Koda, NobukoMicrostructural analysis of rapid-solidified (melt-spun) FeGa alloys with 17.3at.%Ga and bulk alloys with 12-20at.%Ga using transmission electron microscope was carried out. Dark field and high resolution image analysis show all the samples are inhomogeneous with fine texture of 5-10nm. Although the expected crystal structure is bcc for all the samples, bulk samples with 12-20at.%-Ga contain additional phases other than bcc phase. Tetragonal modulation of DO3 and superlattice with diagonal arrangement of two B2(CsCl-type) cells in bcc gave the best identification for observed diffraction patterns. Tetragonality calculated from mismatch between observed diffraction spots and the calculation for the assumed tetragonal structure was approximately 1.1.en-USThesisEngineering, Materials Science