Abstract
The Laves phase TiCr2 is readily amorphized by 1 MeV Kr irradiation at temperatures below about 250 K. After an ion dose of order 1019 m-2, however, the amorphous phase (a-TiCr2) gradually transforms to the metastable bcc structure without measureable change of composition. This reaction proceeds by a nucleation and growth mechanism and by growth of any bcc material in the initial microstructure. An in situ study of the temperature dependence of the interface velocity in the temperature range 80-180 K has been conducted in the HVEM-Tandem User Facility at Argonne, which allows simultaneous ion irradiation and TEM observation. A single tilt liquid helium stage was employed with a sample of Cr+30 at. pct. Ti, prepared for TEM by mechanical dimpling and ion milling. The sample initially was composed of two phases, the Laves phase TiCr2 and the Cr-rich bcc phase β. During the experiment the temperature was measured and controlled by a platinum resistance thermometer attached to the stage cold block.
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