Statistical analysis of yield strength spectrum from nanoindentation for identification of constituent phases in steel

Abstract

In this study, the extension of the statistical analysis application into yield strength of constituent phases of steel was conducted. A larger number of nanoindentation tests was carried out on a type of popular structural steel SS400. The mechanical properties, such as elastic modulus, hardness, and yield strength of the indented material were extracted from nanoindentation load-depth curves. The statistical analysis was then applied to analysis the material properties spectra. The experimental and analysis results revealed that the yield strength spectrum obtained from nanoindentation tests can be used in the accurate and reliable identification of the constituent microstructural phases and their strength in structural steel by applying statistical deconvolution analysis. For the present steel, three microstructural phases are known as low characteristic ferrite, high characteristic ferrite, and pearlite with the corresponding yield strength value of a y = 296.1 ± 30.8 MPa, a y = 423.6 ± 34.3 MPa, and a y = 573.1 ± 38.9, respectively.