In situ transmission electron microscopy of ion irradiated Fe-Pt alloy thin films

We report the microstructural evolution during irradiation of FePt and FePt 25 at. % thin films sputter deposited onto electron transparent silicon monoxide substrates. The films were studied in situ for 500 keV Kr+ irradiation up to a fluence of 10(15) ions/cm(2) or 4 displacements/atom (dpa). Upon irradiation to approximately 1 dpa, the initial disconnected granular morphology became continuous. In particular, for FePt, accelerated grain growth was observed once the continuous morphology was achieved during ambient temperature irradiation. No atomistic (chemical) ordering from the as-deposited A1 phase into either the L1(0) FePt or L1(2) Fe3Pt phases was observed during ambient temperature irradiation. After irradiation, the specimens were then in situ annealed. The intermetallic ordering temperature, compared to that of an unirradiated film, was lowered by approximate to 200 degrees C for FePt 25 at. %. No decrease in the ordering temperature was observed for irradiated FePt. The rate of FePt grain growth during annealing was very similar for both irradiated and unirradiated films over the 25-650 degrees C temperature range investigated. (c) 2006 American Institute of Physics.