Strain hardening of flat samples of two–dimensional high purity Al polycrystals

• Date: 2020
• Main Authors: Badiyan, E.E., Tonkopryad, A.G., Ftomov, Ye.V., Shekhovtsov, O.V.
• Format: Article
• Language: English
• Published: Національний науковий центр «Харківський фізико-технічний інститут» НАН України 2020
• Series: Вопросы атомной науки и техники
• Subjects: Pure materials and the vacuum technologies
• Online Access: http://dspace.nbuv.gov.ua/handle/123456789/194345
• Journal Title: Digital Library of Periodicals of National Academy of Sciences of Ukraine
• Cite this: Strain hardening of flat samples of two–dimensional high purity Al polycrystals / E.E. Badiyan, A.G. Tonkopryad, Ye.V. Ftomov, O.V. Shekhovtsov // Problems of atomic science and tecnology. — 2020. — № 1. — С. 51-55. — Бібліогр.: 10 назв. — англ.

Using the dislocation–kinetic approach based on equations describing the evolution of the average dislocation density in a material with an increase in shear strain, size effects have been theoretically studied that are associated with the effect on the strain hardening of the sample of the average grain size dₛ xsand thickness D and are caused by the dependence of the kinetic equation terms on dₛ and D. Established in a common way using the Taylor relation and experimentally confirmed the relationship between the flow stress σ and the strain degree ε was used to analyze the strain hardening of flat samples of two–dimensional high–purity Al polycrystals with different grain sizes in the range ~ 50μm < dₛ < ~ 1mm and various thicknesses in the range of ~ 50μm < Dₛ < ~ 1mm under uniaxial tension with a constant strain rate at moderate temperatures. It was shown that the dependence of the offset yield strenght σ₀.₂ on the grain size dₛ almost vanishes at dₛ > 300μm. It was found that the values of σ₀.₂ and the strain-hardening coefficient θ = dσ / dε decrease with increasing thickness D of the sample. These decreasing dependences are replaced by increasing ones with increasing degree of deformation. Stress σ and coefficient θ increase with increasing ratio D / dₛ at all stages of deformation.