Effects of temperatures on microstructure evolution and deformation behavior of Fe–32Ni by in-situ EBSD

Abstract

Fe–32Ni alloy has attracted the attention of researchers owing to its excellent thermal expansion properties and mechanical properties. In this study, the macroscopic mechanical properties, surface morphology, crystal orientation, evolution of grain boundary and kernel average misorientation (KAM) and deformation mechanism of Fe–32Ni alloy were systematically investigated by in-situ loading equipment from 25 °C to 800 °C combined with electron backscatter diffraction (EBSD). The results showed that the grains with (111) and (101) orientations formed a special ring texture in {100} and {110} poles of the polar diagram after grain deformation and rotation. The rotational ability of the grains with (111) and (101) orientations were significantly promoted as the temperature increased. The number and proportion of low-angle grain boundaries (LAGBs) increased with increasing strain and temperature. By analyzing the microstructure evolution during in-situ EBSD testing, it was found that the rotation of the crystals significantly improved the deformability of the material. The effect of selective passage for dislocations by LAGBs both enhanced the plasticity and caused hardening of the material. Dislocations tended to accumulate at grain boundaries causing strain concentration. Cracks sprouted at grain boundaries and expand along the grain boundaries. This study can provide profound insights on the deformation mechanism of Fe–32Ni alloy for the possible design and process optimization.