Medical Musings: Can Engel solve the amorphous metal puzzle?

The potential for injection molded amorphous metals in the medical market took a big step forward with the announcement that Engel Austria GmbH (Schwertberg) will join forces with Liquidmetal Technologies (Rancho Santa Margarita, CA).

The goal is to develop net shape parts that are stronger, and possibly more cost effective, than metals and composite plastics currently used for precession medical instruments and devices, hearing aids, implants, and dental tools.

The amorphous metal ("liquid glass") technology is fascinating, but the route to commercial success has been daunting since its invention in 1993 by Caltech professor William Johnson . He cofounded Liquidmetal Technologies, which launched golf heads as its first commercial product. The retail business of Liquidmetal Golf was discontinued in September 2001, but the company is still pursuing sporting goods and other applications.

The company went public in 2002 with share prices above $20. But as debt piled up, the stock price has plummeted. The share price in early October 2011 was around 20 cents. Liquidmetal Technologies stock is now being quoted over-the-counter on the Bulletin Board Electronic Quotation Service under the trading symbol LQMT.OB.

Yet the technology is intriguing.

Amorphous alloys are unique materials that retain a random atomic structure when they solidify, in contrast to the crystalline atomic structure that forms in other metals and alloys.

Amorphous structures don't have the inherent weaknesses found in crystalline structures. In laboratory testing, zirconium-titanium Liquidmetal alloys are approximately 250% stronger than commonly used titanium alloys such as Ti-6Al-4V, but they also have some of the beneficial processing characteristics more commonly associated with plastics.

That plastics-like processing advantage has been the missing piece, however.

Liquidmetal had been focusing on cast metal processes, and its equipment partner has been Buhler Die Casting (Uzwil, Swtizerland). The companies announced development of a new machine for Liquidmetal in 2007.

Injection molding holds the promise of faster processing times and design of highly intricate shapes.

But injection molding Liquidmetal will be a challenge.

Certain combinations of metals can be formed into amorphous shapes through a rapid quenching process. The "critical cooling rates" for early amorphous alloys were extremely high, on the order of 10 6 deg C/sec. New alloys are better, and Johnson and other Liquidmetal scientists are working on other metal cocktails that are better suited for injection molding. A Zr--Ti--Ni--Cu-Be-based amorphous alloy made by Liquidmetal Technologies under the tradename Vitreloy-1 can be processed in the thermoplastic temperature range up to a factor of 10 times longer than a marginal amorphous alloy (such as a Cu--Ti--Ni--Zr base).

 Extremely rapid cooling will be a challenge for injection molding.

In die casting, molds are often made of high-conductivity metals such as copper, steel, tungsten, or molybdenum composites to expedite heat extraction from the molten alloy.

The specific technology being explored in the partnership is confidential, but I envision a process in which tanks inject liquid metals into a barrel that cools the melt, which is then squirted into mold cavities where the material is rapidly cooled below its glass transition temperature. One challenge will be maintaining the heat level of the

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