
An alloy of iron and aluminium is as good as titanium, at a tenth of the cost - RachelF
http://www.economist.com/news/science-and-technology/21642107-alloy-iron-and-aluminium-good-titanium-tenth
======
damoncali
Cool, but I wonder about stiffness. When I was an aero engineer, we tended to
use aluminum because most of our designs were limited by stiffness, not
strength. Since aluminum is lighter than either steel or titanium, you can
take advantage of geometry (which greatly impacts stiffness) without
sacrificing weight. Strength was only rarely the bottleneck. Interestingly,
the stiffness to weight ratio of aluminum, steel and titanium are all
approximately equal.

We did occasionally use titanium, but usually some sort of steel was a better
choice when strength was the issue. It's just the way it works out. It's also
worth noting that for the work I did, cost was never an issue (NASA) -
material costs were basically insignificant. We could use whatever we wanted.

~~~
at-fates-hands
Just as an aside, when I was working at a bike shop, we had a guy come in and
was looking for a road bike. After some small talk, he told me he owned a
cryogenics lab and said they could freeze anything, including bike parts.
Doing so, made them permanently in the range of 20-30% stiffer than the
original material. Most guys at the shop thought about frames, cranksets,
drivetrains, forks etc. Places on the bike which experience high levels of
torsional flex and stress.

I'm wondering how many engineers ever thought about using cryogenics to
enhance the stiffness properties of metals to achieve higher levels of
performance.

The cost to do it was around $1,500 if I remember correctly. A pretty small
fee to get what I'd consider a big gain in performance.

~~~
chromaton
I don't have much experience with cryo treating, but heat treating to gain
strength is quite commonly done, especially for metals that are too hard to
work in their strongest state, or for metals that lose their heat treat when
welded.

~~~
eitally
Here's a watch industry instance of cold hardening steel:
[http://www.damaskousa.com/technology-
watchcase.asp](http://www.damaskousa.com/technology-watchcase.asp)

------
VBprogrammer
'As good as' is a silly phrase to use in metallurgy. Are we talking
machinability, castability, tensile strength or hardness. Not to mention less
obvious issues like food safety or resistance to corrosion?

There are very many alloys of both aluminium and steel all of which have there
uses. To say this one is as good as titanium means very little.

~~~
maxerickson
The linked abstract is somewhat clearer:

[http://www.nature.com/nature/journal/v518/n7537/full/nature1...](http://www.nature.com/nature/journal/v518/n7537/full/nature14144.html)

 _The specific tensile strength and ductility of the developed steel improve
on those of the lightest and strongest metallic materials known, titanium
alloys_

So presumably it is stronger and somewhat more workable than titanium.

------
wycx
Now that nature lets you read articles for free you can actually go and read
the original paper.

In the paper the authors had to heat treat the steel at 900 °C for 15 mins to
generate the microstructure that gave the properties they wanted.

So, what does welding do to the microstructure? Does this material need to be
heat treated again at 900 °C after welding? Does the the hard-but-brittle B2
intermetallic reform in the HAZ?

~~~
TheCraiggers
Interesting question, although I'm not sure it applies much in the real world.
Aren't the welds themselves typically the weakest link in a build? Seems like
the engineering tricks used to keep welds under stress from ripping apart
would also benefit the affected metal in the HAZ.

~~~
chromaton
Welds can be stronger than the HAZ. See this video from Lincoln Electric on
welding chrome-moly:
[http://youtu.be/W5dVAT9PTmw?t=7m53s](http://youtu.be/W5dVAT9PTmw?t=7m53s)

~~~
djcapelis
Yep! Generally if your weld breaks before the material in the HAZ it is
considered a bad weld and certified welders working under structural standards
are generally required to produce welds that are stronger than this.

(Not actually a certified welder right now, but I have a brief familiarity
with the D1 structural standards as getting a cert is something I've looked
into.)

------
trhway
>By manipulating the structure of steel on a nanometre scale, Dr Kim has
produced a material which has the strength and the lightness of titanium
alloys but will, when produced at scale, cost a tenth as much.

i wonder what if the same to be applied to titanium.

>Steel is useful because it is strong and cheap. But it is also heavy. It has,
therefore, always been useless for applications such as aircraft.

[http://en.wikipedia.org/wiki/Mikoyan-
Gurevich_MiG-25](http://en.wikipedia.org/wiki/Mikoyan-Gurevich_MiG-25)

"The MiG-25 was constructed from 80% nickel steel alloy, 11% aluminium, and 9%
titanium."

~~~
arethuza
On the other hand, the Soviets managed to build a class of attack submarines
using titanium hulls:

[http://en.wikipedia.org/wiki/Alfa-
class_submarine](http://en.wikipedia.org/wiki/Alfa-class_submarine)

~~~
vonmoltke
The _Sierra_ s also had titanium pressure hulls. Both classes suffered from
major maintenance issues, though, because the titanium was prone to cracking
from the severe pressure changes during dives. The Soviets switched back to
steel for the _Akula_ class.

------
phkahler
So the steel companies are finally getting scared enough to innovate. There
are people trying to dramatically reduce the cost of titanium, Ford is dumping
steel for aluminum, composites are even replacing aluminum in aircraft. Steel
is starting to look like a relic of the 1700's rather than the great material
it has been for so long.

When I worked in EVs, one of the old timers (a guy almost 80 years old) told
me the best steel for the motors should have some Boron in it. Some particular
alloy that would have lower core loss at higher frequencies. But none of the
big steel companies were interested in making it for us. They just wanted to
make what they make.

So even if it's not as great as it sounds, I'm glad somebody is doing
something with steel.

~~~
Gravityloss
There are lots of steel factories around the world. Some smaller ones have
specialized in rarer steels.

~~~
bigger_cheese
As a materials engineer who works for a steel company (although my background
is in blast furnaces and iron ore smelting - not micro alloying) maybe I can
shed some light.

It largely comes down to enconomies of scale you can certainly make
specialised grades of steel but often times it is not profitable to do so.
Steelmaking is like most manufacturing process, cost decreases with scale.
Usually the specialised grades simply aren't in high enough demand to recoup
the costs involved in producing them.

For some grades the techniques to produce them are suitably differnt from
standard grades that lines needs to be diverted and retooled to handle them,
which impacts on yield and causes losses due to downtime etc. Not to mention
many of the specialised alloying elements like Niobium etc. are also stupidly
expensive. Buying these in small quanities is probably not ideal and I'd
imagine its probably risky to buy in bulk because orders may not be filled
quickly and business doesn't tend to like having capital tied up in raw
material stockpiles.

Competition is also very fierce, for a while there has been an excess of steel
capacity largely driven by rapid expansion of China's steelmaking capacity. So
there is a lot of pressure on keeping operating costs per tonne low all of
this kind of leads companies towards where the biggest returns are, which is
producing the high volume steels at lowest cost. Thus most of research effort
gets directed here as well. Thats not to say R&D isn't happening into
specialised grades, its just not where the big payoffs are currently.

------
alricb
Some data:

The yield strength of that new material is from about 1 GPa to 1.4 GPa, vs.
830 MPa for Ti6Al4V (Steel and Aluminium vary, depending on the alloy).

It has a density of 6.82 g/cm3, vs 4.43 for the titanium alloy, 7.85 for
ordinary steel or 2.70 for 6061 Aluminium.

Apparently Ti6Al4V costs around $20/kg, so the new alloy would cost around
$2/kg, vs. around $2.70/kg for 6061 Aluminium or $0.85/kg for cold-rolled
steel.

Prices: [http://www.metalprices.com/metal/steel/steelbenchmarker-
cold...](http://www.metalprices.com/metal/steel/steelbenchmarker-cold-rolled-
coil-usa)
[http://www.metalprices.com/metal/aluminum/aluminum-6061-extr...](http://www.metalprices.com/metal/aluminum/aluminum-6061-extrusion-
billet-price) [http://www.metalprices.com/metal/titanium/titanium-
ingot-6al...](http://www.metalprices.com/metal/titanium/titanium-
ingot-6al-4v-usa)

As for the modulus of elasticity, it isn't mentioned in the article. The usual
figure for steel is 210 GPa. The titanium alloy is around 114 GPa, and 6061
Aluminium is 69 GPa.

The low density is fairly big new. Compared to mild steel, you can have a 15%
larger volume for the same weight, so you might be ahead on stiffness even if
the MoE is smaller.

------
nakedrobot2
Not a moment too soon for the Tall Tower Project.
[http://hieroglyph.asu.edu/project/the-tall-
tower/](http://hieroglyph.asu.edu/project/the-tall-tower/)

~~~
luke_s
While it's undoubtedly very cool to build something very, very ... very, very
tall, what would such a tower be used for?

~~~
onion2k
What's the Eiffel Tower _for_? The Statue of Liberty? Nelson's Column? The St.
Louis Gateway Arch?

They're symbols. They bring people together around a common talking point, to
recognise and remember who we are and what we can do together.

If it really needs a purpose the Very Tall Tower could be an awesome base-
jumping venue.

------
Animats
It will be good if this is real. Nature articles about nanotechnology which
claim "huge breakthrough to be commercialized real soon now" are all too
frequent. Then we never hear about the technology again.

For aerospace, the big advantage of titanium is a high melting point. This
material won't have that, which is probably why the authors talk about
automotive applications. For automotive applications, a question is whether
these new properties will survive ordinary manufacturing processes. Casting,
probably not, but maybe the process can be applied to castings later as a
heat-treating step. What about rolling and stamping?

~~~
rsfern
In the original article they say they cold-roll, recrystallize, then strain
harden. So definitely no casting, because the recrystallization is where the
magic happens. Rolling and casting should be fine though. They say that the
alloy is mostly compatible with current steel processing infrastructure, so it
looks promising.

------
upofadown
With aircraft the basic issue is strength to weight, not just weight. If the
material is stronger you can use less of it. The trend today is to make
aircraft out of really strong fibres embedded in plastic.

~~~
Tuna-Fish
The new material has the strength to weight of titanium.

~~~
tsotha
Titanium is no better than aluminum. The reason they use titanium in aircraft
is its ability to withstand heat.

------
daniel-levin
Since the original paper is behind a paywall (at least for me), can anyone
explain the specifics of what the researchers did to produce this new alloy?

>> Dr Kim and his colleagues have, however, found that a fifth ingredient,
nickel, overcomes this problem.

I'd imagine that it didn't take a world-class team of scientists to have come
up with the idea of alloying using nickel. There is no way materials
scientists and metallurgists hadn't tried this by now, so what did they do
differently?

~~~
rsfern
Materials Science PhD student here, I'll do my best.

The morphology of the brittle B2-FeAl intermetallic compound is the key. In
the conventional lightweight steel alloys, the B2 intermetallics make the
alloy brittle (so they don't work harden very well), so in the past
researchers optimized their alloys to avoid forming these intermetallics [0].
The nickel promotes the nucleation of the intermetallic particles during heat
treatment [1], so that you get a more-or-less uniform distribution of many
nanocrystalline B2 particles, instead of a smaller number of larger or more
clustered B2 domains. The small B2 particles contribute to strain hardening by
pinning dislocation motion, without reducing the ductility of the alloy.

From the Nature letter:

[0]: "One of the general concepts employed until now in the alloy design of
Fe-Al-Mn-C-based, high-aluminium, low-density steel has been the suppression
of ‘brittle’ intermetallic compound formation by stabilizing the ‘ductile’
austenite matrix."

[1]: "To expand the stability domain of B2 above the recrystallization
temperature (normally, 800–900 °C) of deformed austenite, the alloying recipe
of an austenitic low-density steel was modified by adding 5 weight per cent
nickel (Ni), which is one of the most effective elements for forming B2 with
aluminium."

------
jcrei
Made me think of Rearden metal from Atlas Shrugged

~~~
joakleaf
Yes, me too. As I recall, Rearden metal was about 10x as strong as the
competitors'.

I guess Rearden was based on real life Andrew Carnegie who helped ignite the
use of steel for construction
([http://en.wikipedia.org/wiki/Andrew_Carnegie](http://en.wikipedia.org/wiki/Andrew_Carnegie)).

I assume Ayn Rand based all her characters on former industry giants
(railroads, steel, oil).

~~~
shiven
One can only imagine the fun she would have had with a main character based on
Steve Jobs or Jeff Bezos!

~~~
csours
Don't know why you are being downvoted, these guys are notable for being
perceived as not giving fig for what other people thought, and being
successful doing it.

------
tsotha
>An alloy of iron, aluminium and carbon (steel’s other essential ingredient)
is too brittle to be useful. Adding manganese helps a bit, but not enough for
aluminium-steel to be used in vehicles.

>Dr Kim and his colleagues have, however, found that a fifth ingredient,
nickel, overcomes this problem.

As far as I know turbine blades are typically made of iron-nickel alloys. What
is the new part of this discovery?

------
ohitsdom
Every year I am reading these kinds of articles, keep thinking we are going to
have amazing materials in 5 years.

~~~
DennisP
This one has a major steel company planning to start production in one year.

------
ris
Which is all great but as far as I'm aware one of the major reasons for
titanium's use was its high melting point. Nothing is said of how this
compares here.

------
chromaton
Has anyone tried a titanium-iron-nickel alloy?

I would have thought every alloy combination would have been tried by now, but
I guess there's still new things to be learned.

------
gaius
This, if it works, is worth quite literally millions as times as much as
another "social network" or stupid app, but I'll wager the team aren't "acqui-
hired" for $19Bn.

~~~
ghshephard
I'm interested in where you came up with the "literal" worth comparison.

Perhaps what you meant to say is that, "I personally feel that this new steel
alloy is worth more than whatsapp, and, I would be personally prepared to pay
at a valuation of 1 million times greater than the whatsappp valuation. So,
going back in time, if I had a choice of owning 10% of whatsapp for a $10,000
investment (valuing whatsapp at $100K), or 0.00001% of the company producing
this alloy (valuing it at $100B, or 1 million times as much as whatsapp, I
would take the 0.00001% for my $10,000 instead of the 10% share of whatsapp
for $10,000).

Is that literally how you feel?

~~~
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------
dschiptsov
Rearden metal?)

