Deformation Joining Research Opens Door to New Materials
Argonne researchers are studying ways to combine advanced materials such as ceramic, intermetallics, cermets, and metal matrix composites (MMCs) together for use in complex vehicle engine components, as well as for aerospace, transportation, and energy applications.
High-tech materials offer many benefits for use in heavy vehicle engines, among them:
- Lighter weight
- Ability to withstand higher engine temperatures with less wear
- Lower manufacturing and environmental costs than steel
- Chemical stability
Many of these high-tech materials lend themselves well to being formed into fairly simple and straightforward shapes, but because of high cost and technical limitations, they often cannot be used for more complex shapes unless they can somehow be bonded to other materials.
Deformation Joining
For dissimilar materials to be used together in a part or component, they must be joined in a way so they can withstand the stresses to which the part will be subjected. One method of joining dissimilar materials together is called deformation joining.
In this process, two or more materials are bonded together by stressing each material to the point where it changes its dimensions (plastic deformation) and the individual grains of one material intersperses with the grains of the other materials. The technique has tremendous potential for overcoming the difficulties of using high-tech materials for the manufacture of complex engine parts.
Plastic Flow Joining
Argonne researchers are exploring methods of joining by plastic flow using ceramic and metallic materials with very promising results. They initially worked with zirconia-toughened alumina ceramics of the family Y-TZP/Al2O3 with different volume fractions to study the bonding of similar and dissimilar materials. They chose these particular materials because of their highly stable microstructure and superplastic behavior at temperatures above 1300°C. After joining the materials together, the researchers examined the material bonds with a scanning electron microscope. Calculations of the stress that results from the different coefficient of thermal expansions predicted that the fracture of the joined sample would not occur at the joint. The prediction was in accord with the observations.
Better Bonds with Nanocrystalline Materials
To produce a better bond, the Argonne team has incorporated nanocrystalline interlayers, applied either by a using a solid thin slice, or even by spraying the nanocrystalline material between layers of different ceramic materials. The superior mechanical properties of nanocrystalline materials improve the structural stability of the joint, because nanocrystalline materials require lower temperatures for bonding and less deformation of the ceramics being joined.
Inventions & Patents
Argonne researchers, in conjunction with Ohio State University, have produced novel mini oxygen sensors with an internal reference using nanocrystalline interlayers. In order to work, the sensor containing a metal/metal-oxide powder that decomposes at high temperatures to produce an oxygen atmosphere that serves as the internal reference must be gas tight and robust. The sensor won an R&D 100 award in 2005.
Argonne has patented the deformation joining technique and applied for several more patents on the technique and the mini oxygen sensor. Argonne researchers have successfully produced strong bonds in materials such as such as intermetallics, cermets, electronic ceramics, fiber-reinforced composites, and metal matrix composites.
October 2007
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