Materials scientists have been trying for years to discover and develop a product that could be molded into complex shapes with the ease and low expense of plastic while retaining the strength and durability of metal. Recently, a team led by Dr. Jan Schroers, a materials scientist at Yale University and the former Director of Research at Liquidmetal Technologies, has recently developed some metal alloys that can be blow molded like plastics into complex shapes that can't be achieved using regular metal, without sacrificing the strength or durability that metal affords.
Liquidmetal is a commercial name for a series of bulk metallic glass (BMG) alloys developed by a CalTech research team and marketed by a firm called Liquidmetal® Technologies. BMG alloys are solid at room temperature, but they become increasingly soft and liquescent at higher temperatures rather than exhibiting a fixed melting point as with a conventional metal.
It’s the atomic structure of a BMG alloy that differentiates it from a conventional metal. The atomic structure of a conventional metal is crystalline, with repeating crystal patterns in planes, and usually containing dislocations, or irregularities, in the structure. The tendency of the crystalline structure to slip and deform under load limits the overall mechanical performance of conventional metals.
The atomic structure of BMG alloys is amorphous, where no discernible patterns exist in the atomic structure. The absence of grain boundaries and dislocations results in a material with a large elastic strain limit and a very high yield strength, close to the theoretical limit. As an example, one zirconium-based BMG alloy exhibits a yield strength of up to 2 GPa and an elastic strain limit of about 2%. BMG alloys also demonstrate excellent corrosion resistance, very high hardness, and excellent anti-wearing characteristics, while also being able to be heat-formed in processes similar to those used with thermoplastics.
Liquidmetal was introduced commercially in 2003 and has been used to manufacture electronic casings, medical devices, jewelry materials, and sporting goods. Die-casting is the main manufacturing process, but it is subject to conflicting demands. The conditions needed to obtain high-quality casts are slow cooling and small temperature gradients. In a die-cast process, the liquid BMG must fill the entire mold cavity while at the same time be cooled fast enough to avoid crystallization. This makes casting of parts with complex geometries difficult.
Schroers claims that the alloys can be blow molded just as cheaply and as easily as plastic. So far his team has created several complex shapes, such as metallic bottles, watch cases, miniature resonators, and biomedical implants that are seamless, twice as strong as steel, and can be molded in less than a minute.
On the tech blog Cult of Mac, Schroers said it is likely Apple, who has been interested in the possibilities afforded by BMGs for some time, will invest heavily in commercializing the technology. Apple has a long history of pioneering cutting-edge manufacturing techniques, and its long-standing interest in design makes it likely to explore the material’s capabilities.
Sources
“Amorphous Metal Alloys Form Like Plastics”, Advanced Materials & Processes, January 2006, Jan Schroers and Neil Paton
“Thermoplastic blow molding of metals”, Materials Today, Jan-Feb 2011, Volume 14, Number 1-2, Jan Schroers, Thomas M. Hodge, Golden Kumar, Hari Raman, Anthony J. Barne, Quoc Pham, and Theodore A. Waniuk.Yale University.
“Stronger than steel, novel metals are as moldable as plastic.” ScienceDaily, 8 Feb, 2011. Web.
“The Superplastic Forming of Bulk Metallic Glasses”, Journal of Metals, 2005, 57, 35-39, Jan Schroers
 |
Dr. Jan Shroers with metal bottle
Photo courtesy of Dr. Shroers |
It’s the atomic structure of a BMG alloy that differentiates it from a conventional metal. The atomic structure of a conventional metal is crystalline, with repeating crystal patterns in planes, and usually containing dislocations, or irregularities, in the structure. The tendency of the crystalline structure to slip and deform under load limits the overall mechanical performance of conventional metals.
The atomic structure of BMG alloys is amorphous, where no discernible patterns exist in the atomic structure. The absence of grain boundaries and dislocations results in a material with a large elastic strain limit and a very high yield strength, close to the theoretical limit. As an example, one zirconium-based BMG alloy exhibits a yield strength of up to 2 GPa and an elastic strain limit of about 2%. BMG alloys also demonstrate excellent corrosion resistance, very high hardness, and excellent anti-wearing characteristics, while also being able to be heat-formed in processes similar to those used with thermoplastics.
Liquidmetal was introduced commercially in 2003 and has been used to manufacture electronic casings, medical devices, jewelry materials, and sporting goods. Die-casting is the main manufacturing process, but it is subject to conflicting demands. The conditions needed to obtain high-quality casts are slow cooling and small temperature gradients. In a die-cast process, the liquid BMG must fill the entire mold cavity while at the same time be cooled fast enough to avoid crystallization. This makes casting of parts with complex geometries difficult.
Schroers claims that the alloys can be blow molded just as cheaply and as easily as plastic. So far his team has created several complex shapes, such as metallic bottles, watch cases, miniature resonators, and biomedical implants that are seamless, twice as strong as steel, and can be molded in less than a minute.
On the tech blog Cult of Mac, Schroers said it is likely Apple, who has been interested in the possibilities afforded by BMGs for some time, will invest heavily in commercializing the technology. Apple has a long history of pioneering cutting-edge manufacturing techniques, and its long-standing interest in design makes it likely to explore the material’s capabilities.
Sources
“Amorphous Metal Alloys Form Like Plastics”, Advanced Materials & Processes, January 2006, Jan Schroers and Neil Paton
“Thermoplastic blow molding of metals”, Materials Today, Jan-Feb 2011, Volume 14, Number 1-2, Jan Schroers, Thomas M. Hodge, Golden Kumar, Hari Raman, Anthony J. Barne, Quoc Pham, and Theodore A. Waniuk.Yale University.
“Stronger than steel, novel metals are as moldable as plastic.” ScienceDaily, 8 Feb, 2011. Web.
“The Superplastic Forming of Bulk Metallic Glasses”, Journal of Metals, 2005, 57, 35-39, Jan Schroers
No comments:
Post a Comment