Phase transformations of σ-FeCr induced by ball milling

Abstract

A tetragonal sigma phase σ-Fe 0.54 Cr 0.46 transforms gradually into a bcc phase by ball-milling in argon. Mössbauer spectroscopy shows further the presence of an amorphous phase. It starts to form after 25 h of milling in our experimental conditions.

Influence of atomic ordering on sigma phase precipitation of the Fe50Cr50 alloy

“…The difference between these two values is strictly a consequence of the preparation method. It is well known that in alloys produced by MA, the crystallite size decreases with the milling time due to the fragility which is induced by microstress inside the grains [11].…”

“…In the MA sample spectrum appears a singlet whose IS is 0.087 mm/s. Costa et al have obtained this component in the Mössbauer spectra of Fe-Cr alloys with similar concentrations and they attributed it to bcc Fe-Cr amorphous grains [11,18,19]. Costa et al prepared their alloys by MA samples of r-FeCr tetrahedral structure which was transformed into a bcc structure with milling time.…”

“…Cr, is to retard the precipitation of sigma structure when the material is subjected to high temperatures. The occurrence of this structure is not immediate, experimental studies have shown that the heating time necessary to completely precipitate the structure may vary from a few days to several weeks depending of the heating temperature [6,[8][9][10][11]. The purity of the alloy as well as the presence of carbon in small amounts retards the formation of the sigma phase [12].…”

Debye temperature of nanocrystalline Fe–Cr alloys obtained by mechanical alloying

“…In particular, in equiatomic or near-equiatomic FeCr alloys milled in vacuum or argon atmosphere, this effect was observed both in alpha and sigma phases, e.g. [29][30][31][32]. …”

Sigma-Phase in Fe-Cr and Fe-V Alloy Systems and its Physical Properties

“…Concerning the application of MS to study the issue, the first one was devoted to the investigation of such transformation in Fe-Cr alloys induced by ball milling [62,63]. Both nano-grained as well as policrystalline samples of σ-Fe 54 Cr 46 alloys were ball-milled in argon atmosphere.…”