Relaxation mechanisms in Fe-Al-C alloys

Abstract

The relaxation spectrum of Fe-Al alloys has been studied as a function of Al content and ordering reaction in Fe-Al. Three types of relaxation peaks are observed, with activation energies between 0.8 and 3 eV. Snoek-type relaxation is studied in Fe-(0 to 50 at. pct)Al and compared with the Snoek relaxation in pure iron (C in ␣ -Fe), chromium (C in Cr), and niobium (O in Nb). The snoek-type relaxation peak in iron (at 314 K for 1 Hz) shifts to higher temperatures with increasing Al content in iron. Significant changes in the peak parameters occur when ␣ -Fe is alloyed with Al, because of the ordering reaction in Fe-Al. Peculiarities of the carbon-atom distribution in ordered and disordered Fe-Al alloys are discussed using an atom-interaction model, in which the elastic interaction is supplemented by the chemical C-Al interaction. Two other peaks are observed only when a certain Al content is exceeded: a Zener peak for Fe-(Ͼ10 pct)Al and an X peak for Fe-(Ͼ26 pct)Al. Parameters of these peaks are discussed with respect to alloy structure. Three hypotheses are discussed for the X-peak mechanism with an activation energy about 1.7 eV. A map of relaxation peaks in the Fe-Al system is constructed.

The internal friction peaks correlated to the relaxation of atomic defects in Fe47Al53 alloy

“…A similar phenomenon was also observed by other researchers and they found that the IF peak appearing at around 390 C in Fee(28e35)Al alloys can be divided into two peaks, i.e. X L and X H peaks but they did not give the different explanations [2,3].…”

“…The similar effect of the RDM during the IF measurement has been discussed in Refs. [3,16] and it will not be discussed in the present study. In comparison to Figs.…”

“…Five IF peaks have been observed and the operative mechanisms have been well documented [2]. They are as follows: (1) the dislocation-related relaxation IF peak with an average activation energy of about 0.5 eV appearing at a temperature range of À70 C to À25 C; (2) the Snoek peak due to the diffusion of interstitial carbon (C) atoms with the activation energy ranging from 0.8 to 1.3 eV depending on the Al content; (3) the peak that is correlated to the vacancies and C atoms that only appear in alloys with an Al content (at%) of over 25; (4) the Zener peak caused by the stress-induced reorientation of Al atom pairs with the activation energy in the range of 2.2e2.9 eV and (5) the grain boundary relaxation peak. It has been found that the Al content significantly influences the IF behavior of FeeAl alloys.…”

“…It has been found that the Al content significantly influences the IF behavior of FeeAl alloys. With increasing Al content, the Snoek peak shifts to high temperatures and becomes broad as a result of CeAl long-range 'elastic' interaction [2,3], while the IF peak that is correlated to the vacancies and C atoms is elevated due to the increase in the vacancy concentration [3,4]. In the alloys with relatively high Al contents such as more than 25 at%, ordering significantly suppresses the Zener relaxation [2,5], and the Zener peak is impossible appearing in completely ordered structures [6].…”

Internal Friction of Nitrogen-Doped Zr-Based Glassy Composite Alloy

“…For example, Fe-Al-C crystalline alloys show high internal friction induced by the carbon. 23) In the process for preparing the dispersed ZrN glassy composite alloys in this study, the starting AlN was decomposed to be Al and N.…”