Effect of Cold Working and Annealing on Grain Size and Hardness of a Zr-2.5Nb Alloy

Samples of Zr-2.5 wt.% Nb alloy, obtained from pressure tube, were annealed in the temperature range 700– 900 °C up to 100 h to investigate the grain growth behaviour. The grain size increases with annealing time ( ) and temperature ( according to the relationship ∈ exp((– 387 kJ/mol)/RT). Room temperature hardness increases with the increasing annealing temperature and grain size, which is ascribed to the transformation of β- phase into martensitic α' and the substructure developed during quenching. The grain sizes, produced by further cold working and annealing for short time (< 1 h), and the corresponding hardness values, however, support the Hall-Petch type relationship in the limited cases.