Atomistic Simulation The Effect Of Alloying Elements On Crack Propagation In The Ni-based Single Crystal Superalloys

Ni-based single-crystal (SC) superalloys are important high-temperature materials for their outstanding high-temperature mechanical properties, and they are used in turbine blades of advanced aircraft engines. Because of the chemical composition and structural character, the properties of the y/y’interface have a great influence on the performance of Ni-based superalloys. The γ/γ’interface is also one of the factors for crack propagation. The Ni3Al phase is the important strengthening phase for Ni-based superalloys, and has a direct influence on the mechanical properties of the superalloys. The addition of alloying elements, such as Re, Ru, Mo, W, Ta, can effectively strengthen the mechanical properties of the y/y’interface and improve the stability of superalloys.In the present study, the molecular dynamics simulations with the Ni-Al-X (X= Re, Ru, Co, W) EAM potential and the discrete-variational method are used, to investigate the effect of alloying elements on the crack propagation of Ni-based single crystal superalloys.The influences of the alloying elements Re, Ru, Co, and W on the propagation of the Ni/Ni3Al interface crack at low (5 K) and high temperatures (1273 K) are investigated, respectively. The simulation results show that Re, Ru and W can improve the mechanical properties of superalloys. At low temperature (5 K), the alloying elements Re, Ru and W restrict the brittle propagation of the Ni/Ni3Al interface crack, and the crack tip of the Ni/Ni3Al interface becomes blunter with the addition of Re, Ru or W atoms at high temperature (1273 K); Re, Ru, Co and W have the trend to promote the dislocation emission of the crack tip at high temperature. W has the greatest effect on the propagation of Ni/Ni3Al interface at low and high temperatures.We clarify the reasons of Re, Ru and W restrict the brittle propagation of the Ni/Ni3Al interface crack at low temperature (5 K) and the mechanism of Re, Ru, Co and W have the trend to promote the dislocation emission of the crack tip at high temperature (1273 K).The effect of Re and W on the brittle fracture in a Ni3Al crack at the three crack orientations ((010)[001], (101)[010] and (010)[101]) are investigated, respectively. It is found that Re and W may strengthen the Ni3Al phase and improve the deformation resistance of the materials; Re and W can prevent crack advancement, promote crack healing in Ni3Al and improve the brittle fracture stress of the Ni3Al crack, with W exhibiting a better effect; The bonding strengths of Ni-Re and Ni-W are greater than that of Ni-Al, with Ni-W exhibiting the strongest bond.