Atomistic simulations of mechanical characteristics dependency on relative density, grain size, and temperature of nanoporous tungsten

Abstract

A series of atomistic simulations are adopted to explore the influences of relative density, grain size, and temperature on the tensile characteristics of nanoporous tungsten (NPW). Results illustrate that the dominant mechanism of deformation for monocrystalline NPW is the combination of twin boundaries (TBs) migration and 1/2 〈111〉 dislocation movement. The relative density, which has a positive relationship with stiffness and strength, significantly affects the mechanical properties of NPW. With relative density growing from 0.30 to 0.60, Young’s modulus, UTS, and yield strength of monocrystalline NPW increase from 18.55, 0.65, and 0.45 GPa to 93.78, 2.93, and 2.59 GPa, respectively. Young’s modulus and relative density have a quadratic relationship, meaning that the dominant deformation is the bending deformation of ligaments during the elastic stage. The scaling law for yield strength reveals that the axial yielding of ligaments dominates the yielding behavior of NPW. The relationship between mean grain size (5.00 ∼ 17.07 nm) and strength follows the reverse Hall-Petch relation. Besides, the effect of temperature on mechanical characteristics is discussed. With the increase of temperature from 10 K to 1500 K, Young’s modulus of monocrystalline NPW and nanocrystalline NPW (d = 5.00, 10.99, and 17.07 nm) decrease from 69.24, 51.73, 61.08, and 63.75 GPa to 48.98, 34.77, 44.65, and 49.05 GPa. The findings systematically reveal the mechanical properties of NPW under tension and provide guidance for its application.