The deformation rate, atomic mobility and mechanical properties of metals

Abstract

The dependences of diffusion coefficients in metals with different crystal lattice (b.c.c., f.c.c., h.c.p., b.c.t.), subjected to pulse effects by different types of processing in a wide range of strain rates (10^-2 - 10⁶ s^-1) without heating and at T < 0,5 T_pl. studied by m ethods based on the use of radioactive indicators ⁵⁵Fe, ⁹⁵Nb, ⁶⁰Co, ⁶⁵Zn, ⁶³Ni, ²⁶Al, ⁴⁴Ti (layer-by-layer radiometric analysis of residual integral activity, macro- and microautoradiography). Used such types of processing as ultrasonic shock treatment, diffusion welding, shock load, magnetic pulse processing, etc. On the same materials subjected to the same types of processing, mechanical characteristics (impact strength, microhardness, tensile strength, etc.) were determined. In addition, literature data related to the determination of some mechanical characteristics in the deformation of metals at different speeds were used.
It turned out that with increasing the rate of plastic deformation there is not only an increase in the mobility of atoms, but also a decrease in differences in the values of the diffusion coefficients of intrinsic atoms and other diffusers in different metals. Despite the large difference in melting temperatures, in particular zinc and niobium, their self-diffusion coefficients in the migration of atoms without heating at a rate of 10⁶ s^-1 differ only 1.5 times, while at 1 s-1 the difference in the mobility of atoms is 4 orders of magnitude.
It is shown that the velocity dependences of diffusion and mechanical characteristics can be rectilinear, have extremum or inflection, but they will be approximately the same for diffusion coefficients and parameters that characterize the mechanical properties of metals under impulse loads.
Establishing the type of velocity dependences for diffusion and mechanical characteristics makes it possible to determine intermediate and extrapolated values for both characteristics, as well as on the schedule of one dependence to predict the shape of the other with a certain accuracy.