Dislocation mechanics based constitutive equations for tungsten deformation and fracturing

In this paper temperature, strain rate, strain hardening and grain size influences are described with the bcc constitutive equation σ = σG + B0exp(-βT) + Kεn + kl-1/2 where σ is an a thermal stress for solutes and initial dislocation density, B0 and β = β0 - β1, kn e are thermal activation parameters, X and n ∼0.5 are strain hardening parameters, k is the Hall-Petch microstructural stress intensity and l is the grain diameter. Uniform strain measurements are used to obtain the strain hardening parameters. The ductile/brittle transition behavior is described by using, also, a Hall-Petch relation for the cleavage fracture stress. The analysis is related to W-7Ni- 3Fe cylinder impact (Taylor) test experiments