Influence of dilute silicon addition on the oxidation resistance and tensile properties of modified Zircaloy-4

Si-added modified Zircaloy-4 (Zry-4) and Zr–Si binary alloys were developed to evaluate the effect of silicon addition on zirconium based alloys for high burn-up application. The silicon content varied from 0 to 0.1 wt% for both the alloys. The relationships between alloy chemistry, microstructure, mechanical property and oxidation behavior were investigated. The ultimate tensile strength of the modified Zry-4 generally increased with the increase in silicon content. The optimum silicon content for improved oxidation resistance turned out to be 0.01 wt% from the weight gain measurement. The weight gain decreased with decreasing Si content from 0.1 to 0.01 wt% although the Si free specimen showed higher weight gain than the 0.01 wt% Si specimen. The details of microstuctural change with silicon addition and its influence on tensile properties and oxidation resistance are discussed; the effects of silicon on the oxide crystal structure, second phase precipitates and microstructure of the metal matrix are studied.