An SEM study of β-phase decomposition during the annealing of Zr-2.5% Nb alloy

Abstract The effect of annealing on the decomposition of the β-phase in Zr-2.5% Nb pressure tube material was studied by SEM (scanning electron microscopy). Annealing was carried out at 400°C for 0, 24 and 1000 h. Previous to annealing, the specimens were electrolytically hydrided, the final hydrogen amount being about 60 μg/g. Long time annealing causes the β-phase ligaments to decompose into smaller particles. Hydrides are formed along the β-phase ligaments and they become shorter as the lengths of the ligaments decrease with annealing. The SEM technique proved to be useful in studying the decomposition of the β-phase ligaments.