Investigation of energy balance in nanocrystalline titanium under cyclic loading

Abstract

The paper investigates thermodynamics of the cyclic deformation of the bulk nanostructural titanium Grade 2 prepared by the method of intensive plastic deformation. The peculiarities of energy balance in nanocrystalline titanium were investigated using IR techniques for fast determination of the fatigue limit. The polycrystalline titanium exhibits an ordinary behavior. After passing the fatigue limit the temperature rises abruptly due to a sharp change of the damage accumulation kinetics. The dependence of temperature kinetics on the stress amplitude in the nanocrystalline titanium is linear up to a failure of the specimen. This fact allows us to conclude that nanocrystalline titanium, characterized by a specific state of the ensemble of grain-boundary defects, has a unique structural mechanism for energy absorption and dissipation and can use this mechanism both at small and high stress amplitudes. Based on these experimental results and our previous theoretical investigation on collective properties of mesodefect ensemble we propose to investigate a poly-nanostructural transition in metals by analogy with phase transitions. © Springer Science + Business Media B.V. 2009.