Papers by Keyword: Zr Alloy

Abstract: In this paper, there are tow part of module for predicting the Annealing heat treatments of Zr tube. The artificial neural network (ANN) were used for relationship between mechanical property and annealing parameters. The genetic algorithm (GA) were used for Annealing heat treatments of Zr tube. The best ANN network architecture is 2-8-3, and the optimum values of momentum factor is 0.8 while the Crossover is also 0.8 by ANN-GA, which can be efficiently track the effect of annealing Heat treatment on properties for Zr-4 alloy. Keywords: Zr alloy, Heat Treatment, mechanical propert

Abstract: Zr1 Nb1 Sn0.2 Fe alloy exhibited the transition of the stress exponent from 6.5 to 7.5 in the lower stress region to 4.2 in the higher stress region. The reduction of stress exponent at high stresses in Zr1 Nb1 Sn0.2 Fe can be explained in terms of the dynamic solutedislocation effect. The temperature range of dynamic strain aging generally increases with increase of strain rate. The dynamic strain aging due to oxygen atoms observed in Zr alloys at temperatures between 300°C and 400°C during tensile test at the strain rate of 1 x10^-3/sec should occur below 300°C in creep because the creep rates (1 x 10^-6 and 1 x10^-8) are much lower. Since solute atoms which can act as mobile obstacles are Sn and oxygen, the solute-dislocation interaction for the strengthening of creep resistance at intermediate temperatures is likely caused by Sn atoms. Dislocation networks and pile-ups around the precipitates were observed at the applied stress of 80MPa. And dislocations were observed to be distributed more or less randomly at the applied stress of 120 MPa. The more homogeneous distribution of dislocation in the region of low stress exponent at 120 MPa is thought to be caused by the dynamic strain aging effect of Sn atoms.

Abstract: The effects of Fe addition on the precipitate characteristics and out-of-pile corrosion behavior of Zr-1Nb-xFe alloys, with x=0, 0.2 and 0.4 respectively, were investigated. The experimental results showed that the alloy with the composition of Zr-1Nb-0.4Fe had the best corrosion resistance and the alloy with the composition of Zr-1Nb-0.2Fe had the worst corrosion resistance. The relationship between the corrosion behavior and the microstructures including precipitate characteristics was discussed, and the elements contents, area fraction, as well as the mean diameter of the precipitate were analyzed. The β-Nb precipitate was found in Zr-1Nb alloy, both Zr (Nb,Fe)₂ precipitate and β-Nb precipitate were formed in Zr-1Nb-0.2Fe alloy, while only Zr (Nb,Fe)₂ precipitate was observed in Zr-1Nb-0.4Fe alloy. It has been found that the size of precipitates increased with the increasing of Fe content. This work indicated that the Fe content dominates the crystal structure, volume fraction and the element contents of the precipitate, which affect the corrosion resistance of Zr alloy.

Abstract: The authors have developed a new friction-stir welding (FSW) tool that enables to weld high-softening-temperature materials (HSTMs), such as steels, titanium and zirconium alloys. The new tool is made of a Co-based heat-resistant alloy strengthened by precipitating intermetallics, Co₃(Al,W), with a L1₂ structure at high temperatures. The Co-based alloy tool exhibits yield strengths higher than 500 MPa at 1000 deg C, so it might have a great potential as a tool material for FSW of HSTMs. In this study, the feasibility of using the Co-based alloy tool with various HSTMs was examined. Changes in the tool shape during FSW and the weld appearances produced with the Co-based alloy tool will be briefly shown.

Abstract: The recrystallization of a Zr-2Hf alloy sheet deformed by plane strain compression at room temperature and then heat treated in the temperature range 500-650°C is studied. The microstructure, local and global crystallographic textures are investigated by EBSD and X-ray techniques. The as-deformed condition exhibits a heterogeneous microstructure composed of highly and less deformed zones, the EBSD indexing of the latter ones being more reliable. The asdeformed condition displays a (0001) < 0 1 10 > crystallographic texture. The evolution of the microstructure during recrystallization very much depends on the amount of local deformation. Recrystallization begins in highly deformed zones, new grains having two variants of texture components, {0001} < 0 1 10 > and {0001} < 0 2 11 >. Some change of preferred orientations concomitant with grain growth at 600 and 650°C has been observed with a decrease in the {0001} < 0 1 10 > component and an increase in the {0001} < 0 2 11 > component.