Effect of second phase particles on the dynamic recrystallization in Ni-W alloys during thermal compression

The existence of second phase particles may raise the deformation heterogeneity in the alloys, providing favorable sites of recrystallization nucleation in thermal deformation. The influence of large W second phase p articles (>1 µm) on the dynamic recrystallization in Ni-42W alloys (with 42 wt% W) is studied in this paper by electron backscattered diffraction (EBSD). The Ni-42W alloys are composed by NiW matrix and W particles. The W particles are of two kinds of shapes including ellipsoidal shape with a diameter of 3–10 µm and rod-like shape with 3 µm in width and 5–15 µm in length. The phenomenon of particles stimulated nucleation is observed in the Ni-42W alloys during thermal deformation. The recrystallized grains are located not only at the areas with high-angle grain boundaries but also at the deformation heterogeneities around W particles. A divergent distribution of deformation heterogeneities is formed around the ellipsoidal W particles and the distortion degree near the adjacent ellipsoidal particles can be accumulated. Large distortion exists at the tips of the rod-like particles. The deformation is weak at the middle region between rod-like particles with parallel alignment, which is not conducive to recrystallization nucleation. Based on the EBSD results, the dynamic recrystallization evolution diagram is established for Ni-42W alloys with large second phase particles.