An EBSD analysis of Fe-36%Ni alloy processed by HPT at ambient and a warm temperature

Electron backscatter diffraction (EBSD) was used to evaluate the evolution of microstructure and texture in an Fe-36%Ni (wt. %) alloy after processing by high-pressure torsion (HPT) up to 10 turns at ambient temperature and 250 °C. HPT processing led to a strong microstructural refinement with average grain sizes of ∼0.30 and ∼0.24 μm at ambient temperature and 250 °C, respectively. The high-angle grain boundary fraction was slightly higher after processing at 250 °C and gradually increased with increasing numbers of HPT turns to saturate after 5 turns. The crystallographic texture after HPT processing at ambient temperature was characterized by typical A and B fibers of a simple shear FCC texture with domination of the B component. By contrast, the A, B and C components developed during HPT processing at 250 °C with C as the dominant texture component. The microhardness values for both HPT deformation conditions were very similar with a continuous increase with increasing HPT turns and almost saturation after 5 HPT turns. The grain size dependence of the microhardness followed the Hall-Petch relationship. The explanation for the microstructure, texture and microhardness difference was attributed to a dynamic recovery process that operates during processing at 250 °C.