Nanotwinning and tensile behavior in cold-welded high-entropy-alloy nanowires

Abstract

Since the fabrication technique for high-entropy alloy (HEA) nanowires/nanopillars is still in its infancy, neither experimental nor modeling analyses of their cold-welding performance have been reported. Based on insights accumulated in our previous experiments and simulations regarding cold-welded metallic nanowires, in this study, the cold-welding performance of HEA nanowires is probed by atomistic simulations. Among different materials, our simulations reveal that extensively twinned structures are formed in CoCrMnFeNi samples, but not in CoCrCuFeNi or Ni samples. The larger fracture strain in certain HEAs is due to the improved ductility around the fracturing area as well as multiple twinning. Unlike in Ni samples, the fracture strains in HEA samples, regardless of being cuboid or cylindrical, are improved by shrinking the sample size. Among different orientations, the [010]-direction monocrystalline nanowires fail at a strain over 0.6, which is almost double that of the [111] direction. The fracture strains in polycrystalline HEA samples are, on average, larger than those in polycrystalline Ni samples. Furthermore, fracture strains in randomly generated polycrystalline HEA samples are more predictable than those in polycrystalline Ni samples with identical grain configurations. As previously reported, dislocation emission is still a prerequisite to fracture in all cold-welded samples.

Thermal stress-assisted formation of submicron pillars from a thin film of CoCrCuFeNi high entropy alloy: experiments and simulations

“…In particular, MD simulation has been widely adopted in probing the pertinent deformation mechanism in HEA materials. 31–37…”

Molecular dynamics simulations of cold welding of nanoporous amorphous alloys: effects of welding conditions and microstructures

“…During the entire simulation cycle, the stress-time curve is smooth without a zigzag pattern, different from the cold welding of crystalline materials. 3,13,63 The underlying mechanism is the absence of dislocation activation in amorphous materials. This smooth stress characteristic implies that the cold welding for amorphous nanomaterials might be experimentally implemented more easily than that for crystalline nanomaterials.…”

“…Numerous methods have been developed to join/weld nanomaterials, such as explosive welding, thermal bonding, friction welding, and cold welding. [1][2][3][4][5] Among them, cold welding can be conducted without additional loads (or tiny loads) and heat assistance. Hence, the cold-welded components do not experience acute structural impairment and have almost the same physical, chemical, and mechanical properties as the parent materials.…”

Nanowelding in Whole‐Lifetime Bottom‐Up Manufacturing: From Assembly to Service

“…In addition, the modeling analyses were used to investigate the cold welding performance of high entropy alloy NWs/nanopillars whose fabrication technique is still scarce. [ 136 ] The insights from the atomistic simulations on their deformation twinning and mechanical performance can readily help assess the merits of the cold welded sample surface fasteners. The healing nanogap is necessary and essential for the manufacturing and maintaining of nanoelectronic devices.…”