Miniaturized Disk-Bend Testing and Microstructure of 3.8 Mev Zr3+ Irradiated Zr3Al

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Abstract
The mechanical behavior of Zr3Al irradiated with 3.8 MeV Zr3+, ions has been investigated using a miniaturized disk bend test (MDBT). The samples tested were 3 mm in diameter and either nominally 100 or 250 μ m thick. They were irradiated at 250 °C to peak doses varying from 0.0041 to 2 displacements per atom (dpa). The yield stresses, σy, of the thin specimens were independent of dose, within experimental error, and comparable to that of unirradiated Zr3 Al. However, for the thick specimens σy was significantly larger for the irradiated material, possibly increasing to a maximum at a peak dose between 0.02 and 0.06 dpa. The relative insensitivity of σy of the thin specimens to irradiation, compared to the thick ones, is a surprising result for which we have no satisfactory explanation. Examination by transmission electron microscopy showed that Zr3Al begins to undergo chemical disorder at a dose of only 0.02 dpa and Is nearly completely disordered at 0.41 dpa. Electron diffraction indicates the presence of satellite reflections along 〈110〉 in {001} diffraction patterns. The nature of the defects responsible for these has not yet been determined, although rather similar effects have been observed in electron and Kr+-ion irradiated Zr3Al and attributed to elastic softening of the lattice. The possible roles of these defects, as well as disordering, are discussed.