Abstract:Ti5553-xFe (x=0.4, 1.2, 2.0, wt.%) alloys have been designed and fabricated through BE (blended element) sintering to investigate the effect of Fe-addition on athermal w-phase transformation, α-phase evolution and age hardening behavior. The results show that the formation of athermal w-phase is fully suppressed in water-quenched specimens when Fe-addition is up to 2 wt.%. The relevant timescales of a formation during initial stages of aging indicate that incubation time increases with Fe-addition. Further aging results in continuous nucleation and growth of a-phase but finer intragranular a lamellae exhibit in Ti5553-2Fe alloy. In addition, the width and extent of grain boundary a-film increase slightly with incremental Fe-addition, especially in furnace cooling condition. Result of Vickers hardness manifests that Fe-addition leads to a strong hardening effect in both solution and aging treatment. The solid solution strengthening is quantitatively estimated by ab initio calculation based on the Labusch-Nabarro model. The evolution of a-precipitate is rationalized by Gibbs free energy. The prominent hardening effect of Ti5553-2Fe alloy is attributed to both large lattice misfit of b-matrix and fine a-precipitate distribution.

Key words: Fe-modified Ti5553 alloy; a-phase evolution; hardening behavior; Pandat calculation