Structural transition and ductility enhancement of a tungsten heavy alloy under high pressure

Abstract

High pressure structural transformation of 95 W-3.5Ni-1.5Fe alloy was investigated by in-situ high pressure synchrotron radiate-on X-ray diffraction technique. Starting sample was compressed to 52.1 GPa in a diamond anvil cell under hydrostatic condition at ambient temperature. Experimental results demonstrated that the extreme compressive stress led to a set of reversible structural evolution. The grain size, atomic positions, bond distance and unit cell volume exhibited remarkable dependence on high pressure. The equation of state (EOS) together with bulk modulus K0 = 409(11) GPa and K0’ = 6.4(0.8) GPa of tungsten phase and K0 = 221(9) GPa and K0′=7.2(0.8) GPa of matrix phase were obtained based on the unit cell volume data varies with pressure for the first time. In addition, the structure responses of tungsten heavy alloy under high pressure and high temperature were revealed by large volume cubic press. Results indicated that the thermo-mechanical coupling effect facilitated the dynamic recrystallization process. Three-dimensional discrete dislocation plasticity simulations were proposed to illustrate the formation and evolution of screw dislocation in body-center cubic under various hydrostatic pressures. Results demonstrated that the extreme compression conditions fueled the nucleation and propagation of screw dislocations, which can be looked upon as the significant contributors to dislocation density increasing and ductility strengthening.