Sm10Fe90−xTixalloys(x=0, 1, 3, 4, 5, 6, 8, 10) were prepared by rapid quenching and sequent annealing. Structural transformations from amorphous, metastable-to-equilibrium phases, and magnetic properties of their nitrides were systematically investigated. ACaCu5-type metastable phase was formed for0⩽x⩽10as the crystallization of the amorphous alloys occurred below 700 °C. TheCaCu5-type structure is transformed into aTbCu7-type one with increased annealing temperature (above 700 °C). These alloys have different structures includingTh2Zn17type for0⩽x⩽3,TbCu7type for3<x<6,andThMn12type for6⩽x⩽10,at high annealing temperatures (above 950 °C). Nitrogenation was carried out at 460 °C for 6 h. The best hard magnetic properties are obtained after nitriding forx=3.It givesiHc=17.6kOe,4&pgr;Mr=7.7kG, and(BH)max=6.8MGOe for theTbCu7-type phase andiHc=8.6kOe,4&pgr;Mr=8.4kG, and(BH)max=10.2MGOe for theCaCu5-type one. Although the coercivity of theCaCu5-type phase is lower than that of theTbCu7-type one, enhanced remanence of the former has been observed. ©1997 American Institute of Physics.