Tantalum alloys have been used by the U.S. Department of Energy as structural alloys for radioisotope based thermal to electrical power systems since the 1960s. Tantalum alloys are attractive for high temperature structural applications due to their high melting point, excellent formability, good thermal conductivity, good ductility (even at low temperatures), corrosion resistance, and weldability. Tantalum alloys have demonstrated sufficient high‐temperature toughness to survive prolonged exposure to the radioisotope power‐system working environment. Typically, the fabrication of power systems requires the welding of various components including the structural members made of tantalum alloys. Issues such as thermodynamics, lattice structure, weld pool dynamics, material purity and contamination, and welding atmosphere purity all potentially confound the understanding of the differences between the weldment properties of the different tantalum‐based alloys. The objective of this paper is to outline the thermodynamically favorable material phases in tantalum alloys, with and without small amounts of hafnium, during and following solidification, based on the results derived from the FactSage© Integrated Thermodynamic Databank. In addition, Transition Electron Microscopy (TEM) data will show for the first time, the changes occurring in the HfC before and after welding, and the data will elucidate the role HfC plays in pinning grain boundaries.


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    Title :

    Thermodynamic Prediction of Compositional Phases Confirmed by Transmission Electron Microscopy on Tantalum‐Based Alloy Weldments



    Conference:

    SPACE TECHNOLOGY AND APPLICATIONS INTERNATIONAL FORUM-STAIF 2007: 11th Conf Thermophys.Applic.in Micrograv.; 24th Symp Space Nucl.Pwr.Propulsion; 5th Conf Hum/Robotic Techn & Vision Space Explor.; 5th Symp Space Coloniz.; 4th Symp New Frontrs & Future Con ; 2007 ; Albuquerque, New Mexico (USA)


    Published in:

    AIP Conference Proceedings ; 880 , 1 ; 229-233


    Publication date :

    2007-01-30


    Size :

    5 pages





    Type of media :

    Conference paper


    Type of material :

    Electronic Resource


    Language :

    English



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