Effect of niobium and titanium on tin precipitation in Fe alloys

In an attempt to manage tin segregation in steel, the formation of intermet allic compounds of tin with niobium, titanium, and aluminium was investigat ed. Two series of alloys based on Fe, Sn, and Al with either Nb or Ti addit ions were prepared by ase melting under argon. After cold lolling, the allo ys were annealed at 850 degrees C for 96 h. The microstructures were studie d using scanning electron microscopy transmission electron microscopy energ y, dispersive X-ray spectroscopy, and microprobe analysis. The level of Nb addition was found to affect the for marion of Sn rich compounds. For small Nb additions, no Sn containing compounds were found whereas the higher Nb alloy exhibited a Fe2Nb based Laves phase containing about 1 at.-%Sn. Some eta-Fe2Nb3, which was associated with the alumina formation, was also found but did not contain tin. No Sn compounds were found with Ti additions. The experimental observations were compared with thermodynamic calculations pe rformed using MTDATA software. MST/4255.