Tech Thursday: Amorphous Metal Mania
If you follow materials, or have taken a materials class lately, you've probably heard about Liquidmetal Technologies and what they are billing as the "3rd revolution" of manufacturing. They look at technological innovation in the last century as centering on two major revolutions: The discovery of how to create cheap steel, and the introduction of inexpensive thermoplastics. They hope that their new innovations in amorphous metals will have a similar impact on the manufacture of products.
But why would these new metals cause such a change?
For that, we need a little explanation of what makes metals non-crystalline in the first place. Contrary to recent press, amorphous metals have been available for some time now. The first non-crystalline metals were made in the 1950's. Researchers found that if you shot a molten blob of a specific gold-phosphorus alloy at a copper plate, it would splat, and cool so fast that there was no time for crystals to form in the resulting solid. Later, scientists developed a method of continuously cooling a special alloy on a super-cooled spinning metal drum to form a ribbon of metal. But the newest innovations allow large pieces of non-crystaline metal to be cast, even if cooled foirly slowly.
The thing that is so special about non-crystalline metals is two-part:
First, because there are no crystals, there are no tiny boundaries between the crystals (called grain boundaries). These grain boundaries are what makes it possible to form metal by hammering or bending; The metal grains squish around each other along the boundaries, resulting in permanent (or plastic) deformation. This is also the culprit behind metal bumpers that get bent out of shape, and the lack of "springiness" in cast iron or steel. Without boundaries, amorphous metal mainly deforms elastically, rather than plastically, so that most of the energy that went into deforming it can be recovered, and there is less chance of a dimensional change in the part.
Secondly, when metals crystallize in a mold -- like in die-cast-cars -- the metal is full of randomly-oriented crystals. This random orientation causes the metal to be much weaker than if a comparable part was milled out of rolled or extruded metal, who's grains have been stretched for better strength along a certain axis. This is why very few high-performance metal parts are die cast, since the resulting part is much weaker than a roll-formed, stamped, or extruded piece. This makes crystalline metals poor candidates for injection molding. Non-crystalline metals, on the other hand, are the same whether you cast them in a cellphone shape, or a brick shape. So these new metals are perfect for injection molding to almost the final shape (these metals still shrink when they cool, like all metals, so high-tolerance parts will need some cleanup)
So what are they good for?
Right now, both liquidmetal, and the amorphous steel from University of Virginia are both patented, and therefore pretty expensive to use. So far, most applications have been pretty typical of the "super cool new material" route: Golf clubs, tennis rackets, and other high-margin, high tech sports equipment.
But if new "open source" alloys are made public, or after the initial patents expire, the actual metals themselves will definitely come down in price. Once that happens, the prospect of injection molded metal is very exciting. Metal parts are traditionally expensive, because they are slower and more labor intensive to mass produce. Consider the recent explosion of use of aluminum in scooters and other low-priced toys. This has been largely fueled by the increased availability of extrusion, and extruded parts, which are much lower labor than milled parts, with lower tooling costs than stamping, and therefore are much cheaper.
Injection molding could do the same for non-crystalline metals. The material itself, minus licensing fees from patents, is not that expensive to make, so once the patents expire, we should be in for something pretty exciting.
Where can I learn more?
Here's a demonstration and explanation of the high elasticity of this new metal, with video.
Metglas makes amorphous metals for the electronics industry, and their site is worth exploring.
AZoM has an unbelievably big database of metal information that's definitely worth browsing.
Copyright 2004-2006 Dominic Muren and IDFuel Team