February 11, 2002

Electrical Field Research at NC State Applied to Materials Processing

An example of the influence of an electric field on the microstructure of a superplastically deformed aluminum alloy: (a) deformed without field and (b) deformed with field. The elimination of porosity by the field gives a significant increase in the strength and ductility of the aluminum alloy.

Contemporary life depends on many kinds of materials, most of which are produced by sophisticated processes.  Producing the materials that make advances in technology possible is not without costs, however.  In many cases creating new materials requires high expenditures of money and energy.

One NC State researcher is working to help the materials industry find less expensive and more efficient ways to process ceramics and metals.  Dr. Hans Conrad, professor emeritus of materials science and engineering, has been conducting research on the effects of electrical fields on these materials for 15 years.  His work is sponsored by the US Army Research Office.

According to Conrad, industry has long taken three external parameters into account during materials processing:  temperature, stress or pressure and time.  The potential effects of electrical fields have not commonly been considered.  However in many cases these effects, which can include phase changes and microstructure alterations, can be important, even at low electrical current levels.

Traditionally alloys were created to increase hardness of metals, but in some cases the same effect can be achieved using electrical fields, said Conrad.  In the case of metals, changes during processing caused by low-current electrical fields are permanent.  There are many industrial processes that can benefit from this treatment.  For example, steel can be hardened by rapid cooling in water, but this treatment carries the risk of distortion and cracking.  If steel is cooled in oil these risks are reduced, but the resulting steel is not as hard.  An elegant solution to this problem involves applying an electrical field to the steel-oil bath — the resulting product is as hard as water-treated steel but free of cracks and distortions.  Also, sintering, or heating to produce consolidation, of iron powder compacts can be enhanced with electric fields.

Using electrical fields on ceramics can be beneficial during processing by reducing the flow stress, or amount of pressure required to produce changes in the form or shape of the ceramic.  Substantial energy could be saved in industrial processes if low-current electrical fields were used to manipulate the product.

Numerous materials can be manipulated more efficiently using electrical field technology, and the practical applications of this technique are many.  For instance, microelectronic package elements such as boards and connections may be produced with improved properties by manipulating the tin alloy using this technology.  Also, the auto industry would like to use more aluminum in cars to reduce the weight and use gasoline more efficiently, but the aluminum must be sufficiently ductile to undergo the severe forming operations dictated by the designers.  By applying electrical fields during processing, aluminum can be made as strong and ductile as steel.  Conrad hopes to expand his work with the auto industry to explore this application.

According to Conrad, “Electrical field research in materials science is important for all phenomena and processes.  Mechanical properties effects are very significant — we hope to expand our studies in this area in the near future.”  The benefits of Conrad’s research are substantial, for all of us depend on the efficient production of high-quality materials with the lowest expenditure of energy and pollution of the environment.

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Media Contacts:  Dr. Hans Conrad, 919/515-7443, hans_conrad@ncsu.edu, Linda E. Rudd, 919/515-3848, linda _rudd@ncsu.edu