Microstructure evolution and grain refinement behavior during hot deformation of Fe micro-alloyed Ti-6Al-4V

In this study, the effect of Fe addition on microstructure evolution and grain refinement mechanism during hot deformation of new Ti-6Al-4V-xFe (x = 0–0.9 wt%) alloys were investigated. The peak stress showed a decreasing trend, and the microstructure presented obvious grain refinement with the increase of Fe content. The flow softening behavior was contributed by dynamic recovery (DRV) and dynamic recrystallization (DRX). The average grain size decreased from 52.2 μm to 11.3 μm, and the fraction of the high angle grain boundary (HAGB) increased from 66.49% to 76.33% when Fe concentration increased from 0 wt% to 0.9 wt%. Fe addition also facilitated in the annihilation of the dislocations, which resulted in a decrease in the average ρ^GND density. The high Schmid factor (>0.45) content increased with the Fe content in the basal slip (0001) <112¯0> and prismatic slip {101¯1} <112¯3> of the α phase, as well as in the {112¯} <111> and {123¯} <111> slip systems of the β phase. All evidence indicated that Fe addition promoted the hot workability of the Ti-6Al-4V-xFe (x = 0–0.9 wt%) alloys and refined the grain size during hot deformation.