Brittle versus ductile behaviour of nanotwinned copper: A molecular dynamics study

Abstract

Nanotwinned copper (Cu) exhibits an unusual combination of ultra-high yield strength and high ductility. A brittle-to-ductile transition was previously experimentally observed in nanotwinned Cu despite Cu being an intrinsically ductile metal. However, the atomic mechanisms responsible for brittle fracture and ductile fracture in nanotwinned Cu are still not clear. In this study, molecular dynamics (MD) simulations at different temperatures have been performed to investigate the fracture behaviour of a nanotwinned Cu specimen with a single-edge-notched crack whose surface coincides with a twin boundary. Three temperature ranges are identified, indicative of distinct fracture regimes, under tensile straining perpendicular to the twin boundary. Below 1.1 K, the crack propagates in a brittle fashion. Between 2 K and 30 K a dynamic brittle-to-ductile transition is observed. Above 40 K the crack propagates in a ductile mode. A detailed analysis has been carried out to understand the atomic fracture mechanism in each fracture regime. Between 2 K and 30 K a dynamic brittle-to-ductile transition is observed. Above 40 K the crack propagates in a ductile mode. A detailed analysis has been carried out to understand the atomic fracture mechanism in each fracture regime.

Nanotwinned and hierarchical nanotwinned metals: a review of experimental, computational and theoretical efforts

“…[68][69][70][71][72][73][74] According to the molecular dynamics (MD) simulation results, the brittle/ductile deformation modes of NT metals can be affected by the thickness of materials and environmental temperature. 75,76 The plastic anisotropy has also been validated. [77][78][79][80] The exceptional torsion capability of nanowires is accessible by domino detwinning.…”

Fatigue and Mechanical Behavior of Ti-6Al-4V Alloy with CrN and TiN Coating Deposited by Magnetic Filtered Cathodic Vacuum Arc Process

“…This could delay the emission of dislocation in the substrate compared to the free surface. Although mechanical properties differences exist between the coatings and substrate, experiments and molecular dynamic simulations have demonstrated that the coatings could affect the plastic deformation of the substrate [24]. This is attributed to the different lattice parameters and crystalline structures of the brittle coatings from that of the metal substrate.…”

Mechanical properties of gold twinned nanocubes under different triaxial tensile rates

“…[1] shows that the defect emission and propagation in fivefold twinned silver nanowire is prevented by the preexisting twin boundaries. Creep mechanisms in nanotwinned metals [2], dynamics of grain boundary atoms in the bulk nanocrystalline aluminum [3], plastic deformation of nanocrystalline copper [4], deformation behavior of nanopillars with and without twin boundary [5], the fracture behavior of a nanotwinned Cu specimen [6,7], secondary twinning contribution to the ductility of the magnesium nanowire [8] Uniaxial tensile loading is dissatisfactory for complex stress states. The mechanics properties of gold twin nanocubes under different triaxial tensile rates are derived in this paper.…”