Obtaining a stress-strain diagram using tensile testing machines involves testing a sample of large volume. An alternative to such tests is the automated ball indentation test (ABI test) designed to determine the dependence of stress on plastic deformation of metallic materials and structural elements. The aim of this study is to investigate the applicability of the technique developed for plotting a stress-strain diagram using large spherical indenters (of 250–1500 μm in diameter) for work with a microspherical indenter with a diameter of 5 μm. The use of such an indenter makes it possible to study small-sized material samples, from which it is impossible to prepare samples for a standard uniaxial tensile experiment. The indenter of small diameter is used to study individual phases of heterogeneous materials and grain boundaries as well as thin films, coatings, and surface layers of the sample. In this study, the shape of the obtained imprints on the surface of the samples is examined both by a noncontact method using confocal optical 3D-profilometry and by a contact method using atomic-force microscopy. The noncontact method, as it has a higher speed, is used to determine the grain sizes of alloys; the contact method, as it has a higher lateral resolution, is used to measure the diameter of imprints. A series of experiments are carried out on tensile testing of alloys on a universal testing machine and on indentation of samples made from the same alloys. The values of elastic moduli and temporary resistances of the V95, VT1, and VT6 alloys are obtained, which coincide within the error limits in two different experiments. Stress-strain diagrams are plotted experimentally using instrumental indentation and analysis of the geometry of residual imprints when using a spherical tip made of a single crystal diamond with a small radius of curvature (of 2.5 μm).
Kushnereva et al. (Wed,) studied this question.