ISE and fracture toughness evaluation by Vickers hardness testing of an Al3Nb-Nb2Al-AlNbNi in situ composite

The aim of this work is to present correlations between Vickers indentation cracks and fracture toughness of an Al3Nb+Nb2Al+AlNbNi in situ composite. Correlations between the resulting crack parameters and indentation load suggested that the radial-median model resulted in a better fit to the experimental data. The hardness value was found to change according to the indentation load applied. Low indentation loads resulted in high hardness values, while the application of higher loads decreased the hardness. Experimental results indicate that Vickers hardness varied from 8.6 to 9.5 GPa, which is due to the indentation size effect (ISE). Fracture toughness was calculated based on several models and the results were found to vary in a broad range of values. The fracture toughness obtained from Vickers indentation was in the order of 1.65-2.26 MPa m(1/2). (C) 2008 Elsevier B.V. All rights reserved.