Precipitation and growth study of intermetallics and their effect on oxidation behavior in Zr-Sn-Fe-Cr alloy

摘要

Microstructural evolution of the second phase precipitates and their microchemistry in Zr-Sn-Fe-Cr alloy during various alpha annealing heat treatments have been investigated by transmission electron microscopy and energy dispersive spectrometer attached with scanning transmission microscopy. Two types of precipitates, namely, Zr - rich Zr _2(FeCr) with aspect ratio one and Zr lean Zr(FeCr) _2 with parallelepiped morphology were identified. Size distribution of the precipitates was estimated from small angle neutron scattering. The effect of precipitate size, its distribution and matrix microstructure on the oxidation behavior of the alloy was studied during accelerated autoclaving. The shorter duration annealing at 700°C does not improve the oxidation resistance of the alloy as it would lead to formation of non uniform distribution of alloying elements and precipitates in the matrix. It is revealed that alpha annealing at 700°C for 10 h imparts a significant resistance to oxidation as well as substantial formation of Zr(FeCr) _2 precipitates.