Mesoscopic Structural States at the Nanoscale in Surface Layers of Titanium and Its Alloy Ti-6Al-4V in Ultrasonic and Electron Beam Treatment

Ultrasonic and electron beam treatment of commercial titanium VT1-0 and its alloy VT6 (Ti-6Al-4V) produces a nonequilibrium grain-subgrain hierarchical substructure in the surface layer, which causes a multiscale fragmentation of the material and reveals a damping effect. When cooled in the gradient temperature field (during electron beam treatment) and when the beta phase of the initial alloy is destroyed by ultrasound, the high-temperature bcc structure of the surface layer undergoes a nonequilibrium phase transition into an hcp alpha-phase structure. The excess specific volume of the beta phase is hierarchically distributed in the a phase through the growth of nonequilibrium alpha ' and alpha '' martensite, and in the form of local omega-phase precipitation along the grain boundaries of the alpha phase. The specific volume of the nonequilibrium phases exceeds the specific volume of the alpha phase. This eliminates the formation of micropores and causes material fragmentation at the micro- and nanoscale structural levels during the nonequilibrium beta -> alpha phase transition. The growing alpha ' laths cause the fragmentation of the alpha phase at the microscale level. The alpha '' laths grow within the nonequilibrium alpha ' laths; they have a thickness of similar to 1.5 nm and fragment the material at the nanoscale level. This process is controlled by the electronic subsystem that creates nanoscale mesoscopic structural states for the formation of nonequilibrium martensite phases. The reversible elastoplastic deformation of the nonequilibrium martensite phases at the nanoscale level governs the damping effect of the surface layer subjected to ultrasonic or electron beam treatment. The generation of nanoscale mesoscopic structural states and the related new mechanism of reversible deformation in the conditions of broken translational invariance of the lattice in a deformable solid has been confirmed experimentally.