Strain hardening exponent is an important mechanical property usually obtained from tensile tests, which implies that a specific specimen preparation and long routines of calculus should be performed. An alternative way to obtain this property is the use of spherical indentation hardness, measuring the profiles of indentation morphology: piling up or sinking in. In the present investigation, the indentation morphologies observed after tests with a spherical indenter for aluminium alloys (AA 6063-T5 and AA 1350) and steels (AISI 1020 and AISI 316L) are presented. Indentation tests were performed with different sphere diameters and test loads, to obey the Meyer law and to keep constant the relation between load and indentation diameter, varying the plastic strain level. Tensile tests were performed to make use of reference values. The residual profiles were obtained using a two-dimensional profilometer. The results allow discussing the range of validity of several models proposed in the literature. For some test conditions, 316L stainless steel and 1350 aluminium alloy partially recovered present an unexpected behaviour, which the models are unable to predict.

Indentation morphologies depend on the mechanical properties of materials, especially the strainhardening exponent and yield strength-to-elastic modulus ratio. Hernot et al.1 described a model that can be used to obtain the indentation morphology index from properties determined in tensile tests. The model is used here with two aluminum alloys and 1020 steel tested under spherical indentation with different loads and ball diameters. There was good agreement between the values predicted by the model and the experimental findings for all the materials tested except partially recovered AA1350 aluminum alloy (H24 condition). This exception is discussed and a possible explanation for it is sought in other experimental deviations and in microstructural inhomogeneities.