abstract
In this work, the effect of the indentation load on the results of hardness and fracture toughness, determined by Vickers micro-hardness measurements, of some glasses and glass-ceramics has been investigated. Furthermore, in order to verify the effect of crystallinity on the results, glasses of composition 52.75 wt.% 3CaO center dot P2O5, 30 wt.% SiO2 and 17.25 wt.% MgO were fused at 1600 degrees C for 4 h and annealed at 700 degrees C for 2h, and further heat-treated at 700, 775, 800 and 900 degrees C for 4h. The obtained materials were analyzed by high resolution X-ray diffraction, HRXRD, to determine the crystallization degree in function of the heat-treatment temperature. The hardness of the different specimens was determined by Vickers' micro-hardness measurements under various loads. It has been observed that with increasing crystallization of the materials their hardness increased. Furthermore, it has been possible to verify the so-called indentation size effect (ISE), i.e. hardness decreases as the indentation depth, under higher loads, increases. This effect has been more pronounced in the glass-ceramic samples. Fracture toughness has been determined by the crack length induced by the Vickers indentations and relating them to the applied loads. Glass materials presented a fracture pattern with characteristics of cleavage, forming cracks of the half-penny shaped type, while the glass-ceramic materials exhibited crack bridging effects and Palmqvist type cracks. (C) 2011 Elsevier B.V. All rights reserved.
keywords
IN-VITRO BIOACTIVITY; MECHANICAL-PROPERTIES; GLASS-CERAMICS; SYSTEM; CRACK; LOAD; INDENTATIONS
subject category
Science & Technology - Other Topics; Materials Science; Metallurgy & Metallurgical Engineering
authors
Daguano, JKMF; Suzuki, PA; Strecker, K; Fernandes, MHFV; Santos, C
our authors
Maria Helena Figueira Vaz Fernandes
Associate Professoracknowledgements
The authors would like to thank FAPESP for financial support received under grant no.07/50681-3 and 04/04386-1, and the LNLS laboratory for the use of the high resolution X-ray diffractometer. We are also in depth with Prof. Dr. E. D. Zanotto and the LaMaV, UFS-Car, for fusing the base glass and to Prof. Dr. E. C. Ziemath, UNESP, Rio Claro, for helpful discussions.