Metal Alloys of the Future?

High Entropy Alloys are a fascinating new area of research, so today we're going to try and make some HEA nanoparticles and explain what makes this research so exciting

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==== Timeline ====
0:00 Intro
0:38 Traditional Alloying
2:37 High Entropy Alloys
4:55 Fabrication
7:43 Results
8:30 Large Particles
9:31 Small Particles
11:07 Almost HEA but not quite
11:52 Cross-section
12:46 Success!

[jamesfrishkoff]

Really neat video. Garage electron microscopy is badass and your channel does a fantastic job popularizing concepts which are not widely known in the pop-science world. There are some places where I have to say this video could really be shored up technically, though. The big one is that, in my professional opinion (my postgrad work is all in HEA alloy design), the alloys produced here don't meet the usual working definitions for high entropy/multi-principal element alloys. The laser sputtering process you're using produces very non-equilibrium structures, because of the very fast cooling rate as well as intrinsic size effects. Most "true" HEAs produce a single solid solution phase, or a dual-phase structure, at equilibrium conditions. Or, in some newer definitions that have started to get used in the last 5 years or so, it just has to make a "simple", intermetallic free microstructure when subjected to a high temperature homogenization treatment followed by a water quench. There is a lot of debate still about whether the single-phase HEAs like CoCrFeMnNi are *really* single phase if you take them to equilibrium, but that's way off in the weeds. The other big point I'd correct is that "high entropy alloy" has turned out to be a sort of un-useful name for these alloys. The idea that the mixing entropy stabilizes the single-phase structure, which you talk about around 3:10-3:30, has fallen out of favor for metals. I believe for ceramics it is still considered useful. Very curious readers might try and sci-hub themselves a copy of Dan Miracle & Oleg Senkov's massive critical review article 5 years back: "A critical review of high entropy alloys and related concepts, " Acta Materialia 122 (2017).

[doctorpurple]

I read that some Japanese researchers made a high entropy alloy of all (or most? I can't remember) the platinum group metals. The super alloy was an extremely powerful catalyst for electrochemical redox reactions (they had hydrogen fuel cells in mind for this alloy). But more interesting than the material was the preparation process, they took all the constituent metals in dissolved salt form, (I think it was mostly nitrates?) And poured the mixture into a reducing solution while stirring. The metals reduced together and formed particles of the high entropy alloy. The process seems extremely easy to replicate but I am not going to buy all of the platinum group metals, I am not a billionaire lol. But I do wonder if the same chemical method would work for other metals?

[notnt]

I work in Aluminium research and the intermetallics in 3xxx and other alloys are very important in achieving the large deformations seen in deep drawing and other wrought aluminium processes. Yes, they can have some undesirable properties, but also some very important ones.

[Fireheart]

2:27 For those who don’t know, the sea monsters on old maps weren’t just for decoration; they were “actually” there and should be sailed around.

[newtonbomb]

A couple years back I brewed up a theoretical process for making a high entropy alloy in bulk with relatively uncomplicated procedures using powdered metals with appropriate phase transition temperatures in a welded steel canister (similar to techniques used by some to make damascus steel). Idk if it would work tbh, haven't had the shop space or correct tools to attempt since I dreamt it up, but I call theoretical product "chaos silver" in my head lol

[alirezanazarahari]

As someone who did a part of his M.Sc. on High entropy alloys (HEAs) and is currently doing his Ph.D. on it, I have some comments to mention that might be useful for you:
1- The choice of elements is one of the most important aspects of making high entropy alloys. The two most successful alloys (Cantor and Senkov) are made of elements with very similar valence electron number and atomic radius (and some other properties). This similarity prevents the formation of intermetallic phases inside the HEAs that gives them those exceptional properties. The elements you chose are highly unlikely to form HEAs due to this dissimilarity.
2- As other people mentioned, the conventional explanation for entropy in HEAs effect has proven not entirely correct. To be more specific, the free Gibbs energy for the formation of intermetallic phases is made of both entropy and enthalpy parts and while the addition of more than 5 elements can increase the entropy of the alloy, it will also increase the chance of formation of intermetallic phases due to lower enthalpy of formation. Thus, maybe trying the same method for a lower number of elements (4 or 5) would be more successful.
3- The production method plays a significant role in the quality of high entropy alloys. For example, many of the HEAs with refractory metals are highly sensitive to oxidation and can flake off very quickly (called pesting). Also, the lattice mismatch can cause stresses that can break down samples while cooling down. On the other hand, I have seen many metallic glasses with high entropy compositions. So it is doable.
Overall, excellent video and good luck!

[DanielSMatthews]

Sound like a good excuse to request a microgravity experiment on the ISS. Aslo what happens if you deposit your layers as thin as possible, even at the risk of incomplete coverage for each layer?

[markp]

The amount of detail in this video for people quite new to alloys is amazing. It's also quite clear.
Thank you.

[AlphaPhoenixChannel]

I've never played with depositing on glass, but when depositing on Gallium Nitride (Or AlGaAs) I remember an adhesion layer of titanium or nickel was always used. Even without annealing, I think those were just kinda stickier first layers. In this case do you really want the alloy to remain stuck during the process or not? - I know almost nothing about high entropy alloys and this is way cool.

I love the idea of using the laser to create extremely small melt and quench areas. Not sure what your sputtering setup looks like so this ranges from "impossible" to "really annoying", but I'm curious if you tried a very coarse digital alloying where you'd lay down repeated thinner layers 123123123 rather than 111222333. of course it looked like your laser was pretty effectively melting all of it at once, so maybe this would make no difference at all, but I figured it was worth a question! if most of the blobs you found adhered were in mechanically adjacent layers, maybe that might tell.

Cool stuff!

[barefootalien]

Whoa... that triangular phase-space diagram was eye-opening. There's _so much room_ to explore in the middle of that! Who knows what kind of superconductivity or other weird properties we might unlock, especially with very finely controlled deposition like what Alpha Phoenix did for his Ph.D.

[ryant.]

I’ve now worked on a couple projects involving this field. Something I found interesting is how different research groups define HEAs. I worked with a HEA that had the presence of an intermetallic which some definitions of HEA do not define as a HEA (not solid solution). Another alloy only had three of the five Cantor alloy elements in equal concentrations, making it a medium entropy alloy (Smix<1.5). Lastly, a refractory alloy with four elements could be argued to not be a HEA due to not having >5 elements. I found all three of these alloys fascinating, and all had very unique properties not found in conventional alloys. Complex concentrated alloys (CCAs) can be used to describe all three of those (as all HEAs are CCAs), but it has much less of a ring. Many pioneers in the field stick to the strict definition of HEAs, but I find does not ring as well to people outside the field. So I somewhat incorrectly refer to all as HEAs

[Mireaze]

The idea of hard ductile materials has officially broken my brain, I don't know if I'll ever be able to think again

[CuriousScientist]

The cooling rate is crucial in forming phases in these alloys, and I think that the way you produced those "HEAs" contributed to the unsuccessful attempt. Rapid cooling rates are not favourable for creating solid solutions. As you mentioned, arc melting is a better way, or induction melting is also a great way of making small lab-scale melts. Also, you picked very different metals that do not like to form a homogeneous solid solution. The FeNiCuAlZr alloy has a <1 mixing tendency[1] and its valence electron concentration (VEC) is 7.2 which is just in the region where HEAs like to form mixed (FCC-BCC) phases[2]. You may want to try NiCoFeCr or MoNbTaVW, these are very classical HEAs. Also nowadays, the "classical HEA definitions" such as the sluggish diffusion, the configurational entropy as stabilizing/driving force against intermetallic phase formation, the atomic mismatch, cocktail-effect...etc. are debated. There are actually attempts in the industry to make HEA-like materials, but the rules are really taken flexibly so the alloys actually become feasible and producible.

[1]:
[2]: doi.org/10.1063/1.3587228

[dj.thedestroyer]

As someone who tig welds 5052 aluminum, I have always wondered about the process of making it 6061 vs 5052. This helped me understand it a lot better, thank you!

[mitchellreep]

Seems similar to metallic glass (amorphous metal). Look into how they are manufactured. They are quickly chilled before the alloy has a chance to separate and recrystallize. Interesting video on metallic glass was posted by Tim on the Grand Illusions channel. Video is titled "Atomic Trampoline".

[mrs]

Soon as I saw your shop, instant sub, you're not just some person reading off studyings and tainting them with random opinions, you obviously practice something with metallurgy or material science. Very cool

[BRUXXUS]

Super fascinating stuff. I love all the interesting fields and topics you bring to our attention.
Also... a high energy ball mill sounds like it would be one of the most deafening pieces of equipment imaginable. haha

[andymouse]

Fascinating ! as always, do you have some new equipment in the lab that you haven't shown ? I don't think I've seen the sputter coater shown at the beginning, pretty good results I think for first try please keep up this great work...cheers.

[BoschPianoMusic]

Very interesting, and thank you for posting the HEA lectures because now I sure want to learn more about it!

[AmpedGaming]

I have to say, as a materials science student, I absolutely love your content. You are able to communicate these complex phenomena clearly and in a way that makes sense to people who haven't taken years of classes on the subject. Thank you for this quality content and keep up the good work!