Characterization of nuclear fuel rod cladding zirconium alloys

Zirconium alloys are very important for nuclear industry with their outstanding features. Due to enhanced mechanical and physical properties, Zircaloy-4 is the most popular zirconium alloy. Although zirconium alloys are produced by many techniques, cold rolling has been chosen for this study owing to its ease of use and cheapness. In this study, Zircaloy-4 rods are heat treated and cold rolled to different (15%, 30%, 45%, 60%, and 75%) reduction ratios to determine the effect of heat treatment and cold rolling on physical and mechanical properties. X-ray diffractometer (XRD) is used for phase analysis, atomic force microscope (AFM) and surface roughness tester are used for surface analysis, scanning electron microscope (SEM) is used for fractography study, energy dispersive spectroscope (EDS) is used for elemental analysis, and optical microscope is used to examine the microstructure. Mechanical properties are investigated using universal mechanical tester (UMT) and micro Vickers hardness tester. It is found that hardness increased with increasing reduction ratio. Increase in hardness altered the fracture from ductile to brittle. Surface roughness decreased with increasing reduction ratio. Oxygen absorption decreased with decreasing surface roughness. Absorbed oxygen did not create a new phase due to dissolving in interstitial positions. There is only Zr-α phase in all samples. Keywords: Zirconium alloys, Zircaloy-4, nuclear fuel cladding, cold rolling, surface roughness, mechanical properties.