Sm 2 Fe 17Àx Ti x N compounds were prepared from the starting Sm 2 Fe 17Àx Ti x alloy by nitrogenation processes for 2, 4, 6 and 10 h. The microstructure and crystal lattice parameters of the Sm 2 Fe 17Àx Ti x N system were presented in detail. The main phase of all Sm 2 Fe 17Àx Ti x N (with x ¼ 0; 0.5, 1.0 and 2.0) compounds behave the Th 2 Zn 17 -type structure, tiny a-Fe, SmFe 2 , FeTi, Fe 2 Ti phases may coexist. Ti dissolves into three different phases: Sm 2 (Fe,Ti) 17 , Fe x Ti and a-Fe(Ti). With increasing Ti content, corresponding characteristic peaks of Sm 2 Fe 17Àx Ti x shift to lower angles and the increment (DV/V) of unit cell volume for Sm 2 Fe 15 Ti 2 were increased up to 3.898%. However, the deviation amplitude D2y for the same sample was nearly not changed with the increasing of 2y angle from 20 to 70 . For the same Sm 2 Fe 17Àx Ti x , corresponding characteristic peaks of Sm 2 Fe 17Àx Ti x N also shift to lower angles with the increasing of nitriding time. Furthermore, D2y for high angles was more negative than that for lower angles. D2y of samples with high Ti content was more negative than that with low Ti content when nitrogenized for less than 6 h, but D2y of corresponding peaks for all Sm 2 Fe 17Àx Ti x N samples behaved in the same way when nitrogenated for over 6 h. The maximum D2y deviation value at 2y=70 was over 2.2 after being nitrogenated for 10 h. The maximum lattice parameters, a ¼ 8:82 ( A 2 , c ¼ 12:88 ( A, V ¼ 868 ( A 3 , and DV/V=10.19% were obtained, but c=a ¼ 1:45 was not changed. The saturation magnetization value of all Sm 2 Fe 17Àx Ti x N were limited in the scope of 88-1100 kA/m, so the saturation magnetization was not obviously improved for the Ti substitution for some Fe atoms in this alloy.