Microstructural influence on high temperature creep flow of Zr–1%NbO alloy in near-α, (α + β), and β temperature ranges in a high vacuum environment

Uniaxial tensile creep tests were carried out at 650–1100 °C in a high vacuum environment on Zr–1%NbO tubes with various microstructures. The effect of microstructure on creep flow in the (α + β) temperature range is significant (the creep rate being modified by up to three orders of magnitude) under stresses lower than 10 MPa, that is, for stress values of one order of magnitude lower than those characteristic of prototypical Loss-of-coolant-accident (LOCA) conditions. Under stresses higher than about 20 MPa, this effect is much smaller. No transformation-induced plasticity was detected from anisothermal creep tests, once the creep strain was thoroughly taken into account to process experimental strain vs. time data.