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.