Microstructure evolution and mechanical properties of cup-shaped specimens prepared by rotary backward extrusion

Abstract

Rotary backward extrusion (RBE) has been proven to be a useful method for preparing high-performance cup-shaped specimens. However, previous relevant studies aimed to investigate small samples. In this paper, large cup-shaped specimens were prepared by RBE at rotary speeds of 0.35 r/min and 0.9 r/min. The microstructural evolution and properties were analyzed for different regions of the cup wall. The results showed that the obtained microstructure became finer from the outer to inner region, and increasing the rotary speed improved the deformation uniformity and mechanical properties. Continuous dynamic recrystallization (CDRX) and discontinuous dynamic recrystallization (DDRX) actively contributed to hot deformation. High recrystallization effectively weakened the texture intensity, and the inner region at a rotary speed of 0.9 r/min showed an abnormal texture; this phenomenon was attributed to the activation of nonbasal slip brought by high strains and rare earth contents. Refinement strengthening was a major mechanism during RBE; the highest recrystallization of the region reached 93.1%, and its yield strength (YS), ultimate strength (UTS), and elongation (EL) values were ∼219.3 MPa, ∼298.2 MPa, ∼15.2%, respectively.