Adiabatic shear localization of tungsten based heterogeneous multilayer structures

It has been shown that tungsten (W) and other refractory metals with body-centered cubic (bcc) structures with a grain size d in the ultrafine grain (UFG, 100 nm < d < 1000 nm) or nanocrystalline (NC, d < 100 nm) regimes exhibit adiabatic shear localization under uniaxial high strain rate compression. This is especially true if the UFG/NC microstructure is produced by top-down methods such as severe plastic deformation (SPD). Such adiabatic shear localization is a long-sought-after behavior for certain applications. But limitations in the physical dimensions of bulk SPD products remain a hurdle to practical applications of such UFG/NC bcc metals and alloys. In this work, cold-rolled W sheets are joined by diffusion bonding into a bulk sample that retains the plastic deformation mode of monolithic cold-rolled W. The microstructure and mechanical properties, particularly at high strain rate, are evaluated and discussed. Because the as-rolled microstructure survived the diffusion bonding process, the propensity for adiabatic shear localization in the bonded heterogeneous multilayer structure is retained as well. It is envisioned that diffusion bonding could serve as a promising and scalable fabrication approach for UFG/NC bcc refractory metals in the desired applications.