Effects of high rates of loading on the deformation behavior and failure mechanisms of hexagonal close-packed metals and alloys

A substantial amount of work has been performed on the effect of high rates of loading on the deformation and failure of fee and bcc metals. In contrast, the influence of high strain rates and temperature on the flow stress of hcp metals has received relatively little attention, and the modes of dynamic failure of these materials are poorly characterized. The low symmetry of these materials and the development of twinning lead to a particularly rich set of potential mechanisms for deformation and failure at high rates. This article reviews results of high-strain-rate deformation and dynamic failure studies on hcp metals, with a focus on titanium, Ti-6Al-4V, and hafnium. Strain rates as high as 10(5) s(-1) are considered, and observations of adiabatic shear localization and subsequent failure are discussed.