EBSD investigation on the evolution of microstructure and grain boundaries in coarse-grained Ni–48Al upon large deformation at elevated temperature

•Most grain boundaries are HAGBs for coarse-grained Ni–48Al intermetallics.•Subgrain boundaries and LAGBs with misorientation angles less than 5° are formed at the early deformation stage.•LAGBs gradually transform to higher angle LAGBs, and finally transform to HAGBs.•The evolution of grain boundaries results in the significant grain refinement.•A dynamic equilibrium exists between the formation of new boundaries and the transformation of LAGBs to HAGBs.

The evolution of microstructure and grain boundaries were investigated in coarse-grained Ni–48Al intermetallics during plastic deformation at 1075 °C with the initial strain rate of 1.5 × 10−3 s−1 using electron backscatter diffraction (EBSD) technique. Before deformation, most grain boundaries were high-angled (HAGBs), with several particular angles being predominant. During initial deformation, low-angle grain boundaries (LAGBs) with misorientation less than 5° began to evolve. The misorientation of the newly-formed LAGBs increased with the increase of deformation, meanwhile, grain boundaries with misorientations between 6 and 15° were gradually observed, and finally transformed into HAGBs (misorientation angle > 15°). There appeared a steady state transition from the formation of new LAGBs to the transformation into high-angle grain boundaries. As a result, the grain size was refined continuously with the deformation strain.