This is really cool metallurgy. They start with an alloy and deform it and because of elemental size mismatch they can cause the alloy to self assemble into nanoscale crystals with three different structures
As an aside, “super alloy” is not the best wording choice on the part of the author of this sciencealert article, superalloys are an established alloy family that follow a different design strategy and have a very different composition profile https://en.wikipedia.org/wiki/Superalloy
What aspect do you consider basic? I haven’t had a chance to read more than the abstract because of the paywall, but the really interesting thing here is the mechanically induced transformation that leads to a 3-phase nanocrystalline alloy. I haven’t understood the “fully coherent” part from just the abstract, but I think it’s a very novel report. It means they have three different crystal structures with seamless interfaces because all the atoms line up at where the crystals meet. To do that with three structures is remarkable. I’m not sure if it’s the first example, but I’m only aware of alloys with two coherent phases (some superalloys for example)
There’s some precedent for mechanical deformation to get nanocrystalline grain structure, and some precedent for mechanically induced phase transformations (see TrIP steels) but I consider both of those concepts pretty advanced
TrIP is probably the closest thing, but I’m not sure how widely known there are among the “metal forging” community? TrIP is usually targeting well known phase transformations to two-phase microstructures, here we have three nanostructured phases.
Finally high entropy alloys are absolutely not well understood, even if the idea of mixing a lot of elements and getting a disordered solution seems simple on its face.
> Tests showed the new alloy achieved a compressive yield strength of more than two gigapascals while retaining its ductility, meaning it bends without breaking.
This is sleight-of-hand.
For metals, the operative properties are usually ultimate tensile strength and tensile yield strength. Compressive strength is typically a non-factor for most engineering alloys; only concrete is judged by its compressive strength, and sometimes various engineering ceramics. (e.g. SiC, compressive strength = 3.9 GPa.)
About ten years ago, there were a lot of papers on amorphous metal alloys that had "extreme strength" -- compressive strengths in the 5-6 GPa range -- but tensile strength was not reported and very low. Some measure of ductility was also present, but it too was very low. Those amorphous alloys were classical brittle materials; more ceramic-like than metal-like. I fear the same is probably the case here, with the alloy potentially fracturing along crystal type grain boundaries.
Until they report actual tensile strength and elongation, don't believe the hype. High compressive strengths are not very useful.
I mean, it depends on the use case right? Modern tall buildings/skyscrapers with metal framing use metal pillars where high compressive strength is very useful.
Absolutely nobody is using an expensive novel alloy for 2GPa compressive strength. A 2GPa tensile strength, depending on various other factors such as corrosion resistance and thermal properties, could however be very interesting. (The strongest bulk steel alloys generally peak at ~3.6GPa tensile, which is approximately their theoretical maximum, but there are a lot of applications where steel simply can't be used. Nickel superalloys are typically 0.9 to 1.1GPa UTS.)
That's true, but it's still factor and if price comes down having that much compressive strength at your disposal could be an interesting choice for supertall skyscrapers.
2GPa isn't a super-high value for compressive strength. Regular tool steels can exceed it. Technical ceramics routinely exceed it. If you normalize to weight, various cement/concrete formulations can also surpass it.
Also, the price of a Ta-Hf-Zr-Nb-Ti alloy isn't especially elastic. Tantalum in particular is an unavoidably expensive element.
I'll grant that what would be exceptional is a metal with a >2GPa compressive strength, a >2GPa tensile strength, and decent damage tolerance and ductility. I don't think that this paper describes a material with that outstanding combination of properties, though -- it's much more likely to describe a simple brittle material.
Interestingly, the design of beams and the like (used for columns) still means tensile strength is the limiting factor, not compressive strength.
For compressive strength alone to matter, you’d essentially need a solid steel column - which is so prohibitively heavy, it would often end up collapsing under it’s own weight (in tensile failure, most likely) before it got up to a useful height.
Not only the initial strength is important but also the susceptiveness to crack growth during many years of stress. No idea how this structure would perform on this aspect.
Hm I just read an article here recently that was saying that Americans had an edge in jet turbine blades production over china because Americans figured out how to make single crystal jet turbines using this same method. I wonder what the difference is.
The Veritasium video on how jet engine turbine blades are "grown" in an aligned crystalline structure for enhanced material properties (e.g. thermal performance) is absolutely fascinating & well worth a watch:
The basics are pretty distributed, further work involved increasing lifespan at high temperatures, but also some work towards switching at least some turbine stages from separated blades into "blisks" - entire turbine stage is one crystal, including the hub.
I've heard it said that growing crystals in gravity is tricky... If we could do this in space, gravity free, we could get better crystals.
Is that correct? Pardon for asking a bit of a question to your comment. I don't know too much about growing crystals for things like jet engine blades.
I, too, heard this but in a different context: pharma growing pure crystals for analysis by x-ray diffraction. There was a discussion a while back whether these lab-grown crystals were truly contributing to ISS’s reason to exist or an excuse to keep the lab going.
As hard as ever. US and USSR and EU has this tech, China, India and others still don't. When USSR tech was sold left and right in 1990s, China could not replicate it, although they surely got the documentation back then. Even now they can't build a reliable gas generator from 70s and are stuck at 1960s level with R-25 MiG-21-style engine replicas. They still try and fail to build AL-31 analogs (1978, Su-27 engine).
This is an American-Pro forum, you will only get dislikes promoting the idea that USSR had any technology or morality matching or exceeding Western superiority ;)
Not sure if troll or misguided, but you know there are people still alive today that can talk about that moral superiority from experience, right? Just ask them, read their stories, etc. If this is how we're talking about that part of the world in that time-frame, I shudder to think how it'll be talked about when there aren't any more people from that period around. We kinda can see that with the neo- movements...
There's a long and distinguished history of thinking your enemies tech is better than it is. See wehraboos and tankies.
In all fairness though, if your enemies are just Afghan tribemen of Vietnamese farmers with an AK you don't have much of an excuse for losing. But even then you can can the moral high ground because you value life more than them.
Yes, it's all propaganda. But they are distinct tools (approaches?). It's fine to say your enemy has better equipment though, because that gives you an excuse for more R&D and gives you an excuse if you didn't win, why the win took longer, why the win was 'honourable' despite the win seeming inevitable by every conventional metric.
To be slightly more kind. I suppose you could argue this helps the peace afterwards.
If you say the beaten adversary was a worthy opponent, they can help keep their heads high. The Allies are now friends with Germany and Japan. I'm sure some reframing comes along with that.
So far as I know you could say Americans, but it is specifically Canada that most of the best engines are coming out of. Maybe Pratt and Whitney are using blades from USA, IDK, but anyone in jet aviation will be able to tell you the world would be fucked without Pratt.
"Steel is one of the classic alloy examples: mostly iron with a dash of carbon and other elements, making it much stronger and harder than iron on its own."
Statements like this had me confused for years about how steel is made. Steel is raw iron ore with some carbon removed. (Among other things) Pure iron isn't common in nature, it's usually found instead with too much carbon. That is, to have the properties we like in steel.
Main contaminate in iron ore is oxygen. The refining process is mostly removing stuff yes.
"Steel" is defined as carbon content between .02% and 2%. If the metal has less than that it's wrought iron. If it had more than that it's cast iron.
So steel is a range of carbon contents that gives particularly useful properties.
Historically the lower end of that was higher but with that addition of other alloys we have "low carbon steels" that behave like steel with very little carbon.
Presumably, some initial information was fed into the start of this reporting process. Multiple stages of this process had near-total incomprehension of the information yet performed full ingestion and reconstitution of it anyway, leading to this terminally-confused output.
The science daily article is just incorrect to call this a superalloy, which it is not. This is a high entropy refractory alloy (HfNbTaTiZr), superalloys are usually based on lighter metals and they usually have only one dominant element while HEAs have 4+ dominant elements
I guess I'm not impressed that some totally different alloy is stronger than steel. You can't change both method and alloy and claim that the method is better. Presumably the paper compared the same alloy using the normal and the new method, but this article omitted that essential information, and in so doing destroyed the result.
And as a personal exercise in intellectual humility, I cast my eyes over the supplementary materials (as those are free-to-the-public)… I’d recommend it:
I get a huge thrill out of looking at serious work outside my expertise. When I’m tempted to imagine the proposition is as simple as it seems from the headline (or the article, or the editor’s note, or the abstract), it excites me to remember just how deeply and carefully and thoroughly people think through things I barely understand.
Interesting for products where the resulting alloy just needs machining - lathing, milling, drilling etc, but more interesting will be what processes will be needed to weld or form such alloyed metals.
Existing high-strength alloys like MP35N are already extraordinarily difficult to machine. The "super alloy" in the story is said to have a compressive yield strength of 2 gigapascals, which is about MP35N tensile yield. Sounds like this "super alloy" isn't that much stronger than existing high strength alloys. It does have some fairly exotic alloying elements, tantalum, niobium and hafnium that probably don't come cheap. This super alloy will be used only in a very few applications.
I have not struck MP35N afaik before, and interesting to see its use in commercial settings, and even available as bolts and nuts. Certainly not fun to machine [1]
It's hard to know just how much stronger this new processing of the alloy is than other common high strength alloys, as they list compressive yield and not tensile yield strength ... that's if the person writing didn't get the two terms confused.
As a note, I use duckduckgo and smirked somewhat at its search assist results for the few efforts to find the compressive yield of Bisalloy 400 (something I've had to drill) - checking out the listed sources it was clear it had mistakenly used the tensile yield ...
As an illustration for the differences, I found a page [2] for 4140 alloy and similar yield strengths. 4140 is reasonably workable, drilling isn't the greatest amount of effort either before it's tempered and annealed.
>It's two times stronger than steel, three times stronger than aluminum, and twice as strong as the same alloy made in a conventional way.
Ugh. The most basic bitch metallurgy discussion possible.
Oh! It’s stronger than aluminum?! So is bronze, we’ve hard that for awhile! Is the new material lighter than aluminum while being stronger? Is it corrosion resistant? Is it machinable? Can you weld it? Does it oxidize? Does it lose all its strength under moderate heat? Does it temper, do you have to temper it? Is it inert? Can it extrude? Can it be formed into billet or just plate/bar? Does it shatter?
Oh but 2x stronger than <some steel> and 3x stronger than <some aluminum>… is that 2024 aluminum? 6061 common, 7075 aero? Is the steel cold roll or 600-series inconel?
This is an area where if you don’t know what you are talking about, STFU, because anything you say is just going to be embarrassing. This is a you don’t know what you don’t know topic.
As to “high entropy metals”, I’ve heard about this for awhile, I would expect it to be stupid low yield, stupid expensive, and hard to use. There is probably some grade-40 titanium ultra alloy that could make the same “strength” claims but no articles about it because it’s “cost prohibitive”.
… I count this as clickbait metallurgy. No thanks.
Indeed, such "high-entropy" alloys have been known for decades, but they are rarely used because of high cost.
There is only one new fact in this research, which is however very interesting.
By mechanical working of the alloy, its crystal structure has changed to a mixture of grains with 3 different crystal structures, instead of being composed of homogeneous grains, like most solid-solution metallic alloys.
This change of crystal structure induced by mechanical working has doubled the strength of an already strong alloy, which is the novel and interesting result of this research.
The reason why this could happen is that the alloy contains similar amounts of metals that normally have distinct crystal structures. In alloys with a dominant metal, the alloy tends to have the same crystal structure as that metal, but in this alloy none of the crystal structures is preferred, so the grains take one of them randomly, during deep mechanical deformation.
I want to live in a world where these (important!) points are surfaced without their presenter sounding like they were personally insulted, and are frustrated to have to bring them up.
"How dare this Science paper summary designed for mass consumption, not meet my personal standards of metallurgical detail! Don't they know I read them?!"
The paper: https://www.science.org/doi/10.1126/science.aec4995
As an aside, “super alloy” is not the best wording choice on the part of the author of this sciencealert article, superalloys are an established alloy family that follow a different design strategy and have a very different composition profile https://en.wikipedia.org/wiki/Superalloy
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