Low stress creep behavior of Zircaloy-2 vis-a-vis zirconium

Zircaloy-2 is a popular zirconium base nuclear fuel cladding material having tin as a major alloying additions along with Fe, Ni and Cr, each around 0.1 wt %. Low stress creep behavior of a-zirconium and zircaloy-2 has been studied employing helical spring specimens. Detailed experimental results are reported and analyzed elsewhere. Here we present data on a-Zr and zircaloy-2 obtained under identical test conditions of grain size and test temperature with the aim of bringing out the effect of alloying additions to zirconium through the results obtained on the low stress creep behavior of zircaloy-2. The high purity zirconium contained, by ppm, 110 Sn, 350 Fe, 37 Ni, 150 Cr and 880 O while zircaloy-2 contained, by wt %, 1.3 Sn, 0.16 Fe, 0.06 Cr, 0.04 Ni and 0.11 O. Helical spring specimens of wire radius 500μm and spring radius 0.012m were employed in both the cases. Spring specimens were annealed under vacuum (Zr at 923K/1.8ks and zircaloy-2 at 1113K/2.7ks) while on mandrel to develop a matching grain size in both the materials. The mean linear intercept grain size was found to be 16.8μm in alpha zirconium and 16.6μm in zircaloy-2. Close coiled helices were creep tested at 873K using the set-up and procedure described elsewhere. The maximum applied stress was 5.3MN/m2 in the case of zirconium while the same in the case of zircaloy-2 was 3.9MN/m2. Deflection versus time curves for tests conducted at 873K for both the materials are shown in this paper