Aging Effect on Corrosion and Microstructure of Zr-1.5Nb-0.4Sn-0.2Fe-0.1Cr Alloy

A variety of Nb-containing Zr alloys have been developed as the fuel cladding materials for several decades, since the corrosion resistance was improved by the Nb addition as an alloying element. However, the corrosion behavior of Nb-containing Zr alloys, with especially high Nb content more than 1.0 wt %, is greatly affected by thermal processing . They reported that the corrosion properties of the Nb containing Zr alloys were considerably affected by the microstructure conditions such as the Nb-concentration in the matrix and the second phase types. On the other hand, the aging effect is generally introduced to improve the corrosion resistance for Zr-based alloys, and this improved corrosion resistance was shown to be related to the microstructure changes. The Zr-1.5Nb-0.4Sn-0.2Fe-0.1Cr composition for applying the fuel cladding material was newly developed at KAERI after a systematic control of the alloying elements. Since this new alloy system contains an especially high Nb content, it is necessary to study the aging effect on the corrosion and microstructure change to increase the corrosion resistance. Therefore, the purpose of this work is to elucidate the optimum aging conditions for the Zr-1.5Nb-0.4Sn-0.2Fe-0.1Cr alloy