High strain rate deformation behavior of tantalum

Tantalum, beyond showing a favorable strong increase in strength with increase in strain rate, is also shown to give at Split Hopkinson Pressure Bar (SHPB) strain rates evidence of increased ductility, say, as measured by the uniform strain preceding the maximum load point in a tensile test. Such SHPB measurements are related to BCC and FCC metal predictions resulting from a dislocation mechanics based constitutive equation analysis. The higher strength and ductility at SHPB rates are attributed to the onset of an added rate of dislocation generation. In addition, strain aging in commercial tantalum materials at conventional laboratory strain rates and ambient temperatures is shown to exert a strong influence on the prediction of plastic instability behavior and presents a complication in relating the strain rate dependencies in conventional and SHPB tests.