Point defects in FeAl

Abstract

Point defects in annealed B2-phase FeAl samples in the range 47-53 at.% Fe were studied using 57Fe MSssbauer spectroscopy. Spectra were analyzed using local environment models according to which point defects in atomic shells close to probe atoms induce shifts in the nuclear monopole interaction. For well-annealed samples, better results were obtained assuming only the presence of Fe~ antisite and VFe vacancy defects, and not of AIFe antisite defects. Monopole interactions of 57Fe probes on the Fe and Al sublattices having no defects in the first two shells were about + 0.27 and -0.03 mms -1, respectively, with respect to Fe in alpha-Fe metal. The shifts induced by Fe~ and VFe defects in the first shells of Fe probes on the Fe and Al sublattices were -0.15 and -0.24 mm s -1, respectively, and, in the second shells, +0.06 and +0.011 mms -1. In addition to structural defects needed to accommodate deviations from stoichiometry, annealed samples were found to contain several percents of Fe~ and VFe defects due to lattice disorder, with greater disorder in Fe-deficient alloys.PACS 61.72.Cc -Kinetics of defect formation and annealing. PACS 61.66.Dk -Alloys. PACS 76.80 -M5ssbauer effect; other y-ray spectroscopy. PACS 01.30.Cc -Conference proceedings.

Bonding of Cr and V in FeAl B2 phase

“…According to theoretical study [11], the predominant defects in the stoichiometric FeAl B2 structure are vacancies on the Fe sites and the Fe antisites on Al sites, which were confirmed experimentally by Mö ssbauer spectroscopy [12]. The FeAl B2 phase contains a negligible amount of defects such as aluminum antisites and the vacancies on Al sublattices [13].…”

Embedded atom method study of the interactions between point defects in iron aluminides: Double defects

“…The development of new, more ductile, Fe-Al alloys depends on a thorough understanding of their properties, implicating a better comprehension of the properties and behaviour of defects in these materials. Experimental [3][4][5] as well as theoretical studies [6][7][8][9][10][11] suggest that iron aluminides present complex point defects, especially double defects. In addition, it has been demonstrated that 'quenched-in' vacancies are responsible for a large strengthening effect both on B2 FeAl [12] and on disordered (A2) Fe-Al alloys [13,14].…”

Atomic Arrangement in B2 FeAl Prepared by Self-Propagated High-Temperature Synthesis at Varying Al Content and Annealing

“…It means that thermal defects in B2 FeAl consist of Fe sublattice vacancies and antisite atoms, while constitutional defects consist of Fe antisites in the Fe-rich side and Fe vacancies in the Al-rich side. The triple-defect structure of B2 FeAl has been confirmed also by MS [3] and PAC analysis [2]. It is worth noticing here that no traces of Al-antisites (or vacancies) were detected.…”

“…So, it could be suggested that such pre-existing disorder may have affected the final defect structure of B2 FeAl. On the other hand, the atomic arrangement of B2 FeAl may also be influenced by the multiphase composition of analyzed powders as compared to monophase B2 FeAl studied in [1][2][3][4]. However, this assumption needs additional study.…”

“…Experimental study of thermal and constitutional defects formed in B2 FeAl has been carried out by XRD, perturbed angular correlation (PAC), 57 Fe MS [1][2][3]. XRD investigations of a in B2 FeAl within stoichiometric composition elucidated its triple-defect structure [1].…”