The matrix composition in one Zircaloy-2 (Zry-2) and four Zircaloy-4 (Zry-4) materials has been measured with the atom probe technique. It was found that only about 10% of the alloying elements Fe, Cr, and Ni added to the alloy remain in solid solution in the matrix of nuclear fuel claddings. No significant difference in matrix concentration of Fe and Cr could be detected in Zry-4 materials with different heat treatment and different corrosion resistance. Even a Zry-4 material analyzed directly after a β-quench operation had a matrix concentration of only 0.02 wt% Fe and 0.03 wt% Cr.

Atom probe analysis was also used to study the oxide-metal interface in oxide layers formed in dry air and water on needle shaped Zry-4 specimens. Transmission electron microscopy of the oxide layers showed that these were approximately 10 nm thick and contained 5 nm sized oxide crystallites in an amorphous layer. According to atom probe analysis, the thin oxide layers had a low oxygen content, less than 50 atomic percent.