| Abstract |
| The effects of cooling rates from 400 to 200℃ on hydride reorientation were investigated using ring specimens of 250 ppm and 500 ppm H Zr-Nb cladding tubes. For no stress conditions with cooling rates of 2.5 and 25.0℃/min, the 250 ppm H specimens show that hydride plates are reprecipitated only in a circumferential direction during the cooling from 400 to 200℃, but the hydride plates appear to be much shorter for the 25.0℃/min cooling rate. However, the 500 ppm H specimens show that hydride plates are reprecipitated as a mixture of circumferential and radial hydride plates for the 25.0℃/min cooling rate. This mixed hydride plates may be caused by a blocking effect of circumferential hydrides undissolved on the one hand and by a considerable tensile hoop stress locally generated by a large difference in the cooling rates between outer and interior layers on the other hand. For 150 MPa tensile hoop stress conditions with a cooling rate of 2.5℃/min, the 500 ppm H specimens show a relatively shorter radial hydride plates than the 250 ppm H specimens, which may be explained by a blocking effect of undissolved circumferential hydride plates in the 500 ppm H specimens. Tensile tests for the specimens experiencing the cooling from 400 to 200℃ under the 150 MPa hoop stress conditions indicate that there is little impact of hydrogen content on ultimate tensile strengths but the 250 ppm H specimens generate less plastic elongation and more noticeable cleavage fracture than the 500 ppmH specimens, which may be caused by relatively longer |
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| Key Words |
| hydride, alloy, deformation, ductility, tensile test |
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