Effect of deformation behavior on the evolution of microstructure of RAFM steel subject to closed-dual equal channel angular pressing

Abstract

In this paper, the microstructure evolution of RAFM steels during multi-pass closed dual-equal channel angular pressing was studied. The results show that multi-pass closed dual-equal channel angular pressing deformation can significantly refine the grain and precipitation size. The average grain size of martensitic lath is refined from ∼3.16 μm to ∼0.71 μm, after four passes. The average size of M23C6 precipitation in elongation and shear deformation zone decreases from 132.14 nm to 109.97 nm and 107.79 nm, respectively. The average size of MX precipitation in elongation and shear deformation zone decreases from 51.8 nm to 35.54 nm and 28.56 nm. The initial volume fraction of M23C6 and MX precipitation is 3.48% and 0.59%, respectively. With the increase of deformation passes, the volume fraction of both precipitations shows a trend of increasing first and then decreasing. The volume fraction of M23C6 precipitation in elongation and shear deformation zone reached the peak value of 4.18% and 4.10% after the second and third pass and was 3.21% and 2.91% after four passes of deformation, respectively. The volume fraction of MX precipitation in elongation and shear deformation zone reached the maximum of 1.84% and 1.71% at the third pass, respectively. After four passes of deformation, the volume fraction of both regions are 1.72%, and 1.67%, respectively.