The Mössbauer effect was used to investigate the cementite state in cold‐worked steel. An intensive dissociation of cementite is found at plastic deformation of the steel with the structure of plate perlite. For deformation of 93% this dissociation amounts to 50%. The effect of dissociation was not observed in the steel with granular perlite. The fact that cementite dissociates at deformation may be explained by the increase of bond energy between C atoms and dislocations as compared to that for carbon in the cementite lattice. Alloying with the elements which decrease the bond of dislocations and substitutional impurities has the result that the cementite becomes much more stable at deformation. This is shown on the example of steel containing cobalt. The latter fact influences strongly the mechanical properties of a cold worked steel.

No abstract

The effect of localized magnetic moments on the positron annihilation was first found in dilute solid solutions of Fe in Pd (1). The concentration dependence of the relative probability for positron annihilation with conduction electrons (W ) in CoAl alloys has shown (2) that in the range of stoichiometric composition the W value is essentially increased. This feature may be accounted for by the positron interaction with structural vacancies and the localized electronic states. The existence of localized magnetic states in CoAl alloys with slight excess of cobalt atoms (50.5 at% co) was confirmed by nuclear magnetic resonance experiments (3). P P Some information has been reported (4) about the formation of localized magnetic moments in FeAl alloys in the range of stoichiometric composition and the present investigation has been undertaken to study their effect on the positron annihilation parameters. The experiments were carried out for FeAl alloys with b.c.c.CsCl type structure containing 32 to 52 at% Al.FeAl alloys with 48, 49, 50, 51, and 52 at% A1 were obtained by melting carbonyl iron and high-purity aluminium in an induction furnace in argon atmosphere. Subsequent chemical analysis has indicated that alloy compositions differ slightly from the above mentioned values. The ingots were subjected to homogeneizing annealing in vacuum at 1000 C for 24 h. The samples were cut from the inner part of ingots.Angular distribution curves for 2 r positron annihilation in FeAl alloys were measured using a VA-64 apparatus. 0 Fig. 1 shows the dependence of the relative probability for positron annihilation with conduction electrons on concentration. It is seen clearly that the alloy with 51 at% Fe has a W value by % 10% larger than that for the rest of alloys under investigation for which W is about the same. P P Previously studied CoAl alloys (2) exhibit the presence of structural vacancies for concentrations with excess A1 atoms (compared with the equi-atomic composition)

An analysis of the degree of positron localization on alloy components is developed in application t o palladium, tantalum, and yttrium hydrides. The method is based on the account of positron-ionic core electron interaction. From the results a conclusion is made about a principal positron localization on metallic components. The degree of the localization depends on the nature of the transition metals. The electronic structure of a hydrogen ion can be changed from the partial "proton" state (Pd-H) up to nearly the complete "proton" state (Y-H). The anionic hydrogen state is excluded.Die Analysierungsmethode fur den Positronenlokalisierungsgrad an den Legierungskomponente wird fur die Anwendung aof Palladium-, Tantal-und Yttriumhydride weiterentwickelt. Die Nethode beruht auf dcr Positronen-Ionenrumpf -Elektronenwechselwirkung. Aus den Ergebnissen dieser Arbeit werden Schlusse uber die prinzipielle Positronenlokalisierung a n den metallischen Komponenten gezogen. Der Grad der Lokalisierung hangt von der Natur des Ubergangsnietalls ab. Die elektronische Strukt,ur eines Wasserstoffions kann von dem partiellen p protonen"-Zustand (Pd-H) zu dem nahezu vollstandigen ,,Protonen"-Zustand (Y-H) geandert werden. Der anionische Wasserstoffznstand wird ausgesehlossen. 21*

A study is made of the anisotropy of the properties of tungsten single crystals for equivalent crystallographic orientations relative to the growth axis. An essential difference in the interplanar spacings for samples with equivalent faces perpendicular and parallel to the growth axis was found. For the compared equivalent planes differences in the positron annihilation parameters were observed which point to an anisotropy of the Fermi surface caused by carbon atoms with an anisotropic electron configuration. The sublimation energy for equivalent faces is also shown to be anisotropic.