Effects of hydrogen on microstructure and hot deformability of directionally solidified Ti–44Al–6Nb–1Cr alloy

Abstract

Effect of hydrogen on microstructure and the hot flow behavior of the directionally solidified Ti–44Al–6Nb–1Cr (at.%) alloy was studied. Ti–44Al–6Nb–1Cr alloys were prepared by vacuum induction melting (as-cast alloy) and cold crucible directional solidification (CCDS). Effects of hydrogen on the hot deformation behavior were tested on Gleeble-1500D at 1373 K and 1473 K under strain rate of 0.01 s−1. Results show that the volume fraction of B2 phase is increased after CCDS due to the solute distribution. The residual B2 phase in the hydrogenated alloy is more than that in unhydrogenated alloy because hydrogen is beta stabilizing element and stabilizes the B2 phase. The peak stress of the CCDS alloy is higher than that of as-cast alloy at the same deformation condition due to the directional solidified microstructure. Hydrogen can decrease peak stress of the as-cast alloy and CCDS alloy significantly, which is decreased by about 46% and 43% respectively. This is attributed to the hydrogen-promoted dynamic recrystallization and hydrogen-increased the volume fraction of B2 phase.