TRUE FRACTURE STRESS OF UMP SAMPLES OF ALLOY AL-6101

Abstract

This paper presents the results of the work on determining the true fracture stresses of cylindrical samples of the ultrafine-grained structure of alloy 6001, obtained by the ECAP-K method, and comparing them with similar data for the coarse-grained structure of the same alloy, obtained by standard heat treatment. This work was carried out to correctly describe the mechanical behavior of the material in CG and UFG states. The analysis made it possible to reveal that the true deformation to fracture in the IS state and in the UFG state of alloy 6101, taking into account the measurement error, is the same. In this case, the true fracture stress of specimens with an UFG structure is noticeably higher than the true fracture stress of specimens with an IS structure. The increase in strength and yield strength as a result of ECAP-K processing is determined by a decrease in the grain size of the alloy according to the Hall–Petch law. An explanation is proposed for the increase in the true fracture stress of samples during grain refinement based on the compilation of the Hall–Petch law and the Zener–Strote model – the criterion for pore formation on a particle when stresses at the matrix/particle boundary reach critical values.