Atomistic Simulations of Compression Tests on Ni₃Al Nanocubes

Abstract

Supplementary Material Available OnlineThe deformation behaviour of nano-sized Ni 3 Al cubes with {100} side surfaces is investigated under uniaxial compression using constant-temperature molecular dynamics simulations at 300 K. The simulations reproduce key features of recently performed nanocompression experiments, namely the lack of strain hardening, homogeneous deformation of the entire sample and overall high stress levels of the order of 3-5 GPa. According to the simulations, the critical initial step is the formation of a pseudo-twin structure, which then further deforms by Shockley partial dislocations. These deformation mechanisms differ significantly from bulk Ni 3 Al and are rationalized in terms of generalized stacking fault energies and resolved shear stresses.

In situ investigation of MgO nanocube deformation at room temperature

“…Finally, the compression tests were performed using two external potentials (see Fig. 1e) which model an infinite flat punch and the substrate [54,55]. To model uniaxial compression along the [0 0 1] direction, the top indenter was subjected to a constant displacement rate equivalent to an engineering strain rate of 10 8 s À1 .…”

Review Article: Case studies in future trends of computational and experimental nanomechanics

“…198,199 These variables can affect fracture toughness by modifying dislocation character, nucleation, and mobility which shift the DBT temperature (DBTT) by hundreds of degrees. Recent studies from multiple disciplines, including geology, 200,201 physics, 202 civil engineering, 194 materials science, 147,203 and theoretical mechanics and applied mechanics, 192,193 have resulted in a consensus on what the key variables controlling the DBT are, but a comprehensive theory remains elusive. This is due to a lack of data needed to evaluate all the variables and their interactions.…”

“…145,146 This method is used to interpret and predict occurring elementary processes that also applies for dislocation nucleation in NPs. 120,147 Finally, one additional feature of the plastic deformation regime of NPs is that fracture is generally less common and a brittle-to-ductile transition often occurs. 148,149 The fact that decreasing size induces the impossibility of comminuting small particles by compression 150 is a long-timeknown phenomenon that however makes more sense looking at the stability of NPs functional properties.…”

Size-dependent plastic deformation and failure mechanisms of nanotwinned Ni3Al: Insights from an atomistic cracking model

“…It can predict very accurate lattice and mechanical properties, energetics of point defects and planer faults, which are of vital importance to study the cracking behavior of Ni 3 Al [41]. It has been widely used to investigate the deformation mechanisms of Ni 3 Al nanostructures, which include both nanowire and nanocube [40,39]. To drive the propagation of mode I crack, long-range uniaxial tensile loading on 111 〈 〉direction (perpendicular to the crack surface and twin plane) is applied with a constant strain rate of 10 8 s À 1 .…”

“…Depending on specific problems, MD can recognize important deformation mechanisms even at high strain rates [13,[34][35][36][37][38]. In the case of Ni 3 Al, atomistic simulations have already shown novel deformation mechanisms when the sample size is reduced to the form of nanocubes [39], or nanopillars [40]. Here we focus on the fracture of Ni 3 Al nanotwinned structures with a reliable empirical potential [41].…”