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TRODUCTION

DUE to its relatively high ductility, good corrosion resistance, and low absorption of neutrons, Zr has received considerable attention from a variety of industries, including nuclear and chemical.[1–3] As such, efforts have been undertaken to understand the mechanical response of Zr subjected to various loading conditions.[4–14] These studies have shown that the mechanical response of high-purity zirconium is sensitive to interstitial content, grain size, texture, strain rate, and temperature. Specifically, strain rate and temperature have been shown to influence yield stresses and workhardening rates.[4] These effects have been explained in terms of the relative activation of twinning versus slip.[6] Although considerable work has been devoted to examine the mechanical response of Zr deformed in uniaxial stress and strain states, relatively little is understood about the behavior of Zr under more complex loading conditions. To shed light into the mechanical behavior of Zr under such conditions, we recently reported our findings on the influence of texture on the dynamic, large-strain deformation of Zr.[15] Higher elongations were observed in samples possessing most of their crystallites preferentially orientated such that prismatic slip was favored. However, our previous study did not examine the effect of temperature, which is expected to influence the relative contribution of slip and twinning during deformation, ultimately dictating the large-strain failure response. To this end, bulletshaped Zr specimens were dynamically extruded at room temperature and 523 K (250 C). The deformed microstructures have been characterized in detail to understand the influence of temperature on the behavior JUAN P. ESCOBEDO, Lecturer, is with the UNSW Australia, Canberra, BC 2610, Australia. Contact e-mail: j.escobedo-diaz@adfa. edu.au ELLEN K. CERRETA, RICARDO A. LEBENSOHN, and GEORGE T. GRAY III, Scientists, DANIEL T. MARTINEZ and CARL P. TRUJILLO, Technologists, are with the Los Alamos National Laboratory, Los Alamos, NM 87545. Manuscript submitted March 18, 2014. METALLURGICAL AND MATERIALS TRANSACTIONS A

of Zr. The findings from this study yield insight toward an advanced understanding of the coupled influence of large-strain loading and temperature on the deformation of Zr.

II.

EXPERIMENTAL METHODS

A synopsis of the experimental conditions is reproduced in Figure 1, further details can be found in Reference 15. All specimens were prepared from clockrolled and annealed (823 K (550 C) for 1 hour), highpurity Zr and had similar microstructural features as those reported in:[14] an average grain size of 15 to 20 lm and a strong basal texture aligned with the through- thickness direction of the plate, as evidenced by the red color in Figure 1(a). The chemical composition is provided in Table I. Dynamic tensile extrusion tests were conducted in a modified Taylor Gun Apparatus.[16] A heating system was added to the apparatus to conduct tests at elevated temperatures (523 K (250 C)). Bullet-shaped Zr specimens (Figure 1(b)) w