High-temperature mechanical behavior of cold-worked stress-relieved Zr-2.5Nb

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The mechanical behavior of cold-worked stress-relieved Zr-2.5Nb pressure tube material used in pressurized heavy-water reactors is summarized in terms of ultimate tensile strength (UTS), yield strength (YS), and percentage elongation to fracture, strain-rate sensitivity (m), strain-hardening index (n), and activation energy for the self-diffusion of zirconium. Tensile tests carried out in the temperature range of 298 to 773 K at three different strain rates are used to calculaten andm. At higher temperatures, UTS, YS, percentage elongation, and n are found to be strain rate dependent. The plateaus observed in curves for UTS or YS versus temperature are typical of dynamic strain aging behavior. The drop in strength at high temperature is correlated with the self-diffusion of zirconium in α-phase zirconium by comparing the activation energies of the two phenomena. Transmission electron microstructures of thin foils from samples tested at ambient temperature and at 773 K are used to explain the observed variation ofn andm with test temperature. A similar trend in the variation ofm and percentage elongation with temperature is also explained.

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Kapoor, K., Murlidharan, K. & Sreedharan, K.M. High-temperature mechanical behavior of cold-worked stress-relieved Zr-2.5Nb. JMEP 4, 610–616 (1995).

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  • activation energy
  • dynamic strain aging
  • percentage elongation
  • self-diffusion
  • strain hardening index
  • strain rate sensitivity
  • ultimate tensile
  • strength
  • yield strength
  • Zr-2.5Nb