Effect of V substitution by ti on the phase transition temperatures and matrix/precipitates lattice misfit of the 76FE-12AL-12V superalloy

Fe-Al based alloys have a remarkable potential for high temperature structural applications, provided that the limitation of their low creep resistance is solved. Third element addition (Nb, Ti, Zr or Ta) has proven to perform the task, at the expense of a low ductility. In previous works we have investigated ferritic alloys in the\ Fe-Al-V system with coherent precipitation of the L21 phase (Fe2AlV) in the A2 matrix. Among possible alloys, we chose the 76Fe-12Al-12V superalloy for filing a L21 precipitation with spherical morphology and void coalescence at high temperature. The new task is to find a fourth alloy element in order to increase the temperature equilibrium of the two phases A2+L21 field and consequently the maximum application tem-perature. Isothermal sections of the Fe rich corner on ternary Fe-Al-V and Fe-Al-Ti phase diagrams have similar phase fields. Besides, by comparing the formation energies between L21 intermetallics of Ti and V, it is expected a higher equilibrium temperature for the Fe2TiAl than for Fe2VAl. Therefore we select titanium as a possible 4th alloy element in the 76Fe-12Al-12V superalloy We show in this work that vanadium substi-tution by titanium slightly increases the temperature limit for the A2 + L21 phase field while cancelling the lattice misfit between matrix and precipitates for Ti content between 0.5 and 1 at. % and positively increasing it for Ti contents greater than 1 at. %. Besides, we demonstrate that coarsening rate is increased with Ti addi-tion and morphology is modified from spherical to cubic.