Crystallisation of oxygen-stabilised amorphous phase in a Zr50Cu50 alloy

The crystallisation of the oxygen-stabilised amorphous phase in a Zr50Cu50 alloy has been investigated by means of neutron diffraction and electron microscopy. The crystallisation microstructure consists of ZrO2, Zr2Cu and Zr7Cu10. A two-stage crystallisation mechanism is suggested: (i) primary crystallisation of Zr2Cu and (ii) formation of nanocrystals ZrO2 and Zr7Cu10. In (i), it is proposed, Zr2Cu crystallises from the oxygen-stabilised amorphous phase, leaving an oxygen- and copper-enriched matrix ; Zr2Cu rapidly grows and eventually attains a grain size of about 100 nm. In (ii), it is suggested, the residual amorphous matrix crystallises into nanocrystals ZrO2 and Zr7Cu10 due to the sluggish growth of ZrO2 and to the already formed ZrO2 which acts as a growth barrier to Zr7Cu10. In this case there is no particular orientation relationship between Zr2Cu and Zr7Cu10.