Author Topic: What Are the Strongest Alloys?  (Read 30414 times)

Offline sanman

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What Are the Strongest Alloys?
« on: 02/05/2015 03:44 am »
What are the strongest alloys for building spacecraft? While we all know that carbon composites are generally lighter, they can't be used everywhere, and their strength is of course directional.

I remember reading in the past about how alloys from Titanium, Beryllium and Chromium were the best for aerospace, and how the Orion capsule is using even lighter aluminum-lithium alloys.

Here's a report about the development of a new alloy which is supposedly as light as aluminum and at least as strong than titanium:

http://www.spacedaily.com/reports/New_high_entropy_alloy_light_as_aluminum_as_strong_as_titanium_999.html

Quote
Researchers from North Carolina State University and Qatar University have developed a new "high-entropy" metal alloy that has a higher strength-to-weight ratio than any other existing metal material.
...
"The density is comparable to aluminum, but it is stronger than titanium alloys," says Dr. Carl Koch, Kobe Steel Distinguished Professor of Materials Science and Engineering at NC State and senior author of a paper on the work.

"It has a combination of high strength and low density that is, as far as we can tell, unmatched by any other metallic material. The strength-to-weight ratio is comparable to some ceramics, but we think it's tougher - less brittle - than ceramics."

Here's also an interesting article from The Economist talking about a new iron-aluminum-nickel alloy that is claimed to have comparable strength to titanium, but at a tenth the cost:

http://www.economist.com/news/science-and-technology/21642107-alloy-iron-and-aluminium-good-titanium-tenth

How much scope is there for further improvements in alloy properties, and what are the best candidates?

Offline Hanelyp

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Re: What Are the Strongest Alloys?
« Reply #1 on: 02/05/2015 04:17 am »
Strongest for what kind of loads?  At what temperature?  What other operating conditions?  Some alloys that deliver superior performance at modest temperature lose most of their strength before they get very warm.  Extremely hard high tensile materials can be brittle.  Carbon fiber is very strong, and retains strength at high temperatures, but burns if you get it hot in an oxygen atmosphere.

Offline CyclerPilot

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Re: What Are the Strongest Alloys?
« Reply #2 on: 02/05/2015 05:00 am »
Hanelyp has it right.  There are other factors to consider.  The primary property is strength to weight, but other properties can make our break its utility for a given application.
 
Aluminum lithium alloys work well because they combine good strength to weight, good toughness, and are relatively easy to process (weldable, machinable, etc.)

Titanium based alloys all suffer from being difficult/expensive to process.  They absorb oxygen at elevated temps, and become brittle.

The two you linked both seem to be sacrificing ductility for tensile strength, but there probably is some net benefit.  If they have a fatigue limit, they could have one advantage over aluminum alloys.

The cool thing about metallurgy is that an addition of just a few percent or a different heat treat can greatly change the properties of an alloy and fix a shortcoming.  When there is a large financial incentive, more materials research is done, and they hone in on some ideal alloys (see nickel superalloys as an example).

Offline john smith 19

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Re: What Are the Strongest Alloys?
« Reply #3 on: 02/05/2015 06:06 am »
Here's a report about the development of a new alloy which is supposedly as light as aluminum and at least as strong than titanium:

http://www.spacedaily.com/reports/New_high_entropy_alloy_light_as_aluminum_as_strong_as_titanium_999.html

Here's also an interesting article from The Economist talking about a new iron-aluminum-nickel alloy that is claimed to have comparable strength to titanium, but at a tenth the cost:

http://www.economist.com/news/science-and-technology/21642107-alloy-iron-and-aluminium-good-titanium-tenth

How much scope is there for further improvements in alloy properties, and what are the best candidates?
Actually between these 2 I'd say quite a lot. The second is more interesting than the first since it's the sort of notion any metallurgist could have had in say the last century (large scale Aluminum alloy use got going with airships) but it looks like this guy has made it work, and that  I suspect needed a lot of modelling and diagnostic tools that didn't exist for most of that time.

If the alloy can be welded like Steel, rather than Aluminum, with closer to Aluminum's density this could be a real winner, as well as opening up the field for other 2 main element alloys
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Offline Prober

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Re: What Are the Strongest Alloys?
« Reply #4 on: 02/05/2015 03:51 pm »
Hanelyp has it right.  There are other factors to consider.  The primary property is strength to weight, but other properties can make our break its utility for a given application.
 
Aluminum lithium alloys work well because they combine good strength to weight, good toughness, and are relatively easy to process (weldable, machinable, etc.)

Titanium based alloys all suffer from being difficult/expensive to process.  They absorb oxygen at elevated temps, and become brittle.

The two you linked both seem to be sacrificing ductility for tensile strength, but there probably is some net benefit.  If they have a fatigue limit, they could have one advantage over aluminum alloys.

The cool thing about metallurgy is that an addition of just a few percent or a different heat treat can greatly change the properties of an alloy and fix a shortcoming.  When there is a large financial incentive, more materials research is done, and they hone in on some ideal alloys (see nickel superalloys as an example).

see things are much different in Additive manufacturing as we control each and every layer for all parameters.  This applies to metals, plastics or composites, It's still a very much new science but loaded with a great deal of excitement. 
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Offline Fsci123

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Re: What Are the Strongest Alloys?
« Reply #5 on: 02/07/2015 04:03 pm »
Why aren't carbon composites suitable on spacecraft? It would seem that in a microgravity environment with little external acceleration(like on a space station module) they would be perfect for the job.

Offline Robotbeat

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Re: What Are the Strongest Alloys?
« Reply #6 on: 02/07/2015 04:19 pm »
They DO use carbon composites on spacecraft. It's just that aluminum is a lot easier to machine and overall is simpler to design and use.

BTW, an important property that aerospace designers optimize for is elastic modulus, i.e. stiffness. It is, however, inversely proportional to resilience (given the same strength) from a mathematical point of view. In other words, stiffer structures are more brittle. Personally, I think stiffness is over-rated (toughness is likewise under-rated), at least in aerospace, since it leads to operational and fabrication complexities. But of course, this strongly depends on your application.
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Offline cambrianera

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Re: What Are the Strongest Alloys?
« Reply #7 on: 02/07/2015 04:44 pm »
BTW, an important property that aerospace designers optimize for is elastic modulus, i.e. stiffness. It is, however, inversely proportional to resilience (given the same strength) from a mathematical point of view. In other words, stiffer structures are more brittle. Personally, I think stiffness is over-rated (toughness is likewise under-rated), at least in aerospace, since it leads to operational and fabrication complexities. But of course, this strongly depends on your application.
No, stiffness and resilience are only loosely related.
Stiffness is the reaction of material to external forces, resilience is the capacity of material to absorb and dissipate great amount of energy before breaking
The complementary (inverse) of stiffness is flexibility
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Offline Robotbeat

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Re: What Are the Strongest Alloys?
« Reply #8 on: 02/07/2015 05:40 pm »
BTW, an important property that aerospace designers optimize for is elastic modulus, i.e. stiffness. It is, however, inversely proportional to resilience (given the same strength) from a mathematical point of view. In other words, stiffer structures are more brittle. Personally, I think stiffness is over-rated (toughness is likewise under-rated), at least in aerospace, since it leads to operational and fabrication complexities. But of course, this strongly depends on your application.
No, stiffness and resilience are only loosely related.
Stiffness is the reaction of material to external forces, resilience is the capacity of material to absorb and dissipate great amount of energy before breaking
The complementary (inverse) of stiffness is flexibility
Oh, I'm quite right, I assure you! Check it for yourself. (It's kind of interesting, actually, though really pretty simple.)

You are right that resilience is the capacity of a material to absorb and dissipate energy before breaking (or actually, in the case of resilience, it's /yielding/, but for toughness it's breaking). But this is, mathematically, inversely proportional to stiffness for the same strength. See here:
http://en.wikipedia.org/wiki/Resilience

U is resilience, E is Young's modulus. (Sigma is stress, and Sigmay is the stress at yield, i.e. the yield strength.) Very clearly, they are inversely proportional.

The reason for this is simple. Stiffness is the slope of the stress vs strain curve (especially in the elastic region). Resilience is the area under the stress vs strain curve in the elastic region, and yield strength is the limit of elastic strain.

To relate this to energy absorption, consider that energy is force times distance. Another way of defining elastic modulus (i.e. stiffness or Young's Modulus) is how much strain it takes to reach yield strength (the limit of the linear region). If it takes more strain, then the material has less stiffness. Strain is proportional to the distance that the material is deforming, thus to find the energy absorbed (per unit volume), you're just finding the area of that triangle, i.e. the maximum strain (before yield) times the yield strength (i.e. maximum stress before yield). So, you get the equation above.

tl;dr: Yield strength is height of the triangle (whose area is defined as resilience), elastic modulus is the slope. If the height of the triangle is the same, then a greater slope will mean a smaller area triangle.
« Last Edit: 02/07/2015 05:53 pm by Robotbeat »
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Offline Robotbeat

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Re: What Are the Strongest Alloys?
« Reply #9 on: 02/07/2015 05:46 pm »
Note that I'm almost always careful to research stuff before I post a claim (and I word it very carefully) because on the Internet I KNOW someone will try to correct me if they think I'm wrong. :)
« Last Edit: 02/07/2015 05:48 pm by Robotbeat »
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Offline cambrianera

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Re: What Are the Strongest Alloys?
« Reply #10 on: 02/07/2015 06:08 pm »
Unfortunately you are still wrong.
The formula you show is valid only for the linear part of the stress-strain curve; from the Wikipedia article:
The modulus of resilience is defined as the maximum energy that can be absorbed per unit volume without creating a permanent distortion. It can be calculated by integrating the stress-strain curve from zero to the elastic limit.
Integrating the linear part you get that formula.
But true resilient material can be recognized by the elastoplastic stress-strain curve (slope then a constant stress deformation) and here the formula has no validity.
I stress, stiffness and resilience are only loosely related.
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Offline cambrianera

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Re: What Are the Strongest Alloys?
« Reply #11 on: 02/07/2015 06:46 pm »
Food for thought: which material is stiffer, and which is more resilient?
Black curve or red curve?
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Offline Robotbeat

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Re: What Are the Strongest Alloys?
« Reply #12 on: 02/07/2015 07:02 pm »
Trick question. The red curve isn't linear, you just added it. :) It doesn't obey Hooke's Law, so we can't talk about resilience in the textbook sense. But if we were to force the conversation, you'd have to use a much lower yield strength for the red curve since it loses linearity much sooner than the black curve.

Also, the area shaded under the curve in your picture is toughness, not resilience.

A nice "ah, you're right! I was mistaken. That is kind of interesting." would've sufficed. :)

How are you even arguing about this, by the way? It's literally basic textbook material science stuff.
« Last Edit: 02/07/2015 07:03 pm by Robotbeat »
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Offline Lee Jay

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Re: What Are the Strongest Alloys?
« Reply #13 on: 02/07/2015 07:04 pm »
You two are talking past each other.  Resilience is about the linear portion of the stress-strain curve (resistance to yielding or plastic deformation, if you will).  After that, you're talking about ductility, malleability, and more generally plasticity.  Toughness is more of a resistance to crack growth once a crack has already formed.  All of these are relevant to different situations.

Offline Robotbeat

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Re: What Are the Strongest Alloys?
« Reply #14 on: 02/07/2015 07:11 pm »
Unfortunately you are still wrong.
The formula you show is valid only for the linear part of the stress-strain curve; from the Wikipedia article:
The modulus of resilience is defined as the maximum energy that can be absorbed per unit volume without creating a permanent distortion. It can be calculated by integrating the stress-strain curve from zero to the elastic limit.
Integrating the linear part you get that formula.
But true resilient material can be recognized by the elastoplastic stress-strain curve (slope then a constant stress deformation) and here the formula has no validity.
Nope! That's toughness, not resilience. Either use the industry standard, textbook definitions or don't go correcting people who do. By standard definitions, I'm clearly right and you're clearly wrong (in your contradiction). No shame in that, by the way.


Quote
I stress, stiffness and resilience are only loosely related.
Except they aren't "loosely related." Elastic modulus (i.e. stiffness) and resilience are inversely proportional, as any material science textbook would show you. There's no "loosely" in there, it flows directly from the definitions. Good pun, by the way! :))
« Last Edit: 02/07/2015 07:15 pm by Robotbeat »
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Offline cambrianera

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Re: What Are the Strongest Alloys?
« Reply #15 on: 02/07/2015 08:01 pm »
Unfortunately you are still wrong.
The formula you show is valid only for the linear part of the stress-strain curve; from the Wikipedia article:
The modulus of resilience is defined as the maximum energy that can be absorbed per unit volume without creating a permanent distortion. It can be calculated by integrating the stress-strain curve from zero to the elastic limit.
Integrating the linear part you get that formula.
But true resilient material can be recognized by the elastoplastic stress-strain curve (slope then a constant stress deformation) and here the formula has no validity.
Nope! That's toughness, not resilience. Either use the industry standard, textbook definitions or don't go correcting people who do. By standard definitions, I'm clearly right and you're clearly wrong (in your contradiction). No shame in that, by the way.


Quote
I stress, stiffness and resilience are only loosely related.
Except they aren't "loosely related." Elastic modulus (i.e. stiffness) and resilience are inversely proportional, as any material science textbook would show you. There's no "loosely" in there, it flows directly from the definitions. Good pun, by the way! :))

Ok, you are right on that, I stumbled badly upon a nice "false friend", no way to turn  it otherwise.
Nevertheless, you mix the terms wildly in your original post:
BTW, an important property that aerospace designers optimize for is elastic modulus, i.e. stiffness. It is, however, inversely proportional to resilience (given the same strength) from a mathematical point of view. In other words, stiffer structures are more brittle. Personally, I think stiffness is over-rated (toughness is likewise under-rated), at least in aerospace, since it leads to operational and fabrication complexities. But of course, this strongly depends on your application.
(bold mine)
And in this case, stiffness and brittleness/toughness are loosely related.
Oh to be young again. . .

Offline Robotbeat

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Re: What Are the Strongest Alloys?
« Reply #16 on: 02/07/2015 08:21 pm »
I still stand behind that statement, too. It's not "wrong," in the strict sense and some of it is subjective (ie my opinion about what is under- or over-rated). Toughness /is/ important and tends to be inversely proportional to stiffness, although not in the strict way that resilience is (although of course toughness includes resilience).

Anyway, strength is itself quite important to toughness and resilience. But it is also correlated with elastic modulus (though of course not in the strict sense).
« Last Edit: 02/07/2015 08:22 pm by Robotbeat »
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Offline sanman

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Re: What Are the Strongest Alloys?
« Reply #17 on: 02/19/2015 12:19 pm »
A company called Modumetal has come out with a new nano-laminated metal process which apparently increases strength tenfold and can also be used to increase corrosion resistance:

http://www.technologyreview.com/news/534796/nano-manufacturing-makes-steel-10-times-stronger/

Hmm, I wonder if this process is compatible with 3D printing?

Maybe the increased corrosion resistance could be useful for an RD-180 style of closed-cycle engine.

Offline john smith 19

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Re: What Are the Strongest Alloys?
« Reply #18 on: 02/19/2015 01:57 pm »
A company called Modumetal has come out with a new nano-laminated metal process which apparently increases strength tenfold and can also be used to increase corrosion resistance:

http://www.technologyreview.com/news/534796/nano-manufacturing-makes-steel-10-times-stronger/

Hmm, I wonder if this process is compatible with 3D printing?

Maybe the increased corrosion resistance could be useful for an RD-180 style of closed-cycle engine.
Not really. It's an electroforming method to mfg large ingots by varying the voltage in the bath. IIRC that varies what element plates out, giving something akin to a Samurai sword (layers of high carbon steel folded over with layers of low carbon steel) to give a very strong, but quite expensive article.

As with all such developments you have zero pedigree in terms of down stream processes you can use or life expectancy estimates. It should be very good, but until they make stuff out of it and put them in oil fields (there partner is an oil company) who knows?
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Offline sanman

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Re: What Are the Strongest Alloys?
« Reply #19 on: 02/19/2015 02:18 pm »
I thought electroforming is already the method of choice for fabricating regenerative cooling channels.

The reason why I mentioned 3D printing, is because this technique of varying the voltage as you go could then be used to manipulate the material properties on the small scale, across the printing process.

There has already been research into electroforming as a 3d printing technique, using lasers to thermally catalyze where the deposition occurs.

Offline Stormbringer

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Re: What Are the Strongest Alloys?
« Reply #20 on: 05/13/2015 06:07 am »
it may not be the strongest but this is cool stuff:

http://phys.org/news/2015-05-metal-composite-literally-boat.html
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Offline john smith 19

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Re: What Are the Strongest Alloys?
« Reply #21 on: 05/13/2015 03:44 pm »
I thought electroforming is already the method of choice for fabricating regenerative cooling channels.
It is but historically it's been applied to making finished components. What they seem to be targeting is more a "semi finished" material. IE it's a blog of the stuff you can machine, press or (maybe) weld into your finished part.
Quote
The reason why I mentioned 3D printing, is because this technique of varying the voltage as you go could then be used to manipulate the material properties on the small scale, across the printing process.
AFAIK No 3D printer uses this, although the recent work by a team using controlled exposure to Oxygen to radically accelerate the process is, at an electron transport level, manipulating charge.
Quote
There has already been research into electroforming as a 3d printing technique, using lasers to thermally catalyze where the deposition occurs.
This is interesting to me. I was aware that people had used lasers to catalyze etching (especially of semiconductors) to create high aspect ratio holes.
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Offline john smith 19

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Re: What Are the Strongest Alloys?
« Reply #22 on: 05/13/2015 03:48 pm »
it may not be the strongest but this is cool stuff:

http://phys.org/news/2015-05-metal-composite-literally-boat.html
Yes it's clever but Magnesium alloys are not especially strong (they are very light). They have some history in some of the early rocket stages were built with them. In the 60's NASA even looked at them for LH2 storage on stages (just about the toughest challenge possible)
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline wizzzard3

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Re: What Are the Strongest Alloys?
« Reply #23 on: 05/16/2015 06:32 am »
http://www.flashbainite.com/
for maximum strength steel
« Last Edit: 05/16/2015 06:32 am by wizzzard3 »

Offline MP99

Re: What Are the Strongest Alloys?
« Reply #24 on: 05/16/2015 07:36 am »


The cool thing about metallurgy is that an addition of just a few percent or a different heat treat can greatly change the properties of an alloy and fix a shortcoming.

(Sorry, replying to a post from a while ago.)

If heat treatment is important, how is that affected when materials are welded?

Cheers, Martin

Offline john smith 19

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Re: What Are the Strongest Alloys?
« Reply #25 on: 05/16/2015 07:53 am »
If heat treatment is important, how is that affected when materials are welded?

Simply put, badly.   :(

An exception is the use of Friction Stir Welding, where the metal is not actually melted, otherwise you need to keep the Heat Affect Zone as narrow as possible, where laser (pioneered by Airbus) and electron beam welding have been popular.


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Offline R7

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Re: What Are the Strongest Alloys?
« Reply #26 on: 05/16/2015 08:04 am »
If heat treatment is important, how is that affected when materials are welded?

Pretty much always adversely, welds have poorer strength than unaffected material. Some alloys benefit from post-weld heat treatment but AFAIK it is more about removing stresses, does not return original material strength but ensures that the weld doesn't suddenly crack.

Some methods to address the weld strength problem;

- Have thicker material at weld seams than elsewhere in the object.

- heat treat the entire object after it is welded.

- friction stir welding, FSW.

FSW produces welds of near original strength because it does not rise the material temperature as much as traditional arc welding.

Oh js19 beat me to it, hitting post anyway...  :)
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Offline R7

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Re: What Are the Strongest Alloys?
« Reply #27 on: 05/16/2015 08:29 am »
This post contains an important lesson;

I'm thinking if there are remnants of neutron stars in your back yard, you iz a lucky ducky!

http://www.sciencedaily.com/releases/2009/05/090506110202.htm

In the article;

Quote
Squeezed together by gravitational force, the crust can withstand a breaking strain 10 billion times the pressure it would take to snap steel.

Oh wow, 10 billion times the strength of steel, this material would be wicked, no?

But elsewhere in the article;

Quote
The only things more dense are black holes, as a teaspoonful of neutron star matter would weigh about 100 million tons.

Lets investigate the densities;

Steel: around 7800kg/m3

Neutron star: 100,000,000,000kg/0.000,005m3 = 2x1016kg/m3

It turns out neutron star stuff is about 2.6 trillion times denser than steel. Unfortunate corollary is that the specific strength of neutron star stuff is less than half percent of steel's.

Not a good material for rocketry at all. Even as ballast it would be dubious due to unnaturally high point load it would cause.

High specific strength is what is sought after, not just absolute strength.
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Offline john smith 19

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Re: What Are the Strongest Alloys?
« Reply #28 on: 05/16/2015 05:16 pm »
High strength  is what is sought after, not just absolute strength.
Excellent point.

This is a very important factor for flight. It's why Magnesium (poor absolute strength) is good (and was used on some early US rocket stages, usually with storable propellants). The lightness counteracts the weakness. As always in design it was good enough to get the job done, which is what counts.

But it's ability to burn quite well has always made rocket engineers nervous. Interestingly in similar test Aluminum does not work out much better in LOX, the re forming oxide layer seems to keep people happy to use it.

BTW on welding heat treated alloys we probably should mention diffusion bonding, another non melting process. Works great with Titanium, as the oxide dissolves in the metal. Sadly that does not work with Aluminum, although Aluminum DB does seem to have been extensively researched I can't find anyone who uses it. Car radiators seem to use vacuum brazing with an intermediate layer instead. :(
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Offline Stormbringer

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Re: What Are the Strongest Alloys?
« Reply #29 on: 05/16/2015 08:21 pm »
There are some next to fantasy prospects that could be possible in the future: Atoms made with substitutes for the regular protons and neutrons and even electrons. Because these would be tiny compared to normal atoms (as much as 2000 times smaller) the bonding strength would be exponentially greater than the electronic and nuclear bonding strength of regular matter.
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Offline QuantumG

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Re: What Are the Strongest Alloys?
« Reply #30 on: 05/16/2015 10:37 pm »
There are some next to fantasy prospects that could be possible in the future: Atoms made with substitutes for the regular protons and neutrons and even electrons. Because these would be tiny compared to normal atoms (as much as 2000 times smaller) the bonding strength would be exponentially greater than the electronic and nuclear bonding strength of regular matter.

Have you priced those lately? I'm not made of money!
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Offline R7

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Re: What Are the Strongest Alloys?
« Reply #31 on: 05/17/2015 06:22 am »
Referring to my previous post; what would be the density of stuff made out of these brave new mini-atoms?
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Offline sanman

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Re: What Are the Strongest Alloys?
« Reply #32 on: 05/17/2015 10:20 pm »
Neutronium is pretty dense - very heavily used by all races in the Star Trek universe

http://en.memory-alpha.org/wiki/Neutronium

Not sure how good it would work in the real world.

But metallic hydrogen is speculated to be very lightweight

http://en.wikipedia.org/wiki/Metallic_hydrogen

Offline Stormbringer

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Re: What Are the Strongest Alloys?
« Reply #33 on: 05/17/2015 10:35 pm »
Referring to my previous post; what would be the density of stuff made out of these brave new mini-atoms?
Yeah. In three ways these would be more dense than normal matter. First, the nucleons would be closer together. Secondly, the atoms would be closer together. Finally, the electronic shells and bonds would be smaller. The exact figures would depend on which particle or topological defect was used to substitute for the regular nuclear components and electrons. The ultimate example would be substituting with monopoles:

Quote
The smallest magatoms have diameters of 3E-19 m, 300 million times smaller than an atom of conventional matter. As a typical magatom is 10,000 times heavier than a typical conventional atom, magmatter’s typical density is 1E33 kg/m3. Since force is energy per unit distance, the force needed to break a magchemical bond is larger than that needed to break an electronic chemical bond by a factor of the energy scaling (300 GeV / 13.7 eV) divided by the length scaling, or 7 million trillion (7E18). The strength of a material is usually defined as the force per unit area required to make the material fail. Since each magchemical bond can withstand 7E18 times greater force, and there are (300 million)2 times more bonds per unit area, the strength of magmatter is about 8E35 times greater than that of its normal matter equivalent.

From:  http://www.orionsarm.com/eg-article/48630634d2591

A Scifi site but when it comes to monopoles they use peer reviewed sources for their science to the largest extent possible. Their monopole matter stuff is heavy on peer reviewed sources (at least six papers at one point. )The handwavium comes from other aspects of the site.
« Last Edit: 05/17/2015 10:48 pm by Stormbringer »
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Offline Robotbeat

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Re: What Are the Strongest Alloys?
« Reply #34 on: 05/17/2015 10:54 pm »
High strength  is what is sought after, not just absolute strength.
Excellent point.

This is a very important factor for flight. It's why Magnesium (poor absolute strength) is good (and was used on some early US rocket stages, usually with storable propellants). The lightness counteracts the weakness. As always in design it was good enough to get the job done, which is what counts.

But it's ability to burn quite well has always made rocket engineers nervous. Interestingly in similar test Aluminum does not work out much better in LOX, the re forming oxide layer seems to keep people happy to use it.

BTW on welding heat treated alloys we probably should mention diffusion bonding, another non melting process. Works great with Titanium, as the oxide dissolves in the metal. Sadly that does not work with Aluminum, although Aluminum DB does seem to have been extensively researched I can't find anyone who uses it. Car radiators seem to use vacuum brazing with an intermediate layer instead. :(
The figure of merit you are looking for is actually specific strength, which is strength divided by density. On this figure, the best magnesium alloys are about the same as the best aluminum ones.

But there is one aspect where magnesium is better: Buckling. For a beam that is compressed, you want to make the beam as wide as you can to resist buckling (say, a hollow tube). But if you make it too wide (and thus thinner walled), it buckles in another mode. You can get around this self-buckling by adding fine structure, but that's expensive and can be complicated. However, if you use a material that has the same specific strength (and specific modulus) but lower density, then you can get better buckling resistance without having to add complex structure. You can easily cast the thing you're trying to make, which is much faster and cheaper than using a really fancy multi-axis CNC machine or 3D printing (which is slow and only feasible for smallish parts, plus can sometimes suffer a slight knock-down in material properties) or needing to weld together parts (which can also add weak points). So magnesium is still a fantastic and even superior metal to use for certain applications.
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Offline Stormbringer

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Re: What Are the Strongest Alloys?
« Reply #35 on: 05/17/2015 10:56 pm »
I would also guess that monopole matter would have no unstable elements or isotopes in it's periodic table. E.G; elements above Monopole Bismuth would be completely stable. Monopole matter decay uses a different process than w bosons or meson mediated decay. I think it would be mediated by certain species of monopole or by mono-antiparticle annihilation.
« Last Edit: 05/17/2015 10:57 pm by Stormbringer »
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Offline john smith 19

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Re: What Are the Strongest Alloys?
« Reply #36 on: 05/19/2015 12:02 am »
I would also guess that monopole matter would have no unstable elements or isotopes in it's periodic table. E.G; elements above Monopole Bismuth would be completely stable. Monopole matter decay uses a different process than w bosons or meson mediated decay. I think it would be mediated by certain species of monopole or by mono-antiparticle annihilation.
But has anyone seen a monopole in the wild yet?
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Offline KelvinZero

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Re: What Are the Strongest Alloys?
« Reply #37 on: 05/19/2015 01:04 am »
But has anyone seen a monopole in the wild yet?
On the wacky side, I heard somewhere that if you could ever pull quarks apart (eg the quark and antiquark of a meson?) the energy put in would be so great as to create new particles in the bridge so they would remain connected and the force would not drop regardless of distance.

This is the closest I could find to a reference:
http://www.scienceforums.net/topic/62746-why-cant-you-isolate-a-quark/

Offline Stormbringer

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Re: What Are the Strongest Alloys?
« Reply #38 on: 05/20/2015 07:43 am »
I would also guess that monopole matter would have no unstable elements or isotopes in it's periodic table. E.G; elements above Monopole Bismuth would be completely stable. Monopole matter decay uses a different process than w bosons or meson mediated decay. I think it would be mediated by certain species of monopole or by mono-antiparticle annihilation.
But has anyone seen a monopole in the wild yet?
we are getting closer. they have em down to quantum vacuum level now. There was an article a couple of weeks back saying that quantum mechanical monopoles had been found and that this will help establish the parameters for searching for the cosmic ones.
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Offline Stormbringer

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Re: What Are the Strongest Alloys?
« Reply #39 on: 06/29/2018 05:28 pm »
monopoles are real? or is this just another example of emergent monopole like behavior?

https://phys.org/news/2018-06-quantum-gas-reveals-path-bending-monopole.html

If it is yet another emergent monopole the cosmos is getting crowded with them...
This would be like the third one I have read about that appears under different circumstances than the first two examples.
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Offline john smith 19

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Re: What Are the Strongest Alloys?
« Reply #40 on: 06/29/2018 06:55 pm »
monopoles are real? or is this just another example of emergent monopole like behavior?

https://phys.org/news/2018-06-quantum-gas-reveals-path-bending-monopole.html

If it is yet another emergent monopole the cosmos is getting crowded with them...
This would be like the third one I have read about that appears under different circumstances than the first two examples.
It's not clear.  Something that looks like like a Yang monopole seems to have been demonstrated.
Wheather it's an actual single (albeit very small) object, or a cluster, is not clear.

On the upside this shifts the probabilities of physical models that accept monopoles against models that don't allow them to exist.

That's good from a wider physics perspective. Might have implications for EM drives etc.
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Offline Stormbringer

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Re: What Are the Strongest Alloys?
« Reply #41 on: 06/29/2018 10:29 pm »
yes it does not appear clear to me either. it could be emergent behavior like the older discoveries but the article makes that seem ambiguous because though several particles and external energy inputs are involved and thus the structure for an emergent effect is possible the article then goes on to talk about spatial effects or measurements that agree with yang monopole predictions and so on but that clearly (to them) diverge from standard model predictions so I am confused. I was hoping someone with more expertise could look at it and provide a more informed evaluation than me.

I have read that direct detection of monopole particles would require a detector the mass of Jupiter if actual monopoles even exist.
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