Effects of tin and niobium on mechanical properties of Zr-based alloys for the nuclear fuel cladding

The mechanical properties of Zr-based binary(Zr-xNb, Zr-xSn) and ternary alloy systems (Zr-0.8-xNb, and Zr-0.4Nb-xSn) were investigated with the additions of Nb and Sn as alloying elements to Zr metal for the development of the advanced nuclear fuel cladding materials. As the content of Nb or Sn element increased, the strengths of the Zr-based alloys tended to be increased continuously at 400 deg C as well as room temperature showing almost the same values regardless of alloying elements. These behaviors would be due mainly to the solid solution strengthening by the high solubility limit of the Sn element in Zr-xSn and Zr-0.4Nb-xSn systems, but to the mixed effects of both solid solution and precipitation strengthenings by lower solubility limit of Nb element, relative to that of the Sn element, in Zr-xNb and Zr-0.8Nb-xNb systems. Especially, the Zr-based alloys had more finer grains with the increase in the content of the Nb element regardless of various contents of the Sn element. This grain refinement with the addition of the Nb element would also affect the increase in the strength of the Zr-based alloys