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LT 10 is a new version of LT program designed to analysis of Positron Annihilation Lifetime Spectra (PALS). The new program is equipped with a new user interface and other features unavailable in its previous versions. It has been created again in a modern programming language and is now compatible with the latest operating systems.

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The positron lifetime spectroscopy is employed to study vacancy formation in intermetallic phases of DO3 and B2 structures from Fe-Al system as a function of Al concentration, ternary additive (Cr) and their thermal treatment. Lifetime spectra were fitted en block by a simple trapping model encoded directly to the software (computer program LT-9). In the investigated range of Al concentration (28, 38, 42, and 45 at%) only two types of defects are found. In DO3 region a single type of defects (characterized by positron lifetime τ 1 = 170 ± 2 ps) is detected and indicated as vacancies in the Fe sublattice (VFe). In B2 region a small amount of an additional type of defects (characterized by positron lifetime τ 2 = 214 ± 13 ps) appears. Supposedly, these are vacancies in Al sublattice (V Al ). For Fe28Al and Fe28Al5Cr samples changes in V Fe concentration are determined as a function of the sample composition, annealing time at 1000• C and quenching the samples to air and oil. The defect concentration increases with increase in Al content. For FeAl with Al above 38 at%, the total concentration of defects is so high that positrons are exclusively trapped by defects. Therefore the concentrations V Al and V Fe cannot be determined separately. However, the ratio of V Al concentration to VFe concentration is estimated as a function of Al content.

The concentrations of quenched‐in vacancies in Fe‐Al and Fe‐Al‐Cr systems after their various thermal treatment were studied by positron lifetime spectroscopy. The experimental data were analyzed with the 2‐state trapping model directly implemented to the code of the computer program (LT‐9 2). The number of quenched‐in vacancies strongly depends on the rate of quenching. For fast quenched samples the atomic concentration is of order of 10–4 and it radically falls after annealing at 500 °C for 0.5 h. A comparison of Fe28Al and Fe28Al5Cr samples, after analogical heat treatment, showed that chromium addition caused a systematical decrease of the resistant vacancy concentrations. In the samples that were slowly cooled after quenching at 1000 °C the positrons are trapped at precipitates of minor alloying elements. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)