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Abstract: Electron backscatter diffraction, electron channeling contrast, secondary electron imaging techniques and micro-hardness tests are jointly employed to investigate the precipitate evolution and recrystallization of a Zr–0.85Sn–0.4Nb–0.4Fe–0.1Cr–0.05Cu alloy during aging between 600 and 700°C following β-quenching treatment. Results show that the implemented quenching produces plate structures with specific orientations. For specimens aged at lower temperature or for shorter time, the plate structures maintain yet second phase particles (SPPs) precipitate along the plate boundaries. For specimens aged at higher temperature or for longer time, recrystallizations are completed. The recrystallized structure presents irregular grain shapes, non-uniform grain sizes and randomly distributed SPPs. In spite of the morphology discrepancies, some recrystallization grains inherit the orientation feature of the prior α plates. With increasing temperature and time, hardness decreases and no hardness peak is observed. Reasons accounting for the formation of different microstructural features are tentatively discussed. [Copyright &y& Elsevier]

Abstract: The growth behavior of the second phase particles (SPPs) in a Zr–Sn–Nb–Fe–Cr–Cu alloy during aging (600–700°C, 30–1800min) has been investigated using scanning electron microscopy (SEM) and an image analysis technique. Microstructural observations show that the precipitated SPPs distribute linearly along the boundaries of α plates at the initial aging stage. As the aging time prolongs and/or temperature increases, the linear distribution feature of SPPs weakens gradually and finally a random distribution is formed. A numerical analysis confirms that the growth of SPPs follows well the second order kinetics of Kahlweit theory and the activation energy is experimentally determined to be 194kJ/mol. The reason for the larger growth activation energy of the SPPs in the experimental alloy, compared to that in Zircaloy-4, is discussed and ascribed to the addition of Nb element. [Copyright &y& Elsevier]

Abstract: The formation and evolution of the adiabatic shear bands in the zirconium alloy impacted by split Hopkinson pressure bar were investigated by means of the experimental design. The different strain levels in the zirconium alloy subjected to high strain rate loading were first designed by two times impact at almost same strain rate. Only deformed bands were formed in the zirconium alloy impacted once, and two types of adiabatic shear bands, namely deformed bands and transformed bands, were distinguished in the zirconium alloy impacted twice. Microstructural observation shows that the deformed bands showed the severe strain localization, and the transformed bands composed the ultrafine and equiaxed grains. The formation of the ultrafine and equiaxed grains in the transformed bands could be attributed to the rotational dynamic recrystallization mechanism. Based on the characterization of the ASBs formed at different strain stages, the evolution process of the ASBs is proposed. The deformed bands are suggested as the initial stage of the transformed bands formation, and the transformed bands are considered as the further development of the deformed bands. The microhardness measurements show that the microhardness values in the transformed bands were higher than that of the deformed bands and original sample because of strain hardening and grain refining. [Copyright &y& Elsevier]