Toughest Metallic Material on Earth?

sgt1372

sgt1372

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Looks interesting
Eventually they will make steel light Saber hybrid blades
Likely won't be available to us small taters however
 
Interesting, looks like it's also highly ductile, so perhaps wouldn't be ideal for edge retention. Looking forward to some expert weigh-ins!

It also appears that super high toughness is at 20K, and appears to rely on a phase transition at low temp, not exactly a practical temperature for EDC :cool: I read the abstract for the paper (in Science, so this one was deemed pretty impactful!), doesn't appear they have room temp measurements, but I'll download the full one when I have a chance and am at an IP with full access.
 
Docscoot said:
Interesting, looks like it's also highly ductile, so perhaps wouldn't be ideal for edge retention. Looking forward to some expert weigh-ins!
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Unfortunately not every tough steel or material out there is ideal for a blade
 
20 Kelvin is pretty cold ... too cold to worry about your knife. :)
 
bdmicarta said:
That's the definition of toughness.
For something to take an edge it needs strength, high yield strength.
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Ductility is certainly not the definition of toughness. Toughness is influenced by ductility (can take high strain) as well as strength (can take high stress), basically being able to take any beating and not break. Edge holding is about hardness and wear resistance, and often runs counter to toughness, ie ceramics have exceptional edge holding but low toughness.
 
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Larrin said:
We already could use steels with much higher toughness in knives, but we choose not to because the strength and wear resistance are too low.
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There’s the man! Could you clarify what you mean by the strength comment? All things being equal, doesn’t increasing strength (as in yield strength before deformation or fracture) lead to increased toughness as well?
 
Docscoot said:
There’s the man! Could you clarify what you mean by the strength comment? All things being equal, doesn’t increasing strength (as in yield strength before deformation or fracture) lead to increased toughness as well?
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In steel strength and ductility are at odds with each other, that's the nature of the material. There is a tradeoff- increase one property and it decreases the other. As we play with different alloys we can increase both properties a little bit, we can change the point where the tradeoff occurs, things like that, but there is still the tradeoff.
When strength increases, ductility decreases. Consider the Charpy test for toughness- having more strength makes it harder to deform the specimen but since ductility is decreased the specimen likely fractures sooner before it can absorb much energy.

Docscoot said:
Ductility is certainly not the definition of toughness. Toughness is influenced by ductility (can take high strain) as well as strength (can take high stress), basically being able to take any beating and not break. Edge holding is about hardness and wear resistance, and often runs counter to toughness, ie ceramics have exceptional edge holding but low toughness.
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Toughness is influenced by ductility and strength, but more by ductility. High strength usually reduces ductility, leads to less resistance to fracture, the specimen fractures before it can absorb much energy. I've seen lower strength specimens that bent the full amount because they had more ductility and absorbed a lot of energy so they have a high toughness score, they never fractured at all. The specimen stayed in one piece. You want the strongest material that will provide the ductility, but increasing the strength beyond that works against you.
 
bdmicarta said:
In steel strength and ductility are at odds with each other, that's the nature of the material. There is a tradeoff- increase one property and it decreases the other. As we play with different alloys we can increase both properties a little bit, we can change the point where the tradeoff occurs, things like that, but there is still the tradeoff.
When strength increases, ductility decreases. Consider the Charpy test for toughness- having more strength makes it harder to deform the specimen but since ductility is decreased the specimen likely fractures sooner before it can absorb much energy.


Toughness is influenced by ductility and strength, but more by ductility. High strength usually reduces ductility, leads to less resistance to fracture, the specimen fractures before it can absorb much energy. I've seen lower strength specimens that bent the full amount because they had more ductility and absorbed a lot of energy so they have a high toughness score, they never fractured at all. The specimen stayed in one piece. You want the strongest material that will provide the ductility, but increasing the strength beyond that works against you.
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Gotcha, your first post threw me off a bit but this all makes perfect sense to me! I was imagining a case with infinite strength and zero ductility, which technically would be infinitely tough as well (assume strength is in any sort of force load, not just tensile or compressive) but that just isn’t realistic as a metal I suppose, and the toughness we care a lot about is the fine edge being resistant to fracture which favors ductility.
 
There are several different definitions of toughness, one is the area under the tensile curve (total energy absorbed) which includes both strength and ductility. However, in most cases increasing strength leads to a smaller area under the curve so even by that definition being softer is usually better. At least within steel. Steel can be both stronger and more ductile than several other metals, for example.
 
Larrin said:
There are several different definitions of toughness, one is the area under the tensile curve (total energy absorbed) which includes both strength and ductility. However, in most cases increasing strength leads to a smaller area under the curve so even by that definition being softer is usually better. At least within steel. Steel can be both stronger and more ductile than several other metals, for example.
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Makes perfect sense. I work with polymers so my intuitions are a little off on metallurgy I suspect, I need to read some more of your online resources Larrin to remedy this!
 
sgt1372 said:
Just found this article which claims that the subject material is the "toughest [metalic] material on earth."

Anyone (including Larrin Larrin ) know anything about this and, if so, would it be a suitable material for making knife blades?

See: Say Hello To the Toughest Material On Earth

See also: Exceptional Fracture Toughness of CrCoNi Based Medium & High Entropy Alloys at 20 Kelvin
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interesting that they label it the strongest - in their own article they're saying 500 MPa - which is yes, 5x better than the best steels

however...
"In 2000, a multiwalled carbon nanotube was tested to have a tensile strength of 63 gigapascals"
from
en.wikipedia.org

Carbon nanotube - Wikipedia

en.wikipedia.org en.wikipedia.org

having said that - a composite of this stuff with CNT structures should be extremely interesting
 
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