Nanocrystallization in amorphous Fe40Ni40(Si+B)19Mo1–2 ribbons

Abstract Cut Fe 40 Ni 40 (Si+B) 19 Mo 1–2 ribbons were annealed for 2 h at various temperatures between 350°C and 600°C. XRD and Mossbauer effect spectroscopy (ME) measurements were then performed on all of the ribbons. The magnetic properties of several ribbons were measured using a vibrating sample magnetometer (VSM). A differential thermal analysis scan (over the range 20–800°C) of the as-cast ribbon showed two phase transitions; the first at 454°C and the second at 525°C. Both the XRD and ME spectra of the as cast, the 350°C and 400°C annealed ribbons showed that they were amorphous. The ME spectra of the 450°C, 475°C and 500°C annealed ribbons showed that these ribbons contained α-Fe, α-Fe(Si) and t-Fe 2 B nanocrystallites. For the ribbons annealed above 550°C, crystallites of t-Fe 2 B, t-Fe 3 B, t-Fe 5 SiB 2 and FCC-FeNi appeared, with the α-Fe and α-Fe(Si) crystallites disappearing. The sextets of all of the Fe compounds appeared in the ME spectra of the 525°C annealed ribbon. The VSM measurements supported the picture of a two-stage phase transitions; amorphous phase→a nanocrystalline phase (Fe-containing nanocrystallites in an amorphous matrix) at 454°C and then a second transition, the nanocrystalline phase→a disordered alloy containing Fe–B and Fe–Ni crystallites at 525°C.