Time-differential length change measurements for thermal defect investigations: Intermetallic B2-FeAl and B2-NiAl compounds, a case study

Time-differential length change measurements after temperature changes were developed and applied to the study of high-temperature atomic defect in th e case of intermetallic alloys. The enthalpies H-l(F) = 1.0 +/- 0.1 eV or H -l(E) = 1.5 +/- 0.2 eV derived for B2-Fe55Al45 from the temperature-depende nt amplitudes and time constants of the length change, respectively, coinci de with the vacancy formation and migration enthalpies H-V(F) and H-V(M) fr om earlier positron studies. This demonstrates the feasibility of the techn ique. By this technique, for the first time, the enthalpies H-V(M) = 1.8 +/ - 0.1 eV and H-V(F) = 1.5 +/- 0.25 eV in B2-Ni47Al53 were determined.