Incoloy 028 合金不连续动态再结晶中链状组织形成机理研究

During hot deformation, discontinuous dynamic recrystallization (DDRX) taking place by nucleation and growth in materials with low to medium stacking fault energies (SFEs), plays a crucial role in grain refinement, especially for the material with coarse grains. In order to study the formation mechanism of typical microstructure (necklace structure) during DDRX, the behavior of Incoloy 028 alloy at temperature range of 1000~1150℃ and the strain rates of 0.001~1 s^-1 was investigated by means of thermodynamic simulation, EBSD and TEM. The results show that with the decrease of deformation temperature or the increase of strain rate, the mechanism of DDRX is transformed from the traditional type nucleating at triple junctions, into necklace structure which dominated by the multilayer nucleation mechanism. The first strand of recrystallized grain is nucleated through the bulging of serrated grain boundaries which is assisted by twinning at the back of the fluctuation. With the increase of the true strain, the large strain gradient in the deformation band develops rapidly resulting in the transformation of the subgrain boundary into a high angle grain boundary, and then the second/followed layer nucleation occurs by the rotation of subboundaries accompanied with nucleation at triple junction. Twin boundaries are formed by straininduced grain boundaries migration and disappeared after nucleation to enhance the recrystallization grain boundary mobility, and then formed again during growth to lower the interfacial energy of the system.