Tensile strength of polycrystalline NiAl nanowires: A molecular dynamics study

In this thesis, polycrystalline nanowire models of NiAl alloy were created and the stress-strain behavior of these models was investigated by using the molecular dynamic simulations. For this purpose, physical interactions between atoms are modeled by the embedded atom method and simulations are performed with open source code LAMMPS package. A total of six different models with square-shaped in size of 2x2nm 2 , 3x3nm 2 , 4x4nm 2 , 5x5nm 2 , 6x6nm 2 , and 7x7nm 2 and 10nm length were prepared. Also, each model has been replicated to contain four different numbers of grains, but the almost same shaped. The number of grains in the models are 2, 3, 4, and 5. Thus, while at least the small model contains 3100 atoms, the largest model contains 40000 atoms. The prepared models were first thermodynamically relaxed at 300K temperature for 20000 time steps each of 2fs. and settled in stable structures. Then, on the model nanowires, tensile forces were applied in the z direction with a speed of 1m/s strain until the fracture point. In this process, thermodynamic, mechanical and structural properties of the models have been determined by performing molecular dynamic calculations. From the obtained results, Young modules and yield strengths of nanowires were calculated from the stress-strain curves. The results are discussed in comparison with the literature.