Elastoplastic properties of microand submicrocrystalline metals and alloys

The problem of application of physical acoustic methods to studying the mechanisms that control plastic deformation and fracture is considered using micro- and submicrocrystalline materials (Be, Al, Ti, Al–Sc alloy, Cu–Nb laminated material) as examples. The influence of grain boundaries on the acoustic (elastic, inelastic) properties of polycrystalline micro- and nanostructured metallic materials is analyzed. Experimental results are presented for a wide oscillating-stress amplitude range, from 0.2 to 50 MPa. The experimental data are discussed in terms of the theoretical concepts of oscillatory dislocation mobility, which depends on both the short-range stress fields around point defects and the long-range fields of internal stresses. It is shown that various types of discontinuities, such as pores and microcracks, noticeably influence the acoustic properties. The aspects of the relation, similarity, and difference between acoustic and mechanical (plasticity, strength) tests of polycrystalline materials with micro- and nanosized structural elements are discussed.