Pressure-driven structural transformation and lattice deformation in TiB reinforced titanium matrix composites: An in-situ synchrotron x-ray diffraction study

Understanding the mechanical responses of structural materials to extreme pressures has particular implication for not only their intrinsic solid properties, e.g., phase transformation, equation of state, lattice deformation, but also the mechanical engineering for extreme environments. In this work, the structural transformation of TiB reinforced Ti (Ti-TiBw) composite particles under hydrostatic, uniaxial and dynamic pressures has been comparatively investigated by diamond anvil cells combined with in-situ synchrotron x-ray diffraction. According to the variation of critical pressure of α → ω martensitic transformation, it is found that, under uniaxial pressure, the presence of nano-TiBw network could largely enhance structural resistance to deviatoric stress for the composites. A fit to the equation of state of Ti-TiBw composites under hydrostatic and uniaxial pressure yields the bulk modulus of ∼120 and ∼ 133 GPa, respectively, which increases 2.56% and 11.76% relative to pure Ti. Furthermore, the lattice deformation behaviors in Ti-TiBw composites and pure Ti during martensitic and its reversible transformation vary with pressure, deviatoric stress and compression rate. Due to the constraints by rigid TiBw network rather than “soft” grain boundary, the lattice deformation along the basal, prismatic, and pyramidal planes in Ti-TiBw system suggests an isotropic behavior, though the deviatoric strain of basal plane displays obvious dependence upon uniaxial pressure.