Effects of Different Temperature Paths During Reciprocating Upsetting-Extrusion on Dynamic Recrystallization Refinement of VW93A Alloy

In this paper, the grain refinement mechanism of VW93A alloy under different temperature paths during reciprocating upsetting and extrusion processes were investigated, and elucidates the evolution mechanism of long-period stacking order Long-period stacked ordered (LPSO) phase with different shapes. It is found that with the increase of the cumulative strain, the alloy microstructure of constant temperature reciprocating (CTR) and decrease temperature reciprocating upsetting-extrusion (DTR) is significantly refined, and the refinement mechanisms are mainly CDRX (continuous dynamic recrystallization) and DDRX (discontinuous dynamic recrystallization). Under the combined action of non-basal slip and second-phase particle-stimulated nucleation (PSN), the dynamic recrystallization (DRX) degree of CTR-treated alloy was higher and the structure was more uniform. The early commencement and production of dislocation walls facilitated by LPSO phase kinking, as well as the occurrence of non-basal slip under these deformation conditions, are the primary causes of the CTR-treated alloy's quick refining. The more fragmented LPSO phase in the deformed alloy is conducive to the nucleation and microstructure homogenization of dynamic recrystallization. Furthermore, following three deformations, a high number of small needle-like phases precipitate, which effectively pins the recrystallized grains' grain borders and inhibits their growth.

Graphical Abstract