Ability of molecular dynamics to take into account the tension/compression asymmetry in the Ni/Ni₃Al systems observed in nickel base superalloys

AN Dieng and C Gerard and J Cormier and JC Grandidier, JOURNAL OF NANOPARTICLE RESEARCH, 25, 206 (2023).

DOI: 10.1007/s11051-023-05815-1

Using molecular dynamics simulations, the mechanical behavior of the Ni/Ni3Al gamma/gamma' system has been studied by performing tensile and compression tests at room and high temperature. Before loading tests, the Ni/Ni3Al gamma/gamma' system is first thermally relaxed. This relaxation step leads to the formation of misfit dislocations resulting from the difference between the lattice parameters of the gamma and gamma' phases. Simulation tests show that when the temperature increases, there is a decrease in the elastic modulus and the yield stress of the system whatever the loading direction. This is due to the increase of the dislocations density. Depending on the loading direction, our simulations reveal a tension/compression asymmetry which decreases with increasing temperature. This behavior is discussed by taking into account the dislocations ability to glide according to the difference of properties between phases depending on the loading direction and the evolution of the gamma/gamma' lattice misfit as a function of the temperature.

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