Breaking thermodynamic and kinetic barriers in superalloy homogenization process by electropulsing to improve mechanical properties

Highlights: • The electropulsing breaks through the thermodynamic and kinetic barriers in thermal homogenization, which reduces the temperature and significantly shortens the process. • The electropulsing avoids grain coarsening, thereby improving the plasticity of the ingot. • The energy difference caused by the selective distribution of current promotes the η phase lamella to dissolve along its gap. -- Abstract: During the solidification of superalloy, dendrite segregation will be inevitably formed, causing uneven structure and performance. Segregation elimination and atomic diffusion in the alloy need to overcome kinetic and thermodynamic limitations. However, traditional thermal homogenization has disadvantages such as high energy consumption and low efficiency. Moreover, the coarse grains after the traditional treatment deteriorate the workability. Here it was found that the limitations of the thermal homogenization process can be broken through electropulsing. The electrical free energy can change the thermodynamic state of the system, reducing the dissolution temperature of η phases precipitated in the interdendritic space to a lower one of 1100 °C. Meanwhile, electromigration increases the atomic diffusion rate and significantly shortens the processing time. The time decrease effectively prevents the grain growth, which will further improve the workability of the ingot. Compared with the thermal homogenization process, the sample treated by pulsed electric current has better plasticity.