A super-strong alloy of copper and tantalum was created that can withstand extreme impact and temperature, providing high strength and good electrical conductivity. The alloy is a model system with structure that can be passed on to other alternative material systems. Materials based on iron or aluminum, for example, could be used for protection and lethality applications. The alloy also has the potential to be used on spacecraft for deep-space exploration. The same methodology can be applied to other materials, such as nickel or iron, to develop more resilient transportation and sustainable infrastructures.

Most structural metals experience sudden deformation when subjected to extreme impact and temperature, such as the force from an automobile accident or the impact that occurs during a ballistic event. When a typical metal deforms at a fast rate, it loses its ability to deform in a ductile way and becomes brittle, absorbing relatively little energy prior to fracture or failure.

This instability motivated researchers to improve the toughness of coarse-grained metals and alloys to prevent metal deformation and failure. They created a nanocrystalline alloy of copper and tantalum with engineering-enhanced properties to make it maintain a relatively consistent level of mechanical strength and microstructure stability. The material, with an average grain size of about 50 nanometers, remains stable when formed into usable parts or shapes.

The unusual combination of properties in the copper-tantalum alloy results from a processing route that creates distinct nanoclusters of tantalum. As temperature increases, these nanoclusters don't significantly change in size or spacing, which leads to the material's notable stability and strength.

The alloy can withstand high rates of impact and temperatures in excess of 80 percent of their melting point, which is higher than 1,073 kelvin or greater than 1472 °F, with very little change in its microstructure.

The copper-tantalum alloy originally was developed to replace copper-beryllium, a high-performance alloy known for its strength, conductivity, hardness, and corrosion-resistance. Copper-beryllium is critical for a range of applications, but the handling, manufacturing, and machining of beryllium can cause a serious lung condition called chronic beryllium disease.

The researchers continue to work toward replacing copper-beryllium with an equally superior metal alloy with similarities in its mechanical properties of strength, conductivity, hardness, and corrosion-resistance — the copper-tantalum alloy is a step toward that goal.

For more information, contact the Army Research Laboratory Public Affairs Office at 301-394-3590.


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This article first appeared in the January, 2019 issue of Tech Briefs Magazine.

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