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mickeyf
05-14-2011, 12:35 AM
Non-crystallized injection-moldable blah blah whatever...? What metals are used/ could work? Machinability effected?

http://www.theregister.co.uk/2011/05/13/metal_glass_injection_moulding/

saltmine
05-14-2011, 12:38 AM
Ah yes. I remember them in "Star Trek, The Movie" acquiring a bunch of it to make tanks for the whales to live in, aboard the Enterprise....Science fiction, and now it's REAL??

mickeyf
05-14-2011, 12:44 AM
Well, hey , they also invented cell phones, pad computers... there's currently a contest (lost the url) to come up with a tri-corder....

Bruce Griffing
05-14-2011, 12:54 AM
Solid metals are either crystalline or amorphous (glass like). Amorphous metals, in ribbon form, have been use for quite some time in transformer and other magnetic applications. They are made by squirting a thin stream of molten metal onto a very rapidly spinning cold wheel. The molten material solidifies so fast that crystalline structure does not form. The continuous ribbon, thus formed, is further processed into things like transformer cores. It is hard to imagine cooling a metal in a mold fast enough to produce amorphous material. Color me skeptical.

Evan
05-14-2011, 01:40 AM
Beating Crystallization in Glass-Forming Metals by Millisecond Heating and Processing

1. William L. Johnson*,
2. Georg Kaltenboeck,
3. Marios D. Demetriou,
4. Joseph P. Schramm,
5. Xiao Liu,
6. Konrad Samwer,
7. C. Paul Kim, and
8. Douglas C. Hofmann


The development of metal alloys that form glasses at modest cooling rates has stimulated broad scientific and technological interest. However, intervening crystallization of the liquid in even the most robust bulk metallic glass-formers is orders of magnitude faster than in many common polymers and silicate glass-forming liquids. Crystallization limits experimental studies of the undercooled liquid and hampers efforts to plastically process metallic glasses. We have developed a method to rapidly and uniformly heat a metallic glass at rates of 106 kelvin per second to temperatures spanning the undercooled liquid region. Liquid properties are subsequently measured on millisecond time scales at previously inaccessible temperatures under near-adiabatic conditions. Rapid thermoplastic forming of the undercooled liquid into complex net shapes is implemented under rheological conditions typically used in molding of plastics. By operating in the millisecond regime, we are able to “beat” the intervening crystallization and successfully process even marginal glass-forming alloys with very limited stability against crystallization that are not processable by conventional heating.


http://www.sciencemag.org/content/332/6031/828.abstract?sid=f80a245d-e767-45ff-91eb-3719b3bbbb44

Sounds real to me. Could be very interesting. This calls for a little more research.

darryl
05-14-2011, 03:03 AM
You can apply huge amounts of power to a sample for a short time, and the sample will absorb that energy and become hot- I'm alright with that so far. But how can you withdraw that amount of energy in the same short time? This would be a fundamental and far-reaching discovery were it possible. Something would be able to lose say a thousand degrees of temperature in a small fraction of a second without that heat having to flow into something else. The brute force method has been brought up- a thin film can lose heat to a cold 'collector' in intimate contact.

If there's something to this, I think it must be that the metal is 'plasticized' by the sheer number of electrons being forced through it, and it's not actually heated to that high of a temperature.

Astronowanabe
05-14-2011, 04:07 AM
standing in for Tiffie

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

I looked into it a few years back when Pyrex became scarce for thin light cast-able scope mirrors with no heat retention problems.
they could only produce fairly small items when I checked

J Tiers
05-14-2011, 08:17 PM
As far as the magnetic cores, yes, quite real, at least one client is using them with very good results (at least with THAT part of their new invention).

but there are limits on what you can do to the material as far as processing..... various properties can get messed up. The cutting of the thin sheets had to be done in a specific way to avoid problems (I can't talk about that, but whatever method you think of is probably wrong).

That being the case, I am not sure that the material is practical unless it is stable against likely environmental conditions of use.

If there is a chance of uncontrolled heating/cooling, any properties that depend on a specific heat treatment may not be reliable...... I.e. a car fire on a bridge should not damage/weaken the structure and make it fall down, assuming that the heating is not extreme..... it is fairly certain that such an event might happen.

Likewise, a fire in a building should not produce weakening and collapse at least for some significant time. That's why "lagging" is often applied to the structural steel.

Evan
05-14-2011, 10:55 PM
If there's something to this, I think it must be that the metal is 'plasticized' by the sheer number of electrons being forced through it, and it's not actually heated to that high of a temperature.


It's being heated. There isn't any other description that is consistent with physics. What they are doing is heating it just enough to put the metalglass into the bottom of the supercooled liquid zone. This is the same as melting regular glass. Although glass does not undergo a phase transition when it becomes fluid it does pass through a critical temperature.

Amorphous solids such as ordinary glass are not supercooled fluids and do not flow at normal environmental temperatures. This is because they are below a critical temperature under which the atoms and molecules are locked in place by atomic forces and do not have sufficient energy, on average, to exhibit mobility. Once a glass is heated above that critical temperature the molecules (and atoms) have enough energy to overcome the binding forces that hold them in place and the glass becomes a fluid. Like many fluids it is possible to hold them in this state for a period of time before crystallization begins, especially if the fluid is extremely pure and lacks nucleation sites that promote the formation of crystals.

Crystallization isn't an instant process because it requires that the molecules reorient to match thier neighbours. By heating extremely quickly a window of time is opened during which the material is fluid.

While the glass is in this state they propose that it can be very quickly formed (they mention milliseconds) by processes that resemble injection molding. The mold will undoubtedly be chilled and sections will be thin. When the plastic metalglass hit the mold it will freeze below the critical temperature before it can crystallize.

Rustybolt
05-14-2011, 11:06 PM
Vitreous metal.
I posted about it about a year ago.
Thay are already making artificial hips out of it.

darryl
05-15-2011, 02:02 AM
Thanks for that explanation, Evan. My only problem with it is that you start with a material that has crystalline form- you say that crystallization doesn't happen so quickly, but might that also mean that crystallization is not 'dissolved' so quickly also? We're talking about a lump of metal here that we want to convert from crystalline into amorphous-

Evan
05-15-2011, 02:48 AM
We are really talking about special alloys that are much easier to keep in an amorphous state. I haven't tried looking up what they are but I am betting that they may be "micro alloys" where very small amounts of certain elements change the properties radically. It may also be a matter of ultra pure materials.

Astronowanabe
05-15-2011, 05:18 AM
The paper said they were starting from amorphous billet (not kidding) and subjecting the already glassy metal high energy to get it to flow in the mold.

So I see their contribution more as a method for reshaping of glassy metal while keeping it glassy than (re) inventing glassy metals. But their process might help the problems of scale, making small pellets of glassy metal has been done for decades, it is molding larger pieces has not worked well. If they can economically take several pounds of pellets and flash fuse them into a single molded object then they will have earned their fortune.

macona
05-15-2011, 03:10 PM
Actually, the term billet in this case is, for once, justified.