a1 Materials and Engineering Physics Program, Ames Laboratory (United States Department of Energy), Ames, Iowa 50011
a2 Department of Aerospace Engineering, Iowa State University, Ames, Iowa 50011
a3 Materials and Engineering Physics Program, Ames Laboratory (United States Department of Energy), Ames, Iowa 50011
Bulk samples of an ultrafine-grained tungsten–tantalum composite alloy have been synthesized by consolidating mechanically milled composite powders. The grain growth during densification is limited due to the submicron-scale layering of the individual metals in the composite particles and the relatively low sintering temperature (1300 °C). The ultrafine microstructure of the high-density (∼99% theoretical density) samples leads to a high yield stress of ∼3 GPa under quasi-static uniaxial compression. A tendency for Ta-rich solid-solution formation during densification was observed, and the high-temperature phase equilibria in the composite powders were examined further using high-energy x-ray diffraction at temperatures up to 1300 °C.
(Received June 20 2007)
(Accepted September 20 2007)