Densification and plastic deformation under microindentation in silicate glasses and the relation to hardness and crack resistance

Abstract

To quantify and study the densification and plastic deformation under Vicker's indentation we prepared a series of simple soda-lime-silicate glasses with different modifying ion contents and four glasses with constant silica content but potassium and/or barium substituted for sodium and/or calcium. The densification and plastic deformation in these glasses were determined using atomic force microscopy (AFM) by measuring each sample twice, i.e., once immediately following indentation, and once after annealing to relax the densified volume. The results show that the densified volume of the glasses decreases approximately linearly with the bulk modulus, and the plastic deformation volume with silica mole fraction. These results have important implications in the prediction of hardness and crack resistance (i.e. load for crack initiation) from composition.

Plasticity, crack initiation and defect resistance in alkali-borosilicate glasses: From normal to anomalous behavior

“…1 in Section 3. At first view, this result is in contradiction to previous studies in which decreasing V R with increasing ν has been reported [49,53,79]. Recalling the NMR-based structural model of Yun and Bray [36], the incorporation of Na 2 O initially converts BØ 3 triangles into [BØ 4 ] − tetrahedra [36,116,117].…”

“…Although the available data in this system is rather limited, a local maximum of V R is clearly visible for SiO 2 -rich glasses and pure SiO 2 in particular [49,53,68,69]. These findings are quite consistent with the observations made, e.g., on alkali-alkaline earth silicate glasses [49,79]. They indicate that the SiO 2 sub-network governs the densification of SiO 2 -rich sodium-borosilicate glasses.…”

“…Despite the obvious experimental limitations of this method, a strong compositional dependence of V R has been reported for aluminosilicate as well as alkali-alkaline earth silicate glasses [79,135,136]. Similarly, such a compositional dependence is confirmed also for the present system of Na 2 O-B 2 O 3 -SiO 2 , presented in Fig.…”

“…The inset shows V R as a function of the atomic packing density C g . aluminosilicate and alkali-alkaline earth silicate glasses, were added for comparison [47,49,53,79,135,136]. Values from Refs.…”

Densification contribution as a function of strain rate under indentation of terbium-doped aluminophosphate glass

“…A method to estimate the contribution of densification mechanism to the total plastic deformation of the glass matrix under indentation is the heating of the indented sample up to 0.9T g (glass transition temperature), that causes the recovery of the indentation depth, the measure of which is believed to assess what part of the imprint volume is formed due to the permanent compression of material [8,11]. Using this method, it was shown that not only the structure of the glass is responsible for the development of one or another deformation mechanism, but also the geometry of the indenter [12,13] is responsible for the creation of a specific stress state of the deformed region [14].…”