Effects of Stress‐Aging Pretreatment on Hot Deformation Behavior and Microstructure Evolution of a Ni–Cr–Nb–Mo–Ti Alloy.

Hot deformation behavior and microstructure evolution of stress and stress‐free aged NiCrNbMoTi alloy are investigated by hot compressive tests. The impacts of stress aging upon the flow softening and dynamic recrystallization (DRX) behavior are analyzed. Also, the variations of dislocation substructures are studied. The basket‐weave δ‐phases induced by stress‐aging pretreatment can refine grains during hot deformation. On the one hand, the basket‐weave δ‐phases mutually intersect and form some enclosure spaces. Then, the dislocations which are restrained in these enclosure spaces can increase the potential sites for DRX nucleation. On the other hand, the growth of DRX grain is significantly hindered by the basket‐weave δ‐phases. The peak stress increases substantially as the stress‐aging stress rises. The dislocations pinned near the basket‐weave δ‐phases can hinder the migration of grain boundaries and accelerate the DRX process during hot deformation. [ABSTRACT FROM AUTHOR]