Hot-Ductility Behavior of Tantalum-Tungsten Alloys

Pure tantalum (Ta) is known to exhibit slow-strain-rate embrittlement if exposed to oxygen-rich environments, particularly at elevated temperatures [1], however complementary behavior is not well understood in tantalum-tungsten (Ta-W) alloys that are preferrable for use in applications requiring enhanced strength. Thus the purpose of this work was to expand the understanding of extent of embrittlement, and loss of ductility, with temperature increase to tantalum-tungsten alloys, i.e. tantalum-2.5 wt% tungsten (Ta-2.5W) and tantalum -10 wt% tungsten (Ta-10W) in oxygen-rich environments Hot-ductility (tensile) tests were performed using a Gleeble® 3500 to identify the presence (or absence) of ductility loss as a function of test temperature (400-900 °C) and strain rate (10^-4-10²/s), in either air or vacuum. At quasi-static rates, a loss of ductility (quantified via reduction in area measurements, %RA) was observed in both Ta-2.5W and Ta-10W specimens tested in air versus vacuum at temperatures of 600 °C and above, with %RA decreasing with increasing temperature. In contrast no notable loss of ductility was observed in specimens tested in air at high rates. Fracture surface and microstructural characterization of the hot-ductility specimens, and their relationships to reduction in ductility and oxygen uptake, will be discussed.