Tensile Properties and Deformation Mechanism of Novel Ni-Co-Based Superalloy

The mechanical properties and deformation mechanism of a novel Ni-Co- based superalloys at room temperature (25 degrees C) and medium temperature (650, 700 and 750 degrees C) were studied using SEM, EBSD and TEM. The results show that the yield strength and elongation of the alloy at room temperature are 1176 MPa and 22.5%, respectively, and present decreasing trend with the temperature increasing. At room temperature, the main deformation mechanism is that a large number of dislocations slip, and the partial dislocations shear the gamma ' particles into isolated stacking faults. When the temperature reaches 650 degrees C, it is observed that microtwins run through the secondary gamma ' particles and gamma matrix, but it is mainly deformed by continuous stacking faults shearing secondary gamma ' particles and gamma matrix. At 700-750 degrees C, the secondary gamma ' particles and the gamma matrix are sheared simultaneously by continuous stacking faults and microtwins, and the length of stacking faults and thickness of microtwins increase with the increase in temperature. In the 650-750 degrees C range, the mechanism for shearing a primary gamma ' particles changes from antiphase boundary (APB) to isolated stacking faults. This study discusses the variation of deformation mechanism with temperature and the formation mechanism of microtwins and stacking fault under medium temperature conditions. An atom interchange diffusion model for superlattice extrinsic stacking fault (SESF) formation of a/6<112> partial dislocation shearing gamma ' particles is presented, which explains the formation process of microtwins and provides a reference for the further development of novel Ni- Co-based superalloys with high performance level.