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For finished products, it is sometimes necessary to measure hardness with minimal surface disturbance, where the indentations should not be visible to the naked eye. Applied loads that meet this requirement are below 0.9807 N for common metals. In this load range, the Vickers method is usually affected by the indentation size effect (ISE), which makes it difficult to interpret the measured values. If this effect is not taken into account, the measurement results can be misleading. For this reason, we recommend using the “true hardness”, which is determined using the method presented. This article presents a method for calculating the “true hardness”, which is not influenced by the test force when measuring the micro-hardness and essentially corresponds to the Vickers macro-hardness. Measurements were made using a Hanemann micro-hardness tester at loads in the range of 0.09807 N and 0.9807 N. The size and nature of the ISE and subsequently the “true hardness” were evaluated using Meyer’s power law (index n), the Proportional Sample Resistance (PSR) and the Hays–Kendall method. The measurements were carried out on commonly used non-ferrous metals: Al, Mg, Cu, Ti, Ni, Co and W. A certain limitation of the method is that measurements must be taken on a metallographically polished surface, the quality of which influences the ISE parameters and consequently the “true hardness”.
Keywords: Non-ferrous metals, load, micro-hardness, Indentation Size Effect (ISE), “true hardness”© This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.