Defect analysis in FeAl and FeSi with positron lifetime spectroscopy and Doppler broadening

摘要: Abstract Systematic measurements of thermal defect formation in intermetallic compounds FeAl and FeSi have been carried out by using positron lifetime spectroscopy Doppler broadening. Temperature dependence leads to the effective enthalpy Hfeff, which decreases D03-ordered from 0.92 eV (Fe75Al25) very small value 0.73 (Fe69Al31) with higher concentrations Al, B2-ordered it is nearly constant about 1 eV. In enthalpies 1.21 Fe82Si18 1.04 Fe76Si24 were found. The volume Vfeff can be measured pressure concentration. It found smaller than mean atomic Ω both D03 structures A2-structured FeAl. This indicates that single vacancies are predominant type these structures. B2-FeAl increases 1.44 Ω, explained bound defects containing more one vacancy. At temperatures above 1000 K Al 42 at.% an additional increase lets us suggest a change type, possibly indicating on Al-sublattice. By comparison data differential dilatometric experiments (Kerl R, Wolff J, Hehenkamp Th. Intermettalics, this volume) possible determine trapping rate μ systems for first time. concentration dependent, rising 2.9×10 +14 s −1 6.6×10 Fe76Si24. A high 56.0×10 Fe65Al35.