Dynamic behavior of HIPed Ti–6Al–4V

The overall dynamic properties of hot isostatically pressed (HIPed) Ti–6Al–4V were throughout investigated. MIL-T-9047G was chosen as a standard material for property comparison due to its best combination of strength and ductility. The elastic constants of HIPed Ti–6Al–4V were measured by resonant ultrasound spectroscopy (RUS) method. Three types of Hopkinson bar tests (constitutive relations tests, strain-controlled specimen tests and hat-shaped specimen tests) were conducted on HIPed material as well as on the standard material to evaluate the high-strain-rate properties of HIPed Ti–6Al–4V. Thick wall cylinder explosion test was conducted to compare the post-critical behavior of baseline material (MIL-T-9047G) and Ti–6Al–4V HIPed material. The texture effect in high-strain-rate properties was checked as the main difference between HIPed (texture free) and standard material (grains elongated along the rod axial direction). The results show that the nonmilled HIPed Ti–6Al–4V has similar yield strength and strain-hardening curve in comparison with the standard material in forging direction but has a lower ductility, which is similar to the ductility of standard material normal to forging direction. The same conclusion also generated from the strain controlled specimen tests. The results that obtained in hat-shaped specimen tests show that HIPed material starts shear localization relatively earlier than standard material. This result is somewhat contradicted with the ballistic testing results that show better ballistic performance for HIPed materials in all three types of penetration tests (flat-ended, conical and long-rod) [see Refs. Nesterenko VF, Indrakanti SS, Goldsmith W, Gu Y. In: Staudhammer KP, Murr LE, Meyers MA, editors. Fundamental issues and applications of shock-wave and high-strain-rate phenomena. Amsterdam: Elsevier Science; 2001. p. 593–600; Nesterenko VF, Indrakanti SS, Brar S, Gu Y. Shock compression of condensed matter. AIP Conf Proc 2000; 505(1): 419–22; Nesterenko VF, Indrakanti SS, Brar S, Gu Y. Key Eng. Mater. 2000; 177-180: 243–8; Nesterenko VF, Goldsmith W, Indrakanti SS, Gu Y. Int J Impact Eng 2003; 28(2): 137–60; Gu Y, Indrakanti SS, Nesterenko VF. Shock compression of condensed matter. AIP Conf Proc 2002; 620(1): 1294–7]. The explanation for this contradiction might be the influences coming from the texture, and other microstructure features such as phase content, grain size distribution and fast shear localization propagation path at the grain boundary and the phase interface.