Investigation Of Diffusion Behavior And Mechanical Properties Of Zr-Ni And Zr-Sn System

Zirconium alloys are widely used for nuclear fuel cladding of nuclear reactors because of their excellent nuclear properties,mechanical properties and corrosion resistance.The microstructure and mechanical properties of Zr-based alloy are very important to the safety of nuclear reactor.Therefore,it is necessary to study the microstructure and mechanical properties of Zr-based alloys.Samples of the Zr-Ni and Zr-Sn binary diffusion couples in this work are prepared,and which have been investigated by electron probe microanalysis(EPMA),nanoindentation tester and other equipments.The main conclusions of this work are as follows:(1)All eight intermetallic phases of Zr-Ni phase diagram are found in the interdiffusion zones.The growth mechanism of phases is not diffusion-controlled at the initial transient stage,but which change to diffusion-controlled after long annealing time.The integrated interdiffusion coefficients of intermetallic phases were calculated at different temperatures and the values vary in three orders of magnitude.The interdiffusion coefficient obeys the same rule.The difference of the crystal structure,?-Zr(HCP)and?-Zr(BCC)do not have much influence on diffusion behavior.(2)The decomposed temperature of Ni11Zr9 was determined to be at the range of 930-935 ? from the present experiment.(3)The hardness and Young's modulus of the Zr-Ni IMCs were deduced by nanoindentation.We found that the Young's modulus decreases with the increase of the Zr concentration,where Ni5Zr has the highest Young's modulus of 250.21 GPa and NiZr2 has the lowest value of 76.82 GPa.However,it is without any linear relation to the concentration of Zr,the Ni10Zr7 has the highest hardness as 10.17 GPa,and NiZr2 has the lowest hardness as 5.56 GPa.(4)The interdiffusion coefficients of Zr-5.0at.%Sn system at 1000-1100 ?have been calculated.(5)The hardness and Young's modulus of Zr-5.0at.%Sn diffusion region have been measured by nanoindation When the concentration of Sn in the 0-5.Oat.%range had no significant effect on the Young's modulus of Zr-Sn solid solution.The Zr-Sn solid solution has the maximum hardness 7.1-0.2+0.2 GPa with 2.5-3.5at.%Sn.