| The purpose of this study is to design and fabricate a new zirconium alloy with higher mechanical properties and to characterize it. The new experimental zirconium alloy was Zr-1.0Nb-0.5Sn-0.5Cr-xMo with addition of 0.2, 0.5, 0.7wt.% Mo, respectively. In order to characterize the experimental alloys, annealing heat treatment was done from room temperature(20℃) to 800℃ for 1hr. The tensile strength at room temperature and Vickers micro-hardness have been measured, and the microstructure was observed to identify the distribution and the shape of the precipitates with annealing temperature. Results showed that micro-hardness, ultimate tensile and yield strengths increased with increasing annealing temperature from 300℃ up to 450℃, while ductility remained practically unaffected by annealing. Transmission electron microscopic examination revealed decomposition of α prime phase and formation of fine cylindrical precipitates during annealing at 450℃ for 1hr., and SADP analysis revealed that the precipitates were mainly ZrMo₂, while annealing at 550℃, caused formation of cell boundary and coarsening of the precipitates. Molybdenum, therefore, was found to be a fairly effective element to inhibit the movement of the dislocations during recovery and thus retard the formation of the recrystallized grains. |
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