Tensile mechanical performance of Ni-Co alloy nanowires by molecular dynamics simulation

Abstract

In this present contribution, tensile mechanical properties of Ni-Co alloy nanowires with Co content from 0 to 20% were studied by molecular dynamics. The simulation results show the alloy nanowire with the Co content of 5% has the highest yield value of 9.72 GPa. In addition, more Frank dislocations were generated during the loading process to improve the performance of the alloy nanowire. The Young's modulus increases little by little from 105.68 to 179.78 GPa with the increase of Co content. Secondly, with the increase of temperature, the yield strength gradually decreases to 2.13 GPa. Young's modulus tends to decrease linearly from 170.7 GPa to 48.21 GPa. At the temperatures of 500 K and 700 K, it is easier to form Frank dislocation and Hirth dislocation, respectively, in the loading process. The peak value of the radial distribution function decreases and the number of peaks decreases, indicating the disappearance of the ordered structure. Finally, after the introduction of the surface and inner void, the yield strength of the nanowire drops about to 8.97 and 6.6 GPa, respectively, and the yield strains drop to 0.056 and 0.043. In the case of the existence of internal void, perfect dislocation and Hirth dislocation can be observed in the structure.

Fig. 1. The simulation Ni–Co alloy nanowire configuration. Ni: green; Co: pink atoms.

Fig. 2. (a) Stress–strain curves of Ni–Co alloy nanowires. (b) Yield strength of alloy with different Co content. (c) Young's modulus of alloy with different Co content. (d) Potential energies of Ni–Co alloy nanowires.

Fig. 3. The deformation process of Ni–Co alloy nanowires with a Co content of 10% and an aspect ratio of 8 : 1 under tensile loading with different strains: (a) 0.0478; (b) 0.0627; (c) 0.064; (d) 0.07.

Fig. 4. The relationship between dislocation line length and strain in alloy nanowires with different Co content under tensile loading.

Fig. 5. Dislocation types and length changes in alloy nanowires with different Co content under tensile loading: (a) 0; (b) 5%; (c) 10%; (d) 15%; (e) 20%.

Fig. 6. (a) Stress–strain curves of Ni–Co alloy nanowires. (b) Yield strength of alloy with different temperature. (c) Young's modulus of alloy. (d) Radial distribution function of Ni–Co alloy nanowires.

Fig. 7. Snapshots of nanowire at yield points with different temperature under tensile loading: (a) 300 K; (b) 700 K; (c) 900 K; (d) 1100 K.

Fig. 8. The relationship between dislocation line length and strain in alloy nanowires with different temperatures under tensile loading.

Fig. 9. The dislocation types and length changes of alloy nanowires at different temperatures during loading: (a) 300 K; (b) 500 K; (c) 700 K; (d) 900 K; (e) 1100 K.

Fig. 10. (a) Stress–strain curves of Ni–Co alloy nanowires. (b) Yield strength of alloy with different void defects. (c) Potential energies of Ni–Co alloy nanowires.

Fig. 11. Snapshots of the deformation behavior of the nanowires with surface void in the process of tensile loading with different strains: (a) 0; (b) 0.0558; (c) 0.0572; (d) 0.065.

Fig. 12. Snapshots of the deformation behavior of the nanowires with internal void in the process of tensile loading with different strains: (e) 0; (f) 0.043; (g) 0.045; (h) 0.0548.

Fig. 13. The relationship between dislocation line length and strain in alloy nanowires with different void defect under tensile loading.

Fig. 14. The dislocation types and length of the defective nanowires vary with strain during loading. (a) Perfect nanowire; (b) surface defect nanowire; and (c) internal defect nanowire.