Effects of intermetallic particles on the SCC initiation of zirconium alloys

In order to investigate effects of intermetallic particles on SCC initiation of zirconium alloys, tensile tests were conducted in an iodine atmosphere using zirconium plates with different amounts of impurities, and Zircaloy-2 plates.SCC susceptibility of zirconium increased significantly with its iron content. Even small amounts of iron could form the intermetallic compound ZrFe₂ whose particle size and number increased with iron content. In the case of Zircaloy-2, two different types of ternary compounds were detected, namely Zr(CrFe)₂ and Zr₂(NiFe). Metallographic examinations showed that the particles located at grain boundaries were important sites of SCC initiation in zirconium alloys. The initiation probability increased significantly with the amount of the particles, which supported the strong correlation between SCC susceptibility of zirconium and its iron content.