Artemov Igor' Iosifovich, Doctor of engineering sciences, professor, vice-rector for research and innovative activities, Penza State University (40 Krasnaya street, Penza, Russia), E-mail: email@example.com
Akimov Dmitriy Aleksandrovich, Applicant, Penza State University (40 Krasnaya street, Penza, Russia), E-mail: firstname.lastname@example.org
Krevchik Vladimir Dmitrievich, Doctor of physical and mathematical sciences, professor, dean of the faculty of instrument engineering, information technology and electronics, Penza State University (40 Krasnaya street, Penza, Russia), E-mail: email@example.com
Background. Currently, ion implantation is one of the effective methods of modifying the mechanical properties of metals and alloys [1-4]. The formation of a nanostructured layer (NS) blocks the exit of dislocations to the metal surface and contributes to their consolidation due to the high concentration of implanted ions and radiation defects. As a result, after ion implantation the material is strengthened. However, local accumulations of the implanted admixture contribute to heterogeneous fixation of dislocations in the NS, which can significantly limit the strength characteristics of the material. The aim of this work is to study the possibility of increasing the absolute value of the elasticity of the NS due to acoustostimulated diffusion of local concentrations of the implanted ions, accompanied by the increase in the number of pinned dislocations in the volume of NS.
Materials and methods. The dislocation mechanism of ultrasonic wave attenuation is considered in the framework of the Granato and Lucca model . The formula for the diffusion coefficient is obtained on the basis of the theory of random walks, as well as the idea that the process of energy dissipation by an ultrasonic wave in the NS region with a small number of fixed dislocations can cause diffusion spreading of local local clusters. The problem of diffusion of a local impurity cluster was considered as a problem of diffusion from a layer of finite thickness to a semiboundary body with a reflecting boundary. The solution of the heat conduction equation is obtained for the case of an internal heat source in the NS modeled by an instantaneous point source the power of which is proportional to the energy density of the ultrasonic wave.
Results. It is shown that the diffusion coefficient of the implanted impurity nonlinearly depends on the energy density of the ultrasonic wave and increases significantly with the density of dislocations in those regions of the NS where there is no
fixation of dislocations. The estimation of the number of additional activation jumps of the implanted impurity in the field of the ultrasonic wave, which amounted to 10-2, i.e. one activation jump of the impurity atom accounts for about 102 periods of the ultrasonic wave, is obtained. It is found that the value of additional activation jumps is a nonlinear function of the energy density of the ultrasonic wave W and increases with the growth of the latter approximately as . It is shown that the diffusion spreading of local clusters of implanted impurities in the ultrasonic field leads to an increase in the modulus of elasticity of the HC by about 20% due to an increase in the number of fixed dislocations, which is accompanied by hardening of the material.
Conclusions. In ion-implanted NS, there are additional degrees of freedom to control their mechanical properties by increasing the number of fixed dislocations in the conditions of acoustically stimulated spreading of local clusters of implanted impurities and point defects.
ultrasonic treatment, elastic modulus, nano-structural layer, acousticstimulated spreading of local clusters of implanted impurities, dislocation mechanism of ultrasound attenuation, material hardening
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