Phase separation in Fe-Ti-Al alloy – Structural, magnetic, and Mössbauer study

Highlights: • Fe₇₈Al₂₂ and Fe₇₁Al₂₂Ti₇ alloys are prepared by arc melting. • Structural, macroscopic and microscopic magnetic properties are studied. • Coarse-grained structure is obtained in the Fe-Al sample. • Fine Fe₂TiAl cuboids in Fe-Al(Ti) matrix are seen in the Fe-Al-Ti sample. The influence of Ti substituting partially Fe in Fe – 22 at.% Al alloy on the structure and magnetic properties is investigated experimentally by electron microscopy, X-ray diffraction, Mössbauer spectrometry, and by magnetic measurements at room and low temperatures. The samples in a form of discs prepared by cutting the arc-melted button-type ingots have yielded a coarse-grained structure in the Fe – 22 at.% Al sample and fine Fe-Al-Ti cuboids embedded in Fe-Al(Ti) matrix in the Fe – 22 at.% Al – 7 at.% Ti alloy. The mean cuboids' size was 45 nm and the mean composition was determined to be close to Fe₂TiAl. The as-prepared Fe-Al-Ti samples exhibited substantially reduced saturation magnetization and markedly higher remanent magnetization and coercivity as compared to the as-prepared Fe-Al sample. The thermal treatment of the Fe-Al sample at 1073 K/168 h has changed its magnetic behaviour only slightly, whereas the treatment of the Fe-Al-Ti sample at 1273 K/168 h resulted in remarkable softening of its magnetic properties.