, although
| the industry prefers the term Additive Manufacturing.
| Metal powder bed fusion is a stable, reliable process
| that is being successfully used commercially. It's
| generally confined to high-value applications that
| require extreme geometric complexity, but it can be
| invaluable in industries like aerospace, motorsport and
| medical. The range of viable materials is still somewhat
| limited, but covers a good range from titanium and
| aluminium alloys through to tool steels and heat-
| resistant super-alloys.
|
| https://www.renishaw.com/en/metal-3d-printing--32084
|
| https://www.trumpf.com/en_US/products/machines-
| systems/addit...
|
| https://www.carpenteradditive.com/powderrange-metal-
| powders
| tcpekin wrote:
| This is not a medium entropy alloy, it's a standard alloy in
| terms of the ratio of components, which forms medium entropy
| intermetallic precipitates which gives the alloy it's
| properties. Intermetallic MEA is an odd term I'm not really
| familiar with and would want to look into more, but is a
| little suspicious. Furthermore, while MEAs (3-4 equal primary
| components) and HEAs (5+ equal components) do have good
| mechanical properties, I'd be wary of the atomic size
| argument, last time I've been involved in it, that argument
| has increasingly been questioned, as the atomic size of the
| elements in question are generally pretty similar.
| borkt wrote:
| If you notice these alloy elements add up to 100. This alloy
| can be thought of more as 92% Al with 2% each of the other
| elements. Its a metal-metal matrix composite, primarily pure
| aluminum with localized, tiny grains of what would be thought
| of as a traditional alloy (various aluminum-titanium, aluminum-
| iron, etc. alloys)
| kkfx wrote:
| Mh, how recyclable is this alloy? Because with aluminum alloys
| that's the most important issue (beside the classic fatigue
| phenomenon).
| kergonath wrote:
| I would guess not at all, from the composition.
| throwup238 wrote:
| Why?
|
| The vast majority of alloys can be recycled by just melting
| them down and separating the elements.
| kergonath wrote:
| 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 wrote:
| 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 wrote:
| 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.
| s0rce wrote:
| 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 wrote:
| We can have a look at phase diagrams for this. For
| example, for Fe-Al here:
| 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 660.452degC, 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 655degC and 660.452degC, 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 wrote:
| 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.
| creato wrote:
| 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 wrote:
| 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 wrote:
| 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.
| roamerz wrote:
| I can't see why it couldn't be recycled? Though I think the
| most important issue would be its suitability to its intended
| use case. Recyclability would be somewhere down the list.
| kkfx wrote:
| Because most alloys are damn hard to separate. Aluminum is
| very abundant on earth and we can recycle it to the infinity
| only with energy, so together with glass is a key element of
| a circular economy, unfortunately pure aluminum is next to
| useless, and alloys are hard to recover, that's why I ask. We
| can recover some of them, avional for instance, but many
| others are damn hard.
| jstanley wrote:
| > with aluminum alloys that's the most important issue
|
| To you, maybe. Not to everyone. Different people have different
| priorities.
|
| If there was one single most important issue, we could all
| agree to use the single best alloy and be done with it.
| kkfx wrote:
| Metals, even abundant ones, are not infinite resources and
| recycle scrap metal tend to be much less energivore than
| mining new one, so aluminum per se it can be recycled ad
| infinitum, with just energy, like glass. They are VERY GOOD
| materials because of that. Oh, sure in practice it's not that
| easy because we almost never use pure aluminum, pure glass,
| but as long as the extra elements are very marginal and/or
| easy to separate there are not much issues. They can be
| called circular.
|
| Steel so far it's not because to make new steel out of scrap
| metal we need coke, there are various experiments to recover
| steel only adding energy but so far nothing on scale so while
| recyclable formally (and VERY recycled) it's not circular.
|
| Due to volumes and natural resource limits anything we can do
| ad infinitum is a godsend because we know if we are able to
| produce and recycle enough we will never be short of it.
| That's why it's definitively a general priority. We have
| started to understand that anything we do on scale we also
| must count how to dispose of it and how much resources we
| consume in the process, the era of abundance enough not to
| care is largely ended and the outcome is hard enough to learn
| the lesson.
| Dylan16807 wrote:
| Even if it's not easy to recycle this alloy, it will still
| be easy _enough_. It 's far from "the most important
| issue".
|
| And I give that answer while purposefully ignoring how much
| aluminum there is in the world.
| kkfx wrote:
| You seems to be very sure, but... I'm not much.
|
| Yes, aluminum is abundant, BUT we already have witnessed
| scarcity issues in the supply chain, mostly due to poor
| diversification combined with geopolitical issues, but
| anyway scarcity. Since smelting and scrapping aluminum
| it's roughly easy recyclability is important because it
| can be "domestic" easily, like the one of glass.
|
| Try to see the big picture, not the detail, meaning the
| complexity of current state of things and the fragility
| such complexity imply in a world heating toward a III
| worlds war.
| mensetmanusman wrote:
| Everything is recyclable with enough energy.
| blipvert wrote:
| If it's not transparent and strong enough to build a whale tank
| then I'm not interested.
| A_D_E_P_T wrote:
| Commonplace aluminum alloy 7068 is also "ultrastrong"
| (~710-750MPa, more than the 700MPa in the paper,) and ductile.
|
| WWII-vintage Japanese duralumin (Al-7075) is nearly as strong
| (~600MPa), and very ductile. It's also nearly 100 years old.
|
| I guess the innovation here is that they're making this alloy
| with additive manufacturing techniques? It's not _that_
| noteworthy, IMO. It would be jaw-dropping if it were a 1000MPa
| alloy -- that 's like the Holy Grail for aluminum -- but they're
| still far from that mark.
| RobotToaster wrote:
| >Additive manufacturing was performed by using a laser powder bed
| fusion (LPBF) instrument, SLM 125 HL metal 3D printer in Argon
| atmosphere with the oxygen level below 1000 PPM. Printing was
| conducted by utilizing a 400 W IPG fiber laser (l = 1070 nm) with
| a laser power of 200-300 W
|
| Sounds expensive.
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