Microstructural Changes with N Content in Sm-Fe-N Alloys

The microstructures of Sm
₂
Fe
₁₇
N
_x
(0≪x≪6) powders were observed by transmission electron microscopy (TEM). Sm
₂
Fe
₁₇
N
₂₃
powders nitrided in N
₂
gas have high dislocation densities due to lattice expansion. Sm
₂
Fe
₁₇
N
_x
powders nitrided in a mixture of NH
₃
and H
₂
gases (3≪x≪6) have cell-like structures. The dislocation density increases and the cell diameter decreases with increasing N content, and Sm
₂
Fe
₁₇
N
_5.9
powders consist of 30 to 50 nm in diameter Sm
₂
Fe
₁₇
N
_x
microcrystalline grains surrounded by an amorphous phase. Sm
₂
Fe
₁₇
powders nitrided above 600°C dissociate into SmN and α-Fe phases with characteristic sizes of 10 to 20 nm.