For the first time the Nix–Gao model for indentation size effect was used to estimate the dislocation density in a metal. The estimate of dislocation density obtained by this method, using Ni as a case study, was compared with the values obtained from direct observation by transmission electron microscopy. It was shown that the estimate of dislocation density from indentation hardness measurements, adjusted by the Nix–Gao model, gave values consistent with those obtained by transmission electron microscopy, provided that the proper procedures to minimize errors were adopted. Although the direct observation of dislocations by transmission electron microscopy gave additional structural information, the indirect method to estimate dislocation density based upon hardness measurements was more efficient, since the sample preparation method, measurement procedure and analysis of results were easier and faster.

Determination of Dislocation Density from Hardness Measurements in Metals. S.Graça, R.Colaço, P.A.Carvalho, R.Vilar: Materials Letters, 2008, 62[23], 3812-4