Effect of niobium and titanium on tin precipitation in Fe alloys

In an attempt to manage tin segregation in steel, the formation of intermetallic compounds of tin with niobium, titanium, and aluminium was investigated. Two series of alloys based on Fe, Sn, and Al with either Nb or Ti additions were prepared by arc melting under argon. After cold rolling, the alloys were annealed at 850°C for 96 h. The microstructures were studied using scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, and microprobe analysis. The level of Nb addition was found to affect the formation of Sn rich compounds. For small Nb additions, no Sn containing compounds were found, whereas the higher Nb alloy exhibited a Fe₂ Nb based Laves phase containing about 1 at.-%Sn. Some η-Fe₂ Nb₃, 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 performed using MTDATA software.