The Molecular dynamics simulations of the mechanical behavior of nanostructured and amorphous Al80Ti15Ni5 alloy

Abstract

Classical deformation mechanisms based on crystalline defects of metallic polycrystals are not entirely suitable to describe the mechanical behavior of nanocrystalline and glassy materials. Their inherent complexity creates a real challenge to understand the acting physical phenomena. Thus, the molecular dynamics approach becomes interesting because it allows evaluating the mechanical properties and its related atomic structure. To study the atomic structure's influence on the deformation mechanisms at the nanoscale level of the Al80Ti15Ni5 alloy, molecular dynamics simulations, and post-processing techniques were used in the present work. The results revealed a significant dependency between the Young modulus and the atomic structure. Moreover, the type of structure, i.e., nanocrystalline or amorphous, governs the deformation mechanism type. For the nanocrystalline alloy, grain boundary sliding and diffusion seem to be the dominant deformation processes followed by the less essential emissions of partial dislocations from the grain boundaries. Concerning the amorphous material, the shear transformation zones begin to form in the elastic regime evolving to shear bands, these being the main mechanisms involved in the deformation process. The results also indicate the amorphous structure as a lower limit-case of the nanocrystal. The Al80Ti15Ni5 elastic moduli values were below expectations; for this reason, the effects of unary and ternary interatomic potentials were evaluated for each element.

Inverse Hall-Petch Behavior in Nanocrystalline Aluminum Using Molecular Dynamics

“…The increase in Shockley partials indicates the formation of stacking faults and twinning structures. These results are similar to those obtained for NC Ni (Barboza et al, 2021) and an Al 85 Ti 15 Ni 5 alloy (Barboza et al, 2020). Finally, the increase in partial dislocations for NC Al was also reported in Xu and D ávila (2017), demonstrating that the interatomic potential applied in this work is capable of reproducing such phenomenon.…”

“…It can be used to study alloys (Barboza et al, 2020), glass-forming ability (Aliaga, Lima, et al, 2019;Aliaga, Schimidt, et al, 2018), ceramics and polymers (Tjong, 2013), biocomposites (Kashan and Ali, 2019), and many more systems. Furthermore, computational materials science allows studying phenomena and properties that would be too complex to be tested experimentally due to high pressures/temperatures, deformation rates, heating/cooling rates, or any other physical variable that exceeds the technological capability for actual execution.…”

“…Although there are several interatomic potentials available in the literature for Al, this study used an Embedded Atom Method (EAM) potential parameterized by ourselves via the RAMPAGE technique (Ward et al, 2012). In fact, this potential was initially created to study an Al-Ti-Ni alloy (Barboza et al, 2020). Regarding pure Al, the used potential is capable of reproduce its lattice constant, elastic constants, and cohesive energy.…”

“…Regarding pure Al, the used potential is capable of reproduce its lattice constant, elastic constants, and cohesive energy. More details regarding the parameterization methodology can be seen in Barboza et al (2020). The key idea of the EAM potential is based on the principle that the system's total energy results from the contribution of the pair potential energy between atoms (the result of interaction forces), and a term that depends on the local density at the point where each atom is located (Jang et al, 2021).…”

Molecular Dynamics on Hf-Nb-Ta-Ti-Zr High Entropy Alloy

“…The measured lattice parameter of real samples is 3.4024 Å for the same equiatomic HEA. This slight difference is expected due to variations in methods, such as the system size [65][66][67] and the inherent variability in the typical characterization of real samples. Thus, the values obtained in this work by MD are considered acceptable when compared with the experimental data.…”