Study of the micro-structure and mechanical properties of DZ9 superalloy after a high-temperature aging

The micro-structure and mechanical properties of DZ9 superalloy were studied before, after, and during the high-temperature aging by using scanning electron microscopy (SEM), nanoindentation, and fatigue tests. The obtained results showed that the γ'-phase of the superalloy was significantly coarsened after a long-term aging at 980℃; however, the cubic-shape morphology was basically retained for the γ'-phase. Changes of the hardness and modulus of the eutectic γ'-phase were not apparent; while, these properties were decreased for the dendrite arm of the γ- phase. Moreover, the tensile-strength and lifetime in creep-rupture were also declined under 980 ℃/250 MPa. In addition, aside from aging, both the average elasticity modulus and hardness were higher in the vertical direction of the columnar crystal compared to those in the parallel direction of 〈001〉. It is also of great importance to study the anisotropy of the directional solidification of the nickel-based superalloy and direction of the mechanical properties of the eutectic γ'-phase and the dendrite arm γ'-phase.