Mechanical Alloying Process of a Mixture of α-Fe and γ^′-Fe₄N Powders

Abstract

Bcc-like metastable powder of iron nitride can be synthesized by mechanical alloying of a mixture of elemental Fe and γ′-Fe4N powders. Its heat of formation deduced from differential scanning calorimetry is about +6.5 kJ/mol at a composition of 11 at%N. Both this value and its magnetization at room temperature are in good agreement with those of the bcc-like powder produced by ball milling of elemental Fe powder in NH3 gas atmosphere.

Mechanical Milling Process of High Nitrogen Austenite

“…As a result, whole diffraction spectrum became "bcc-like" as observed in mechanically alloyed powders reported earlier. 4,5) Present results indicate that ball milling process tends to decompose nitrogen martensite as reported by Paseka et al 12) In other words, martensite can not be obtained by prolonged milling as far as present milling condition is concerned. If formation and decomposition of martensite proceeded simultaneously, diffraction lines from martensite should be lost immediately after austenite was depleted.…”

“…With a hope to produce powders of bct iron nitride, mechanical alloying experiments have been carried out by some research groups. [4][5][6][7][8][9][10][11][12][13][14] Present author examined two different approaches, i.e., ball milling of elemental iron powders under NH 3 gas atmosphere 4) and milling of the a-Fe and gЈ-Fe 4 N in Ar gas. 5) Both experiments resulted in formation of metastable iron nitride exhibiting bcc-like diffraction spectra and no enhancement was observed in the magnetization.…”

“…Other research groups also reported essentially the same results. [4][5][6][7][8][11][12][13][14] It is well known that high nitrogen austenite undergoes martensitic transformation at room temperature when it is subjected to plastic deformation. Mechanical alloying is known to be accomplished by repeated kneading of starting powders utilizing kinetic energy of balls in a vial.…”

Mechanically induced phase transition in Fe4N during ball milling and shock compression of powders

“…Likewise the high magnetization and oxidation resistance of ␥ -Fe 4 N make it a candidate for use in magnetic recording [3]. Reports of fabrication of the ␣ -Fe 16 N 2 phase by annealing ball milled iron nitride mixtures have sparked studies on a range of iron nitrides [4][5][6]. The phases produced by ball milling and annealing vary widely in composition and processing parameters.…”

The structure of nitrogen-supersaturated ferrite produced by ball milling

“…In the system Fe-N, ball-milling [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] in particular has been frequently discussed as a possible synthetic route to produce single-phase &''-Fe 16 N 2 , a nitrogen-ordered martensitelike phase, which is claimed to possess unique magnetic properties [23], but has not been produced as single-phase bulk material until now. Two other metastable Fe-N phases could be produced via ball milling: (i) a solid solution of nitrogen in &-iron with a largely extended nitrogen solubility (proposed symbol: &''', [8]) up to about 16.5 at% nitrogen [9] (thus comprising the Fe 16 N 2 composition, i.e.…”