Determination of the Yield Radius and Yield Stress in 2198-T3 Aluminum Alloy by Means of the Dual-Scale Instrumented Indentation Test

Abstract

A new dual-scale instrumented indentation test (DualS-IIT) methodology is here proposed to determine the yield stress (in a tensile-like sense). The methodology involves measuring the bulk yield radius, as defined by the expansion cavity model (ECM), induced by a Vickers macro-indentation in a medium plane cross-section. The bulk yield radius is measured by means of a subsurface nano-hardness survey along the load direction in correspondence to the transition interface between the hemispherical strain hardened region and the surrounding elastic region. The methodology has been applied to an AlLi (A2198-T3) alloy and a yield stress of 297 MPa has been measured (in agreement with a tensile test); moreover, anomalous plastic deformation behaviour has appeared under indentation. The combination of macro-and nano-indentation tests in one single experiment, as in the proposed methodology, offers a unique experimental basis to directly correlate the mechanical properties of a material at two different scales, which at present is an open issue in the research on indentation.

The eddy current diagnostics method for the plastically deformed area sizes evaluation in non-magnetic metals

“…The distribution of deformations in the volume of the metal under the indent is not uniform [8][9][10] -the values of the intensity of deformations gradually decrease as the distance from the indent deep into the deformed metal.…”

“…A plate of a nonmagnetic material containing a plastically deformed area obtained by pressing an indenter was the object for constructing the model. At present, the strains distribution in a metal under an indent during indentation is rather well studied [8][9][10], including in studies conducted by the authors [11,12]. This allows for specifying the shape and size of the plastically deformed area of the metal under the indent in the model, as well as for simulating the change in electrical conductivity in this area and identifying the eddy current control parameters that are most sensitive to changes in its size.…”

Nanoscale and Tensile-Like Properties by an Instrumented Indentation Test on PBF-LB SS 316L Steel

“…A more versatile method to assess the mechanical properties, which also accounts for any eventual microstructural anisotropy, is the instrumented indentation test (IIT). The materials tested in such a method can be in the form of free-standing thin films or multilayers, coatings, or bulk solids [ 11 , 12 , 13 ]. This method permits different scales of the microstructure of the material to be characterized using differently shaped indenters.…”