Effects of Vanadium and Niobium on the Nucleation Kinetics of Proeutectoid Ferrite at Austenite Grain Boundaries in Fe–C and Fe–C–Mn Alloys

Abstract

Nucleation kinetics of proeutectoid ferrite allotriomorphs at austenite grain boundaries were measured in Fe-0.1 mass%C and Fe-0.1 mass%C-2 mass%Mn alloys with small amounts of V or Nb. Nb was one or two orders of magnitude more effective than V in reducing the nucleation kinetics of ferrite compared at the same amount of addition. The segregation of alloying elements to austenite grain boundaries and the formation of atom clusters with carbon or fine coherent precipitates at ferrite nucleation sites were considered as possible causes for the observed suppression of nucleation. However, quantitative agreement with theory or direct experimental evidence is yet to be obtained for these possibilities to be deemed operative in the present alloys.