Effect of deformation parameters on microstructure evolution, flow softening behavior and nanoindentation properties of Nb-24Ti-16Si-2Al-4Fe-5V alloy

The microstructural evolution and the flow softening behavior of Nb-24Ti-16Si-2Al-4Fe-5V alloy during hot deformation under different processing parameters were investigated. Results show that the as-cast Nbss/beta-(Nb, X)5Si3 eutectic structure disappears and becomes the Nbss matrix and beta-(Nb, X)5Si3 blocks after hot deformation, wherein the continuous Nbss matrix consists of fine recrystallized grains. With the increase of deformation temperature, the beta-(Nb, X)5Si3 particles evolve from irregular to quadrilateral shape. The refinement mechanism of the beta-(Nb, X)5Si3 phase can be divided into silicide splitting and continuous dynamic recrystallization (CDRX). Moreover, the decrease of strain rate makes the DRX degree of Nbss increase, while the influence on that of beta-(Nb, X)5Si3 is relatively less. The flow softening behavior of the alloy is mainly controlled by the CDRX behavior of the Nbss phase, and the recrystallization refinement can improve the hardness (H) of the Nbss phase. After deformation, the H values of Nbss will increase with the increase of recrystallization degree, while the H value of beta-(Nb, X)5Si3 phase will increase with the decrease of strain rate.