Plasticity of Materials Determined by the Indentation Method

• Published in: Uspehi fiziki metallov (Online) Vol. 19; no. 3; pp. 271 - 308
• Main Author: Yu. V. Milman, S. I. Chugunova, I. V. Goncharova, А. А. Golubenko
• Format: Journal Article
• Language: English
• Published: G. V. Kurdyumov Institute for Metal Physics of the N.A.S. of Ukraine 01-09-2018
• ISSN: 1608-1021; 2617-0795
• DOI: 10.15407/ufm.19.03.271

In this review, the development of techniques for determining the plasticity of materials by the indentation is considered. The development of methods for determining the plasticity of materials by the indentation is based on the use of fundamental ideas of the physics of strength and plasticity. Significant development of these methods became possible after the introduction of a new plasticity characteristic δ∗=ϵр/ϵt, where ϵр is the plastic deformation, and ϵt is the total deformation. This plasticity characteristic corresponds to the modern physical definitions of plasticity, in contrast to the widely used elongation to failure δ. The new plasticity characteristic is easily determined by standard determination of hardness by the diamond pyramidal indenters at constant load P (designated as δН) and by instrumental nanoindentation (designated as δА, and δН≈δА). A significant advantage of the new plasticity characteristic is the ability to determine it not only for metals, but for materials, which are brittle at the standard mechanical tests (ceramics, thin layers, coatings, etc.), as well. In the development of ideas about theoretical strength, concepts of theoretical plasticity under the dislocation-free and dislocation deformation mechanisms are introduced. A number of studies have established a correlation of δН with the electronic structure of the material and its physical properties. As shown, the Tabor parameter С (C=HM/σS, where HM is the Meyer hardness, and σS is the yield stress) is easily calculated by the δН value. Therefore, indentation allows currently determining simply not only the hardness, but also the plasticity and yielding stress of materials. Thus, indentation became a simple method for determination of the complex of mechanical properties of materials in a wide temperature range using a sample in the form of a metallographic specimen.