Dependence of Vickers microhardness on applied load in indium

摘要

Indentation hardness tests are widely used in both control work and research work in materials science, especially when it is difficult to perform other mechanical tests. In the discussion of the standard Vickers hardness test, it was shown that Meyer's law [1], relating the applied load L and impression diagonal d, yields a constant value for the Meyer index, n, of 2 because of geometric similarity (Kick's law [2]). Thus, hardness should be independent of indentation size. However, the most important and intractable problem associated with Vickers hardness testing at low loads, i.e. micro-indentation hardness testing, is that concerned with the apparent change in hardness value with change in indentation size, namely, the identation size effect. In other words, at very low loads n does not equal 2 for Vickers indentation. More generally there is an increase in microhardness at small loads for most metals and alloys, namely, n < 2.