Mechanical behavior of zirconium and hafnium in tension and compression

The mechanical behavior and substructural evolution of highly textured hafnium (Hf) has been examined in tension and compression and compared to the mechanical response of zirconium (Zr). The quasi-static work-hardening rate as a function of strain for both metals exhibits a compression-tension asymmetry. Both Zr and Hf exhibit a downward work-hardening response in tension, while each displays a parabolic and then concave upward work-hardening behavior in compression. Additionally, Hf displays higher flow stresses than Zr both in tension and compression. The stress-strain and strain-hardening curves for Zr and Hf have been characterized in terms of their propensity for deformation twinning and evolution of substructure with strain. Differences in the work-hardening rates and flow stresses as a function of the sense of the applied load and material are discussed in terms of slip-twin interactions during deformation.